code is no longer based :(

[carveJwlIkooP6JGAAIwe30JlM.git] / player_skate.c

#ifndef PLAYER_SKATE_C
#define PLAYER_SKATE_C

#include "player.h"
#include "audio.h"
#include "vg/vg_perlin.h"
#include "menu.h"
#include "ent_skateshop.h"
#include "addon.h"

static void player__skate_bind(void){
   struct skeleton *sk = &localplayer.skeleton;
   rb_update_transform( &localplayer.rb );

   struct { struct skeleton_anim **anim; const char *name; }
   bindings[] = {
      { &player_skate.anim_grind,        "pose_grind" },
      { &player_skate.anim_grind_jump,   "pose_grind_jump" },
      { &player_skate.anim_stand,        "pose_stand" },
      { &player_skate.anim_highg,        "pose_highg" },
      { &player_skate.anim_air,          "pose_air" },
      { &player_skate.anim_slide,        "pose_slide" },
      { &player_skate.anim_push,         "push" },
      { &player_skate.anim_push_reverse, "push_reverse" },
      { &player_skate.anim_ollie,        "ollie" },
      { &player_skate.anim_ollie_reverse,"ollie_reverse" },
      { &player_skate.anim_grabs,        "grabs" }
   };

   for( u32 i=0; i<vg_list_size(bindings); i++ )
      *bindings[i].anim = skeleton_get_anim( sk, bindings[i].name );
}

static void player__skate_kill_audio(void){
   audio_lock();
   if( player_skate.aud_main ){
      player_skate.aud_main = 
         audio_channel_fadeout( player_skate.aud_main, 0.1f );
   }
   if( player_skate.aud_air ){
      player_skate.aud_air = 
         audio_channel_fadeout( player_skate.aud_air, 0.1f );
   }
   if( player_skate.aud_slide ){
      player_skate.aud_slide = 
         audio_channel_fadeout( player_skate.aud_slide, 0.1f );
   }
   audio_unlock();
}

/* 
 * Collision detection routines
 *
 *
 */

/*
 * Does collision detection on a sphere vs world, and applies some smoothing
 * filters to the manifold afterwards
 */
static int skate_collide_smooth( m4x3f mtx, rb_sphere *sphere, rb_ct *man ){
   world_instance *world = world_current_instance();

   int len = 0;
   len = rb_sphere__scene( mtx, sphere, NULL, &world->rb_geo.inf.scene, man,
                           k_material_flag_walking );

   for( int i=0; i<len; i++ ){
      man[i].rba = &localplayer.rb;
      man[i].rbb = NULL;
   }

   rb_manifold_filter_coplanar( man, len, 0.03f );

   if( len > 1 ){
      rb_manifold_filter_backface( man, len );
      rb_manifold_filter_joint_edges( man, len, 0.03f );
      rb_manifold_filter_pairs( man, len, 0.03f );
   }
   int new_len = rb_manifold_apply_filtered( man, len );
   if( len && !new_len )
      len = 1;
   else
      len = new_len;

   return len;
}

struct grind_info
{
   v3f co, dir, n;
};

static int skate_grind_scansq( v3f pos, v3f dir, float r,
                                  struct grind_info *inf ){
   world_instance *world = world_current_instance();

   v4f plane;
   v3_copy( dir, plane );
   v3_normalize( plane );
   plane[3] = v3_dot( plane, pos );

   boxf box;
   v3_add( pos, (v3f){ r, r, r }, box[1] );
   v3_sub( pos, (v3f){ r, r, r }, box[0] );

   struct grind_sample{
      v2f co;
      v2f normal;
      v3f normal3,
          centroid;
   }
   samples[48];
   int sample_count = 0;

   v2f support_min,
       support_max;

   v3f support_axis;
   v3_cross( plane, (v3f){0,1,0}, support_axis );
   v3_normalize( support_axis );
   
   bh_iter it;
   bh_iter_init_box( 0, &it, box );
   i32 idx;
   
   while( bh_next( world->geo_bh, &it, &idx ) ){
      u32 *ptri = &world->scene_geo.arrindices[ idx*3 ];
      v3f tri[3];

      struct world_surface *surf = world_tri_index_surface(world,ptri[0]);
      if( !(surf->info.flags & k_material_flag_grindable) )
         continue;

      for( int j=0; j<3; j++ )
         v3_copy( world->scene_geo.arrvertices[ptri[j]].co, tri[j] );

      for( int j=0; j<3; j++ ){
         int i0 = j,
             i1 = (j+1) % 3;
         
         struct grind_sample *sample = &samples[ sample_count ];
         v3f co;

         if( plane_segment( plane, tri[i0], tri[i1], co ) ){
            v3f d;
            v3_sub( co, pos, d );
            if( v3_length2( d ) > r*r )
               continue;

            v3f va, vb, normal;
            v3_sub( tri[1], tri[0], va );
            v3_sub( tri[2], tri[0], vb );
            v3_cross( va, vb, normal );

            sample->normal[0] = v3_dot( support_axis, normal );
            sample->normal[1] = normal[1];
            sample->co[0]     = v3_dot( support_axis, d );
            sample->co[1]     = d[1];

            v3_copy( normal, sample->normal3 ); /* normalize later
                                                   if we want to us it */

            v3_muls(                      tri[0], 1.0f/3.0f, sample->centroid );
            v3_muladds( sample->centroid, tri[1], 1.0f/3.0f, sample->centroid );
            v3_muladds( sample->centroid, tri[2], 1.0f/3.0f, sample->centroid );

            v2_normalize( sample->normal );
            sample_count ++;

            if( sample_count == vg_list_size( samples ) )
               goto too_many_samples;
         }
      }
   }

too_many_samples:

   if( sample_count < 2 )
      return 0;

   v3f average_direction,
       average_normal;

   v2f min_co, max_co;
   v2_fill( min_co,  INFINITY );
   v2_fill( max_co, -INFINITY );

   v3_zero( average_direction );
   v3_zero( average_normal );

   int passed_samples = 0;
   
   for( int i=0; i<sample_count-1; i++ ){
      struct grind_sample *si, *sj;

      si = &samples[i];

      for( int j=i+1; j<sample_count; j++ ){
         if( i == j )
            continue;

         sj = &samples[j];

         /* non overlapping */
         if( v2_dist2( si->co, sj->co ) >= (0.01f*0.01f) )
            continue;

         /* not sharp angle */
         if( v2_dot( si->normal, sj->normal ) >= 0.7f )
            continue;

         /* not convex */
         v3f v0;
         v3_sub( sj->centroid, si->centroid, v0 );
         if( v3_dot( v0, si->normal3 ) >= 0.0f ||
             v3_dot( v0, sj->normal3 ) <= 0.0f )
            continue;

         v2_minv( sj->co, min_co, min_co );
         v2_maxv( sj->co, max_co, max_co );
         
         v3f n0, n1, dir;
         v3_copy( si->normal3, n0 );
         v3_copy( sj->normal3, n1 );
         v3_cross( n0, n1, dir );

         if( v3_length2( dir ) <= 0.001f )
            continue;

         v3_normalize( dir );

         /* make sure the directions all face a common hemisphere */
         v3_muls( dir, vg_signf(v3_dot(dir,plane)), dir );
         v3_add( average_direction, dir, average_direction );

         float yi = si->normal3[1],
               yj = sj->normal3[1];

         if( yi > yj ) v3_add( si->normal3, average_normal, average_normal );
         else          v3_add( sj->normal3, average_normal, average_normal );

         passed_samples ++;
      }
   }

   if( !passed_samples )
      return 0;

   if( (v3_length2( average_direction ) <= 0.001f) ||
       (v3_length2( average_normal ) <= 0.001f ) )
      return 0;

   float div = 1.0f/(float)passed_samples;
   v3_normalize( average_direction );
   v3_normalize( average_normal );

   v2f average_coord;
   v2_add( min_co, max_co, average_coord );
   v2_muls( average_coord, 0.5f, average_coord );

   v3_muls( support_axis, average_coord[0], inf->co );
   inf->co[1] += average_coord[1];
   v3_add( pos, inf->co, inf->co );
   v3_copy( average_normal, inf->n );
   v3_copy( average_direction, inf->dir );

   vg_line_point( inf->co, 0.02f, VG__GREEN );
   vg_line_arrow( inf->co, average_direction, 0.3f, VG__GREEN );
   vg_line_arrow( inf->co, inf->n, 0.2f, VG__CYAN );

   return passed_samples;
}

static void reset_jump_info( jump_info *inf ){
   inf->log_length = 0;
   inf->land_dist = 0.0f;
   inf->score = 0.0f;
   inf->type = k_prediction_unset;
   v3_zero( inf->apex );
}

static int create_jumps_to_hit_target( jump_info *jumps,
                                          v3f target, float max_angle_delta,
                                          float gravity ){
   /* calculate the exact 2 solutions to jump onto that grind spot */

   v3f v0;
   v3_sub( target, localplayer.rb.co, v0 );

   v3f ax;
   v3_copy( v0, ax );
   ax[1] = 0.0f;
   v3_normalize( ax );

   v2f d = { v3_dot( ax, v0 ),               v0[1] },
       v = { v3_dot( ax, localplayer.rb.v ), localplayer.rb.v[1] };

   float a = atan2f( v[1], v[0] ),
         m = v2_length( v ),
         root = m*m*m*m - gravity*(gravity*d[0]*d[0] + 2.0f*d[1]*m*m);

   int valid_count = 0;

   if( root > 0.0f ){
      root = sqrtf( root );
      float a0 = atanf( (m*m + root) / (gravity * d[0]) ),
            a1 = atanf( (m*m - root) / (gravity * d[0]) );

      if( fabsf(a0-a) < max_angle_delta ){
         jump_info *inf = &jumps[ valid_count ++ ];
         reset_jump_info( inf );

         v3_muls( ax, cosf( a0 ) * m, inf->v );
         inf->v[1] += sinf( a0 ) * m;
         inf->land_dist = d[0] / (cosf(a0)*m);
         inf->gravity = gravity;

         v3_copy( target, inf->log[inf->log_length ++] );
      }

      if( fabsf(a1-a) < max_angle_delta ){
         jump_info *inf = &jumps[ valid_count ++ ];
         reset_jump_info( inf );

         v3_muls( ax, cosf( a1 ) * m, inf->v );
         inf->v[1] += sinf( a1 ) * m;
         inf->land_dist = d[0] / (cosf(a1)*m);
         inf->gravity = gravity;

         v3_copy( target, inf->log[inf->log_length ++] );
      }
   }

   return valid_count;
}

static void player__approximate_best_trajectory(void){
   world_instance *world0 = world_current_instance();

   float k_trace_delta = k_rb_delta * 10.0f;
   struct player_skate_state *state = &player_skate.state;

   state->air_start = vg.time;
   v3_copy( localplayer.rb.v, state->air_init_v );
   v3_copy( localplayer.rb.co, state->air_init_co );

   player_skate.possible_jump_count = 0;

   v3f axis;
   v3_cross( localplayer.rb.v, localplayer.rb.to_world[1], axis );
   v3_normalize( axis );

   /* at high slopes, Y component is low */
   float upness      = localplayer.rb.to_world[1][1],
         angle_begin = -(1.0f-fabsf( upness )),
         angle_end   =   1.0f;

   struct grind_info grind;
   int grind_located = 0;
   float grind_located_gravity = k_gravity;


   v3f launch_v_bounds[2];

   for( int i=0; i<2; i++ ){
      v3_copy( localplayer.rb.v, launch_v_bounds[i] );
      float ang = (float[]){ angle_begin, angle_end }[ i ];
            ang *= 0.15f;

      v4f qbias;
      q_axis_angle( qbias, axis, ang );
      q_mulv( qbias, launch_v_bounds[i], launch_v_bounds[i] );
   }

   for( int m=0;m<=30; m++ ){
      jump_info *inf = 
         &player_skate.possible_jumps[ player_skate.possible_jump_count ++ ];
      reset_jump_info( inf );

      v3f launch_co, launch_v, co0, co1;
      v3_copy( localplayer.rb.co, launch_co );
      v3_copy( localplayer.rb.v,  launch_v );
      v3_copy( launch_co, co0 );
      world_instance *trace_world = world0;

      float vt  = (float)m * (1.0f/30.0f),
            ang = vg_lerpf( angle_begin, angle_end, vt ) * 0.15f;

      v4f qbias;
      q_axis_angle( qbias, axis, ang );
      q_mulv( qbias, launch_v, launch_v );

      float yaw_sketch = 1.0f-fabsf(upness);

      float yaw_bias = ((float)(m%3) - 1.0f) * 0.08f * yaw_sketch;
      q_axis_angle( qbias, localplayer.rb.to_world[1], yaw_bias );
      q_mulv( qbias, launch_v, launch_v );

      float gravity_bias = vg_lerpf( 0.85f, 1.4f, vt ),
            gravity      = k_gravity * gravity_bias;
      inf->gravity = gravity;
      v3_copy( launch_v, inf->v );

      for( int i=1; i<=50; i++ ){
         float t = (float)i * k_trace_delta;

         v3_muls( launch_v, t, co1 );
         co1[1] += -0.5f * gravity * t*t;
         v3_add( launch_co, co1, co1 );

         float launch_vy = launch_v[1];

         int search_for_grind = 1;
         if( grind_located ) search_for_grind = 0;
         if( launch_vy - gravity*t > 0.0f ) search_for_grind = 0;

         /* REFACTOR */

         v3f closest={0.0f,0.0f,0.0f};
         if( search_for_grind ){
            if( bh_closest_point(trace_world->geo_bh,co1,closest,1.0f) != -1 ){
               float min_dist = 0.75f;
                     min_dist *= min_dist;

               if( v3_dist2( closest, launch_co ) < min_dist )
                  search_for_grind = 0;

               v3f bound[2];

               for( int j=0; j<2; j++ ){
                  v3_muls( launch_v_bounds[j], t, bound[j] );
                  bound[j][1] += -0.5f*gravity*t*t;
                  v3_add( launch_co, bound[j], bound[j] );
               }

               float limh = vg_minf( 2.0f, t ),
                     minh = vg_minf( bound[0][1], bound[1][1] )-limh,
                     maxh = vg_maxf( bound[0][1], bound[1][1] )+limh;

               if( (closest[1] < minh) || (closest[1] > maxh) ){
                  search_for_grind = 0;
               }
            }
            else
               search_for_grind = 0;
         }

         if( search_for_grind ){
            v3f ve;
            v3_copy( launch_v, ve );
            ve[1] += -gravity * t;

            if( skate_grind_scansq( closest, ve, 0.5f, &grind ) ){
               /* check alignment */
               v2f v0 = { ve[0], ve[2] },
                   v1 = { grind.dir[0], grind.dir[2] };

               v2_normalize( v0 );
               v2_normalize( v1 );

               float a = v2_dot( v0, v1 );

               float a_min = cosf( VG_PIf * 0.185f );
               if( state->grind_cooldown )
                  a_min = cosf( VG_PIf * 0.05f );

