I was trying to get Blinn highlights working with my raytracer, and kept
getting ugly artifacts. After trying a bunch of things, I finally
compiled without -O2, and the artifacts went away.
Here's what I mean:
http://syn.cs.pdx.edu/~jsnow/glome/Glome.hs-noartifact.png
http://syn.cs.pdx.edu/~jsnow/glome/Glome.hs-artifact.png
Here's the offending code, run "./make" and "./run" and you should see
the artifacts if your setup is the same as mine. (Requires OpenGL.)
http://syn.cs.pdx.edu/~jsnow/glome/glome.hs-0.2-bug.tar.gz
The artifacts also go away if I use -fvia-C. It doesn't seem to matter
whether I use Floats or Doubles in the rendering code. The artifacts
also show up with -O1. Have I stumbled across a known compiler bug? Or
perhaps an OpenGL bug? (The bug could, of course, be in my code, but
then one might expect to get the same erroneous output every time
regardless of compiler flags.)
To reiterate, I'm using ghc 8.6.2.
thanks,
-jim
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