[Radiance-general] strange behaviour, may be only radiance or ma cosx?

[Greg Ward]

Dear Radiance Alpha Testers:

Make sure you download the new version of srcobstr.c I just checked in  
-- 2.10, because I introduced an even worse bug in my last fix that  
caused an internal error for distant sources.

-Greg

> From: Greg Ward <gward at lmi.net>
> Date: September 10, 2004 9:13:30 AM PDT
>
> Saved you?  As the creator of the shadow cache, which was the source  
> of this error, I think I was the spoiler in this case....
>
> It was a subtle bug, though -- not the usual stupid one.  Because of  
> the way the shadow cache works, it only tests for intersection with a  
> suspected blocker, assuming that any intersection with the potential  
> blocker implies that it is in the way of the source.  In the case of a  
> sphere with a source inside, a ray directed towards the source will  
> also intersect the opposite side of the sphere, but not after passing  
> through the source -- a condition I wasn't checking for (until now).   
> The same thing would have happened with a cone or cylinder with a  
> source inside, though I obviously never tested these cases either, as  
> I hadn't noticed the problem before, and I'm sure it was there from  
> the start.
>
> I had assumed that since I was working on the shadow cache earlier  
> this week, that I had made some silly mistake in my changes, which is  
> what threw me off in my debugging.  I wish I had a decent debugging  
> environment -- what I have is the old hacker's fallback:  fprintf().
>
> -Greg
>
> P.S.  You can download the latest check-in of srcobstr.c from:
>
> 	http://www.radiance-online.org/cgi-bin/viewcvs.cgi/ray/src/rt/ 
> srcobstr.c
>
> It will be included in tomorrow's HEAD release.