               /* check speed */
               if( (fabsf(v3_dot( ve, grind.dir ))>=k_grind_axel_min_vel) &&
                   (a >= a_min) && 
                   (fabsf(grind.dir[1]) < 0.70710678118654752f))
               {
                  grind_located = 1;
                  grind_located_gravity = inf->gravity;
               }
            }
         }

         if( trace_world->rendering_gate ){
            ent_gate *gate = trace_world->rendering_gate;
            if( gate_intersect( gate, co1, co0 ) ){
               m4x3_mulv( gate->transport, co0, co0 );
               m4x3_mulv( gate->transport, co1, co1 );
               m3x3_mulv( gate->transport, launch_v, launch_v);
               m4x3_mulv( gate->transport, launch_co, launch_co );
            }
         }

         float t1;
         v3f n;

         float scan_radius = k_board_radius;
               scan_radius *= vg_clampf( t, 0.02f, 1.0f );

         int idx = spherecast_world( trace_world, co0, co1, scan_radius, &t1, n,
                                     k_material_flag_walking );
         if( idx != -1 ){
            v3f co;
            v3_lerp( co0, co1, t1, co );
            v3_copy( co, inf->log[ inf->log_length ++ ] ); 

            v3_copy( n, inf->n );
            u32 *tri = &trace_world->scene_geo.arrindices[ idx*3 ];
            struct world_surface *surf = 
               world_tri_index_surface( trace_world, tri[0] );

            inf->type = k_prediction_land;

            v3f ve;
            v3_copy( launch_v, ve );
            ve[1] += -gravity * t;

            inf->score = -v3_dot( ve, inf->n );
            inf->land_dist = t + k_trace_delta * t1;

            /* Bias prediction towords ramps */
            if( !(surf->info.flags & k_material_flag_skate_target) )
               inf->score *= 10.0f;

            if( surf->info.flags & k_material_flag_boundary )
               player_skate.possible_jump_count --;

            break;
         }
         
         if( i % 3 == 0 )
            v3_copy( co1, inf->log[ inf->log_length ++ ] ); 
         v3_copy( co1, co0 );
      }

      if( inf->type == k_prediction_unset )
         player_skate.possible_jump_count --;
   }

   if( grind_located ){
      jump_info grind_jumps[2];
      
      int valid_count = 
         create_jumps_to_hit_target( grind_jumps, grind.co, 
                                     0.175f*VG_PIf, grind_located_gravity );

      /* knock out original landing points in the 1m area */
      for( u32 j=0; j<player_skate.possible_jump_count; j++ ){
         jump_info *jump = &player_skate.possible_jumps[ j ];
         float dist = v3_dist2( jump->log[jump->log_length-1], grind.co );
         float descale = 1.0f-vg_minf(1.0f,dist);
         jump->score += descale*3.0f;
      }

      for( int i=0; i<valid_count; i++ ){
         jump_info *jump = &grind_jumps[i];
         jump->type = k_prediction_grind;

         v3f launch_v, launch_co, co0, co1;

         v3_copy( jump->v, launch_v );
         v3_copy( localplayer.rb.co, launch_co );
         
         float t = 0.05f * jump->land_dist;
         v3_muls( launch_v, t, co0 );
         co0[1] += -0.5f * jump->gravity * t*t;
         v3_add( launch_co, co0, co0 );

         /* rough scan to make sure we dont collide with anything */
         for( int j=1; j<=16; j++ ){
            t  = (float)j*(1.0f/16.0f);
            t *= 0.9f;
            t += 0.05f;
            t *= jump->land_dist;

            v3_muls( launch_v, t, co1 );
            co1[1] += -0.5f * jump->gravity * t*t;
            v3_add( launch_co, co1, co1 );
            
            float t1;
            v3f n;

            int idx = spherecast_world( world0, co0,co1,
                                        k_board_radius*0.1f, &t1, n, 
                                        k_material_flag_walking );
            if( idx != -1 ){
               goto invalidated_grind;
            }

            v3_copy( co1, co0 );
         }

         v3_copy( grind.n, jump->n );

         /* determine score */
         v3f ve;
         v3_copy( jump->v, ve );
         ve[1] += -jump->gravity*jump->land_dist;
         jump->score = -v3_dot( ve, grind.n ) * 0.9f;

         player_skate.possible_jumps[ player_skate.possible_jump_count ++ ] = 
            *jump;

         continue;
invalidated_grind:;
      }
   }


   float score_min =  INFINITY,
         score_max = -INFINITY;

   jump_info *best = NULL;

   for( int i=0; i<player_skate.possible_jump_count; i ++ ){
      jump_info *jump = &player_skate.possible_jumps[i];

      if( jump->score < score_min )
         best = jump;

      score_min = vg_minf( score_min, jump->score );
      score_max = vg_maxf( score_max, jump->score );
   }

   for( int i=0; i<player_skate.possible_jump_count; i ++ ){
      jump_info *jump = &player_skate.possible_jumps[i];
      float s = jump->score;

      s -= score_min;
      s /= (score_max-score_min);
      s  = 1.0f - s;

      jump->score = s;
      jump->colour = s * 255.0f;

      if( jump == best )
         jump->colour <<= 16;
      else if( jump->type == k_prediction_land )
         jump->colour <<= 8;
      
      jump->colour |= 0xff000000;
   }

   if( best ){
      v3_copy( best->n, state->land_normal );
      v3_copy( best->v, localplayer.rb.v );
      state->land_dist = best->land_dist;
      state->gravity_bias = best->gravity;

      if( best->type == k_prediction_grind ){
         state->activity = k_skate_activity_air_to_grind;
      }

      v2f steer;
      joystick_state( k_srjoystick_steer, steer );
      v2_normalize_clamp( steer );

      if( (fabsf(steer[1]) > 0.5f) && (state->land_dist >= 1.5f) ){
         state->flip_rate = (1.0f/state->land_dist) * vg_signf(steer[1]) *
                                 state->reverse ;
         state->flip_time = 0.0f;
         v3_copy( localplayer.rb.to_world[0], state->flip_axis );
      }
      else{
         state->flip_rate = 0.0f;
         v3_zero( state->flip_axis );
      }
   }
   else
      v3_copy( (v3f){0,1,0}, state->land_normal );
}

/*
 *
 * Varius physics models
 * ------------------------------------------------
 */

/*
 * Air control, no real physics
 */
static void skate_apply_air_model(void){
   struct player_skate_state *state = &player_skate.state;

   if( state->activity_prev > k_skate_activity_air_to_grind )
      player__approximate_best_trajectory();

   float angle = v3_dot( localplayer.rb.to_world[1], state->land_normal );
   angle = vg_clampf( angle, -1.0f, 1.0f );
   v3f axis; 
   v3_cross( localplayer.rb.to_world[1], state->land_normal, axis );

   v4f correction;
   q_axis_angle( correction, axis, 
                  acosf(angle)*2.0f*VG_TIMESTEP_FIXED );
   q_mul( correction, localplayer.rb.q, localplayer.rb.q );
}

static enum trick_type player_skate_trick_input(void);
static void skate_apply_trick_model(void){
   struct player_skate_state *state = &player_skate.state;

   v3f Fd, Fs, F;
   v3f strength = { 3.7f, 3.6f, 8.0f };

   v3_muls( state->trick_residualv, -4.0f , Fd );
   v3_muls( state->trick_residuald, -10.0f, Fs );
   v3_add( Fd, Fs, F );
   v3_mul( strength, F, F );

   v3_muladds( state->trick_residualv, F, k_rb_delta, 
               state->trick_residualv );
   v3_muladds( state->trick_residuald, state->trick_residualv,
               k_rb_delta, state->trick_residuald );

   if( state->activity <= k_skate_activity_air_to_grind ){
      if( v3_length2( state->trick_vel ) < 0.0001f )
         return;

      int carry_on = player_skate_trick_input();

      /* we assume velocities share a common divisor, in which case the 
       * interval is the minimum value (if not zero) */

      float min_rate = 99999.0f;

      for( int i=0; i<3; i++ ){
         float v = state->trick_vel[i];
         if( (v > 0.0f) && (v < min_rate) )
            min_rate = v;
      }

      float interval = 1.0f / min_rate,
            current  = floorf( state->trick_time / interval ),
            next_end = (current+1.0f) * interval;


      /* integrate trick velocities */
      v3_muladds( state->trick_euler, state->trick_vel, k_rb_delta,
                  state->trick_euler );

      if( !carry_on && (state->trick_time + k_rb_delta >= next_end) ){
         state->trick_time = 0.0f;
         state->trick_euler[0] = roundf( state->trick_euler[0] );
         state->trick_euler[1] = roundf( state->trick_euler[1] );
         state->trick_euler[2] = roundf( state->trick_euler[2] );
         v3_copy( state->trick_vel, state->trick_residualv );
         v3_zero( state->trick_vel );
      }

      state->trick_time += k_rb_delta;
   }
   else{
      if( (v3_length2(state->trick_vel) >= 0.0001f ) &&
          state->trick_time > 0.2f)
      {
         player__skate_kill_audio();
         player__dead_transition();
      }

      state->trick_euler[0] = roundf( state->trick_euler[0] );
      state->trick_euler[1] = roundf( state->trick_euler[1] );
      state->trick_euler[2] = roundf( state->trick_euler[2] );
      state->trick_time = 0.0f;
      v3_zero( state->trick_vel );
   }
}

static void skate_apply_grab_model(void){
   struct player_skate_state *state = &player_skate.state;

   float grabt = axis_state( k_sraxis_grab );

   if( grabt > 0.5f ){
      v2_muladds( state->grab_mouse_delta, vg.mouse_delta, 0.02f, 
                  state->grab_mouse_delta );

      v2_normalize_clamp( state->grab_mouse_delta );
   }
   else
      v2_zero( state->grab_mouse_delta );

   state->grabbing = vg_lerpf( state->grabbing, grabt, 8.4f*k_rb_delta );
}

static void skate_apply_steering_model(void){
   struct player_skate_state *state = &player_skate.state;

   v2f jsteer;
   joystick_state( k_srjoystick_steer, jsteer );

   /* Steering */
   float steer = jsteer[0],
         grab  = axis_state( k_sraxis_grab );

   steer = vg_signf( steer ) * steer*steer * k_steer_ground;

   v3f steer_axis;
   v3_muls( localplayer.rb.to_world[1], -vg_signf( steer ), steer_axis );

   float rate = 26.0f,
         top  = 1.0f;

   if( state->activity <= k_skate_activity_air_to_grind ){
      rate = 6.0f * fabsf(steer);
      top  = 1.5f;
   }
   else{
      /* rotate slower when grabbing on ground */
      steer *= (1.0f-(state->jump_charge+grab)*0.4f);

      if( state->activity == k_skate_activity_grind_5050 ){
         rate = 0.0f;
         top  = 0.0f;
      }

      else if( state->activity >= k_skate_activity_grind_any ){
         rate *= fabsf(steer);

         float a = 0.8f * -steer * k_rb_delta;

         v4f q;
         q_axis_angle( q, localplayer.rb.to_world[1], a );
         q_mulv( q, player_skate.grind_vec, player_skate.grind_vec );

         v3_normalize( player_skate.grind_vec );
      }

      else if( state->manual_direction ){
         rate = 35.0f;
         top  = 1.5f;
      }
      
      if( grab < 0.5f ){
         top *= 1.0f+v3_length( state->throw_v )*k_mmthrow_steer;
      }
   }

   float current  = v3_dot( localplayer.rb.to_world[1], localplayer.rb.w ),
         addspeed = (steer * -top) - current,
         maxaccel = rate * k_rb_delta,
         accel    = vg_clampf( addspeed, -maxaccel, maxaccel );

   v3_muladds( localplayer.rb.w, localplayer.rb.to_world[1], 
               accel, localplayer.rb.w );
}

/*
 * Computes friction and surface interface model
 */
static void skate_apply_friction_model(void){
   struct player_skate_state *state = &player_skate.state;

   /*
    * Computing localized friction forces for controlling the character
    * Friction across X is significantly more than Z
    */

   v3f vel;
   m3x3_mulv( localplayer.rb.to_local, localplayer.rb.v, vel );
   float slip = 0.0f;
   
   if( fabsf(vel[2]) > 0.01f )
      slip = fabsf(-vel[0] / vel[2]) * vg_signf(vel[0]);

   if( fabsf( slip ) > 1.2f )
      slip = vg_signf( slip ) * 1.2f;

   state->slip = slip;
   state->reverse = -vg_signf(vel[2]);

   vel[0] += vg_cfrictf( vel[0], k_friction_lat * k_rb_delta );
   vel[2] += vg_cfrictf( vel[2], k_friction_resistance * k_rb_delta );

   /* Pushing additive force */

   if( !button_press( k_srbind_jump ) ){
      if( button_press( k_srbind_push ) || (vg.time-state->start_push<0.75) )
      {
         if( (vg.time - state->cur_push) > 0.25 )
            state->start_push = vg.time;

         state->cur_push = vg.time;

         double push_time = vg.time - state->start_push;

         float cycle_time = push_time*k_push_cycle_rate,
               accel      = k_push_accel * (sinf(cycle_time)*0.5f+0.5f),
               amt        = accel * VG_TIMESTEP_FIXED,
               current    = v3_length( vel ),
               new_vel    = vg_minf( current + amt, k_max_push_speed ),
               delta      = new_vel - vg_minf( current, k_max_push_speed );

         vel[2] += delta * -state->reverse;
      }
   }

   /* Send back to velocity */
   m3x3_mulv( localplayer.rb.to_world, vel, localplayer.rb.v );
}

static void skate_apply_jump_model(void){
   struct player_skate_state *state = &player_skate.state;
   int charging_jump_prev = state->charging_jump;
   state->charging_jump = button_press( k_srbind_jump );

   /* Cannot charge this in air */
   if( state->activity <= k_skate_activity_air_to_grind ){
      state->charging_jump = 0;
      return;
   }

   if( state->charging_jump ){
      state->jump_charge += k_rb_delta * k_jump_charge_speed;

      if( !charging_jump_prev )
         state->jump_dir = state->reverse>0.0f? 1: 0;
   }
   else{
      state->jump_charge -= k_jump_charge_speed * k_rb_delta;
   }

   state->jump_charge = vg_clampf( state->jump_charge, 0.0f, 1.0f );

   /* player let go after charging past 0.2: trigger jump */
   if( (!state->charging_jump) && (state->jump_charge > 0.2f) ){
      v3f jumpdir;
      
