[Radiance-general] Deterministic calculations with Radiance

[Randolph Fritz]

Perhaps with carefully chosen models and parameters?  I would expect
it to be possible to compare well-chosen test scenes with appropriate
parameters between versions, as well as with actual physical models,
so long as a random number generator of reasonable quality is used.
Seems to me such combinations of scenes and parameters would be
excellent testing and debugging tools.  (Having the physical models
for comparison would be *most* excellent, but let us not assume there
is a budget for them!)

Randolph, still drowning here in Portland, Oregon.

On Fri, Feb 04, 2005 at 10:04:19AM -0800, Greg Ward wrote:
> Perhaps.  If the pixel sampling rate were high enough (e.g. pfilt -x 
> /10 -y /10), you might get some stability.  At that point, you 
> shouldn't have to worry about the random number generator.  However, 
> the MC ray tracing literature is full of examples where even 200+ 
> samples/pixel is not enough to avoid large variance in some regions, 
> and the same can be true for Radiance, especially with specular 
> samples.
> 
> -G
> 
> >From: Randolph Fritz <randolph at panix.com>
> >Date: February 4, 2005 9:48:23 AM PST
> >
> >On Thu, Feb 03, 2005 at 11:09:33PM -0800, Greg Ward wrote:
> >>Yes, but what's the point?  A change in the compiler or a minor
> >>alteration of the code that makes no difference to the results but
> >>affects the order in which rays are traced will completely defeat such
> >>a test.  How can we do regression testing with something that 
> >>unstable?
> >
> >Could we perhaps "blur" the two light maps before comparing them?
> >
> >Randolph
> 
> 
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