src/engine/geometry.c

   1 #include "geometry.h"
   2
   3 #include <stddef.h>
   4
   5 Transform identity() {
   6         return (Transform) { .a1 = 1.0f, .a2 = 0.0f, .a3 = 0.0f, .a4 = 0.0f,
   7                              .b1 = 0.0f, .b2 = 1.0f, .b3 = 0.0f, .b4 = 0.0f,
   8                              .c1 = 0.0f, .c2 = 0.0f, .c3 = 1.0f, .c4 = 0.0f,
   9                              .d1 = 0.0f, .d2 = 0.0f, .d3 = 0.0f, .d4 = 1.0f };
  10 }
  11
  12 Transform multiply(Transform t1, Transform t2) {
  13         GLfloat* a = (GLfloat*) &t1;
  14         GLfloat* b = (GLfloat*) &t2;
  15
  16         for (size_t row = 0; row < 4; ++row) {
  17                 for (size_t col = 0; col < 4; ++col) {
  18                         b[(row * 4) + col] =
  19                                 a[(row * 4) + 0] * b[(0 * 4) + col]
  20                                 + a[(row * 4) + 1] * b[(1 * 4) + col]
  21                                 + a[(row * 4) + 2] * b[(2 * 4) + col]
  22                                 + a[(row * 4) + 3] * b[(3 * 4) + col];
  23                 }
  24         }
  25         return t2;
  26 }
  27
  28 void translate(Transform* transform, Vector3D vec) {
  29         *transform = multiply(
  30                 (Transform) { .a1 = 1.0f, .a2 = 0.0f, .a3 = 0.0f, .a4 = vec.x,
  31                               .b1 = 0.0f, .b2 = 1.0f, .b3 = 0.0f, .b4 = vec.y,
  32                               .c1 = 0.0f, .c2 = 0.0f, .c3 = 1.0f, .c4 = vec.z,
  33                               .d1 = 0.0f, .d2 = 0.0f, .d3 = 0.0f, .d4 = 1.0f },
  34                 *transform);
  35 }
  36
  37 Vector3D translationOf(Transform transform) {
  38         return (Vector3D) { transform.a4, transform.b4, transform.c4 };
  39 }