      /* Launch more up if alignment is up else improve velocity */
      float aup = localplayer.rb.to_world[1][1],
            mod = 0.5f,
            dir = mod + fabsf(aup)*(1.0f-mod);

      if( state->activity == k_skate_activity_ground ){
         v3_copy( localplayer.rb.v, jumpdir );
         v3_normalize( jumpdir );
         v3_muls( jumpdir, 1.0f-dir, jumpdir );
         v3_muladds( jumpdir, localplayer.rb.to_world[1], dir, jumpdir );
         v3_normalize( jumpdir );
      }else{
         v3_copy( state->up_dir, jumpdir );
         state->grind_cooldown = 30;
         state->activity = k_skate_activity_ground;

         v2f steer;
         joystick_state( k_srjoystick_steer, steer );

         float tilt  = steer[0] * 0.3f;
               tilt *= vg_signf(v3_dot( localplayer.rb.v, 
                                        player_skate.grind_dir ));

         v4f qtilt;
         q_axis_angle( qtilt, player_skate.grind_dir, tilt );
         q_mulv( qtilt, jumpdir, jumpdir );
      }
      state->surface_cooldown = 10;
      
      float force = k_jump_force*state->jump_charge;
      v3_muladds( localplayer.rb.v, jumpdir, force, localplayer.rb.v );
      state->jump_charge = 0.0f;
      state->jump_time = vg.time;
      player__networked_sfx( k_player_subsystem_skate, 32, 
                             k_player_skate_soundeffect_jump,
                             localplayer.rb.co, 1.0f );
   }
}

static void skate_apply_pump_model(void){
   struct player_skate_state *state = &player_skate.state;

   if( state->activity != k_skate_activity_ground ){
      v3_zero( state->throw_v );
      return;
   }

   /* Throw / collect routine 
    */
   if( axis_state( k_sraxis_grab ) > 0.5f ){
      if( state->activity == k_skate_activity_ground ){
         /* Throw */
         v3_muls( localplayer.rb.to_world[1], k_mmthrow_scale, state->throw_v );
      }
   }
   else{
      /* Collect */
      float doty = v3_dot( localplayer.rb.to_world[1], state->throw_v );
      
      v3f Fl, Fv;
      v3_muladds( state->throw_v, localplayer.rb.to_world[1], -doty, Fl);

      if( state->activity == k_skate_activity_ground ){
         if( v3_length2(localplayer.rb.v)<(20.0f*20.0f) ){
            v3_muladds( localplayer.rb.v, Fl, 
                        k_mmcollect_lat, localplayer.rb.v );
         }
         v3_muladds( state->throw_v, Fl, -k_mmcollect_lat, state->throw_v );
      }

      v3_muls( localplayer.rb.to_world[1], -doty, Fv );
      v3_muladds( localplayer.rb.v,     Fv, k_mmcollect_vert, localplayer.rb.v );
      v3_muladds( state->throw_v, Fv, k_mmcollect_vert, state->throw_v );
   }

   /* Decay */
   if( v3_length2( state->throw_v ) > 0.0001f ){
      v3f dir;
      v3_copy( state->throw_v, dir );
      v3_normalize( dir );

      float max = v3_dot( dir, state->throw_v ),
            amt = vg_minf( k_mmdecay * k_rb_delta, max );
      v3_muladds( state->throw_v, dir, -amt, state->throw_v );
   }
}

static void skate_apply_cog_model(void){
   struct player_skate_state *state = &player_skate.state;

   v3f ideal_cog, ideal_diff, ideal_dir;
   v3_copy( state->up_dir, ideal_dir );
   v3_normalize( ideal_dir );

   float grab = axis_state( k_sraxis_grab );
   v3_muladds( localplayer.rb.co, ideal_dir, 1.0f-grab, ideal_cog );
   v3_sub( ideal_cog, state->cog, ideal_diff );

   /* Apply velocities */
   v3f rv;
   v3_sub( localplayer.rb.v, state->cog_v, rv );

   v3f F;
   v3_muls( ideal_diff, -k_cog_spring * k_rb_rate, F );
   v3_muladds( F, rv,   -k_cog_damp * k_rb_rate, F );

   float ra = k_cog_mass_ratio,
         rb = 1.0f-k_cog_mass_ratio;

   /* Apply forces & intergrate */
   v3_muladds( state->cog_v, F, -rb, state->cog_v );
   state->cog_v[1] += -9.8f * k_rb_delta;
   v3_muladds( state->cog, state->cog_v, k_rb_delta, state->cog );
}

static void skate_integrate(void){
   struct player_skate_state *state = &player_skate.state;

   float rate_x = 1.0f - (k_rb_delta * 3.0f),
         rate_z = rate_x,
         rate_y = 1.0f;

   if( state->activity >= k_skate_activity_grind_any ){
      rate_x = 1.0f-(16.0f*k_rb_delta);
      rate_y = 1.0f-(10.0f*k_rb_delta);
      rate_z = 1.0f-(40.0f*k_rb_delta);
   }

   float wx = v3_dot( localplayer.rb.w, localplayer.rb.to_world[0] ) * rate_x,
         wy = v3_dot( localplayer.rb.w, localplayer.rb.to_world[1] ) * rate_y,
         wz = v3_dot( localplayer.rb.w, localplayer.rb.to_world[2] ) * rate_z;

   v3_muls(                  localplayer.rb.to_world[0], wx, localplayer.rb.w );
   v3_muladds( localplayer.rb.w, localplayer.rb.to_world[1], wy, 
               localplayer.rb.w );
   v3_muladds( localplayer.rb.w, localplayer.rb.to_world[2], wz, 
               localplayer.rb.w );

   state->flip_time += state->flip_rate * k_rb_delta;
   rb_update_transform( &localplayer.rb );
}

static enum trick_type player_skate_trick_input(void){
   return (button_press( k_srbind_trick0 )     ) |
          (button_press( k_srbind_trick1 ) << 1) |
          (button_press( k_srbind_trick2 ) << 1) |
          (button_press( k_srbind_trick2 )     );
}

static void player__skate_pre_update(void){
   struct player_skate_state *state = &player_skate.state;

   if( button_down( k_srbind_use ) ){
      localplayer.subsystem = k_player_subsystem_walk;

      v3f angles;
      v3_copy( localplayer.cam.angles, localplayer.angles );
      localplayer.angles[2] = 0.0f;

      v3f newpos, offset;
      m4x3_mulv( localplayer.rb.to_world, (v3f){0.0f,1.0f,0.0f}, newpos );
      v3_add( newpos, (v3f){0.0f,-1.0f,0.0f}, newpos );
      v3_sub( localplayer.rb.co, newpos, offset );
      v3_copy( newpos, localplayer.rb.co );

      player__begin_holdout( offset );
      player__skate_kill_audio();
      player__walk_transition();
      return;
   }

   if( state->activity <= k_skate_activity_air_to_grind ){
      enum trick_type trick = k_trick_type_none;
      if( (trick = player_skate_trick_input()) ){
         if( (vg.time - state->jump_time) < 0.1f ){
            v3_zero( state->trick_vel );
            state->trick_time = 0.0f;

            if( trick == k_trick_type_kickflip ){
               state->trick_vel[0] = 3.0f;
            }
            else if( trick == k_trick_type_shuvit ){
               state->trick_vel[2] = 3.0f;
            }
            else if( trick == k_trick_type_treflip ){
               state->trick_vel[0] = 2.0f;
               state->trick_vel[2] = 2.0f;
            }
            state->trick_type = trick;
         }
      }
   }
   else
      state->trick_type = k_trick_type_none;
}

static void player__skate_post_update(void){
   struct player_skate_state *state = &player_skate.state;

   for( int i=0; i<player_skate.possible_jump_count; i++ ){
      jump_info *jump = &player_skate.possible_jumps[i];

      if( jump->log_length == 0 ){
         vg_fatal_error( "assert: jump->log_length == 0\n" );
      }
      
      for( int j=0; j<jump->log_length - 1; j ++ ){
         float brightness = jump->score*jump->score*jump->score;
         v3f p1;
         v3_lerp( jump->log[j], jump->log[j+1], brightness, p1 );
         vg_line( jump->log[j], p1, jump->colour );
      }

      vg_line_cross( jump->log[jump->log_length-1], jump->colour, 0.25f );

      v3f p1;
      v3_add( jump->log[jump->log_length-1], jump->n, p1 );
      vg_line( jump->log[jump->log_length-1], p1, 0xffffffff );

      vg_line_point( jump->apex, 0.02f, 0xffffffff );
   }

   audio_lock();

   float air   = state->activity <= k_skate_activity_air_to_grind? 1.0f: 0.0f,
         speed = v3_length( localplayer.rb.v ),
         attn  = vg_minf( 1.0f, speed*0.1f ),
         slide = vg_clampf( fabsf(state->slip), 0.0f, 1.0f );

   if( state->activity >= k_skate_activity_grind_any ){
      slide = 0.0f;
   }

   f32 gate        = skaterift.time_rate,
       vol_main    = sqrtf( (1.0f-air)*attn*(1.0f-slide) * 0.4f ) * gate,
       vol_air     = sqrtf(       air *attn * 0.5f )              * gate,
       vol_slide   = sqrtf( (1.0f-air)*attn*slide * 0.25f )       * gate;

   const u32 flags = AUDIO_FLAG_SPACIAL_3D|AUDIO_FLAG_LOOP;

   if( !player_skate.aud_air ){
      player_skate.aud_air = audio_get_first_idle_channel();
      if( player_skate.aud_air )
         audio_channel_init( player_skate.aud_air, &audio_board[1], flags );
   }

   if( !player_skate.aud_slide ){
      player_skate.aud_slide = audio_get_first_idle_channel();
      if( player_skate.aud_slide ) 
         audio_channel_init( player_skate.aud_slide, &audio_board[2], flags );
   }


   /* brrrrrrrrrrrt sound for tiles and stuff 
    * --------------------------------------------------------*/
   float sidechain_amt = 0.0f,
         hz            = vg_maxf( speed * 2.0f, 2.0f );

   if( (player_skate.surface == k_surface_prop_tiles) &&
       (state->activity < k_skate_activity_grind_any) )
      sidechain_amt = 1.0f;
   else
      sidechain_amt = 0.0f;

   audio_set_lfo_frequency( 0, hz );
   audio_set_lfo_wave( 0, k_lfo_polynomial_bipolar, 
                          vg_lerpf( 250.0f, 80.0f, attn ) );

   if( player_skate.sample_change_cooldown > 0.0f ){
      player_skate.sample_change_cooldown -= vg.time_frame_delta;
   }
   else{
      int sample_type = k_skate_sample_concrete;

      if( state->activity == k_skate_activity_grind_5050 ){
         if( player_skate.surface == k_surface_prop_metal )
            sample_type = k_skate_sample_metal_scrape_generic;
         else
            sample_type = k_skate_sample_concrete_scrape_metal;
      }
      else if( (state->activity == k_skate_activity_grind_back50) ||
               (state->activity == k_skate_activity_grind_front50) )
      {
         if( player_skate.surface == k_surface_prop_metal ){
            sample_type = k_skate_sample_metal_scrape_generic;
         }
         else{
            float a = v3_dot( localplayer.rb.to_world[2], 
                              player_skate.grind_dir );
            if( fabsf(a) > 0.70710678118654752f )
               sample_type = k_skate_sample_concrete_scrape_wood;
            else 
               sample_type = k_skate_sample_concrete_scrape_metal;
         }
      }
      else if( state->activity == k_skate_activity_grind_boardslide ){
         if( player_skate.surface == k_surface_prop_metal )
            sample_type = k_skate_sample_metal_scrape_generic;
         else
            sample_type = k_skate_sample_concrete_scrape_wood;
      }

      audio_clip *relevant_samples[] = {
         &audio_board[0],
         &audio_board[0],
         &audio_board[7],
         &audio_board[6],
         &audio_board[5]
      };

      if( (player_skate.main_sample_type != sample_type) || 
          (!player_skate.aud_main) ){

         player_skate.aud_main = 
            audio_channel_crossfade( player_skate.aud_main, 
                                     relevant_samples[sample_type],
                                     0.06f, flags );
         player_skate.sample_change_cooldown = 0.1f;
         player_skate.main_sample_type = sample_type;
      }
   }

   if( player_skate.aud_main ){
      player_skate.aud_main->colour = 0x00103efe;
      audio_channel_set_spacial( player_skate.aud_main, 
                                 localplayer.rb.co, 40.0f );
      //audio_channel_slope_volume( player_skate.aud_main, 0.05f, vol_main );
      audio_channel_edit_volume( player_skate.aud_main, vol_main, 1 );
      audio_channel_sidechain_lfo( player_skate.aud_main, 0, sidechain_amt );

      float rate = 1.0f + (attn-0.5f)*0.2f;
      audio_channel_set_sampling_rate( player_skate.aud_main, rate );
   }

   if( player_skate.aud_slide ){
      player_skate.aud_slide->colour = 0x00103efe;
      audio_channel_set_spacial( player_skate.aud_slide, 
                                 localplayer.rb.co, 40.0f );
      //audio_channel_slope_volume( player_skate.aud_slide, 0.05f, vol_slide );
      audio_channel_edit_volume( player_skate.aud_slide, vol_slide, 1 );
      audio_channel_sidechain_lfo( player_skate.aud_slide, 0, sidechain_amt );
   }

   if( player_skate.aud_air ){
      player_skate.aud_air->colour = 0x00103efe;
      audio_channel_set_spacial( player_skate.aud_air, 
                                 localplayer.rb.co, 40.0f );
      //audio_channel_slope_volume( player_skate.aud_air, 0.05f, vol_air );
      audio_channel_edit_volume( player_skate.aud_air, vol_air, 1 );
   }

   audio_unlock();
}

/*
 * truck alignment model at ra(local)
 * returns 1 if valid surface:
 *             surface_normal will be filled out with an averaged normal vector
 *             axel_dir will be the direction from left to right wheels
 *
 * returns 0 if no good surface found
 */
static 
int skate_compute_surface_alignment( v3f ra, u32 colour,
                                     v3f surface_normal, v3f axel_dir ){
   world_instance *world = world_current_instance();

   v3f truck, left, right;
   m4x3_mulv( localplayer.rb.to_world, ra, truck );

   v3_muladds( truck, localplayer.rb.to_world[0], -k_board_width, left  );
   v3_muladds( truck, localplayer.rb.to_world[0],  k_board_width, right );
   vg_line( left, right, colour );

   float k_max_truck_flex = VG_PIf * 0.25f;
   
   ray_hit ray_l, ray_r;

   v3f dir;
   v3_muls( localplayer.rb.to_world[1], -1.0f, dir );

   int res_l = 0, res_r = 0;

   for( int i=0; i<8; i++ ){
      float t = 1.0f - (float)i * (1.0f/8.0f);
      v3_muladds( truck, localplayer.rb.to_world[0], -k_board_radius*t, left );
      v3_muladds( left,  localplayer.rb.to_world[1],  k_board_radius,   left );
      ray_l.dist = 2.1f * k_board_radius;

