Create orthographic projection function

main.c

@@ -64,7 +64,9 @@ int main(int argc, char *argv[])
 	const mat4_t view = mat4_lookat(cam, tgt, up);
 	const mat4_t proj = mat4_perspective((float)W / H, PI / 8, 0.1, 100.0);
 	const mat4_t vp = mat4_mul(proj, view);
-	const mat4_t light_vp = mat4_lookat(light, tgt, up);
+	const mat4_t light_view = mat4_lookat(light, tgt, up);
+	const mat4_t light_proj = mat4_orthographic(5, 5, 10);
+	const mat4_t light_vp = mat4_mul(light_proj, light_view);
 	mat4_t transforms[NELEMS(gpu_models)] = {
 		mat4_mul(
 		    MAT4_TRANSLATE(1, 0, 0),