# OpenGL [Tao, OpenGL, C#] trying to get the world mouse position

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Hi, I posted this topic on the Tao Framework forum in this topic, but I didn't get much replies. So I'll ask here too.
Quote:
 I'm trying to get the world mouse position, but it doesn't work. I always get something really close to zero [-1.1, 1.1] if my camera is in the center of the screen. and when I move my camera, well, it's close to the camera. Always in the middle of the screen. In my previous project, I did something really similar to this but with Tao 1.3.0-1 Now I'm using Tao 2.0 RC1 with C# 2.0 for some reason in: Gl.glReadPixels((int)winX, (int)winY, 1, 1, Gl.GL_DEPTH_COMPONENT, Gl.GL_FLOAT, (object)winZ); winZ is always equal to 0.0. Is there a bug in this function? It's PROBABLY my camera that does weird stuff??? I don't know, it used to work... I need some help download my project http://iarus.awardspace.com/proto1.03.html 339kB it's really small, you should find the error rapidly the error could be in : - OpenGLForm class : - ScreenToWorldCoordinates(int x, int y) - ReSizeGLScene(int width, int height) - Camera class : - ApplyCameraTransform() Maybe elsewhere, but I don't think so. Thank's
press F1 to see the help screen, it's in French, I know, but just press buttons and you'll see what they do

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Hmm, just an idea but I would try moving your Input call to before your SwapBuffer call and see if that does anything for your ReadPixel call.

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I'm pretty sure you need to get the viewport and then for the winY value use

viewport[1] - winY

Its because the bottom left is the origin of the screen in OpenGL. And your winY value is probably assuming the origin is in the top left.

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I got tired of waiting for someone else to do the job, so I fixed it my self

I don't use the readPixel + UnProject methods, just some simple maths plus some weird fix that I don't really understand... I guess things are not linear or something like that

      /// <summary>      /// THE VIEWPORT __MUST__ BE EQUALS TO [0, 0, WINDOW.CLIENTSIZE.WIDTH, WINDOW.CLIENTSIZE.HEIGHT]      /// or else... boom!!!      /// </summary>      /// <param name="x">MousePosition.x</param>      /// <param name="y">MousePosition.y</param>      /// <returns>world mouse position</returns>      public Vector2 ScreenToWorldCoordinates(int x, int y)      {         int[] viewport = new int[4];         Gl.glGetIntegerv(Gl.GL_VIEWPORT, viewport);         y = viewport[3] - y;                  float halfVpHeight = viewport[3] / 2f;         float halfVpWidth = viewport[2] / 2f;         float halfFovVert = camera.FOV / 2f;         float halfFovHoriz = halfFovVert * viewport[2] / (float)viewport[3];         //camera.Z is how far the camera is pushed back         //Why I "fix" the Z? to "scale" the results         //Where does the Z^1.524 come from? No idea, trial and error, it gives OK results...         float zFixed = (float)Math.Pow(camera.Z, 1.524);                                                                                                                  //180 * PI         float worldY = camera.Position.y + (float)Math.Sin((((y - halfVpHeight) / halfVpHeight) * halfFovVert) / 565.4866776f) * zFixed;         float worldX = camera.Position.x + (float)Math.Sin((((x - halfVpWidth) / halfVpWidth) * halfFovHoriz) / 565.4866776f) * zFixed;         return new Vector2(worldX, worldY);      }

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