      res_l = ray_world( world, left, dir, &ray_l, k_material_flag_walking );

      if( res_l )
         break;
   }

   for( int i=0; i<8; i++ ){
      float t = 1.0f - (float)i * (1.0f/8.0f);
      v3_muladds( truck, localplayer.rb.to_world[0],  k_board_radius*t, right );
      v3_muladds( right, localplayer.rb.to_world[1],  k_board_radius,   right );
      ray_r.dist = 2.1f * k_board_radius;

      res_r = ray_world( world, right, dir, &ray_r, k_material_flag_walking );

      if( res_r )
         break;
   }

   v3f v0;
   v3f midpoint;
   v3f tangent_average;
   v3_muladds( truck, localplayer.rb.to_world[1], -k_board_radius, midpoint );
   v3_zero( tangent_average );

   if( res_l || res_r ){
      v3f p0, p1, t;
      v3_copy( midpoint, p0 );
      v3_copy( midpoint, p1 );

      if( res_l ){
         v3_copy( ray_l.pos, p0 );
         v3_cross( ray_l.normal, localplayer.rb.to_world[0], t );
         v3_add( t, tangent_average, tangent_average );
      }
      if( res_r ){
         v3_copy( ray_r.pos, p1 );
         v3_cross( ray_r.normal, localplayer.rb.to_world[0], t );
         v3_add( t, tangent_average, tangent_average );
      }

      v3_sub( p1, p0, v0 );
      v3_normalize( v0 );
   }
   else{
      /* fallback: use the closes point to the trucks */
      v3f closest;
      int idx = bh_closest_point( world->geo_bh, midpoint, closest, 0.1f );

      if( idx != -1 ){
         u32 *tri = &world->scene_geo.arrindices[ idx * 3 ];
         v3f verts[3];

         for( int j=0; j<3; j++ )
            v3_copy( world->scene_geo.arrvertices[ tri[j] ].co, verts[j] );

         v3f vert0, vert1, n;
         v3_sub( verts[1], verts[0], vert0 );
         v3_sub( verts[2], verts[0], vert1 );
         v3_cross( vert0, vert1, n );
         v3_normalize( n );

         if( v3_dot( n, localplayer.rb.to_world[1] ) < 0.3f )
            return 0;

         v3_cross( n, localplayer.rb.to_world[2], v0 );
         v3_muladds( v0, localplayer.rb.to_world[2],
                     -v3_dot( localplayer.rb.to_world[2], v0 ), v0 );
         v3_normalize( v0 );

         v3f t;
         v3_cross( n, localplayer.rb.to_world[0], t );
         v3_add( t, tangent_average, tangent_average );
      }
      else
         return 0;
   }

   v3_muladds( truck, v0,  k_board_width, right );
   v3_muladds( truck, v0, -k_board_width, left );

   vg_line( left, right, VG__WHITE );

   v3_normalize( tangent_average );
   v3_cross( v0, tangent_average, surface_normal );
   v3_copy( v0, axel_dir );

   return 1;
}

static void skate_weight_distribute(void){
   struct player_skate_state *state = &player_skate.state;
   v3_zero( player_skate.weight_distribution );

   int reverse_dir = v3_dot( localplayer.rb.to_world[2], 
                             localplayer.rb.v ) < 0.0f?1:-1;

   v2f steer;
   joystick_state( k_srjoystick_steer, steer );

   if( state->manual_direction == 0 ){
      if( (steer[1] > 0.7f) && (state->activity == k_skate_activity_ground) &&
          (state->jump_charge <= 0.01f) )
         state->manual_direction = reverse_dir;
   }
   else{
      if( steer[1] < 0.1f ){
         state->manual_direction = 0;
      }
      else{
         if( reverse_dir != state->manual_direction ){
            return;
         }
      }
   }

   if( state->manual_direction ){
      float amt = vg_minf( steer[1] * 8.0f, 1.0f );
      player_skate.weight_distribution[2] = k_board_length * amt * 
                                          (float)state->manual_direction;
   }

   if( state->manual_direction ){
      v3f plane_z;

      m3x3_mulv( localplayer.rb.to_world, player_skate.weight_distribution, 
                 plane_z );
      v3_negate( plane_z, plane_z );

      v3_muladds( plane_z, player_skate.surface_picture,
                  -v3_dot( plane_z, player_skate.surface_picture ), plane_z );
      v3_normalize( plane_z );

      v3_muladds( plane_z, player_skate.surface_picture, 0.3f, plane_z );
      v3_normalize( plane_z );

      v3f p1;
      v3_muladds( localplayer.rb.co, plane_z, 1.5f, p1 );
      vg_line( localplayer.rb.co, p1, VG__GREEN );

      v3f refdir;
      v3_muls( localplayer.rb.to_world[2], -(float)state->manual_direction,
               refdir );

      rb_effect_spring_target_vector( &localplayer.rb, refdir, plane_z,
                                       k_manul_spring, k_manul_dampener,
                                       player_skate.substep_delta );
   }
}

static void skate_adjust_up_direction(void){
   struct player_skate_state *state = &player_skate.state;

   if( state->activity == k_skate_activity_ground ){
      v3f target;
      v3_copy( player_skate.surface_picture, target );

      target[1] += 2.0f * player_skate.surface_picture[1];
      v3_normalize( target );

      v3_lerp( state->up_dir, target,
               8.0f * player_skate.substep_delta, state->up_dir );
   }
   else if( state->activity <= k_skate_activity_air_to_grind ){
      v3_lerp( state->up_dir, localplayer.rb.to_world[1],
               8.0f * player_skate.substep_delta, state->up_dir );
   }
   else{
      v3f avg;
      v3_add( localplayer.rb.to_world[1], (v3f){0,1,0}, avg );
      v3_normalize( avg );

      v3_lerp( state->up_dir, avg,
               6.0f * player_skate.substep_delta, state->up_dir );
   }
}

static int skate_point_visible( v3f origin, v3f target ){
   v3f dir;
   v3_sub( target, origin, dir );
   
   ray_hit ray;
   ray.dist = v3_length( dir );
   v3_muls( dir, 1.0f/ray.dist, dir );
   ray.dist -= 0.025f;

   if( ray_world( world_current_instance(), origin, dir, &ray, 
                  k_material_flag_walking ) )
      return 0;

   return 1;
}

static void skate_grind_orient( struct grind_info *inf, m3x3f mtx ){
   v3_copy( inf->dir, mtx[0] );
   v3_copy( inf->n, mtx[1] );
   v3_cross( mtx[0], mtx[1], mtx[2] );
}

static void skate_grind_friction( struct grind_info *inf, float strength ){
   v3f v2;
   v3_muladds( localplayer.rb.to_world[2], inf->n, 
               -v3_dot( localplayer.rb.to_world[2], inf->n ), v2 );

   float a        = 1.0f-fabsf( v3_dot( v2, inf->dir ) ),
         dir      = vg_signf( v3_dot( localplayer.rb.v, inf->dir ) ),
         F        = a * -dir * k_grind_max_friction;

   v3_muladds( localplayer.rb.v, inf->dir, F*k_rb_delta*strength, 
               localplayer.rb.v );
}

static void skate_grind_decay( struct grind_info *inf, float strength ){
   m3x3f mtx, mtx_inv;
   skate_grind_orient( inf, mtx );
   m3x3_transpose( mtx, mtx_inv );

   v3f v_grind;
   m3x3_mulv( mtx_inv, localplayer.rb.v, v_grind );

   float decay = 1.0f - ( k_rb_delta * k_grind_decayxy * strength );
   v3_mul( v_grind, (v3f){ 1.0f, decay, decay }, v_grind );
   m3x3_mulv( mtx, v_grind, localplayer.rb.v );
}

static void skate_grind_truck_apply( float sign, struct grind_info *inf,
                                        float strength ){
   struct player_skate_state *state = &player_skate.state;

   /* REFACTOR */
   v3f ra = { 0.0f, -k_board_radius, sign * k_board_length };
   v3f raw, wsp;
   m3x3_mulv( localplayer.rb.to_world, ra, raw );
   v3_add( localplayer.rb.co, raw, wsp );

   v3_copy( ra, player_skate.weight_distribution );

   v3f delta;
   v3_sub( inf->co, wsp, delta );

   /* spring force */
   v3_muladds( localplayer.rb.v, delta, k_spring_force*strength*k_rb_delta, 
               localplayer.rb.v );

   skate_grind_decay( inf, strength );
   skate_grind_friction( inf, strength );

   /* yeah yeah yeah yeah */
   v3f raw_nplane, axis;
   v3_muladds( raw, inf->n, -v3_dot( inf->n, raw ), raw_nplane );
   v3_cross( raw_nplane, inf->n, axis );
   v3_normalize( axis );

   /* orientation */
   m3x3f mtx;
   skate_grind_orient( inf, mtx );
   v3f target_fwd, fwd, up, target_up;
   m3x3_mulv( mtx, player_skate.grind_vec, target_fwd );
   v3_copy( raw_nplane, fwd );
   v3_copy( localplayer.rb.to_world[1], up );
   v3_copy( inf->n, target_up );

   v3_muladds( target_fwd, inf->n, -v3_dot(inf->n,target_fwd), target_fwd );
   v3_muladds( fwd, inf->n, -v3_dot(inf->n,fwd), fwd );

   v3_normalize( target_fwd );
   v3_normalize( fwd );

   v2f steer;
   joystick_state( k_srjoystick_steer, steer );

   float way = steer[1] * vg_signf( v3_dot( raw_nplane, localplayer.rb.v ) );

   v4f q;
   q_axis_angle( q, axis, VG_PIf*0.125f * way );
   q_mulv( q, target_up,  target_up );
   q_mulv( q, target_fwd, target_fwd );

   rb_effect_spring_target_vector( &localplayer.rb, up, target_up,
                                    k_grind_spring, 
                                    k_grind_dampener,
                                    k_rb_delta );

   rb_effect_spring_target_vector( &localplayer.rb, fwd, target_fwd,
                                    k_grind_spring*strength, 
                                    k_grind_dampener*strength,
                                    k_rb_delta );

   vg_line_arrow( localplayer.rb.co, target_up, 1.0f, VG__GREEN );
   vg_line_arrow( localplayer.rb.co, fwd, 0.8f, VG__RED );
   vg_line_arrow( localplayer.rb.co, target_fwd, 1.0f, VG__YELOW );

   player_skate.grind_strength = strength;

   /* Fake contact */
   struct grind_limit *limit = 
      &player_skate.limits[ player_skate.limit_count ++ ];
   m4x3_mulv( localplayer.rb.to_local, wsp, limit->ra );
   m3x3_mulv( localplayer.rb.to_local, inf->n, limit->n );
   limit->p = 0.0f;

   v3_copy( inf->dir, player_skate.grind_dir );
}

static void skate_5050_apply( struct grind_info *inf_front,
                                 struct grind_info *inf_back ){
   struct player_skate_state *state = &player_skate.state;
   struct grind_info inf_avg;

   v3_sub( inf_front->co, inf_back->co, inf_avg.dir );
   v3_muladds( inf_back->co, inf_avg.dir, 0.5f, inf_avg.co );
   v3_normalize( inf_avg.dir );

   /* dont ask */
   v3_muls( inf_avg.dir, vg_signf(v3_dot(inf_avg.dir,localplayer.rb.v)), 
            inf_avg.dir );

   v3f axis_front, axis_back, axis;
   v3_cross( inf_front->dir, inf_front->n, axis_front );
   v3_cross( inf_back->dir,  inf_back->n,  axis_back  );
   v3_add( axis_front, axis_back, axis );
   v3_normalize( axis );

   v3_cross( axis, inf_avg.dir, inf_avg.n );
   skate_grind_decay( &inf_avg, 1.0f );

   v2f steer;
   joystick_state( k_srjoystick_steer, steer );

   float way = steer[1] * vg_signf( v3_dot( localplayer.rb.to_world[2], 
                                            localplayer.rb.v ) );
   v4f q;
   v3f up, target_up;
   v3_copy( localplayer.rb.to_world[1], up );
   v3_copy( inf_avg.n, target_up );
   q_axis_angle( q, localplayer.rb.to_world[0], VG_PIf*0.25f * -way );
   q_mulv( q, target_up,  target_up );

   v3_zero( player_skate.weight_distribution );
   player_skate.weight_distribution[2] = k_board_length * -way;

   rb_effect_spring_target_vector( &localplayer.rb, up, target_up,
                                    k_grind_spring, 
                                    k_grind_dampener,
                                    k_rb_delta );
   vg_line_arrow( localplayer.rb.co, up, 1.0f, VG__GREEN );
   vg_line_arrow( localplayer.rb.co, target_up, 1.0f, VG__GREEN );

   v3f fwd_nplane, dir_nplane;
   v3_muladds( localplayer.rb.to_world[2], inf_avg.n,
               -v3_dot( localplayer.rb.to_world[2], inf_avg.n ), fwd_nplane );

   v3f dir;
   v3_muls( inf_avg.dir, v3_dot( fwd_nplane, inf_avg.dir ), dir );
   v3_muladds( dir, inf_avg.n, -v3_dot( dir, inf_avg.n ), dir_nplane );

   v3_normalize( fwd_nplane );
   v3_normalize( dir_nplane );

   rb_effect_spring_target_vector( &localplayer.rb, fwd_nplane, dir_nplane,
                                    1000.0f,
                                    k_grind_dampener,
                                    k_rb_delta );
   vg_line_arrow( localplayer.rb.co, fwd_nplane, 0.8f, VG__RED );
   vg_line_arrow( localplayer.rb.co, dir_nplane, 0.8f, VG__RED );

   v3f pos_front = { 0.0f, -k_board_radius, -1.0f * k_board_length },
       pos_back  = { 0.0f, -k_board_radius,  1.0f * k_board_length },
       delta_front, delta_back, delta_total;

   m4x3_mulv( localplayer.rb.to_world, pos_front, pos_front );
   m4x3_mulv( localplayer.rb.to_world, pos_back,  pos_back  );

   v3_sub( inf_front->co, pos_front, delta_front );
   v3_sub( inf_back->co,  pos_back, delta_back );
   v3_add( delta_front, delta_back, delta_total );

   v3_muladds( localplayer.rb.v, delta_total, 50.0f * k_rb_delta, 
               localplayer.rb.v );

   /* Fake contact */
   struct grind_limit *limit = 
      &player_skate.limits[ player_skate.limit_count ++ ];
   v3_zero( limit->ra );
   m3x3_mulv( localplayer.rb.to_local, inf_avg.n, limit->n );
   limit->p = 0.0f;

   v3_copy( inf_avg.dir, player_skate.grind_dir );
}

static int skate_grind_truck_renew( f32 sign, struct grind_info *inf ){
   struct player_skate_state *state = &player_skate.state;

   v3f wheel_co = { 0.0f, 0.0f,            sign * k_board_length },
       grind_co = { 0.0f, -k_board_radius, sign * k_board_length };

   m4x3_mulv( localplayer.rb.to_world, wheel_co, wheel_co );
   m4x3_mulv( localplayer.rb.to_world, grind_co, grind_co );

