On Fri, Mar 28, 2008 at 6:28 AM, Jim Snow <[EMAIL PROTECTED]> wrote: > 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.
You probably mean 6.8.2. Works for me in all cases. % uname -a Linux madhatter 2.6.22-gentoo-r8 #6 PREEMPT Sat Oct 20 04:19:22 GMT 2007 i686 AMD Turion(tm) 64 Mobile Technology ML-40 AuthenticAMD GNU/Linux % ghc --version The Glorious Glasgow Haskell Compilation System, version 6.8.2 Looks to me like Glome is depending on some very fine details of floating point arithmetic. Luke _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
