Create orthographic projection function

linear_alg.c

@@ -100,6 +100,16 @@ mat4_t mat4_perspective(float aspect, float fov, float near, float far)
 	};
 }
 
+mat4_t mat4_orthographic(float width, float height, float near, float far)
+{
+	return (mat4_t) {
+		{ 1 / width, 0, 0, 0 },
+		{ 0, -1 / height, 0, 0 },
+		{ 0, 0, 1 / (far - near), 0 },
+		{ 0, 0, -near / (far - near), 1 },
+	};
+}
+
 mat4_t mat4_translate_vec3(vec3_t v)
 {
 	return (mat4_t) {

linear_alg.h

@@ -86,6 +86,7 @@ float vec4_dot(vec4_t v, vec4_t u);
 mat4_t mat4_mul(mat4_t m, mat4_t n);
 mat4_t mat4_lookat(vec3_t camera, vec3_t target, vec3_t up);
 mat4_t mat4_perspective(float aspect, float fov, float near, float far);
+mat4_t mat4_orthographic(float width, float height, float near, float far);
 mat4_t mat4_translate_vec3(vec3_t v);
 mat4_t mat4_scale_vec3(vec3_t v);
 mat4_t mat4_rotate_quaternion(vec4_t q);

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),