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 /* lerp position, fov, and angles */
  33 static void camera_lerp( camera *a, camera *b, float t, camera *d ){
  34    v3_lerp( a->pos, b->pos, t, d->pos );
  35    camera_lerp_angles( a->angles, b->angles, t, d->angles );
  36    d->fov = vg_lerpf( a->fov, b->fov, t );
  37 }
  38
  39 static void camera_copy( camera *a, camera *d ){
  40    v3_copy( a->pos, d->pos );
  41    v3_copy( a->angles, d->angles );
  42    d->fov = a->fov;
  43 }
  44
  45 static void m4x3_transform_camera( m4x3f m, camera *cam ){
  46    m4x3_mulv( m, cam->pos, cam->pos );
  47
  48    v3f v0;
  49    v3_angles_vector( cam->angles, v0 );
  50    m3x3_mulv( m, v0, v0 );
  51    v3_normalize( v0 );
  52    v3_angles( v0, cam->angles );
  53 }
  54
  55 /*
  56  * 1) [angles, pos] -> transform
  57  */
  58 static void camera_update_transform( camera *cam )
  59 {
  60    v4f qyaw, qpitch, qcam;
  61    q_axis_angle( qyaw,   (v3f){ 0.0f, 1.0f, 0.0f }, -cam->angles[0] );
  62    q_axis_angle( qpitch, (v3f){ 1.0f, 0.0f, 0.0f }, -cam->angles[1] );
  63
  64    q_mul( qyaw, qpitch, qcam );
  65    q_m3x3( qcam, cam->transform );
  66    v3_copy( cam->pos, cam->transform[3] );
  67 }
  68
  69 /*
  70  * 2) [transform] -> transform_inverse, view matrix
  71  */
  72 static void camera_update_view( camera *cam )
  73 {
  74    m4x4_copy( cam->mtx.v,  cam->mtx_prev.v );
  75    m4x3_invert_affine( cam->transform, cam->transform_inverse );
  76    m4x3_expand( cam->transform_inverse, cam->mtx.v );
  77 }
  78
  79 /*
  80  * 3) [fov,nearz,farz] -> projection matrix
  81  */
  82 static void camera_update_projection( camera *cam )
  83 {
  84    m4x4_copy( cam->mtx.p,  cam->mtx_prev.p );
  85    m4x4_projection( cam->mtx.p, cam->fov,
  86                     (float)vg.window_x / (float)vg.window_y,
  87                     cam->nearz, cam->farz );
  88 }
  89
  90 /*
  91  * 4) [projection matrix, view matrix] -> previous pv, new pv
  92  */
  93 static void camera_finalize( camera *cam )
  94 {
  95    m4x4_copy( cam->mtx.pv, cam->mtx_prev.pv );
  96    m4x4_mul( cam->mtx.p, cam->mtx.v, cam->mtx.pv );
  97 }
  98
  99 /*
 100  * http://www.terathon.com/lengyel/Lengyel-Oblique.pdf
 101  */
 102 static void m4x4_clip_projection( m4x4f mat, v4f plane )
 103 {
 104    v4f c =
 105    {
 106       (vg_signf(plane[0]) + mat[2][0]) / mat[0][0],
 107       (vg_signf(plane[1]) + mat[2][1]) / mat[1][1],
 108       -1.0f,
 109       (1.0f + mat[2][2]) / mat[3][2]
 110    };
 111
 112    v4_muls( plane, 2.0f / v4_dot(plane,c), c );
 113
 114    mat[0][2] = c[0];
 115    mat[1][2] = c[1];
 116    mat[2][2] = c[2] + 1.0f;
 117    mat[3][2] = c[3];
 118 }
 119
 120 /*
 121  * Undoes the above operation
 122  */
 123 static void m4x4_reset_clipping( m4x4f mat, float ffar, float fnear )
 124 {
 125    mat[0][2] = 0.0f;
 126    mat[1][2] = 0.0f;
 127    mat[2][2] = -(ffar + fnear) / (ffar - fnear);
 128    mat[3][2] = -2.0f * ffar * fnear / (ffar - fnear);
 129 }
 130
 131 #endif /* CAMERA_H */