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Sorry to have to bother you again with this clumsy model of the sceptre of
Catherine the Great. But we had some discussions about resuming a rendering in
the beta-test section (a thread from Chaanakya with the subject: Resuming
renders in 3.7 RC6 is confusing at best, broken at worst) and Alain wasn't sure
about the behaviour of POV in scenes using photons. Having this image handy with
reasonable rendering times even on an older dual core pentium, I tried resuming
it after having saved the photon map. I tried two different versions of the
picture. One with a simple sky_sphere (I think it is the one from the examples
of the tutorial):
#declare Himmel = sky_sphere {
pigment {
gradient y
color_map {
[ 0.5 color CornflowerBlue ]
[ 1.0 color MidnightBlue ]
}
scale 2
translate -1
}
}
and the second one with my first attempt with (Pseudo?-) HDRI lighting:
#declare kitchen=sphere {<0, 1, 0>, 650
texture {
pigment {
image_map {
hdr "thekitchen.hdr"
once
interpolate 2
map_type 1
}
rotate <0, -30-135+(16*15), 0> // window is at -30 behind the camera
// attuned to the light source
scale 1
}
finish { emission Bright/2 diffuse 0 }
}
hollow
photons { refraction on reflection on }
}
It is very likely that I misunderstood somehing here. At the moment I'm not
quiete sure where I've stolen the code, but I think it's Jaime's Pseudo-HDRI
approach. But the main fact with this issue here is that I didn't change the
lighting between the resumes. In both examples I stopped and resumed the
rendering at the first block at the shaft and a second time in the near of the
globus cruciger. The first picture here with the simple sky_sphere shows no
flaws but the second one with Jaime's thekitchen.hdr sows strange changes in
color at the points I stopped and resumed the rendering. Has anyone an idea?
Feel free for criticism.
Best regards,
Michael
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Attachments:
Download 'sceptre continue artifact2.jpg' (53 KB)
Preview of image 'sceptre continue artifact2.jpg'
![sceptre continue artifact2.jpg](/povray.binaries.images/attachment/%3Cweb.50366087f6191b69535f0ed20%40news.povray.org%3E/sceptre%20continue%20artifact2.jpg?ttop=443866&toff=1750&preview=1)
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Sorry, mixed up the pictures. Here is the one without flaws and the sky_sphere:
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Attachments:
Download 'sceptre continue artifact3.jpg' (47 KB)
Preview of image 'sceptre continue artifact3.jpg'
![sceptre continue artifact3.jpg](/povray.binaries.images/attachment/%3Cweb.5036626f1042b2d5535f0ed20%40news.povray.org%3E/sceptre%20continue%20artifact3.jpg?ttop=443866&toff=1750&preview=1)
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On 23/08/12 18:55, MichaelJF wrote:
> It is very likely that I misunderstood somehing here. At the moment
> I'm not quiete sure where I've stolen the code, but I think it's
> Jaime's Pseudo-HDRI approach.
No, that's just regular HDRI (my pseudo-HDRI was a trick wich didin0t
use hdr files, just emulated, badly, the dynamic range).
> But the main fact with this issue here
> is that I didn't change the lighting between the resumes. In both
> examples I stopped and resumed the rendering at the first block at
> the shaft and a second time in the near of the globus cruciger. The
> first picture here with the simple sky_sphere shows no flaws but the
> second one with Jaime's thekitchen.hdr sows strange changes in color
> at the points I stopped and resumed the rendering. Has anyone an
> idea? Feel free for criticism.
>
Here you have just radiosity artifacts, which I suppose come from my
thekitchen.hdr (that's why the other image didn't show them). The
reason must be that as the artifacts (circle-like spots) are so largue,
the partial pretrace can't catch them entirely... or something like
that. But the photons seems to have come out OK on the continued renders...
--
Jaime
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Jaime Vives Piqueres <jai### [at] ignorancia org> wrote:
> Here you have just radiosity artifacts, which I suppose come from my
> thekitchen.hdr (that's why the other image didn't show them). The
> reason must be that as the artifacts (circle-like spots) are so largue,
> the partial pretrace can't catch them entirely... or something like
> that.
Many thanks! Yes this solves this riddle. It's the first time I encounter
radiosity artifacts - usually I use predefined settings from rad_def.inc and not
the defaults like here. Even a bit strange in place and shape - the kitchen
window is to the left at an angle of 105 degrees in relation to the camera
position and look at - I mistook them as reflections from the facets. (A little
bit too much brain aerobics to jugde where a rectangular bright area projected
to a sphere will end up with so many reflecting faces...) I first tried IndoorLQ
today which produces the same artifacts but is not very far away from the
defaults. But setting count to 400 nearly eliminated the artifacts. Since the
stone didn't improve much with this settings I will not bother you with a fourth
image of it. Hm, since I will have a POV-HDRI-image I will give your patio a
try...
> But the photons seems to have come out OK on the continued renders...
>
> --
> Jaime
We talked about intended resumes and so I proposed to save the photon map in the
first rendering and load it with the resumed ones. Unlike radiosity maps in the
past photon maps are saved immediately after the calculation, so you can stop an
rendering after the photon calculations and then resume it loading the
precalculated photons. That is why the photons are not affected by the resumes.
Best regards,
Michael
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