gluUnProject

[lishaak]

I have a problem with GLU.gluUnProject() function. I am traying to unproject mouse coordinates in the viewport to the ZX plane in my 3D scene. I wrote the following code:

public Point3D.Double DPtoLP(int x, int y) {
    GLContext context = this.getContext();
    context.makeCurrent();
    final GL OpenGL = context.getGL();
   
    float winX = (float)x;
    float winY = (float)y;
   
    int[] viewport = new int[4];
    double[] modelview = new double[16];
    double[] projection = new double[16];
   
    OpenGL.glGetIntegerv(GL.GL_VIEWPORT, viewport, 0);
    OpenGL.glGetDoublev(GL.GL_MODELVIEW_MATRIX, modelview, 0);
    OpenGL.glGetDoublev(GL.GL_PROJECTION_MATRIX, projection, 0);
   
    winY = (float)viewport[3] - winY;
   
    double[] nearPos = new double[3];
    double[] farPos = new double[3];
   
    glu.gluUnProject(winX, winY, 0.0, modelview, 0, projection, 0, viewport, 0,
        nearPos, 0);
    glu.gluUnProject(winX, winY, 1.0, modelview, 0, projection, 0, viewport, 0,
        farPos, 0);
   
    double sx = farPos[0] - nearPos[0];
    double sy = farPos[1] - nearPos[1];
    double sz = farPos[2] - nearPos[2];
   
    double a = nearPos[0] - (nearPos[1]/sy)*sx;
    double b = nearPos[2] - (nearPos[1]/sy)*sz;
   
    context.release();
   
    return new Point3D.Double(a, 0.0, b);
}

Variables a, b should be x, z coordinates on the XZ plane. But when I execute this code there is complete rubbish in a,b variables. Has anyone any idea why this code does not work? Maybe am making some very silly mistake....