1 files changed, 35 insertions, 1 deletions
diff --git a/src/maths.c b/src/maths.c
index 95283e6..40223c6 100644
--- a/src/maths.c
+++ b/src/maths.c
@@ -2,4 +2,38 @@
 
 vec3 vec3_create(f32 x, f32 y, f32 z) { return (vec3){ x, y, z }; }
 
-vec4 vec4_create(f32 x, f32 y, f32 z, f32 w) { return (vec4){ x, y, z , w }; }
-\ No newline at end of file
+vec4 vec4_create(f32 x, f32 y, f32 z, f32 w) { return (vec4){ x, y, z, w }; }
+
+mat4 mat4_ident() {
+  return (mat4){ .data = { 1.0, 0., 0., 0., 0., 1., 0., 0., 0., 0., 1., 0., 0., 0., 0., 1.0 } };
+}
+
+mat4 mat4_mult(mat4 lhs, mat4 rhs) {
+  mat4 out_matrix = mat4_ident();
+
+  const f32* m1_ptr = lhs.data;
+  const f32* m2_ptr = rhs.data;
+  f32* dst_ptr = out_matrix.data;
+
+  for (i32 i = 0; i < 4; ++i) {
+    for (i32 j = 0; j < 4; ++j) {
+      *dst_ptr = m1_ptr[0] * m2_ptr[0 + j] + m1_ptr[1] * m2_ptr[4 + j] + m1_ptr[2] * m2_ptr[8 + j] +
+                 m1_ptr[3] * m2_ptr[12 + j];
+      dst_ptr++;
+    }
+    m1_ptr += 4;
+  }
+
+  return out_matrix;
+}
+
+mat4 mat4_perspective(f32 fov_radians, f32 aspect_ratio, f32 near_z, f32 far_z) {
+  f32 half_tan_fov = tanf(fov_radians * 0.5f);
+  mat4 out_matrix = { .data = { 0 } };
+  out_matrix.data[0] = 1.0f / (aspect_ratio * half_tan_fov);
+  out_matrix.data[5] = 1.0f / half_tan_fov;
+  out_matrix.data[10] = -((far_z + near_z) / (far_z - near_z));
+  out_matrix.data[11] = -1.0f;
+  out_matrix.data[14] = -((2.0f * far_z * near_z) / (far_z - near_z));
+  return out_matrix;
+}