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Kjell Andersson

OpenGL Floating Point texture not working with GL_RGBA16F_ARB

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I'm having a problem with floating point texture rendering using OpenSceneGraph (which is based on OpenGL). My test setup is the following: * A floating point texture which I manually fill with data in the range of 0.0 - 5.0. * A polygon mapping the texture onto it. * A fragment shader that just reads the value from the texture and outputs it to the screen. I have managed to get it all working nicely when I use a TextureRectangle texture and using the GL_FLOAT_RGBA16_NV format. The problem with this approach is the TextureRectangle usage which forces me to use non normalized texture coordinates (coordinates depend on the size of the texture). Unfortunately I have found out through the web that the GL_FLOAT_RGBA16_NV extension does not support Texture2D which would have been nice for me to use. I have also confirmed that GL_FLOAT_RGBA16_NV with Texture2D does not work, it all just becomes black. My intention was then to switch the texture format to GL_RGBA16F_ARB and use Texture2D. This works to some degree. I get output from my shader, but it seems like the texture input to the shader is wrapped to 0.0 - 1.0. My previous input data that was in the range of 0.0 - 5.0 produced a nice gradient on the screen when using GL_FLOAT_RGBA16_NV but now it has become five stripes each ranging from 0.0 to 1.0 when using GL_RGBA16F_ARB. Somehow it looks like the input texture is not a floating point texture any more but just a normal 8-bit texture even though I specified it to be GL_RGBA16F_ARB. Anyone have any hints on what might be my problem and why I'm not getting any floating point behavior with GL_RGBA16F_ARB? I know that I probably should have pasted some code here but my example is rather big and based on OSG so please ask for the parts that you would like to see that may help in diagnosing the problem. BTW, I'm running on a GeForce 8500 GT.

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ma_hty    100
Half-float texture using ordinary texture target has been supported since Geforce 6. Therefore, you should have no problem to use GL_RGBA16F_ARB as the internal texture format for GL_TEXTURE_2D.

More than likely, you are making some mistakes when you upload the texture to OpenGL.

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Thanks for your input, I have found the problem and solved it now.

The problem was that the size of the floating point texture must be power of two when using GL_RGBA32F_ARB. This was not the case with GL_FLOAT_RGBA16_NV, which supported non-power of two textures.

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