   /* Exit condition: lost grind tracking */
   if( !skate_grind_scansq( grind_co, localplayer.rb.v, 0.3f, inf ) )
      return 0;

   /* Exit condition: cant see grind target directly */
   if( !skate_point_visible( wheel_co, inf->co ) )
      return 0;

   /* Exit condition: minimum velocity not reached, but allow a bit of error */
   float dv   = fabsf(v3_dot( localplayer.rb.v, inf->dir )),
         minv = k_grind_axel_min_vel*0.8f;

   if( dv < minv )
      return 0;

   if( fabsf(v3_dot( inf->dir, player_skate.grind_dir )) < k_grind_max_edge_angle )
      return 0;

   v3_copy( inf->dir, player_skate.grind_dir );
   return 1;
}

static int skate_grind_truck_entry( f32 sign, struct grind_info *inf ){
   struct player_skate_state *state = &player_skate.state;

   /* REFACTOR */
   v3f ra = { 0.0f, -k_board_radius, sign * k_board_length };

   v3f raw, wsp;
   m3x3_mulv( localplayer.rb.to_world, ra, raw );
   v3_add( localplayer.rb.co, raw, wsp );

   if( skate_grind_scansq( wsp, localplayer.rb.v, 0.3, inf ) ){
      if( fabsf(v3_dot( localplayer.rb.v, inf->dir )) < k_grind_axel_min_vel )
         return 0;

      /* velocity should be at least 60% aligned */
      v3f pv, axis;
      v3_cross( inf->n, inf->dir, axis );
      v3_muladds( localplayer.rb.v, inf->n, 
                  -v3_dot( localplayer.rb.v, inf->n ), pv );
      
      if( v3_length2( pv ) < 0.0001f )
         return 0;
      v3_normalize( pv );

      if( fabsf(v3_dot( pv, inf->dir )) < k_grind_axel_max_angle )
         return 0;

      if( v3_dot( localplayer.rb.v, inf->n ) > 0.5f )
         return 0;
      
      v3f local_co, local_dir, local_n;
      m4x3_mulv( localplayer.rb.to_local, inf->co,  local_co );
      m3x3_mulv( localplayer.rb.to_local, inf->dir, local_dir );
      m3x3_mulv( localplayer.rb.to_local, inf->n,   local_n );

      v2f delta = { local_co[0], local_co[2] - k_board_length*sign };

      float truck_height = -(k_board_radius+0.03f);

      v3f rv;
      v3_cross( localplayer.rb.w, raw, rv );
      v3_add( localplayer.rb.v, rv, rv );

      if( (local_co[1] >= truck_height) &&
          (v2_length2( delta ) <= k_board_radius*k_board_radius) )
      {
         return 1;
      }
   }

   return 0;
}

static void skate_boardslide_apply( struct grind_info *inf ){
   struct player_skate_state *state = &player_skate.state;

   v3f local_co, local_dir, local_n;
   m4x3_mulv( localplayer.rb.to_local, inf->co, local_co );
   m3x3_mulv( localplayer.rb.to_local, inf->dir, local_dir );
   m3x3_mulv( localplayer.rb.to_local, inf->n, local_n );

   v3f intersection;
   v3_muladds( local_co, local_dir, local_co[0]/-local_dir[0], 
               intersection );
   v3_copy( intersection, player_skate.weight_distribution );

   skate_grind_decay( inf, 0.0125f );
   skate_grind_friction( inf, 0.25f );

   /* direction alignment */
   v3f dir, perp;
   v3_cross( local_dir, local_n, perp );
   v3_muls( local_dir, vg_signf(local_dir[0]), dir );
   v3_muls( perp, vg_signf(perp[2]), perp );

   m3x3_mulv( localplayer.rb.to_world, dir, dir );
   m3x3_mulv( localplayer.rb.to_world, perp, perp );

   v4f qbalance;
   q_axis_angle( qbalance, dir, local_co[0]*k_grind_balance );
   q_mulv( qbalance, perp, perp );

   rb_effect_spring_target_vector( &localplayer.rb, localplayer.rb.to_world[0],
                                    dir, 
                                    k_grind_spring, k_grind_dampener,
                                    k_rb_delta );

   rb_effect_spring_target_vector( &localplayer.rb, localplayer.rb.to_world[2],
                                    perp,
                                    k_grind_spring, k_grind_dampener,
                                    k_rb_delta );

   vg_line_arrow( localplayer.rb.co, dir, 0.5f, VG__GREEN );
   vg_line_arrow( localplayer.rb.co, perp, 0.5f, VG__BLUE );

   v3_copy( inf->dir, player_skate.grind_dir );
}

static int skate_boardslide_entry( struct grind_info *inf ){
   struct player_skate_state *state = &player_skate.state;

   if( skate_grind_scansq( localplayer.rb.co, 
                           localplayer.rb.to_world[0], k_board_length,
                           inf ) )
   {
      v3f local_co, local_dir;
      m4x3_mulv( localplayer.rb.to_local, inf->co, local_co );
      m3x3_mulv( localplayer.rb.to_local, inf->dir, local_dir );

      if( (fabsf(local_co[2]) <= k_board_length) &&   /* within wood area */
          (local_co[1] >= 0.0f) &&                    /* at deck level */
          (fabsf(local_dir[0]) >= 0.25f) )            /* perpendicular to us */
      {
         if( fabsf(v3_dot( localplayer.rb.v, inf->dir )) < k_grind_axel_min_vel )
            return 0;

         return 1;
      }
   }

   return 0;
}

static int skate_boardslide_renew( struct grind_info *inf ){
   struct player_skate_state *state = &player_skate.state;

   if( !skate_grind_scansq( localplayer.rb.co, 
                            localplayer.rb.to_world[0], k_board_length,
                            inf ) )
      return 0;

   /* Exit condition: cant see grind target directly */
   v3f vis;
   v3_muladds( localplayer.rb.co, localplayer.rb.to_world[1], 0.2f, vis );
   if( !skate_point_visible( vis, inf->co ) )
      return 0;

   /* Exit condition: minimum velocity not reached, but allow a bit of error */
   float dv   = fabsf(v3_dot( localplayer.rb.v, inf->dir )),
         minv = k_grind_axel_min_vel*0.8f;

   if( dv < minv )
      return 0;

   if( fabsf(v3_dot( inf->dir, player_skate.grind_dir )) < k_grind_max_edge_angle )
      return 0;

   return 1;
}

static void skate_store_grind_vec( struct grind_info *inf ){
   struct player_skate_state *state = &player_skate.state;

   m3x3f mtx;
   skate_grind_orient( inf, mtx );
   m3x3_transpose( mtx, mtx );

   v3f raw;
   v3_sub( inf->co, localplayer.rb.co, raw );

   m3x3_mulv( mtx, raw, player_skate.grind_vec );
   v3_normalize( player_skate.grind_vec );
   v3_copy( inf->dir, player_skate.grind_dir );
}

static enum skate_activity skate_availible_grind(void){
   struct player_skate_state *state = &player_skate.state;

   if( state->grind_cooldown > 100 ){
      vg_fatal_error( "wth!\n" );
   }

   /* debounces this state manager a little bit */
   if( state->grind_cooldown ){
      state->grind_cooldown --;
      return k_skate_activity_undefined;
   }

   struct grind_info inf_back50,
                     inf_front50,
                     inf_slide;

   int res_back50  = 0,
       res_front50 = 0,
       res_slide   = 0;

   int allow_back  = 1,
       allow_front = 1;

   v2f steer;
   joystick_state( k_srjoystick_steer, steer );

   if( state->activity == k_skate_activity_grind_5050 || 
       state->activity == k_skate_activity_grind_back50 ||
       state->activity == k_skate_activity_grind_front50 )
   {
      float tilt = steer[1];

      if( fabsf(tilt) >= 0.25f ){
         v3f raw = {0.0f,0.0f,tilt};
         m3x3_mulv( localplayer.rb.to_world, raw, raw );

         float way = tilt * vg_signf( v3_dot( raw, localplayer.rb.v ) );

         if( way < 0.0f ) allow_front = 0;
         else allow_back = 0;
      }
   }

   if( state->activity == k_skate_activity_grind_boardslide ){
      res_slide = skate_boardslide_renew( &inf_slide );
   }
   else if( state->activity == k_skate_activity_grind_back50 ){
      res_back50  = skate_grind_truck_renew( 1.0f, &inf_back50 );

      if( allow_front )
         res_front50 = skate_grind_truck_entry( -1.0f, &inf_front50 );
   }
   else if( state->activity == k_skate_activity_grind_front50 ){
      res_front50 = skate_grind_truck_renew( -1.0f, &inf_front50 );

      if( allow_back )
         res_back50  = skate_grind_truck_entry(  1.0f, &inf_back50 );
   }
   else if( state->activity == k_skate_activity_grind_5050 ){
      if( allow_front )
         res_front50 = skate_grind_truck_renew( -1.0f, &inf_front50 );
      if( allow_back )
         res_back50  = skate_grind_truck_renew(  1.0f, &inf_back50 );
   }
   else{
      res_slide   = skate_boardslide_entry( &inf_slide );

      if( allow_back )
         res_back50  = skate_grind_truck_entry(  1.0f, &inf_back50 );

      if( allow_front )
         res_front50 = skate_grind_truck_entry( -1.0f, &inf_front50 );

      if( res_back50 != res_front50 ){
         int wants_to_do_that = fabsf(steer[1]) >= 0.25f;

         res_back50  &= wants_to_do_that;
         res_front50 &= wants_to_do_that;
      }
   }

   const enum skate_activity table[] =
   {                                      /* slide | back | front */
      k_skate_activity_undefined,         /* 0       0      0     */
      k_skate_activity_grind_front50,     /* 0       0      1     */
      k_skate_activity_grind_back50,      /* 0       1      0     */
      k_skate_activity_grind_5050,        /* 0       1      1     */

      /* slide has priority always */
      k_skate_activity_grind_boardslide,  /* 1       0      0     */
      k_skate_activity_grind_boardslide,  /* 1       0      1     */
      k_skate_activity_grind_boardslide,  /* 1       1      0     */
      k_skate_activity_grind_boardslide,  /* 1       1      1     */
   }
   , new_activity = table[ res_slide << 2 | res_back50 << 1 | res_front50 ];

   if(      new_activity == k_skate_activity_undefined ){
      if( state->activity >= k_skate_activity_grind_any ){
         state->grind_cooldown = 15;
         state->surface_cooldown = 10;
      }
   }
   else if( new_activity == k_skate_activity_grind_boardslide ){
      skate_boardslide_apply( &inf_slide );
   }
   else if( new_activity == k_skate_activity_grind_back50 ){
      if( state->activity != k_skate_activity_grind_back50 )
         skate_store_grind_vec( &inf_back50 );

      skate_grind_truck_apply(  1.0f, &inf_back50, 1.0f );
   }
   else if( new_activity == k_skate_activity_grind_front50 ){
      if( state->activity != k_skate_activity_grind_front50 )
         skate_store_grind_vec( &inf_front50 );

      skate_grind_truck_apply( -1.0f, &inf_front50, 1.0f );
   }
   else if( new_activity == k_skate_activity_grind_5050 )
      skate_5050_apply( &inf_front50, &inf_back50 );

   return new_activity;
}

static void player__skate_update(void){
   struct player_skate_state *state = &player_skate.state;
   world_instance *world = world_current_instance();

   if( world->water.enabled ){
      if( localplayer.rb.co[1]+0.25f < world->water.height ){
#if 0
         player__networked_sfx( k_player_subsystem_walk, 32, 
                                k_player_walk_soundeffect_splash,
                                localplayer.rb.co, 1.0f );
#endif
         player__skate_kill_audio();
         player__dead_transition();
         return;
      }
   }

   v3_copy( localplayer.rb.co, state->prev_pos );
   state->activity_prev = state->activity;
   v3f normal_total;
   v3_zero( normal_total );

   struct board_collider
   {
      v3f   pos;
      float radius;

      u32   colour;

      enum  board_collider_state
      {
         k_collider_state_default,
         k_collider_state_disabled,
         k_collider_state_colliding
      }
      state;
   }
   wheels[] =
   {
      { 
         { 0.0f, 0.0f,    -k_board_length }, 
         .radius = k_board_radius,
         .colour = VG__RED
      },
      { 
         { 0.0f, 0.0f,     k_board_length }, 
         .radius = k_board_radius,
         .colour = VG__GREEN
      }
   };

   float slap = 0.0f;

   if( state->activity <= k_skate_activity_air_to_grind ){
      float min_dist = 0.6f;
      for( int i=0; i<2; i++ ){
         v3f wpos, closest;
         m4x3_mulv( localplayer.rb.to_world, wheels[i].pos, wpos );

         if( bh_closest_point( world->geo_bh, wpos, closest, min_dist ) != -1 ){
            min_dist = vg_minf( min_dist, v3_dist( closest, wpos ) );
         }
      }
      min_dist -= 0.2f;
      float vy = vg_maxf( 0.0f, localplayer.rb.v[1] );
      slap = vg_clampf( (min_dist/0.5f) + vy, 0.0f, 1.0f )*0.3f;
   }
   state->slap = vg_lerpf( state->slap, slap, 10.0f*k_rb_delta );

   wheels[0].pos[1] = state->slap;
   wheels[1].pos[1] = state->slap;


   const int k_wheel_count = 2;

   player_skate.substep = k_rb_delta;
   player_skate.substep_delta = player_skate.substep;
   player_skate.limit_count = 0;

   int substep_count = 0;

   v3_zero( player_skate.surface_picture );

   int prev_contacts[2];

   for( int i=0; i<k_wheel_count; i++ ){
      wheels[i].state = k_collider_state_default;
      prev_contacts[i] = player_skate.wheel_contacts[i];
   }

