On 01/04/2016 04:36 AM, clipka wrote:
> Am 04.01.2016 um 10:06 schrieb Norbert Kern:
>> clipka <ano### [at] anonymousorg> wrote:
>>
>>> For some reason, POV-Ray 3.7 seems to grind to a halt -- possibly
>>> because its handling of max_trace_level with regards to fully
>>> transparent surfaces is different.
>>
>> This explains many issues I've with old scenes.
>> Please can you explain it a bit more in depth?
>
> Transparency without refraction doesn't count towards the
> max_trace_level anymore.
>
> I begin to wonder whether that was a bad idea though.
>
(I've been looking at old blob problems with the blob.cpp code I 
patched, so jumping on thread as this too is a blob scene.)

In addition to performance the image results are also different 3.6 to 
3.7. See: PrfrmDiff36to37.jpg in povray.binaries.images.

--------------------------- (Left image in PrfrmDiff36to37.jpg)
povray3.6 no AA
Rays:          444152349   Saved:          70439961   Max Level: 12/12
(298 seconds)
--------------------------- (Center image in PrfrmDiff36to37.jpg)
povray3.7StableBlobPatched no AA
Rays:        13058131391   Saved:        2261510214   Max Level: 12/12
15200.163 CPU-seconds total
--------------------------- (Right image in PrfrmDiff36to37.jpg)
povray3.7StableBlobPatched no AA. All reflections*0.5
Rays:          279110752   Saved:         136920694   Max Level: 10/12
370.471 CPU-seconds total
---------------------------

The right result I believe is evidence for the 3.6->3.7 transmission 
change Christoph suspects.

Note that reflections >=1 are being used with transmission ==1 in the 
original code so we are getting light amplification on reflection.

---

I also made 3.6 and 3.7 runs with conserve_energy on and performance & 
results were similar though not identical. See: conserve_energy.jpg in 
povray.binaries.images.

--------------------------- (conserve_energy.jpg)
povray3.7StableBlobPatched no AA conserve_energy in finish blocks
Rays:        13058131391   Saved:        2261510214   Max Level: 12/12
15200.163 CPU-seconds total
---------------------------

The conserve energy result is likely too evidence for the 3.6->3.7 
transmission change.

To echo what Norbert suspects, I too have seen different results 
3.6->3.7 where previous code uses values >1.0 in the finish block 
control elements. I've never quite sorted things enough to really 
understand it. Now thinking the transmission change is a part of it. My 
fix is to rework for ranges<=1 in the finish block.

Question: I think the conserve_energy helps & turns the background dark 
because we cannot both reflect at >=1 and transmit at >=1. In other 
words, we don't see through the r=30 sphere to the plane with the 
granite pigment. Is this understanding correct?

Bill P.

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