public Matrix4x4 lookAt(Vector3 eye, Vector3 center, Vector3 up) {
Vector3 forward = (center.subtract(eye)).normalized();
Vector3 side = Vector3.crossProduct(forward, up).normalized();
Vector3 upVector = Vector3.crossProduct(side, forward);
Matrix4x4 m = new Matrix4x4(1);
m.set_value(0, 0, side.x());
m.set_value(1, 0, side.y());
m.set_value(2, 0, side.z());
m.set_value(3, 0, 0.0f);
m.set_value(0, 1, upVector.x());
m.set_value(1, 1, upVector.y());
m.set_value(2, 1, upVector.z());
m.set_value(3, 1, 0.0f);
m.set_value(0, 2, -forward.x());
m.set_value(1, 2, -forward.y());
m.set_value(2, 2, -forward.z());
m.set_value(3, 2, 0.0f);
m.set_value(0, 3, 0.0f);
m.set_value(1, 3, 0.0f);
m.set_value(2, 3, 0.0f);
m.set_value(3, 3, 1.0f);
Matrix4x4 m2 = this.multiply(m);
m2.translate(-eye.x(), -eye.y(), -eye.z());
return m2;
}
