On 9/24/20 2:31 PM, Ash Holsenback wrote:
> image is a comparison of the tracetask.cpp fix that bill ask us to
> try... working with 3.8.0-alpha.10064268. saved aside before and after
> images and did a compare:
>
>
Thanks.
Did you happen to capture the CPU times for the two renders?
Did you use -j, +ss and +wt1 on both renders?
Were you using area lights?
---
Your compare image rekindles thinking about color / intensity and AA
approaches; Rendering large and scaling down vs AA or in combination.
The aa +ag flag/setting. A big pile of subtle trade-offs.
Where the previous am3 implementation was sort of working / stopping on
the threshold test (and not the sample limit) there was too a probable
color result change due the uberpov to v3.8 threshold test change.
Further, that test could get done after a conversion to grey scale
(luminosity) instead - which might work better for what it's trying to
do at the expense of CPU time in the threshold test. I'm not sure what
impact to the render due sampling depth such a change would have.
All said. Let me play devil's advocate for a bit with anti-aliasing
methods. I took the biscuit scene and played with am3 until I thought it
was rendering the the ridges on the biscuits well.
Now I do these three renders with my current v3.8 based povr:
--- am3
povr2 biscuit.pov +am3 +a0.015 +ac0.9 +r5 +w450 +h450
438.641
Pixels: 202500 Samples: 37917505 Smpls/Pxl: 187.25
--- am2
povr2 biscuit.pov +am2 +a0.015 +r5 +w450 +h450
413.702
Pixels: 216225 Samples: 48143226 Smpls/Pxl: 222.65
--- am1
povr2 biscuit.pov +am1 +a0.0 +r9 +w450 +h450
133.385
Pixels: 216000 Samples: 16402500 Smpls/Pxl: 75.94
Attached is an image comparing am1 to am3 in the top row; multiplying
the differences by 5. In the bottom row comparing am2 to am3; again
multiplying differences by 5.
What does it all mean? Lots of things I guess. I am comforted that the
updated scenes match well for color and intensity across all three
methods with the am3 fix.
I also tried v3.8 at commit 74b3ebe for grins expecting a really long
run time (maybe with a color shift to explain yours). Instead I got:
p380 biscuit_v38.pov +am3 +a0.015 +ac0.9 +r5 +w450 +h450
408.578s (The posted fix costs time)
Pixels: 202500 Samples: 0 Smpls/Pxl: 0.00
I didn't use +ss but still the images compare well fixed to non-fixed.
What this confirms is the pre-fix code was 'sometimes' working (no
domain errors).
I looked at the code at commit 551338 (your release) and it matches that
at 74b3ebe - also not an explanation for your color difference.
Extra credit to those of you asking why only am3 gets the image pixel
count right...
Bill P.
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