src/client/frustum.c

   1 #include "frustum.h"
   2
   3 typedef enum
   4 {
   5         PLANE_LEFT,
   6         PLANE_RIGHT,
   7         PLANE_BOTTOM,
   8         PLANE_TOP,
   9         PLANE_NEAR,
  10         PLANE_FAR,
  11         PLANE_COUNT,
  12 } Plane;
  13
  14 static struct
  15 {
  16         vec3 points[8];
  17         vec4 planes[PLANE_COUNT];
  18         int cross_indices[PLANE_COUNT][PLANE_COUNT];
  19 } frustum;
  20
  21 __attribute__((constructor)) static void init_frustum()
  22 {
  23         for (Plane a = 0; a < PLANE_COUNT; a++)
  24                 for (Plane b = 0; b < PLANE_COUNT; b++)
  25                         frustum.cross_indices[a][b] = a * (9 - a) / 2 + b - 1;
  26 }
  27
  28 void frustum_update(mat4x4 view_proj)
  29 {
  30         mat4x4 m;
  31
  32         mat4x4_transpose(m, view_proj);
  33
  34         vec4_add(frustum.planes[PLANE_LEFT], m[3], m[0]);
  35         vec4_sub(frustum.planes[PLANE_RIGHT], m[3], m[0]);
  36         vec4_add(frustum.planes[PLANE_BOTTOM], m[3], m[1]);
  37         vec4_sub(frustum.planes[PLANE_TOP], m[3], m[1]);
  38         vec4_add(frustum.planes[PLANE_NEAR], m[3], m[2]);
  39         vec4_sub(frustum.planes[PLANE_FAR], m[3], m[2]);
  40
  41         int i = 0;
  42         vec3 crosses[PLANE_COUNT * (PLANE_COUNT - 1) / 2];
  43         for (Plane a = 0; a < PLANE_COUNT; a++)
  44                 for (Plane b = a + 1; b < PLANE_COUNT; b++)
  45                         vec3_mul_cross(crosses[i++], frustum.planes[a], frustum.planes[b]);
  46
  47         int j = 0;
  48         for (Plane c = PLANE_NEAR; c <= PLANE_FAR; c++) {
  49                 for (Plane a = PLANE_LEFT; a <= PLANE_RIGHT; a++) {
  50                         for (Plane b = PLANE_BOTTOM; b <= PLANE_TOP; b++) {
  51                                 float d = -1.0f / vec3_mul_inner(frustum.planes[a], crosses[frustum.cross_indices[b][c]]);
  52                                 vec3 w = {frustum.planes[a][3], frustum.planes[b][3], frustum.planes[c][3]};
  53                                 float *res = frustum.points[j++];
  54
  55                                 vec3 res_1_cross = {-crosses[frustum.cross_indices[a][c]][0], -crosses[frustum.cross_indices[a][c]][1], -crosses[frustum.cross_indices[a][c]][2]};
  56
  57                                 res[0] = vec3_mul_inner(crosses[frustum.cross_indices[b][c]], w) * d;
  58                                 res[1] = vec3_mul_inner(res_1_cross, w) * d;
  59                                 res[2] = vec3_mul_inner(crosses[frustum.cross_indices[a][b]], w) * d;
  60                         }
  61                 }
  62         }
  63 }
  64
  65 static bool outside_plane(Plane i, aabb3f32 box)
  66 {
  67         for (int x = 0; x <= 1; x++) {
  68                 for (int y = 0; y <= 1; y++) {
  69                         for (int z = 0; z <= 1; z++) {
  70                                 vec4 plane = {
  71                                         x ? box.max.x : box.min.x,
  72                                         y ? box.max.y : box.min.y,
  73                                         z ? box.max.z : box.min.z,
  74                                         1.0f,
  75                                 };
  76
  77                                 if (vec4_mul_inner(frustum.planes[i], plane) > 0.0)
  78                                         return false;
  79                         }
  80                 }
  81         }
  82
  83         return true;
  84 }
  85
  86 // http://iquilezles.org/www/articles/frustumcorrect/frustumcorrect.htm
  87 bool frustum_is_visible(aabb3f32 box)
  88 {
  89         for (Plane i = 0; i < PLANE_COUNT; i++) {
  90                 if (outside_plane(i, box))
  91                         return false;
  92         }
  93
  94         int box_outside[6] = {0};
  95
  96         for (Plane i = 0; i < PLANE_COUNT; i++) {
  97                 int outside[6] = {
  98                         frustum.points[i][0] > box.max.x,
  99                         frustum.points[i][0] < box.min.x,
 100                         frustum.points[i][1] > box.max.y,
 101                         frustum.points[i][1] < box.min.y,
 102                         frustum.points[i][2] > box.max.z,
 103                         frustum.points[i][2] < box.min.z,
 104                 };
 105
 106                 for (int i = 0; i < 6; i++)
 107                         box_outside[i] += outside[i];
 108         }
 109
 110         for (int i = 0; i < 6; i++) {
 111                 if (box_outside[i] == 8)
 112                         return false;
 113         }
 114
 115         return true;
 116 }