gistfile1.txt

static public int UnProject(Vector3 win, Matrix4 modelMatrix,
	Matrix4 projMatrix, int[] viewport, ref Vector3 obj)
{
	return gluUnProject(win.X, win.Y, win.Z, modelMatrix,
		projMatrix, viewport, ref obj.X, ref obj.Y, ref obj.Z);
}

static int gluUnProject(float winx, float winy, float winz,
	Matrix4 modelMatrix, Matrix4 projMatrix, int[] viewport,
	ref float objx, ref float objy, ref float objz)
{
	Matrix4 finalMatrix;
	Vector4 _in;
	Vector4 _out;

	finalMatrix = Matrix4.Mult(modelMatrix, projMatrix);

	//if (!__gluInvertMatrixd(finalMatrix, finalMatrix)) return(GL_FALSE);
	finalMatrix.Invert();

	_in.X = winx;
	_in.Y = winy;
	_in.Z = winz;
	_in.W = 1.0f;

	/* Map x and y from window coordinates */
	_in.X = (_in.X - viewport[0]) / viewport[2];
	_in.Y = (_in.Y - viewport[1]) / viewport[3];

	/* Map to range -1 to 1 */
	_in.X = _in.X * 2 - 1;
	_in.Y = _in.Y * 2 - 1;
	_in.Z = _in.Z * 2 - 1;

	//__gluMultMatrixVecd(finalMatrix, _in, _out);
	// check if this works:
	_out = Vector4.Transform(_in, finalMatrix);

	if (_out.W == 0.0)
		return (0);
	_out.X /= _out.W;
	_out.Y /= _out.W;
	_out.Z /= _out.W;
	objx = _out.X;
	objy = _out.Y;
	objz = _out.Z;
	return (1);
}