Dual Filtering (or Dual Kawase) is an approximation of Gaussian Blur that can reach much higher Blur sizes at a much lower cost. However it is locked to a 2^n size, which means that currently it isn't possible to use it for blur sizes like 19, 24 and 31.
The Blur works by using the linear sampling of a GPU, combined with down- and upsampling and carefully placed sampling points. This means that there is no need for a linear optimized version of this Blur.
Related: #45, #6
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