   /* check if we can enter or continue grind */
   enum skate_activity grindable_activity = skate_availible_grind();
   if( grindable_activity != k_skate_activity_undefined ){
      state->activity = grindable_activity;
      goto grinding;
   }

   int contact_count = 0;
   for( int i=0; i<2; i++ ){
      v3f normal, axel;
      v3_copy( localplayer.rb.to_world[0], axel );

      if( skate_compute_surface_alignment( wheels[i].pos, 
                                           wheels[i].colour, normal, axel ) )
      {
         rb_effect_spring_target_vector( &localplayer.rb, 
                                          localplayer.rb.to_world[0],
                                          axel,
                                          k_surface_spring, k_surface_dampener,
                                          player_skate.substep_delta );

         v3_add( normal, player_skate.surface_picture, 
                 player_skate.surface_picture );
         contact_count ++;
         player_skate.wheel_contacts[i] = 1;
      }
      else{
         player_skate.wheel_contacts[i] = 0;
      }

      m3x3_mulv( localplayer.rb.to_local, axel, player_skate.truckv0[i] );
   }

   if( state->surface_cooldown ){
      state->surface_cooldown --;
      contact_count = 0;
   }

   if( (prev_contacts[0]+prev_contacts[1] == 1) && (contact_count == 2) ){
      for( int i=0; i<2; i++ ){
         if( !prev_contacts[i] ){
            v3f co;
            m4x3_mulv( localplayer.rb.to_world, wheels[i].pos, co );
            player__networked_sfx( k_player_subsystem_skate, 32, 
                                   k_player_skate_soundeffect_tap,
                                   localplayer.rb.co, 0.75f );
         }
      }
   }

   if( contact_count ){
      state->activity = k_skate_activity_ground;
      state->gravity_bias = k_gravity;
      v3_normalize( player_skate.surface_picture );

      skate_apply_friction_model();
      skate_weight_distribute();
   }
   else{
      if( state->activity > k_skate_activity_air_to_grind )
         state->activity = k_skate_activity_air;

      v3_zero( player_skate.weight_distribution );
      skate_apply_air_model();
   }

grinding:;

   if( state->activity == k_skate_activity_grind_back50 )
      wheels[1].state = k_collider_state_disabled;
   if( state->activity == k_skate_activity_grind_front50 )
      wheels[0].state = k_collider_state_disabled;
   if( state->activity == k_skate_activity_grind_5050 ){
      wheels[0].state = k_collider_state_disabled;
      wheels[1].state = k_collider_state_disabled;
   }

   /* all activities */
   skate_apply_steering_model();
   skate_adjust_up_direction();
   skate_apply_cog_model();
   skate_apply_jump_model();
   skate_apply_grab_model();
   skate_apply_trick_model();
   skate_apply_pump_model();

begin_collision:;

   /*
    * Phase 0: Continous collision detection
    * --------------------------------------------------------------------------
    */

   v3f head_wp0, head_wp1, start_co;
   m4x3_mulv( localplayer.rb.to_world, state->head_position, head_wp0 );
   v3_copy( localplayer.rb.co, start_co );

   /* calculate transform one step into future */
   v3f future_co;
   v4f future_q;
   v3_muladds( localplayer.rb.co, localplayer.rb.v, player_skate.substep, 
               future_co );

   if( v3_length2( localplayer.rb.w ) > 0.0f ){
      v4f rotation;
      v3f axis;
      v3_copy( localplayer.rb.w, axis );
      
      float mag = v3_length( axis );
      v3_divs( axis, mag, axis );
      q_axis_angle( rotation, axis, mag*player_skate.substep );
      q_mul( rotation, localplayer.rb.q, future_q );
      q_normalize( future_q );
   }
   else
      v4_copy( localplayer.rb.q, future_q );

   v3f future_cg, current_cg, cg_offset;
   q_mulv( localplayer.rb.q, player_skate.weight_distribution, current_cg );
   q_mulv( future_q, player_skate.weight_distribution, future_cg );
   v3_sub( future_cg, current_cg, cg_offset );

   /* calculate the minimum time we can move */
   float max_time = player_skate.substep;

   for( int i=0; i<k_wheel_count; i++ ){
      if( wheels[i].state == k_collider_state_disabled )
         continue;

      v3f current, future, r_cg;
      
      q_mulv( future_q, wheels[i].pos, future );
      v3_add( future, future_co, future );
      v3_add( cg_offset, future, future );

      q_mulv( localplayer.rb.q, wheels[i].pos, current );
      v3_add( current, localplayer.rb.co, current );
      
      float t;
      v3f n;

      float cast_radius = wheels[i].radius - k_penetration_slop * 2.0f;
      if( spherecast_world( world, current, future, cast_radius, &t, n,
                            k_material_flag_walking ) != -1)
         max_time = vg_minf( max_time, t * player_skate.substep );
   }

   /* clamp to a fraction of delta, to prevent locking */
   float rate_lock = substep_count;
   rate_lock *= k_rb_delta * 0.1f;
   rate_lock *= rate_lock;

   max_time = vg_maxf( max_time, rate_lock );
   player_skate.substep_delta = max_time;

   /* integrate */
   v3_muladds( localplayer.rb.co, localplayer.rb.v, 
               player_skate.substep_delta, localplayer.rb.co );
   if( v3_length2( localplayer.rb.w ) > 0.0f ){
      v4f rotation;
      v3f axis;
      v3_copy( localplayer.rb.w, axis );
      
      float mag = v3_length( axis );
      v3_divs( axis, mag, axis );
      q_axis_angle( rotation, axis, mag*player_skate.substep_delta );
      q_mul( rotation, localplayer.rb.q, localplayer.rb.q );
      q_normalize( localplayer.rb.q );

      q_mulv( localplayer.rb.q, player_skate.weight_distribution, future_cg );
      v3_sub( current_cg, future_cg, cg_offset );
      v3_add( localplayer.rb.co, cg_offset, localplayer.rb.co );
   }

   rb_update_transform( &localplayer.rb );
   localplayer.rb.v[1] += -state->gravity_bias * player_skate.substep_delta;

   player_skate.substep -= player_skate.substep_delta;

   rb_ct manifold[128];
   int manifold_len = 0;
   /*
    * Phase -1: head detection
    * --------------------------------------------------------------------------
    */
   m4x3_mulv( localplayer.rb.to_world, state->head_position, head_wp1 );

   float t;
   v3f n;
   if( (v3_dist2( head_wp0, head_wp1 ) > 0.001f) &&
       (spherecast_world( world, head_wp0, head_wp1, 0.2f, &t, n,
                          k_material_flag_walking ) != -1) )
   {
      v3_lerp( start_co, localplayer.rb.co, t, localplayer.rb.co );
      rb_update_transform( &localplayer.rb );

      player__skate_kill_audio();
      player__dead_transition();
      return;
   }

   /*
    * Phase 1: Regular collision detection
    * --------------------------------------------------------------------------
    */

   for( int i=0; i<k_wheel_count; i++ ){
      if( wheels[i].state == k_collider_state_disabled )
         continue;

      m4x3f mtx;
      m3x3_identity( mtx );
      m4x3_mulv( localplayer.rb.to_world, wheels[i].pos, mtx[3] );
      
      rb_sphere collider = { .radius = wheels[i].radius };

      rb_ct *man = &manifold[ manifold_len ];

      int l = skate_collide_smooth( mtx, &collider, man );
      if( l )
         wheels[i].state = k_collider_state_colliding;

      manifold_len += l;
   }

   float grind_radius = k_board_radius * 0.75f;
   rb_capsule capsule = { .height = (k_board_length+0.2f)*2.0f, 
                          .radius=grind_radius };
   m4x3f mtx;
   v3_muls( localplayer.rb.to_world[0],  1.0f, mtx[0] );
   v3_muls( localplayer.rb.to_world[2], -1.0f, mtx[1] );
   v3_muls( localplayer.rb.to_world[1],  1.0f, mtx[2] );
   v3_muladds( localplayer.rb.to_world[3], localplayer.rb.to_world[1], 
               grind_radius + k_board_radius*0.25f+state->slap, mtx[3] );

   rb_ct *cman = &manifold[manifold_len];

   int l = rb_capsule__scene( mtx, &capsule, NULL, &world->rb_geo.inf.scene,
                              cman, k_material_flag_walking );

   /* weld joints */
   for( int i=0; i<l; i ++ )
      cman[l].type = k_contact_type_edge;
   rb_manifold_filter_joint_edges( cman, l, 0.03f );
   l = rb_manifold_apply_filtered( cman, l );

   manifold_len += l;

   if( vg_lines.draw )
      vg_line_capsule( mtx, capsule.radius, capsule.height, VG__WHITE );

   /* add limits */
   if( state->activity >= k_skate_activity_grind_any ){
      for( int i=0; i<player_skate.limit_count; i++ ){
         struct grind_limit *limit = &player_skate.limits[i];
         rb_ct *ct = &manifold[ manifold_len ++ ];
         m4x3_mulv( localplayer.rb.to_world, limit->ra, ct->co );
         m3x3_mulv( localplayer.rb.to_world, limit->n, ct->n );
         ct->p = limit->p;
         ct->type = k_contact_type_default;
      }
   }

   /* 
    * Phase 3: Dynamics
    * --------------------------------------------------------------------------
    */


   v3f world_cog;
   m4x3_mulv( localplayer.rb.to_world, 
              player_skate.weight_distribution, world_cog );
   vg_line_point( world_cog, 0.02f, VG__BLACK );

   for( int i=0; i<manifold_len; i ++ ){
      rb_prepare_contact( &manifold[i], player_skate.substep_delta );
      rb_debug_contact( &manifold[i] );
   }

   /* yes, we are currently rebuilding mass matrices every frame. too bad! */
   v3f extent = { k_board_width, 0.1f, k_board_length };
   float ex2 = k_board_interia*extent[0]*extent[0],
         ey2 = k_board_interia*extent[1]*extent[1],
         ez2 = k_board_interia*extent[2]*extent[2];

   float mass = 2.0f * (extent[0]*extent[1]*extent[2]);
   float inv_mass = 1.0f/mass;

   v3f I;
   I[0] = ((1.0f/12.0f) * mass * (ey2+ez2));
   I[1] = ((1.0f/12.0f) * mass * (ex2+ez2));
   I[2] = ((1.0f/12.0f) * mass * (ex2+ey2));

   m3x3f iI;
   m3x3_identity( iI );
   iI[0][0] = I[0];
   iI[1][1] = I[1];
   iI[2][2] = I[2];
   m3x3_inv( iI, iI );

   m3x3f iIw;
   m3x3_mul( iI, localplayer.rb.to_local, iIw );
   m3x3_mul( localplayer.rb.to_world, iIw, iIw );

   for( int j=0; j<10; j++ ){
      for( int i=0; i<manifold_len; i++ ){
         /* 
          * regular dance; calculate velocity & total mass, apply impulse.
          */

         struct contact *ct = &manifold[i];
         
         v3f rv, delta;
         v3_sub( ct->co, world_cog, delta ); 
         v3_cross( localplayer.rb.w, delta, rv );
         v3_add( localplayer.rb.v, rv, rv );

         v3f raCn;
         v3_cross( delta, ct->n, raCn );

         v3f raCnI, rbCnI;
         m3x3_mulv( iIw, raCn, raCnI );

         float normal_mass = 1.0f / (inv_mass + v3_dot(raCn,raCnI)),
               vn = v3_dot( rv, ct->n ),
               lambda = normal_mass * ( -vn );

         float temp = ct->norm_impulse;
         ct->norm_impulse = vg_maxf( temp + lambda, 0.0f );
         lambda = ct->norm_impulse - temp;

         v3f impulse;
         v3_muls( ct->n, lambda, impulse );

         v3_muladds( normal_total, impulse, inv_mass, normal_total );
         v3_muladds( localplayer.rb.v, impulse, inv_mass, localplayer.rb.v );
         v3_cross( delta, impulse, impulse );
         m3x3_mulv( iIw, impulse, impulse );
         v3_add( impulse, localplayer.rb.w, localplayer.rb.w );

         v3_cross( localplayer.rb.w, delta, rv );
         v3_add( localplayer.rb.v, rv, rv );
         vn = v3_dot( rv, ct->n );
      }
   }

   v3f dt;
   rb_depenetrate( manifold, manifold_len, dt );
   v3_add( dt, localplayer.rb.co, localplayer.rb.co );
   rb_update_transform( &localplayer.rb );

   substep_count ++;

   if( player_skate.substep >= 0.0001f )
      goto begin_collision;      /* again! */

   /* 
    * End of collision and dynamics routine
    * --------------------------------------------------------------------------
    */

   f32 nforce = v3_length(normal_total);
   if( nforce > 4.0f ){
      if( nforce > 17.6f ){
         v3_muladds( localplayer.rb.v, normal_total, -1.0f, localplayer.rb.v );
         player__dead_transition();
         player__skate_kill_audio();
         return;
      }

      f32 amt = k_cam_punch;
      if( localplayer.cam_control.camera_mode == k_cam_firstperson ){
         amt *= 0.25f;
      }

      v3_muladds( localplayer.cam_land_punch_v, normal_total, amt,
                  localplayer.cam_land_punch_v );
   }

   player_skate.surface = k_surface_prop_concrete;

   for( int i=0; i<manifold_len; i++ ){
      rb_ct *ct = &manifold[i];
      struct world_surface *surf = world_contact_surface( world, ct );

      if( surf->info.surface_prop > player_skate.surface )
         player_skate.surface = surf->info.surface_prop;
   }

   for( int i=0; i<k_wheel_count; i++ ){
      m4x3f mtx;
      m3x3_copy( localplayer.rb.to_world, mtx );
      m4x3_mulv( localplayer.rb.to_world, wheels[i].pos, mtx[3] );
      vg_line_sphere( mtx, wheels[i].radius,
                      (u32[]){ VG__WHITE, VG__BLACK, 
                            wheels[i].colour }[ wheels[i].state ]);
   }

   skate_integrate();
   vg_line_point( state->cog, 0.02f, VG__WHITE );

   u32 id = world_intersect_gates( world, localplayer.rb.co, state->prev_pos );

   if( id ){
      ent_gate *gate = mdl_arritm( &world->ent_gate, mdl_entity_id_id(id) );

      m4x3_mulv( gate->transport, localplayer.rb.co, localplayer.rb.co );
      m3x3_mulv( gate->transport, localplayer.rb.v,  localplayer.rb.v );
      m4x3_mulv( gate->transport, state->cog,   state->cog );
      m3x3_mulv( gate->transport, state->cog_v, state->cog_v );
      m3x3_mulv( gate->transport, state->throw_v, state->throw_v );
      m3x3_mulv( gate->transport, state->head_position,
                                  state->head_position );
      m3x3_mulv( gate->transport, state->up_dir, state->up_dir );

      v4f transport_rotation;
      m3x3_q( gate->transport, transport_rotation );
      q_mul( transport_rotation, localplayer.rb.q, localplayer.rb.q );
      q_mul( transport_rotation, state->smoothed_rotation,
                                 state->smoothed_rotation );
      rb_update_transform( &localplayer.rb );
      player__pass_gate( id );
   }

