gluUnProject always returns zero

I need gluUnProject to convert screen coordinates to world coordinates and right now I just about have it working. When my app runs it accurately tells me the coordinates on screen which I know are stored in my renderer thread and then pumps out screen coordinates. Unfortunately the screen coordinates seem to have no effect of world coordinates and the world coordinates remain at zero.

Here is my gluUnProject method

public void vector3 (GL11 gl){

        int[] viewport = new int[4];
        float[] modelview = new float[16];
        float[] projection = new float[16];
        float winx, winy, winz;
        float[] newcoords = new float[4];

        gl.glGetIntegerv(GL11.GL_VIEWPORT, viewport, 0);
        ((GL11) gl).glGetFloatv(GL11.GL_MODELVIEW_MATRIX, modelview, 0);
        ((GL11) gl).glGetFloatv(GL11.GL_PROJECTION_MATRIX, projection, 0);

        winx = (float)setx;
        winy = (float)viewport[3] - sety;
        winz = 0;

        GLU.gluUnProject(setx, (float)viewport[3] - sety, 0, modelview, 0, projection, 0, viewport, 0, newcoords, 0);
        posx = (int)newcoords[0];
        posy = (int)newcoords[1];
        posz = (int)newcoords[2];



        Log.d(TAG, "x= " + String.valueOf(posx));
        Log.d(TAG, "y= " + String.valueOf(posy));
        Log.d(TAG, "z= " + String.valueOf(posz));
        }

Now I've searched and found this开发者_JAVA百科 forum post and they came to the conclusion that it was to do with using getFloatv instead of getDoublev, but getDoublev does not seem to be supported by GL11

The method glGetDoublev(int, float[], int) is undefined for the type GL11

and also

The method glGetDoublev(int, double[], int) is undefined for the type GL11

should the double and float thing matter and if so how do I go about using doubles

Thank you

EDIT:

I was told that gluUnproject fails when too close to the near far clipping plane so I set winz to -5 when near is 0 and far is -10. This had no effect on the output.

I also logged each part of the newcoords[] array and they all return something that is NaN (not a number) could this be the problem or something higher up in the algorithm

I'm guessing you're working on the emulator? Its OpenGL implementation is rather buggy, and after testing I found that it returns all zeroes for the following calls:

gl11.glGetIntegerv(GL11.GL_VIEWPORT, viewport, 0);
gl11.glGetFloatv(GL11.GL_MODELVIEW_MATRIX, modelview, 0);
gl11.glGetFloatv(GL11.GL_PROJECTION_MATRIX, projection, 0);

The gluUnProject() function needs to calculate the inverse of the combined modelview-projection matrix, and since these are all zeroes, the inverse does not exist and will consist of NaNs. The resulting newcoords vector is therefor also all Nans.

Try it on a device with a proper OpenGL implementation, it should work. Keep in mind to still divide by newcoords[3] though ;-)