skeleton.h

   1 /*
   2  * Copyright (C) 2021-2022 Mt.ZERO Software, Harry Godden - All Rights Reserved
   3  */
   4
   5 #ifndef SKELETON_H
   6 #define SKELETON_H
   7
   8 #include "model.h"
   9
  10 struct skeleton
  11 {
  12    struct skeleton_bone
  13    {
  14       v3f co, end;
  15       u32 parent;
  16
  17       u32 flags;
  18       int defer;
  19
  20       mdl_keyframe kf;
  21       mdl_bone *orig_bone;
  22
  23       u32 collider;
  24       boxf hitbox;
  25       const char *name;
  26    }
  27    *bones;
  28    u32 bone_count;
  29
  30    struct skeleton_anim
  31    {
  32       const char *name;
  33       u32 length;
  34
  35       float rate;
  36       mdl_keyframe *anim_data;
  37    }
  38    *anims;
  39    u32 anim_count;
  40
  41    m4x3f *final_mtx;
  42
  43    struct skeleton_ik
  44    {
  45       u32 lower, upper, target, pole;
  46       m3x3f ia, ib;
  47    }
  48    *ik;
  49    u32 ik_count;
  50
  51    u32
  52        collider_count,
  53        bindable_count;
  54 };
  55
  56 static u32 skeleton_bone_id( struct skeleton *skele, const char *name )
  57 {
  58    for( u32 i=1; i<skele->bone_count; i++ ){
  59       if( !strcmp( skele->bones[i].name, name ))
  60          return i;
  61    }
  62
  63    vg_error( "skeleton_bone_id( *, \"%s\" );\n", name );
  64    vg_fatal_error( "Bone does not exist\n" );
  65
  66    return 0;
  67 }
  68
  69 static void keyframe_copy_pose( mdl_keyframe *kfa, mdl_keyframe *kfb,
  70                                    int num )
  71 {
  72    for( int i=0; i<num; i++ )
  73       kfb[i] = kfa[i];
  74 }
  75
  76
  77 /* apply a rotation from the perspective of root */
  78 static void keyframe_rotate_around( mdl_keyframe *kf,
  79                                        v3f origin, v3f offset, v4f q )
  80 {
  81    v3f v0, co;
  82    v3_add( kf->co, offset, co );
  83    v3_sub( co, origin, v0 );
  84    q_mulv( q, v0, v0 );
  85    v3_add( v0, origin, co );
  86    v3_sub( co, offset, kf->co );
  87
  88    q_mul( q, kf->q, kf->q );
  89    q_normalize( kf->q );
  90 }
  91
  92 /*
  93  * Lerp between two sets of keyframes and store in dest. Rotations use Nlerp.
  94  */
  95 static void keyframe_lerp_pose( mdl_keyframe *kfa, mdl_keyframe *kfb,
  96                                    float t, mdl_keyframe *kfd, int count )
  97 {
  98    if( t <= 0.0001f ){
  99       keyframe_copy_pose( kfa, kfd, count );
 100       return;
 101    }
 102    else if( t >= 0.9999f ){
 103       keyframe_copy_pose( kfb, kfd, count );
 104       return;
 105    }
 106
 107    for( int i=0; i<count; i++ ){
 108       v3_lerp( kfa[i].co, kfb[i].co, t, kfd[i].co );
 109       q_nlerp( kfa[i].q,  kfb[i].q,  t, kfd[i].q );
 110       v3_lerp( kfa[i].s,  kfb[i].s,  t, kfd[i].s );
 111    }
 112 }
 113
 114 static
 115 void skeleton_lerp_pose( struct skeleton *skele,
 116                          mdl_keyframe *kfa, mdl_keyframe *kfb, float t,
 117                          mdl_keyframe *kfd )
 118 {
 119    keyframe_lerp_pose( kfa, kfb, t, kfd, skele->bone_count-1 );
 120 }
 121
 122 static void skeleton_copy_pose( struct skeleton *skele,
 123                                    mdl_keyframe *kfa, mdl_keyframe *kfd )
 124 {
 125    keyframe_copy_pose( kfa, kfd, skele->bone_count-1 );
 126 }
 127
 128 /*
 129  * Sample animation between 2 closest frames using time value. Output is a
 130  * keyframe buffer that is allocated with an appropriate size
 131  */
 132 static void skeleton_sample_anim( struct skeleton *skele,
 133                                   struct skeleton_anim *anim,
 134                                   float time,
 135                                   mdl_keyframe *output )
 136 {
 137    f32 animtime  = fmodf( time*anim->rate, anim->length ),
 138        animframe = floorf( animtime ),
 139        t = animtime - animframe;
 140
 141    u32 frame = (u32)animframe % anim->length,
