camera.h

   1 #ifndef CAMERA_H
   2 #define CAMERA_H
   3
   4 #include "skaterift.h"
   5
   6 typedef struct camera camera;
   7 struct camera{
   8    /* Input */
   9    v3f angles;
  10    v3f pos;
  11    float fov, nearz, farz;
  12
  13    /* Output */
  14    m4x3f transform,
  15          transform_inverse;
  16
  17    struct camera_mtx{
  18       m4x4f p,
  19             v,
  20             pv;
  21    }
  22    mtx,
  23    mtx_prev;
  24 };
  25
  26 static void camera_lerp_angles( v3f a, v3f b, float t, v3f d ){
  27    d[0] = vg_alerpf( a[0], b[0], t );
  28    d[1] = vg_lerpf(  a[1], b[1], t );
  29    d[2] = vg_lerpf(  a[2], b[2], t );
  30 }
  31
  32 static void camera_lerp( camera *a, camera *b, float t, camera *d ){
  33    v3_lerp( a->pos, b->pos, t, d->pos );
  34    d->angles[0] = vg_alerpf( a->angles[0], b->angles[0], t );
  35    d->angles[1] = vg_lerpf( a->angles[1], b->angles[1], t );
  36    d->angles[2] = vg_lerpf( a->angles[2], b->angles[2], t );
  37    d->fov = vg_lerpf( a->fov, b->fov, t );
  38 }
  39
  40 static void camera_copy( camera *a, camera *d ){
  41    v3_copy( a->pos, d->pos );
  42    v3_copy( a->angles, d->angles );
  43    d->fov = a->fov;
  44 }
  45
  46 /*
  47  * 1) [angles, pos] -> transform
  48  */
  49 static void camera_update_transform( camera *cam )
  50 {
  51    v4f qyaw, qpitch, qcam;
  52    q_axis_angle( qyaw,   (v3f){ 0.0f, 1.0f, 0.0f }, -cam->angles[0] );
  53    q_axis_angle( qpitch, (v3f){ 1.0f, 0.0f, 0.0f }, -cam->angles[1] );
  54
  55    q_mul( qyaw, qpitch, qcam );
  56    q_m3x3( qcam, cam->transform );
  57    v3_copy( cam->pos, cam->transform[3] );
  58 }
  59
  60 /*
  61  * 2) [transform] -> transform_inverse, view matrix
  62  */
  63 static void camera_update_view( camera *cam )
  64 {
  65    m4x4_copy( cam->mtx.v,  cam->mtx_prev.v );
  66    m4x3_invert_affine( cam->transform, cam->transform_inverse );
  67    m4x3_expand( cam->transform_inverse, cam->mtx.v );
  68 }
  69
  70 /*
  71  * 3) [fov,nearz,farz] -> projection matrix
  72  */
  73 static void camera_update_projection( camera *cam )
  74 {
  75    m4x4_copy( cam->mtx.p,  cam->mtx_prev.p );
  76    m4x4_projection( cam->mtx.p, cam->fov,
  77                     (float)vg.window_x / (float)vg.window_y,
  78                     cam->nearz, cam->farz );
  79 }
  80
  81 /*
  82  * 4) [projection matrix, view matrix] -> previous pv, new pv
  83  */
  84 static void camera_finalize( camera *cam )
  85 {
  86    m4x4_copy( cam->mtx.pv, cam->mtx_prev.pv );
  87    m4x4_mul( cam->mtx.p, cam->mtx.v, cam->mtx.pv );
  88 }
  89
  90 /*
  91  * http://www.terathon.com/lengyel/Lengyel-Oblique.pdf
  92  */
  93 static void m4x4_clip_projection( m4x4f mat, v4f plane )
  94 {
  95    v4f c =
  96    {
  97       (vg_signf(plane[0]) + mat[2][0]) / mat[0][0],
  98       (vg_signf(plane[1]) + mat[2][1]) / mat[1][1],
  99       -1.0f,
 100       (1.0f + mat[2][2]) / mat[3][2]
 101    };
 102
 103    v4_muls( plane, 2.0f / v4_dot(plane,c), c );
 104
 105    mat[0][2] = c[0];
 106    mat[1][2] = c[1];
 107    mat[2][2] = c[2] + 1.0f;
 108    mat[3][2] = c[3];
 109 }
 110
 111 /*
 112  * Undoes the above operation
 113  */
 114 static void m4x4_reset_clipping( m4x4f mat, float ffar, float fnear )
 115 {
 116    mat[0][2] = 0.0f;
 117    mat[1][2] = 0.0f;
 118    mat[2][2] = -(ffar + fnear) / (ffar - fnear);
 119    mat[3][2] = -2.0f * ffar * fnear / (ffar - fnear);
 120 }
 121
 122 #endif /* CAMERA_H */