See the attached image. Three columns left to right with images in the
first two rows rendered with 1, 2 and 4 threads. The bottom row is an 8x
multiple of the image pixel differences.
Using the subsurface.pov scene shipped with POV-Ray and the command:
povray -j -d -c -p +wt4 subsurface.pov
changing only the number of threads each time. Ubuntu 16.04. Master
branch as of commit 9c67174 Sat Jan 6 11:58:42 2018 +0100 "Merge branch
I've not seen any differences between single thread renders in a half
dozen runs. Always some difference in multi-thread runs, but the
signature is interesting in that POV-Ray seems to match on some of the
sub blocks. More often ones at the top match, but I've seen render-image
pairs with matching blocks better than half way down into the image.
I know the SSLT code is not in it's final form. Is this a known issue or
should we open up a github issue for it?
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