gluunproject failing because projection zero?

OpenGL Development JOGL Development
#1

I have written a map viewing application that successfully views maps, so the physical coordinates look like (-74,40) with z fairly irrelevant.

Now I want to pick, so I tried to use gluunproject. In order to do it, I need the projection and modelview matrices.

So I wrote:

public void unproject(Viewer v, int x, int y) {
	GL gl = v.getGL();
	GLU glu = v.getGLU();
	double[] projection = new double[16];
	double[] model = new double[16];
	gl.glGetDoublev(GL.GL_PROJECTION_MATRIX, projection);
	gl.glGetDoublev(GL.GL_MODELVIEW_MATRIX, model);

	System.out.println("Projection");
	for (int i = 0; i < projection.length; i+= 4) {
		System.out.println(projection[i] + "\t" + projection[i+1] + "\t" +projection[i+2] + "\t" +projection[i+3]);
	}

	System.out.println("Model");
	for (int i = 0; i < model.length; i+= 4) {
		System.out.println(model[i] + "\t" + model[i+1] + "\t" +model[i+2] + "\t" +model[i+3]);
	}

	int[] view = { viewportX, viewportY, viewportWidth, viewportHeight };
	System.out.println(view[0] + "," + view[1] + "," + view[2] + "," + view[3]);
	double[] px = { -1 };
	double[] py = { -1 };
	double[] pz = { -1 };
	System.out.println(x + "," + y);
	glu.gluUnProject(x, y, 0, model, projection, view, px, py, pz);
	System.out.println(px[0] + "," + py[0] + "," + pz[0]);
}

The values coming out of the projection and modelview matrices are zero. How is this possible, since I am seeing the correct stuff on the screen, obviously the projections are set right?

#2

Are you doing this operation while one of your GLEventListener’s methods is active on the stack? If not, there is no OpenGL context current.

#3

yes, that’s it.

I have to save the matrices from the last render, because they aren’t preserved.

thanks!