 142        next  = (frame+1) % anim->length;
 143
 144    mdl_keyframe *base  = anim->anim_data + (skele->bone_count-1)*frame,
 145                 *nbase = anim->anim_data + (skele->bone_count-1)*next;
 146
 147    skeleton_lerp_pose( skele, base, nbase, t, output );
 148 }
 149
 150 static int skeleton_sample_anim_clamped( struct skeleton *skele,
 151                                          struct skeleton_anim *anim,
 152                                          float time,
 153                                          mdl_keyframe *output )
 154 {
 155    float end = (float)(anim->length-1) / anim->rate;
 156    skeleton_sample_anim( skele, anim, vg_minf( end, time ), output );
 157
 158    if( time > end )
 159       return 0;
 160    else
 161       return 1;
 162 }
 163
 164 typedef enum anim_apply
 165 {
 166    k_anim_apply_always,
 167    k_anim_apply_defer_ik,
 168    k_anim_apply_deffered_only,
 169    k_anim_apply_absolute
 170 }
 171 anim_apply;
 172
 173 static
 174 int should_apply_bone( struct skeleton *skele, u32 id, anim_apply type )
 175 {
 176    struct skeleton_bone *sb = &skele->bones[ id ],
 177                         *sp = &skele->bones[ sb->parent ];
 178
 179    if( type == k_anim_apply_defer_ik ){
 180       if( ((sp->flags & k_bone_flag_ik) && !(sb->flags & k_bone_flag_ik))
 181           || sp->defer )
 182       {
 183          sb->defer = 1;
 184          return 0;
 185       }
 186       else{
 187          sb->defer = 0;
 188          return 1;
 189       }
 190    }
 191    else if( type == k_anim_apply_deffered_only ){
 192       if( sb->defer )
 193          return 1;
 194       else
 195          return 0;
 196    }
 197
 198    return 1;
 199 }
 200
 201 /*
 202  * Apply block of keyframes to skeletons final pose
 203  */
 204 static void skeleton_apply_pose( struct skeleton *skele, mdl_keyframe *pose,
 205                                     anim_apply passtype )
 206 {
 207    if( passtype == k_anim_apply_absolute ){
 208       for( u32 i=1; i<skele->bone_count; i++ ){
 209          mdl_keyframe *kf = &pose[i-1];
 210
 211          v3f *posemtx = skele->final_mtx[i];
 212
 213          q_m3x3( kf->q, posemtx );
 214          v3_copy( kf->co, posemtx[3] );
 215       }
 216       return;
 217    }
 218
 219    m4x3_identity( skele->final_mtx[0] );
 220    skele->bones[0].defer = 0;
 221    skele->bones[0].flags &= ~k_bone_flag_ik;
 222
 223    for( u32 i=1; i<skele->bone_count; i++ ){
 224       struct skeleton_bone *sb = &skele->bones[i],
 225                            *sp = &skele->bones[sb->parent];
 226
 227       if( !should_apply_bone( skele, i, passtype ) )
 228          continue;
 229
 230       sb->defer = 0;
 231
 232       /* process pose */
 233       m4x3f posemtx;
 234
 235       v3f temp_delta;
 236       v3_sub( skele->bones[i].co, skele->bones[sb->parent].co, temp_delta );
 237
 238       /* pose matrix */
 239       mdl_keyframe *kf = &pose[i-1];
 240       q_m3x3( kf->q, posemtx );
 241       v3_copy( kf->co, posemtx[3] );
 242       v3_add( temp_delta, posemtx[3], posemtx[3] );
 243
 244       /* final matrix */
 245       m4x3_mul( skele->final_mtx[ sb->parent ], posemtx, skele->final_mtx[i] );
 246    }
 247 }
 248
 249 /*
 250  * Take the final matrices and decompose it into an absolute positioned anim
 251  */
 252 static void skeleton_decompose_mtx_absolute( struct skeleton *skele,
 253                                                 mdl_keyframe *anim ){
 254    for( u32 i=1; i<skele->bone_count; i++ ){
 255       struct skeleton_bone *sb = &skele->bones[i];
 256       mdl_keyframe *kf = &anim[i-1];
 257       m4x3_decompose( skele->final_mtx[i], kf->co, kf->q, kf->s );
 258    }
 259 }
 260
 261 /*
 262  * creates the reference inverse matrix for an IK bone, as it has an initial
 263  * intrisic rotation based on the direction that the IK is setup..
