aabb transform

aabb_transform.c

CGLM_INLINE
void
glm_aabb_transform(vec3 box[2], mat4 m, vec3 dest[2]) {
  vec3 v[2], xa, xb, ya, yb, za, zb, tmp;

  glm_vec_scale(m[0], box[0][0], xa);
  glm_vec_scale(m[0], box[1][0], xb);

  glm_vec_scale(m[1], box[0][1], ya);
  glm_vec_scale(m[1], box[1][1], yb);

  glm_vec_scale(m[2], box[0][2], za);
  glm_vec_scale(m[2], box[1][2], zb);

  /* min(xa, xb) + min(ya, yb) + min(za, zb) + translation */
  glm_vec_minv(xa, xb, v[0]);
  glm_vec_minv(ya, yb, tmp);
  glm_vec_add(v[0], tmp, v[0]);
  glm_vec_minv(za, zb, tmp);
  glm_vec_add(v[0], tmp, v[0]);
  glm_vec_add(v[0], m[3], v[0]);

  /* max(xa, xb) + max(ya, yb) + max(za, zb) + translation */
  glm_vec_maxv(xa, xb, v[1]);
  glm_vec_maxv(ya, yb, tmp);
  glm_vec_add(v[1], tmp, v[1]);
  glm_vec_maxv(za, zb, tmp);
  glm_vec_add(v[1], tmp, v[1]);
  glm_vec_add(v[1], m[3], v[1]);

  glm_vec_copy(v[0], dest[0]);
  glm_vec_copy(v[1], dest[1]);
}

aabb_transform2.c

CGLM_INLINE
void
glm_aabb_transform2(vec3 box[2], mat4 m, vec3 dest[2]) {
  vec4 v;
  vec4 c[8];
  vec3 min, max, a, b;
  int  i;

  glm_vec_copy(box[0], a);
  glm_vec_copy(box[1], b);

  c[0][0] = a[0];   c[1][0] = b[0];   c[2][0] = a[0];   c[3][0] = a[0];
  c[0][1] = a[1];   c[1][1] = a[1];   c[2][1] = b[1];   c[3][1] = a[1];
  c[0][2] = a[2];   c[1][2] = a[2];   c[2][2] = a[2];   c[3][2] = b[2];
  c[0][3] = 1.0f;   c[1][3] = 1.0f;   c[2][3] = 1.0f;   c[3][3] = 1.0f;

  c[4][0] = b[0];   c[5][0] = a[0];   c[6][0] = b[0];   c[7][0] = b[0];
  c[4][1] = b[1];   c[5][1] = b[1];   c[6][1] = a[1];   c[7][1] = b[1];
  c[4][2] = b[2];   c[5][2] = b[2];   c[6][2] = b[2];   c[7][2] = a[2];
  c[4][3] = 1.0f;   c[5][3] = 1.0f;   c[6][3] = 1.0f;   c[7][3] = 1.0f;

  glm_vec_broadcast(FLT_MAX,  min);
  glm_vec_broadcast(-FLT_MAX, max);

  for (i = 0; i < 8; i++) {
    glm_mat4_mulv(m, c[i], v);

    min[0] = glm_min(min[0], v[0]);
    min[1] = glm_min(min[1], v[1]);
    min[2] = glm_min(min[2], v[2]);

    max[0] = glm_max(max[0], v[0]);
    max[1] = glm_max(max[1], v[1]);
    max[2] = glm_max(max[2], v[2]);
  }

  glm_vec_copy(min, dest[0]);
  glm_vec_copy(max, dest[1]);
}