OpenImageIO/oiio — pull request #229 by lgritz (2012-02-18 08:50:32+00:00)
Title: More efficient subpixel filtering

Alternate proposal to https://github.com/OpenImageIO/oiio/pull/196
I think this is equivalent but is a bit less mysterious.
The idea here is that the filtering ellipse can be so thin that the minorlength is significantly subpixel sized, even at the finest MIP level, which will lead to a high nsamples pointlessly -- the samples will be too close together. So this detects that case and clamps minorlength to be at least 1/2 texel wide, and readjusts aspect, which in turn will end up leading to a sane number of samples along the ellipse axis.