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Am 07.06.2014 15:00, schrieb Sean Day:
> Here is the problem reproduced by stacking 3 spheres.
Looks good as a minimal test scene; can you file a bugreport on
bugs.povray.org with the scene file & probe attached?
Thanks a lot for your help!
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The image looks like radiosity with a high recursion limit.
-Nekar Xenos
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Nekar Xenos wrote:
> The image looks like radiosity with a high recursion limit.
>
> -Nekar Xenos
The image had recursion limit of 3, I have run a render with this set to
2 but still have the same issue.
Sean
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clipka wrote:
> Am 07.06.2014 15:00, schrieb Sean Day:
>
>> Here is the problem reproduced by stacking 3 spheres.
>
> Looks good as a minimal test scene; can you file a bugreport on
> bugs.povray.org with the scene file & probe attached?
>
> Thanks a lot for your help!
>
Hi Clipka,
Bug report filed with the files required to reproduce the issue. I found
I can reproduce it using the default radiosity settings from the insert
menu and without AA the scene renders with the issue in a single pass (I
was using load/save for radiosity) in about 16 seconds on my PC so have
uploaded that example as I am guessing a faster render speed helps in
debugging these things.
If you need anything else let me know and many thanks for your prompt
assistance and the effort you and the whole POV Team put into Povray as
always.
Sean
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clipka wrote:
> Am 07.06.2014 15:00, schrieb Sean Day:
>
>> Here is the problem reproduced by stacking 3 spheres.
>
> Looks good as a minimal test scene; can you file a bugreport on
> bugs.povray.org with the scene file & probe attached?
>
> Thanks a lot for your help!
>
Hi,
I just ran a test without the radiosity block and find I can still
reproduce the issue. The scene still has the subsurface settings and HDR
lighting but without radiosity and the effect is still present. The
additional benefit is this renders in 2 seconds so is quick to test.
Sean
Post a reply to this message
Attachments:
Download 'test.png' (347 KB)
Preview of image 'test.png'
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Sean Day wrote:
> clipka wrote:
>> Am 07.06.2014 15:00, schrieb Sean Day:
>>
>>> Here is the problem reproduced by stacking 3 spheres.
>>
>> Looks good as a minimal test scene; can you file a bugreport on
>> bugs.povray.org with the scene file & probe attached?
>>
>> Thanks a lot for your help!
>>
>
> Hi,
>
> I just ran a test without the radiosity block and find I can still
> reproduce the issue. The scene still has the subsurface settings and HDR
> lighting but without radiosity and the effect is still present. The
> additional benefit is this renders in 2 seconds so is quick to test.
>
>
> Sean
I decided to look into this a bit further as it seems very odd behaviour
(considering I have used SSLT before and not had issues). It seems the
problem is to do with the texture_map and using subsurface. Will update
the bug report and upload a new scene file.
Sean
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> Any effect that can be achieved by tweaking mm_per_unit can also be
> achieved by tweaking the materials' translucency.
This is great piece of information. should'nt it be added to the documentation,
right after "The translucency color, which can alternatively be a float,
determines the strength of the subsurface light transport effect."
So that people don't break the physical accuracy of their whole scenes whenever
tweaking to compensate isolated anomalies on a per object or per texture basis?
(I don't have editing rights on that page of the documentation wiki)
As a sidenote, this could help me to better export Blender's SSS "scale"
parameter wich is per material also, as a factor of the pov translucency color I
guess.
Sorry for going off topic and thanks for your constant bug hunting.
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On 08/25/2014 04:59 AM, Mr wrote:
>
>> Any effect that can be achieved by tweaking mm_per_unit can also be
>> achieved by tweaking the materials' translucency.
>
> This is great piece of information. should'nt it be added to the documentation,
> right after "The translucency color, which can alternatively be a float,
> determines the strength of the subsurface light transport effect."
>
> So that people don't break the physical accuracy of their whole scenes whenever
> tweaking to compensate isolated anomalies on a per object or per texture basis?
>
> (I don't have editing rights on that page of the documentation wiki)
better?
http://wiki.povray.org/content/Reference:Finish#Subsurface_Light_Transport
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James Holsenback <nom### [at] none com> wrote:
> On 08/25/2014 04:59 AM, Mr wrote:
> >
> >> Any effect that can be achieved by tweaking mm_per_unit can also be
> >> achieved by tweaking the materials' translucency.
> >
> > This is great piece of information. should'nt it be added to the documentation,
> > right after "The translucency color, which can alternatively be a float,
> > determines the strength of the subsurface light transport effect."
> >
> > So that people don't break the physical accuracy of their whole scenes whenever
> > tweaking to compensate isolated anomalies on a per object or per texture basis?
> >
> > (I don't have editing rights on that page of the documentation wiki)
>
> better?
> http://wiki.povray.org/content/Reference:Finish#Subsurface_Light_Transport
Thank you, yes, it's enough for me, it does give the clue that was missing about
which parameter to tweak to keep physically correct globals and still finetune
locally
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Am 02.06.2014 um 19:07 schrieb s.day:
> Hi,
>
> Thought I was getting used to using SSLT but I think I have something wrong
> somewhere as my poor ant looks like he is about to spontaneously combust..
>
> I am probably doing something stupid so feel free to point it out, I have had a
> few attempts at adjusting the SSLT settings but I seem to go from not much
> effect to burning him, any ideas/tips would be really appreciated (the most
> appreciated thing would be faster SSLT though ;-)
Hi Sean,
sorry I never got around to analyzing this earlier.
I /think/ I have an idea what may be going on here.
The key to it all is probably that you have interpolation between two
textures involved, with significantly different pigment and subsurface
translucency settings.
Now in subsurface scattering textures the pigment does not do exactly
the same as in classic textures: It does /not/ directly govern the
surface's colour. Instead, from the pigment and the translucency POV-Ray
computes another set of parameters, called the scattering and absorption
coefficients. These govern how much light entering the object is subject
to being scattered and to being entirely absorbed, respectively.
The translation from pigment and translucency to these internal
parameters is chosen in such a way that for a sufficiently large slab
the resulting surface colour effectively /does/ match the pigment
colour. However, as the object gets smaller -- or as you increase the
translucency setting -- the effect of both scattering and absorption
become less and less pronounced. In the end, the object effectively gets
transparent.
Now one more thing to note here is that if the subsurface scattering
parameters are chosen in such a way that absorption is much stronger
than scattering, small objects will appear transparent but tinted.
Now your image has two different textures involved: One of them has
comparatively low transparency; this is the texture that governs the
overall look of the material, which gives it a quite credible opaque
look in general.
The other texture, however, has settings that result in low scattering
but high absorption. This means two things: First, the low scattering
would give the object a glass-like appearance. Second, the high
absorption means that it would be a very dark glass, through which we
can see only exceptionally bright stuff. Which in turn means that this
texture does not have any effect on the overall appearance of the object
(except that interpolating it in means to dim the overall brightness) --
/except/ where the very bright sky probe is visible, which due to the
high refractive index and the convex shape is at the bottom of the object.
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