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OpenGL gluUnProject (...) help needed!!

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Hy guys, I'm developing a c# app, and I've spent a lot of time serching for correct way to map 2d coord of mouse to 3d world coords of the ogl scene, particullary I want to select some point in my scene. I have used this code snippet: public static Point3d GetOGLCoords(int x, int y) { int[] viewport = new int[4]; double[] modelview = new double[16]; double[] projection = new double[16]; float winX, winY, winZ; double posX, posY, posZ; GL.glGetDoublev(GL.GL_MODELVIEW_MATRIX, modelview); GL.glGetDoublev(GL.GL_PROJECTION_MATRIX, projection); GL.glGetIntegerv(GL.GL_VIEWPORT, viewport); winX = (float)x; winY = (float)viewport[3] - (float)y; GL.glReadPixels(x, (int)winY, 1, 1, GL.GL_DEPTH_COMPONENT, GL.GL_FLOAT, out winZ); GLU.gluUnProject(winX, winY, winZ, modelview, projection, viewport, out posX, out posY, out posZ); return new Point3d(posX, posY, posZ); } (from NeHe article #13) where "GL" and "GLU" are related glu and opengl wrapping classes. In my code also I have implemented a simple camera based upon translate and rotate func and gluLookAt(...). my draw func are: protected override void OnPaint(PaintEventArgs e) { if (DC == 0 || RC == 0) return; WGL.wglMakeCurrent(DC, RC); GL.glLoadIdentity(); GL.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT); GL.glClearColor(0.0f, 0.0f, 0.0f, 0.0f); GL.glMatrixMode(GL.GL_PROJECTION); GL.glLoadIdentity(); GL.glOrtho(...); GL.glMatrixMode(GL.GL_MODELVIEW); GL.glLoadIdentity(); GLU.gluLookAt(...); } I have also drawed the point result of the GetOpenGLCoords this is the result: Free Image Hosting at www.ImageShack.us The code seems to work except that the mouse arrow is not at the same position of drawed points Where is my mistake? Thankyou a lot in advance. Mirko (buzzy84)

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