   /* FIXME: Rate limit */
   static int stick_frames = 0;

   if( state->activity >= k_skate_activity_ground )
      stick_frames ++;
   else
      stick_frames = 0;

   if( stick_frames > 5 ) stick_frames =  5;

   if( stick_frames == 4 ){
      if( state->activity == k_skate_activity_ground ){
         if( (fabsf(state->slip) > 0.75f) ){
            player__networked_sfx( k_player_subsystem_skate, 128, 
                                   k_player_skate_soundeffect_land_bad,
                                   localplayer.rb.co, 0.6f );
         }
         else{
            player__networked_sfx( k_player_subsystem_skate, 128, 
                                   k_player_skate_soundeffect_land_good,
                                   localplayer.rb.co, 1.0f );
         }
      }
      else if( player_skate.surface == k_surface_prop_metal ){
         player__networked_sfx( k_player_subsystem_skate, 128, 
                                k_player_skate_soundeffect_grind_metal,
                                localplayer.rb.co, 1.0f );
      }
      else{
         player__networked_sfx( k_player_subsystem_skate, 128, 
                                k_player_skate_soundeffect_grind_wood,
                                localplayer.rb.co, 1.0f );
      }
   } else if( stick_frames == 0 ){
      /* TODO: EXIT SOUNDS */
   }
}

static void player__skate_im_gui(void){
   struct player_skate_state *state = &player_skate.state;
   player__debugtext( 1, "V:  %5.2f %5.2f %5.2f",localplayer.rb.v[0],
                                                localplayer.rb.v[1],
                                                localplayer.rb.v[2] );
   player__debugtext( 1, "CO: %5.2f %5.2f %5.2f",localplayer.rb.co[0],
                                                localplayer.rb.co[1],
                                                localplayer.rb.co[2] );
   player__debugtext( 1, "W:  %5.2f %5.2f %5.2f",localplayer.rb.w[0],
                                                localplayer.rb.w[1],
                                                localplayer.rb.w[2] );

   const char *activity_txt[] = {
      "air",
      "air_to_grind",
      "ground",
      "undefined (INVALID)",
      "grind_any (INVALID)",
      "grind_boardslide",
      "grind_metallic (INVALID)",
      "grind_back50",
      "grind_front50",
      "grind_5050"
   };

   player__debugtext( 1, "activity: %s", activity_txt[state->activity] );
#if 0
   player__debugtext( 1, "steer_s: %5.2f %5.2f [%.2f %.2f]",
                        state->steerx_s, state->steery_s,
                        k_steer_ground, k_steer_air );
#endif
   player__debugtext( 1, "flip: %.4f %.4f", state->flip_rate, 
                                             state->flip_time );
   player__debugtext( 1, "trickv: %.2f %.2f %.2f", 
                           state->trick_vel[0],
                           state->trick_vel[1],
                           state->trick_vel[2] );
   player__debugtext( 1, "tricke: %.2f %.2f %.2f", 
                           state->trick_euler[0],
                           state->trick_euler[1],
                           state->trick_euler[2] );
}

static void player__skate_animate(void){
   struct player_skate_state *state = &player_skate.state;
   struct player_skate_animator *animator = &player_skate.animator;

   /* Head */
   float kheight = 2.0f,
         kleg = 0.6f;

   v3_zero( animator->offset );

   v3f cog_local, cog_ideal;
   m4x3_mulv( localplayer.rb.to_local, state->cog, cog_local );

   v3_copy( state->up_dir, cog_ideal );
   v3_normalize( cog_ideal );
   m3x3_mulv( localplayer.rb.to_local, cog_ideal, cog_ideal );

   v3_sub( cog_ideal, cog_local, animator->offset );

   v3_muls( animator->offset, 4.0f, animator->offset );
   animator->offset[1] *= -1.0f;

   float curspeed  = v3_length( localplayer.rb.v ),
         kickspeed = vg_clampf( curspeed*(1.0f/40.0f), 0.0f, 1.0f ),
         kicks     = (vg_randf64()-0.5f)*2.0f*kickspeed,
         sign      = vg_signf( kicks );

   animator->wobble[0] = vg_lerpf( animator->wobble[0], kicks*kicks*sign, 
                                   6.0f*vg.time_delta);
   animator->wobble[1] = vg_lerpf( animator->wobble[1], animator->wobble[0], 
                                   2.4f*vg.time_delta);

   animator->offset[0] *= 0.26f;
   animator->offset[0] += animator->wobble[1]*3.0f;

   animator->offset[1] *= -0.3f;
   animator->offset[2] *= 0.01f;

   animator->offset[0]=vg_clampf(animator->offset[0],-0.8f,0.8f)*
                                 (1.0f-fabsf(animator->slide)*0.9f);
   animator->offset[1]=vg_clampf(animator->offset[1],-0.5f,0.0f);

   v3f cam_offset;
   v3_mul( animator->offset, (v3f){1.0f,0.3f,1.0f}, cam_offset );
   v3_copy( cam_offset, localplayer.cam_control.tpv_offset_extra );

   /* localized vectors */
   m4x3_mulv( localplayer.rb.to_local, state->cog, animator->local_cog );

   /* 
    * Animation blending
    * ===========================================
    */
   
   /* sliding */
   {
      float desired = 0.0f;
      if( state->activity == k_skate_activity_ground )
         desired = vg_clampf( fabsf( state->slip ), 0.0f, 1.0f );

      animator->slide = vg_lerpf( animator->slide, desired, 2.4f*vg.time_delta);
   }
   
   /* movement information */
   int iair = state->activity <= k_skate_activity_air_to_grind;

   float dirz = state->reverse > 0.0f? 0.0f: 1.0f,
         dirx = state->slip < 0.0f?    0.0f: 1.0f,
         fly  = iair?                    1.0f: 0.0f,
         wdist= player_skate.weight_distribution[2] / k_board_length;

   if( state->activity >= k_skate_activity_grind_any )
      wdist = 0.0f;

   animator->z      = vg_lerpf( animator->z,      dirz,  2.4f*vg.time_delta );
   animator->x      = vg_lerpf( animator->x,      dirx,  0.6f*vg.time_delta );
   animator->fly    = vg_lerpf( animator->fly,    fly,   3.4f*vg.time_delta );
   animator->weight = vg_lerpf( animator->weight, wdist, 9.0f*vg.time_delta );

   float stand = 1.0f - vg_clampf( curspeed * 0.03f, 0.0f, 1.0f );
   animator->stand  = vg_lerpf( animator->stand, stand, 6.0f*vg.time_delta );
   animator->reverse = state->reverse;

   if( fabsf(state->slip) > 0.3f ){
      f32 slide_x = v3_dot(localplayer.rb.v, localplayer.rb.to_world[0]);
      state->delayed_slip_dir = vg_signf(slide_x);
   }

   /* grinding */
   f32 grind=state->activity >= k_skate_activity_grind_any? 1.0f: 0.0f;
   animator->grind = vg_lerpf( animator->grind,  grind, 5.0f*vg.time_delta );

   f32 grind_frame = 0.5f;

   if( state->activity == k_skate_activity_grind_front50 )
      grind_frame = 0.0f;
   else if( state->activity == k_skate_activity_grind_back50 )
      grind_frame = 1.0f;

   animator->grind_balance = vg_lerpf( animator->grind_balance, grind_frame, 
                                5.0f*vg.time_delta );

   /* pushing */
   animator->push_time = vg.time - state->start_push;
   animator->push = vg_lerpf( animator->push, 
                              (vg.time - state->cur_push) < 0.125,
                              6.0f*vg.time_delta );

   /* jumping */
   animator->jump_charge = state->jump_charge;
   animator->jump = vg_lerpf( animator->jump, animator->jump_charge, 
                              8.4f*vg.time_delta );

   /* trick setup */
   animator->jump_dir = state->jump_dir;
   f32 jump_start_frame = 14.0f/30.0f;
   animator->jump_time = animator->jump_charge * jump_start_frame;
   f32 jump_frame = (vg.time - state->jump_time) + jump_start_frame;
   if( jump_frame >= jump_start_frame && jump_frame <= (40.0f/30.0f) )
      animator->jump_time = jump_frame;

   /* trick */
   float jump_t = vg.time-state->jump_time;
   float k=17.0f;
   float h = k*jump_t;
   float extra = h*exp(1.0-h) * (state->jump_dir?1.0f:-1.0f);
         extra *= state->slap * 4.0f;

   v3_add( state->trick_euler, state->trick_residuald, 
            animator->board_euler );
   v3_muls( animator->board_euler, VG_TAUf, animator->board_euler );

   animator->board_euler[0] *= 0.5f;
   animator->board_euler[1] += extra;
   animator->trick_type = state->trick_type;

   /* board lean */
   f32 lean1, lean2 = animator->steer[0] * animator->reverse * -0.36f,
       lean;

   lean1 = animator->slide * animator->delayed_slip_dir;
   if( fabsf(lean1)>fabsf(lean2) ) lean = lean1;
   else                            lean = lean2;

   if( ((int)roundf(animator->board_euler[0]/VG_PIf)) % 2 ) lean = -lean;
   lean = vg_clampf( lean, -1.0f, 1.0f );
   animator->board_lean = 
      vg_lerpf(animator->board_lean, lean, vg.time_delta*18.0f);

   /* feet placement */
   struct player_board *board = 
      addon_cache_item_if_loaded( k_addon_type_board,
                                  localplayer.board_view_slot );
   if( board ){
      if( animator->weight > 0.0f ){
         animator->foot_offset[0] = 
            board->truck_positions[k_board_truck_back][2]+0.3f;
      }
      else{
         animator->foot_offset[1] = 
            board->truck_positions[k_board_truck_front][2]-0.3f;
      }
   }

   f32 slapm = vg_maxf( 1.0f-v3_length2( state->trick_vel ), 0.0f );
   animator->slap = state->slap;
   animator->subslap = vg_lerpf( animator->subslap, slapm, 
                                 vg.time_delta*10.0f );

   f32 l = ((state->activity < k_skate_activity_ground) &&
             v3_length2(state->trick_vel) > 0.1f )? 1: 0;
   animator->trick_foot = vg_lerpf( animator->trick_foot, l, 
                                    8.4f*vg.time_delta );

   /* grab */
   v2f grab_input;
   joystick_state( k_srjoystick_grab, grab_input );
   v2_add( state->grab_mouse_delta, grab_input, grab_input );

   if( v2_length2( grab_input ) <= 0.001f ) grab_input[0] = -1.0f;
   else v2_normalize_clamp( grab_input );
   v2_lerp( animator->grab, grab_input, 2.4f*vg.time_delta, animator->grab );
   animator->grabbing = state->grabbing;

   /* steer */
   joystick_state( k_srjoystick_steer, animator->steer );

   animator->airdir = vg_lerpf( animator->airdir, -animator->steer[0],
                                2.4f*vg.time_delta );
      

   /* flip angle */
   if( (state->activity <= k_skate_activity_air_to_grind) &&
       (fabsf(state->flip_rate) > 0.01f) ){
      float substep = vg.time_fixed_extrapolate;
      float t     = state->flip_time+state->flip_rate*substep*k_rb_delta;
            sign  = vg_signf( t );

      t  = 1.0f - vg_minf( 1.0f, fabsf( t * 1.1f ) );
      t  = sign * (1.0f-t*t);

      f32 angle = vg_clampf( t, -1.0f, 1.0f ) * VG_TAUf,
          distm = state->land_dist * fabsf(state->flip_rate) * 3.0f,
          blend = vg_clampf( 1.0f-distm, 0.0f, 1.0f );
      angle = vg_lerpf( angle, vg_signf(state->flip_rate)*VG_TAUf, blend );
      q_axis_angle( animator->qflip, state->flip_axis, angle );
   }
   else 
      q_identity( animator->qflip );

   /* counter-rotation */
   if( v3_length2( state->up_dir ) > 0.001f ){
      v4_lerp( state->smoothed_rotation, localplayer.rb.q, 
               2.0f*vg.time_frame_delta,
               state->smoothed_rotation );
      q_normalize( state->smoothed_rotation );

      v3f yaw_smooth = {1.0f,0.0f,0.0f};
      q_mulv( state->smoothed_rotation, yaw_smooth, yaw_smooth );
      m3x3_mulv( localplayer.rb.to_local, yaw_smooth, yaw_smooth );
      yaw_smooth[1] = 0.0f;
      v3_normalize( yaw_smooth );

      f32 yaw_counter_rotate  = yaw_smooth[0];
          yaw_counter_rotate  = vg_maxf( 0.7f, yaw_counter_rotate );
          yaw_counter_rotate  = acosf( yaw_counter_rotate );
          yaw_counter_rotate *= 1.0f-animator->fly;

      v3f ndir;
      m3x3_mulv( localplayer.rb.to_local, state->up_dir, ndir );
      v3_normalize( ndir );

      v3f up = { 0.0f, 1.0f, 0.0f };
      float a = v3_dot( ndir, up );
      a = acosf( vg_clampf( a, -1.0f, 1.0f ) );

      v3f axis;
      v4f qcounteryaw, qfixup;
      
      v3_cross( up, ndir, axis );
      q_axis_angle( qfixup, axis, a*2.0f );

      v3_cross( (v3f){1.0f,0.0f,0.0f}, yaw_smooth, axis );
      q_axis_angle( qcounteryaw, axis, yaw_counter_rotate );

      q_mul( qcounteryaw, qfixup, animator->qfixuptotal );
      q_normalize( animator->qfixuptotal );

      v3f p1, p2;
      m3x3_mulv( localplayer.rb.to_world, up, p1 );
      m3x3_mulv( localplayer.rb.to_world, ndir, p2 );

      vg_line_arrow( localplayer.rb.co, p1, 0.5f, VG__PINK );
      vg_line_arrow( localplayer.rb.co, p2, 0.5f, VG__PINK );
   }
   else q_identity( animator->qfixuptotal );
   rb_extrapolate( &localplayer.rb, animator->root_co, animator->root_q );
}
                        
static void player__skate_pose( void *_animator, player_pose *pose ){
   struct skeleton *sk = &localplayer.skeleton;
   struct player_skate_animator *animator = _animator;

   pose->type = k_player_pose_type_ik;
   v3_copy( animator->root_co, pose->root_co );
   v4_copy( animator->root_q, pose->root_q );

   /* transform */
   v3f ext_up,ext_co;
   q_mulv( pose->root_q, (v3f){0.0f,1.0f,0.0f}, ext_up );
   v3_copy( pose->root_co, ext_co );
   v3_muladds( pose->root_co, ext_up, -0.1f, pose->root_co );

   /* apply flip rotation at midpoint */
   q_mul( animator->qflip, pose->root_q, pose->root_q );
   q_normalize( pose->root_q );

   v3f rotation_point, rco;
   v3_muladds( ext_co, ext_up, 0.5f, rotation_point );
   v3_sub( pose->root_co, rotation_point, rco );
   
   q_mulv( animator->qflip, rco, rco );
   v3_add( rco, rotation_point, pose->root_co );

