/**
* @see <a href="gluUnProject.html">gluUnProject</a>
*/
public double [] un_project(double window_x, double window_y,
double window_z, double [] modelview, double [] projection,
int [] viewport)
{
Matrix4d product = new Matrix4d();
Matrix4d.multiply(modelview, projection, product.m);
if (product.invert() == null)
{
return(null);
}
Vector4d A = new Vector4d(window_x, window_y, window_z, 1.0);
// map x and y from window coordinates
A.v [0] = (A.v [0] - viewport [0]) / viewport [2];
A.v [1] = (A.v [1] - viewport [1]) / viewport [3];
// map to range -1 to 1, A = 2*A - I
A.scalar_multiply(2).scalar_minus(1);
A.multiply_right(product);
double d = A.v [3];
if (d == 0)
{
return(null);
}
double [] result = new double [3]; // vs. 4
result [0] = A.v [0] / d;
result [1] = A.v [1] / d;
result [2] = A.v [2] / d;
return(result);
}