clipka nous illumina en ce 2008-12-29 01:06 -->
> .... no, don't panic - I'll keep working on the radiosity as such.
> 
> But I definitely give up trying to get 3.7 radiosity exactly reproduce 3.6
> functionality.
> 
> I have dug through the code multiple times, discovered several discrepancies
> between 3.7.beta.29 and 3.6 causing differences in output, identified several
> others that didn't seem to make a change, stumbled across some old flaws I
> intend to fix, and for sentimentality's sake even re-introduced one flaw that
> wasn't there in 3.7 due to slight differences in the software architecture
> (don't worry, I'll take it back out again :)), all to try and re-create the
> same output as 3.6.
> 
> I have come to the point now that plowing through the whole code over and over
> again has ceased to surface any further discrepancies. And I definitely do
> *not* intend to go through *all* the POV code and revert it back to exact 3.6
> functionality (and after all, maybe some modifications may actually be in there
> for good already :)).
> 
> So I conclude that any residual differences must be rooted in changes to some
> other parts of POV-ray code: Media, photons, area lights, multi-layered
> textures - whatever.
> 
> The remaining discrepancies with the scenes I used for testing are:
> 
> - minor difference in brightness on one of the cube's corners in "cornell.pov"
> 
> - differences in brightness on the object-mapped portion of the pill containers
> in "object_pattern.pov"; tests strongly indicate that these are caused by the
> object-mapped texture, not the radiosity per se
> 
> - differences in brightness of various shadowed parts in "balcony.pov"; tests
> were not conclusive about the true origin of the differences.
> 
> - differences in a self-made scene designed to provoke black-splotch artifacts,
> probably related to differences in trace-level counting (note that the
> black-splotch artifacts will be eliminated anyway)
> 
> - differences in another self-made scene (the "Claustrophobia" shot), probably
> related to black-splotch artifacts and therefore of similar origin
> 
> - totally different results with a self-made, very demanding radiosity scene
> which hasn't actually worked as intended with any POV version at all - again,
> possibly due to differences in trace-level counting.
> 
> 
> From what I see, none of these differences do any general harm to the picture
> (except for the pill-container issus); the pictures simply look different, and
> I find it hard to judge which version is more realistic. I'd usually prefer the
> new output.
> 
> 
> Aside from visual differences, the most notable ones are differences in speed.
> Compared with the MegaPOV 64-bit Linux binaries, some scenes take a bit longer
> with the current code, some render a bit faster. It seems that overall,
> radiosity-only scenes benefit, while non-radiosity scenes all render slightly
> slower, and mixed scenes are somewhat indecisive. This is all pure CPU time
> though, and real-time speed benefits a lot on multicore systems.
> 
> 
> If it was my call, I'd say let's just fix the black-splotch thing, get a few
> details more towards the original Ward paper, make a new beta of it, and see
> what reports come in.
> 
> 
> Main remaining issues:
> 
> - Loading/saving of radiosity samples simply doesn't work yet
> 
> - Radiosity shots are currently not 100% reproduci... duca... um... I mean, you
> can't reproduce the 100% same result on every run.
> 
> 
> 
 From version 3.6 for any radiosity scene: (also for photons)
"Cleanup Parse Warning: This rendering uses the following experimental 
feature(s): radiosity. The desing and implementation of these features is likely 
to change in future version of POV-Ray. Full backward compatibility with the 
current implementation is NOT guarenteed."

This tells me that, in future versions, the way to handle radiosity may change.

This also tels me that the result may change from version to version, even if 
the parameters do stay the same.

So, after seeing that warning, if any scene using radiosity, or photons, don't 
give the same final image between 3.6 end 3.7, i'd say that it's NORMAL and 
EXPECTED.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you have ever said "I don't need 
no steenking modellers!!!"
Stephan Ahonen

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