OpenGL Look At

look.cpp

mat4 lookAt(const vec3& position, const vec3& target, const vec3& up) {
	// Remember, forward is negative z
	vec3 f = normalized(target - position) * -1.0f;
	vec3 r = cross(up, f);
	if (r == vec3(0, 0, 0)) {
		std::cout << "WARNING: mat4 lookAt has invalid right vector\n";
		return mat4(); // Error
	}
	normalize(r);
	vec3 u = normalized(cross(f, r));

	vec3 t = vec3(
		-dot(r, position),
		-dot(u, position),
		-dot(f, position)
	);

	return mat4(
		// Transpose upper 3x3 matrix to invert it
		r.x, u.x, f.x, 0,
		r.y, u.y, f.y, 0,
		r.z, u.z, f.z, 0,
		t.x, t.y, t.z, 1
	);
}