Using compute shaders for reading/writing to textures and FBO

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To see how to use compute shaders for pixelwise working with images, see openFrameworks example examples/gl/computeShaderTextureExample.

Also, I modified this example on using FBO (ofFbo) instead textures (ofTexture).
As I checked, that FBO's textures (fbo.getTextureReference) also works with shader for reading and writing.

So, FBOs can be used in compute shaders as an universal "drawable" textures: it's possible to read and write to them pixelwise, and it's possible to draw in them using OpenGL rendering (fbo.begin()...fbo.end())


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