Vector3f rayToCenter = new Vector3f();
rayToCenter.add(rayFrom, rayForward);
Vector3f dHor = new Vector3f(hor);
dHor.scale(1f / glutScreenWidth);
Vector3f dVert = new Vector3f(vertical);
dVert.scale(1.f / glutScreenHeight);
Vector3f tmp1 = new Vector3f();
Vector3f tmp2 = new Vector3f();
tmp1.scale(0.5f, hor);
tmp2.scale(0.5f, vertical);