Chapter 25. Fast Filter-Width Estimates with Texture Maps
Matt Pharr NVIDIA
This chapter describes a technique for computing an approximation to the derivative of arbitrary quantities in fragment programs. This technique loads special values into each level of a texture mipmap and uses the texture-mapping hardware in an unusual way to cause it to return the results of a derivative computation, giving an indication of how quickly the quantity is changing from pixel to pixel on the screen. Computing derivatives such as these is a critical operation to perform in shaders that compute procedural patterns, because it allows them to perform antialiasing on the patterns they generate by prefiltering them to remove detail that can’t be represented by the ...
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