 264  */
 265 static void skeleton_inverse_for_ik( struct skeleton *skele,
 266                                      v3f ivaxis,
 267                                      u32 id, m3x3f inverse )
 268 {
 269    v3_copy( ivaxis, inverse[0] );
 270    v3_copy( skele->bones[id].end, inverse[1] );
 271    v3_normalize( inverse[1] );
 272    v3_cross( inverse[0], inverse[1], inverse[2] );
 273    m3x3_transpose( inverse, inverse );
 274 }
 275
 276 /*
 277  * Creates inverse rotation matrices which the IK system uses.
 278  */
 279 static void skeleton_create_inverses( struct skeleton *skele )
 280 {
 281    /* IK: inverse 'plane-bone space' axis '(^axis,^bone,...)[base] */
 282    for( u32 i=0; i<skele->ik_count; i++ ){
 283       struct skeleton_ik *ik = &skele->ik[i];
 284
 285       m4x3f inverse;
 286       v3f iv0, iv1, ivaxis;
 287       v3_sub( skele->bones[ik->target].co, skele->bones[ik->lower].co, iv0 );
 288       v3_sub( skele->bones[ik->pole].co,   skele->bones[ik->lower].co, iv1 );
 289       v3_cross( iv0, iv1, ivaxis );
 290       v3_normalize( ivaxis );
 291
 292       skeleton_inverse_for_ik( skele, ivaxis, ik->lower, ik->ia );
 293       skeleton_inverse_for_ik( skele, ivaxis, ik->upper, ik->ib );
 294    }
 295 }
 296
 297 /*
 298  * Apply a model matrix to all bones, should be done last
 299  */
 300 static
 301 void skeleton_apply_transform( struct skeleton *skele, m4x3f transform )
 302 {
 303    for( u32 i=0; i<skele->bone_count; i++ ){
 304       struct skeleton_bone *sb = &skele->bones[i];
 305       m4x3_mul( transform, skele->final_mtx[i], skele->final_mtx[i] );
 306    }
 307 }
 308
 309 /*
 310  * Apply an inverse matrix to all bones which maps vertices from bind space into
 311  * bone relative positions
 312  */
 313 static void skeleton_apply_inverses( struct skeleton *skele )
 314 {
 315    for( u32 i=0; i<skele->bone_count; i++ ){
 316       struct skeleton_bone *sb = &skele->bones[i];
 317       m4x3f inverse;
 318       m3x3_identity( inverse );
 319       v3_negate( sb->co, inverse[3] );
 320
 321       m4x3_mul( skele->final_mtx[i], inverse, skele->final_mtx[i] );
 322    }
 323 }
 324
 325 /*
 326  * Apply all IK modifiers (2 bone ik reference from blender is supported)
 327  */
 328 static void skeleton_apply_ik_pass( struct skeleton *skele )
 329 {
 330    for( u32 i=0; i<skele->ik_count; i++ ){
 331       struct skeleton_ik *ik = &skele->ik[i];
 332
 333       v3f v0, /* base -> target */
 334           v1, /* base -> pole */
 335           vaxis;
 336
 337       v3f co_base,
 338           co_target,
 339           co_pole;
 340
 341       v3_copy( skele->final_mtx[ik->lower][3], co_base );
 342       v3_copy( skele->final_mtx[ik->target][3], co_target );
 343       v3_copy( skele->final_mtx[ik->pole][3], co_pole );
 344
 345       v3_sub( co_target, co_base, v0 );
 346       v3_sub( co_pole, co_base, v1 );
 347       v3_cross( v0, v1, vaxis );
 348       v3_normalize( vaxis );
 349       v3_normalize( v0 );
 350       v3_cross( vaxis, v0, v1 );
 351
 352       /* localize problem into [x:v0,y:v1] 2d plane */
 353       v2f base = { v3_dot( v0, co_base   ), v3_dot( v1, co_base   ) },
 354           end  = { v3_dot( v0, co_target ), v3_dot( v1, co_target ) },
 355           knee;
 356
 357       /* Compute angles (basic trig)*/
 358       v2f delta;
 359       v2_sub( end, base, delta );
 360
 361       float
 362          l1 = v3_length( skele->bones[ik->lower].end ),
 363          l2 = v3_length( skele->bones[ik->upper].end ),
 364          d = vg_clampf( v2_length(delta), fabsf(l1 - l2), l1+l2-0.00001f ),
 365          c = acosf( (l1*l1 + d*d - l2*l2) / (2.0f*l1*d) ),
 366          rot = atan2f( delta[1], delta[0] ) + c - VG_PIf/2.0f;
 367
 368       knee[0] = sinf(-rot) * l1;
 369       knee[1] = cosf(-rot) * l1;
 370
 371       m4x3_identity( skele->final_mtx[ik->lower] );
 372       m4x3_identity( skele->final_mtx[ik->upper] );
