camera.h

   1 #ifndef CAMERA_H
   2 #define CAMERA_H
   3
   4 #include "common.h"
   5
   6 typedef struct camera camera;
   7
   8 struct camera
   9 {
  10    /* Input */
  11    v2f angles;
  12    v3f pos;
  13    float fov, nearz, farz;
  14
  15    /* Output */
  16    m4x3f transform,
  17          transform_inverse;
  18
  19    struct camera_mtx
  20    {
  21       m4x4f p,
  22             v,
  23             pv;
  24    }
  25    mtx,
  26    mtx_prev;
  27 }
  28 VG_STATIC main_camera;
  29
  30 /*
  31  * 1) [angles, pos] -> transform
  32  */
  33 VG_STATIC void camera_update_transform( camera *cam )
  34 {
  35    v4f qyaw, qpitch, qcam;
  36    q_axis_angle( qyaw, (v3f){ 0.0f, 1.0f, 0.0f },   -cam->angles[0] );
  37    q_axis_angle( qpitch, (v3f){ 1.0f, 0.0f, 0.0f }, -cam->angles[1] );
  38
  39    q_mul( qyaw, qpitch, qcam );
  40    q_m3x3( qcam, cam->transform );
  41    v3_copy( cam->pos, cam->transform[3] );
  42 }
  43
  44 /*
  45  * 2) [transform] -> transform_inverse, view matrix
  46  */
  47 VG_STATIC void camera_update_view( camera *cam )
  48 {
  49    m4x4_copy( cam->mtx.v,  cam->mtx_prev.v );
  50    m4x3_invert_affine( cam->transform, cam->transform_inverse );
  51    m4x3_expand( cam->transform_inverse, cam->mtx.v );
  52 }
  53
  54 /*
  55  * 3) [fov,nearz,farz] -> projection matrix
  56  */
  57 VG_STATIC void camera_update_projection( camera *cam )
  58 {
  59    m4x4_copy( cam->mtx.p,  cam->mtx_prev.p );
  60    m4x4_projection( cam->mtx.p, cam->fov,
  61                     (float)vg.window_x / (float)vg.window_y,
  62                     cam->nearz, cam->farz );
  63 }
  64
  65 /*
  66  * 4) [projection matrix, view matrix] -> previous pv, new pv
  67  */
  68 VG_STATIC void camera_finalize( camera *cam )
  69 {
  70    m4x4_copy( cam->mtx.pv, cam->mtx_prev.pv );
  71    m4x4_mul( cam->mtx.p, cam->mtx.v, cam->mtx.pv );
  72 }
  73
  74 /*
  75  * http://www.terathon.com/lengyel/Lengyel-Oblique.pdf
  76  */
  77 VG_STATIC void m4x4_clip_projection( m4x4f mat, v4f plane )
  78 {
  79    v4f c =
  80    {
  81       (vg_signf(plane[0]) + mat[2][0]) / mat[0][0],
  82       (vg_signf(plane[1]) + mat[2][1]) / mat[1][1],
  83       -1.0f,
  84       (1.0f + mat[2][2]) / mat[3][2]
  85    };
  86
  87    v4_muls( plane, 2.0f / v4_dot(plane,c), c );
  88
  89    mat[0][2] = c[0];
  90    mat[1][2] = c[1];
  91    mat[2][2] = c[2] + 1.0f;
  92    mat[3][2] = c[3];
  93 }
  94
  95 /*
  96  * Undoes the above operation
  97  */
  98 VG_STATIC void m4x4_reset_clipping( m4x4f mat, float ffar, float fnear )
  99 {
 100    mat[0][2] = 0.0f;
 101    mat[1][2] = 0.0f;
 102    mat[2][2] = -(ffar + fnear) / (ffar - fnear);
 103    mat[3][2] = -2.0f * ffar * fnear / (ffar - fnear);
 104 }
 105
 106 #endif /* CAMERA_H */