   /* ANIMATIONS 
    * ---------------------------------------------------------------------- */

   mdl_keyframe apose[32], bpose[32];
   mdl_keyframe ground_pose[32];
   {
      /* stand/crouch */
      f32 dir_frame   = animator->z * (15.0f/30.0f),
          stand_blend = animator->offset[1]*-2.0f;

      pose->board.lean = animator->board_lean;

      stand_blend = vg_clampf( 1.0f-animator->local_cog[1], 0, 1 );

      skeleton_sample_anim( sk, player_skate.anim_stand, dir_frame, apose );
      skeleton_sample_anim( sk, player_skate.anim_highg, dir_frame, bpose );
      skeleton_lerp_pose( sk, apose, bpose, stand_blend, apose );

      /* sliding */
      skeleton_sample_anim( sk, player_skate.anim_slide, animator->x * 0.5f, 
                            bpose );
      skeleton_lerp_pose( sk, apose, bpose, animator->slide, apose );

      if( animator->reverse > 0.0f ){
         skeleton_sample_anim( sk, player_skate.anim_push, animator->push_time, 
                               bpose );
      }
      else{
         skeleton_sample_anim( sk, player_skate.anim_push_reverse, 
                               animator->push_time, bpose );
      }
      skeleton_lerp_pose( sk, apose, bpose, animator->push, apose );

      struct skeleton_anim *jump_anim = animator->jump_dir?
                                        player_skate.anim_ollie:
                                        player_skate.anim_ollie_reverse;

      f32 setup_blend = vg_minf( animator->jump, 1.0f );
      skeleton_sample_anim_clamped( sk, jump_anim, animator->jump_time, bpose );
      skeleton_lerp_pose( sk, apose, bpose, setup_blend, ground_pose );
   }
   
   mdl_keyframe air_pose[32];
   {
      float air_frame = (animator->airdir*0.5f+0.5f) * (15.0f/30.0f);
      skeleton_sample_anim( sk, player_skate.anim_air, air_frame, apose );

      float ang = atan2f( animator->grab[0], animator->grab[1] ),
            ang_unit = (ang+VG_PIf) * (1.0f/VG_TAUf),
            grab_frame = ang_unit * (15.0f/30.0f);

      skeleton_sample_anim( sk, player_skate.anim_grabs, grab_frame, bpose );
      skeleton_lerp_pose( sk, apose, bpose, animator->grabbing, air_pose );
   }

   skeleton_lerp_pose( sk, ground_pose, air_pose, animator->fly, 
                       pose->keyframes );

   mdl_keyframe *kf_board    = &pose->keyframes[localplayer.id_board-1],
                *kf_foot_l   = &pose->keyframes[localplayer.id_ik_foot_l-1],
                *kf_foot_r   = &pose->keyframes[localplayer.id_ik_foot_r-1],
                *kf_knee_l   = &pose->keyframes[localplayer.id_ik_knee_l-1],
                *kf_knee_r   = &pose->keyframes[localplayer.id_ik_knee_r-1],
                *kf_hip      = &pose->keyframes[localplayer.id_hip-1],
                *kf_wheels[] = { &pose->keyframes[localplayer.id_wheel_r-1],
                                 &pose->keyframes[localplayer.id_wheel_l-1] };


   mdl_keyframe grind_pose[32];
   {
      f32 frame = animator->grind_balance * 0.5f;

      skeleton_sample_anim( sk, player_skate.anim_grind, frame, apose );
      skeleton_sample_anim( sk, player_skate.anim_grind_jump, frame, bpose );
      skeleton_lerp_pose( sk, apose, bpose, animator->jump, grind_pose );
   }
   skeleton_lerp_pose( sk, pose->keyframes, grind_pose, 
                       animator->grind, pose->keyframes );
   float add_grab_mod = 1.0f - animator->fly;

   /* additive effects */
   u32 apply_to[] = { localplayer.id_hip, 
                      localplayer.id_ik_hand_l,
                      localplayer.id_ik_hand_r,
                      localplayer.id_ik_elbow_l,
                      localplayer.id_ik_elbow_r };

   float apply_rates[] = { 1.0f,
                           0.75f,
                           0.75f,
                           0.75f,
                           0.75f };

   for( int i=0; i<vg_list_size(apply_to); i ++ ){
      pose->keyframes[apply_to[i]-1].co[0] += animator->offset[0]*add_grab_mod;
      pose->keyframes[apply_to[i]-1].co[2] += animator->offset[2]*add_grab_mod;
   }

   /* angle 'correction' */
   v3f origin;
   v3_add( sk->bones[localplayer.id_hip].co, kf_hip->co, origin );

   for( int i=0; i<vg_list_size(apply_to); i ++ ){
      mdl_keyframe *kf = &pose->keyframes[apply_to[i]-1];
      keyframe_rotate_around( kf, origin, sk->bones[apply_to[i]].co,
                              animator->qfixuptotal );
   }

   /* trick rotation */
   v4f qtrick, qyaw, qpitch, qroll;
   q_axis_angle( qyaw,   (v3f){0.0f,1.0f,0.0f}, animator->board_euler[0] );
   q_axis_angle( qpitch, (v3f){1.0f,0.0f,0.0f}, animator->board_euler[1] );
   q_axis_angle( qroll,  (v3f){0.0f,0.0f,1.0f}, animator->board_euler[2] );

   q_mul( qyaw, qroll, qtrick );
   q_mul( qpitch, qtrick, qtrick );
   q_mul( kf_board->q, qtrick, kf_board->q );
   q_normalize( kf_board->q );

   kf_foot_l->co[2] = vg_lerpf( kf_foot_l->co[2], animator->foot_offset[0],
                                 0.5f * animator->weight );
   kf_foot_r->co[2] = vg_lerpf( kf_foot_r->co[2], animator->foot_offset[1],
                                -0.5f * animator->weight );

   kf_foot_l->co[1] += animator->slap;
   kf_foot_r->co[1] += animator->slap;
   kf_knee_l->co[1] += animator->slap;
   kf_knee_r->co[1] += animator->slap;
   kf_board->co[1]  += animator->slap * animator->subslap;
   kf_hip->co[1] += animator->slap * 0.25f;

   if( animator->trick_type == k_trick_type_kickflip ){
      kf_foot_l->co[0] += animator->trick_foot * 0.2f;
      kf_foot_l->co[1] -= animator->trick_foot * 0.18f;
   }
   else if( animator->trick_type == k_trick_type_shuvit ){
      kf_foot_l->co[0] += animator->trick_foot * 0.1f;
      kf_foot_r->co[0] -= animator->trick_foot * 0.15f;
      kf_foot_l->co[1] -= animator->trick_foot * 0.18f;
      kf_foot_r->co[1] -= animator->trick_foot * 0.18f;
   }
   else if( animator->trick_type == k_trick_type_treflip ){
      kf_foot_l->co[0] += animator->trick_foot * 0.2f;
      kf_foot_r->co[0] -= animator->trick_foot * 0.15f;
      kf_foot_l->co[1] -= animator->trick_foot * 0.18f;
      kf_foot_r->co[1] -= animator->trick_foot * 0.18f;
   }

   /* 
    * animation wishlist:
    *    boardslide/grind jump animations
    *    when tricking the slap should not appply or less apply
    *    not animations however DONT target grinds that are vertically down.
    */

   /* truck rotation */
   for( int i=0; i<2; i++ ){
      float a = vg_minf( player_skate.truckv0[i][0], 1.0f );
      a = -acosf( a ) * vg_signf( player_skate.truckv0[i][1] );

      v4f q;
      q_axis_angle( q, (v3f){0.0f,0.0f,1.0f}, a );
      q_mul( q, kf_wheels[i]->q, kf_wheels[i]->q );
      q_normalize( kf_wheels[i]->q );
   }

   {
      mdl_keyframe
         *kf_head    = &pose->keyframes[localplayer.id_head-1],
         *kf_elbow_l = &pose->keyframes[localplayer.id_ik_elbow_l-1],
         *kf_elbow_r = &pose->keyframes[localplayer.id_ik_elbow_r-1],
         *kf_hand_l  = &pose->keyframes[localplayer.id_ik_hand_l-1],
         *kf_hand_r  = &pose->keyframes[localplayer.id_ik_hand_r-1];

      float warble = perlin1d( vg.time, 2.0f, 2, 300 );
            warble *= vg_maxf(animator->grind, fabsf(animator->weight)) * 0.3f;

      v4f qrot;
      q_axis_angle( qrot, (v3f){0.8f,0.7f,0.6f}, warble );

      v3f origin = {0.0f,0.2f,0.0f};
      keyframe_rotate_around( kf_hand_l, origin, 
                              sk->bones[localplayer.id_ik_hand_l].co, qrot );
      keyframe_rotate_around( kf_hand_r, origin, 
                              sk->bones[localplayer.id_ik_hand_r].co, qrot );
      keyframe_rotate_around( kf_hip, origin, 
                              sk->bones[localplayer.id_hip].co, qrot );
      keyframe_rotate_around( kf_elbow_r, origin, 
                              sk->bones[localplayer.id_ik_elbow_r].co, qrot );
      keyframe_rotate_around( kf_elbow_l, origin, 
                              sk->bones[localplayer.id_ik_elbow_l].co, qrot );

      q_inv( qrot, qrot );
      q_mul( qrot, kf_head->q, kf_head->q );
      q_normalize( kf_head->q );
   }
}

static void player__skate_post_animate(void){
   struct player_skate_state *state = &player_skate.state;
   localplayer.cam_velocity_influence = 1.0f;

   v3f head = { 0.0f, 1.8f, 0.0f };
   m4x3_mulv( localplayer.final_mtx[ localplayer.id_head ], 
              head, state->head_position );
   m4x3_mulv( localplayer.rb.to_local, 
              state->head_position, state->head_position );
}

static void player__skate_reset_animator(void){
   struct player_skate_state *state = &player_skate.state;

   memset( &player_skate.animator, 0, sizeof(player_skate.animator) );

   if( state->activity <= k_skate_activity_air_to_grind ) 
      player_skate.animator.fly = 1.0f;
   else 
      player_skate.animator.fly = 0.0f;
}

static void player__skate_clear_mechanics(void){
   struct player_skate_state *state = &player_skate.state;
   state->jump_charge    = 0.0f;
   state->charging_jump  = 0;
   state->jump_dir       = 0;
   v3_zero( state->flip_axis );
   state->flip_time      = 0.0f;
   state->flip_rate      = 0.0f;
   state->reverse        = 0.0f;
   state->slip           = 0.0f;
   state->grabbing       = 0.0f;
   v2_zero( state->grab_mouse_delta );
   state->slap           = 0.0f;
   state->jump_time      = 0.0;
   state->start_push     = 0.0;
   state->cur_push       = 0.0;
   state->air_start      = 0.0;

   v3_zero( state->air_init_v );
   v3_zero( state->air_init_co );

   state->gravity_bias   = k_gravity;
   v3_copy( localplayer.rb.co, state->prev_pos );
   v4_copy( localplayer.rb.q, state->smoothed_rotation );
   v3_zero( state->throw_v );
   v3_zero( state->trick_vel );
   v3_zero( state->trick_euler );
   v3_zero( state->cog_v );
   state->grind_cooldown = 0;
   state->surface_cooldown = 0;
   v3_muladds( localplayer.rb.co, localplayer.rb.to_world[1], 1.0f, state->cog );
   v3_copy( localplayer.rb.to_world[1], state->up_dir );
   v3_copy( localplayer.rb.to_world[1], player_skate.surface_picture );
   v3_copy( localplayer.rb.co, state->prev_pos );
   v3_zero( player_skate.weight_distribution );
}

#include "network_compression.h"

static void player__skate_animator_exchange( bitpack_ctx *ctx, void *data ){
   struct player_skate_animator *animator = data;
   
   bitpack_qv3f( ctx, 24, -1024.0f, 1024.0f, animator->root_co );
   bitpack_qquat( ctx, animator->root_q );

   bitpack_qv3f( ctx, 8, -1.0f, 1.0f, animator->offset );
   bitpack_qv3f( ctx, 8, -1.0f, 1.0f, animator->local_cog );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->slide );
   bitpack_qf32( ctx, 8, -1.0f, 1.0f, &animator->z );
   bitpack_qf32( ctx, 8, -1.0f, 1.0f, &animator->x );

   /* these could likely be pressed down into single bits if needed */
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->fly );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->grind );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->stand );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->push );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->jump );        /*??*/
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->jump_charge ); /*??*/

   /* just the sign bit? */
   bitpack_qf32( ctx, 8, -1.0f, 1.0f, &animator->reverse );
   bitpack_qf32( ctx, 8, -1.0f, 1.0f, &animator->delayed_slip_dir );
   bitpack_bytes( ctx, 1, &animator->jump_dir );
   bitpack_bytes( ctx, 1, &animator->trick_type );

   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->grind_balance );
   bitpack_qf32( ctx, 8, -1.0f, 1.0f, &animator->airdir );
   bitpack_qf32( ctx, 8, -1.0f, 1.0f, &animator->weight );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->trick_foot );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->slap );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->subslap );
   bitpack_qf32( ctx, 8,  0.0f, 1.0f, &animator->grabbing );

   /* animator->wobble is ommited */

   bitpack_qv2f( ctx, 8, -1.0f, 1.0f, animator->foot_offset );
   bitpack_qquat( ctx, animator->qfixuptotal );
   bitpack_qquat( ctx, animator->qflip );

   bitpack_qv3f( ctx, 16, -100.0f, 100.0f, animator->board_euler );
   bitpack_qf32( ctx, 8, -1.0f, 1.0f, &animator->board_lean );
   bitpack_qv2f( ctx, 8, -1.0f, 1.0f, animator->steer );
   bitpack_qv2f( ctx, 8, -1.0f, 1.0f, animator->grab );

   bitpack_qf32( ctx, 16,  0.0f, 120.0f, &animator->push_time );
   bitpack_qf32( ctx, 16,  0.0f, 120.0f, &animator->jump_time );
}

static void player__skate_sfx_oneshot( u8 id, v3f pos, f32 volume ){
   audio_lock();

   if( id == k_player_skate_soundeffect_jump ){
      audio_oneshot_3d( &audio_jumps[vg_randu32()%2], pos, 40.0f, volume );
   }
   else if( id == k_player_skate_soundeffect_tap ){
      audio_oneshot_3d( &audio_taps[vg_randu32()%4], pos, 40.0f, volume );
   }
   else if( id == k_player_skate_soundeffect_land_good ){
      audio_oneshot_3d( &audio_lands[vg_randu32()%3], pos, 40.0f, volume );
   }
   else if( id == k_player_skate_soundeffect_land_bad ){
      audio_oneshot_3d( &audio_lands[vg_randu32()%2+3], pos, 40.0f, volume );
   }
   else if( id == k_player_skate_soundeffect_grind_metal ){
      audio_oneshot_3d( &audio_board[3], pos, 40.0f, volume );
   }
   else if( id == k_player_skate_soundeffect_grind_wood ){
      audio_oneshot_3d( &audio_board[8], pos, 40.0f, volume );
   }

   audio_unlock();
}

#endif /* PLAYER_SKATE_C */