 373
 374       /* create rotation matrix */
 375       v3f co_knee;
 376       v3_muladds( co_base, v0, knee[0], co_knee );
 377       v3_muladds( co_knee, v1, knee[1], co_knee );
 378       vg_line( co_base, co_knee, 0xff00ff00 );
 379
 380       m4x3f transform;
 381       v3_copy( vaxis, transform[0] );
 382       v3_muls( v0, knee[0], transform[1] );
 383       v3_muladds( transform[1], v1, knee[1], transform[1] );
 384       v3_normalize( transform[1] );
 385       v3_cross( transform[0], transform[1], transform[2] );
 386       v3_copy( co_base, transform[3] );
 387
 388       m3x3_mul( transform, ik->ia, transform );
 389       m4x3_copy( transform, skele->final_mtx[ik->lower] );
 390
 391       /* upper/knee bone */
 392       v3_copy( vaxis, transform[0] );
 393       v3_sub( co_target, co_knee, transform[1] );
 394       v3_normalize( transform[1] );
 395       v3_cross( transform[0], transform[1], transform[2] );
 396       v3_copy( co_knee, transform[3] );
 397
 398       m3x3_mul( transform, ik->ib, transform );
 399       m4x3_copy( transform, skele->final_mtx[ik->upper] );
 400    }
 401 }
 402
 403 /*
 404  * Applies the typical operations that you want for an IK rig:
 405  *    Pose, IK, Pose(deferred), Inverses, Transform
 406  */
 407 static void skeleton_apply_standard( struct skeleton *skele, mdl_keyframe *pose,
 408                                      m4x3f transform )
 409 {
 410    skeleton_apply_pose( skele, pose, k_anim_apply_defer_ik );
 411    skeleton_apply_ik_pass( skele );
 412    skeleton_apply_pose( skele, pose, k_anim_apply_deffered_only );
 413    skeleton_apply_inverses( skele );
 414    skeleton_apply_transform( skele, transform );
 415 }
 416
 417 /*
 418  * Get an animation by name
 419  */
 420 static struct skeleton_anim *skeleton_get_anim( struct skeleton *skele,
 421                                                    const char *name )
 422 {
 423    for( u32 i=0; i<skele->anim_count; i++ ){
 424       struct skeleton_anim *anim = &skele->anims[i];
 425
 426       if( !strcmp( anim->name, name ) )
 427          return anim;
 428    }
 429
 430    vg_error( "skeleton_get_anim( *, \"%s\" )\n", name );
 431    vg_fatal_error( "Invalid animation name\n" );
 432
 433    return NULL;
 434 }
 435
 436 static void skeleton_alloc_from( struct skeleton *skele,
 437                                     void *lin_alloc,
 438                                     mdl_context *mdl,
 439                                     mdl_armature *armature )
 440 {
 441    skele->bone_count     = armature->bone_count+1;
 442    skele->anim_count     = armature->anim_count;
 443    skele->ik_count       = 0;
 444    skele->collider_count = 0;
 445
 446    for( u32 i=0; i<armature->bone_count; i++ ){
 447       mdl_bone *bone = mdl_arritm( &mdl->bones, armature->bone_start+i );
 448
 449       if( bone->flags & k_bone_flag_ik )
 450          skele->ik_count ++;
 451
 452       if( bone->collider )
 453          skele->collider_count ++;
 454    }
 455
 456    u32 bone_size = sizeof(struct skeleton_bone) * skele->bone_count,
 457        ik_size   = sizeof(struct skeleton_ik)   * skele->ik_count,
 458        mtx_size  = sizeof(m4x3f)                * skele->bone_count,
 459        anim_size = sizeof(struct skeleton_anim) * skele->anim_count;
 460
 461    skele->bones      = vg_linear_alloc( lin_alloc, bone_size );
 462    skele->ik         = vg_linear_alloc( lin_alloc, ik_size );
 463    skele->final_mtx  = vg_linear_alloc( lin_alloc, mtx_size );
 464    skele->anims      = vg_linear_alloc( lin_alloc, anim_size );
 465
 466    memset( skele->bones, 0, bone_size );
 467    memset( skele->ik, 0, ik_size );
 468    memset( skele->final_mtx, 0, mtx_size );
 469    memset( skele->anims, 0, anim_size );
 470 }
 471
 472 static void skeleton_fatal_err(void)
 473 {
 474    vg_fatal_error( "Skeleton setup failed" );
 475 }
 476
 477 /* Setup an animated skeleton from model. mdl's metadata should stick around */
 478 static void skeleton_setup( struct skeleton *skele,
 479                                void *lin_alloc, mdl_context *mdl )
 480 {
 481    u32 ik_count = 0, collider_count = 0;
 482    skele->bone_count = 0;
 483    skele->bones = NULL;
 484    skele->final_mtx = NULL;
 485    skele->anims = NULL;
 486
 487    if( !mdl->armatures.count ){
 488       vg_error( "No skeleton in model\n" );
 489       skeleton_fatal_err();
 490    }
 491
 492    mdl_armature *armature = mdl_arritm( &mdl->armatures, 0 );
 493    skeleton_alloc_from( skele, lin_alloc, mdl, armature );
 494
 495    for( u32 i=0; i<armature->bone_count; i++ ){
 496       mdl_bone *bone = mdl_arritm( &mdl->bones, armature->bone_start+i );
 497       struct skeleton_bone *sb = &skele->bones[i+1];
 498
 499       v3_copy( bone->co, sb->co );
 500       v3_copy( bone->end, sb->end );
 501
 502       sb->parent = bone->parent;
 503       sb->name   = mdl_pstr( mdl, bone->pstr_name );
 504       sb->flags  = bone->flags;
 505       sb->collider = bone->collider;
 506       sb->orig_bone = bone;
 507
 508       if( sb->flags & k_bone_flag_ik ){
 509          skele->bones[ sb->parent ].flags |= k_bone_flag_ik;
 510
 511          if( ik_count == skele->ik_count ){
 512             vg_error( "Too many ik bones, corrupt model file\n" );
 513             skeleton_fatal_err();
 514          }
 515
 516          struct skeleton_ik *ik = &skele->ik[ ik_count ++ ];
 517          ik->upper = i+1;
 518          ik->lower = bone->parent;
 519          ik->target = bone->ik_target;
 520          ik->pole = bone->ik_pole;
 521       }
 522
 523       box_copy( bone->hitbox, sb->hitbox );
 524
 525       if( bone->collider ){
 526          if( collider_count == skele->collider_count ){
 527             vg_error( "Too many collider bones\n" );
 528             skeleton_fatal_err();
 529          }
 530
 531          collider_count ++;
 532       }
 533    }
 534
 535    /* fill in implicit root bone */
 536    v3_zero( skele->bones[0].co );
 537    v3_copy( (v3f){0.0f,1.0f,0.0f}, skele->bones[0].end );
 538    skele->bones[0].parent = 0xffffffff;
 539    skele->bones[0].flags = 0;
 540    skele->bones[0].name = "[root]";
 541
 542    /* process animation quick refs */
 543    for( u32 i=0; i<skele->anim_count; i++ ){
 544       mdl_animation *anim =
 545          mdl_arritm( &mdl->animations, armature->anim_start+i );
 546
 547       skele->anims[i].rate       = anim->rate;
 548       skele->anims[i].length     = anim->length;
 549       skele->anims[i].name       = mdl_pstr(mdl, anim->pstr_name);
 550       skele->anims[i].anim_data  =
 551          mdl_arritm( &mdl->keyframes, anim->offset );
 552
 553       vg_info( "animation[ %f, %u ] '%s'\n", anim->rate,
 554                                              anim->length,
 555                                              skele->anims[i].name );
 556    }
 557
 558    skeleton_create_inverses( skele );
 559    vg_success( "Loaded skeleton with %u bones\n", skele->bone_count );
 560    vg_success( "                     %u colliders\n", skele->collider_count );
 561 }
 562
 563 static void skeleton_debug( struct skeleton *skele )
 564 {
 565    for( u32 i=1; i<skele->bone_count; i ++ ){
 566       struct skeleton_bone *sb = &skele->bones[i];
 567
 568       v3f p0, p1;
 569       v3_copy( sb->co, p0 );
 570       v3_add( p0, sb->end, p1 );
 571
 572       m4x3_mulv( skele->final_mtx[i], p0, p0 );
 573       m4x3_mulv( skele->final_mtx[i], p1, p1 );
 574
 575       if( sb->flags & k_bone_flag_deform ){
 576          if( sb->flags & k_bone_flag_ik ){
 577             vg_line( p0, p1, 0xff0000ff );
 578          }
 579          else{
 580             vg_line( p0, p1, 0xffcccccc );
 581          }
 582       }
 583       else
 584          vg_line( p0, p1, 0xff00ffff );
 585    }
 586 }
 587
 588 #endif /* SKELETON_H */