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>
> Why do samples need to store their recursion level?
> *Rays* need to know their recursion level when they are traced, but
that's
> all. This is trivial and it's the exact same thing as the regular
raytracing
> process is doing anyways (for reflections and refractions).
Ah, yes, that makes sense. Hadn't thought about that.
> > And finally, pretrace. As I understand it, pretrace is
> > just another pass over the picture in order to check
> > if enough samples are present at any given spot.
>
> AFAIK pretrace is simply a preprocessing step to get some initial
> samples in the scene, thus speeding up the actual raytracing.
But then there wouldn't be a need for several pretrace
passes, would there? I could do one rather detailed pass
right away, and leave it at that. Since POV-Ray normally
works as efficient as possible (there are a lot of really
good programmers working on it), I came to the conclusion
that since sampling is the main factor for the radiosity
calculations, samples are spread and gathered in several
passes, to only place samples where needed.
--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Warp -
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> No.
> Diffuse affects radiosity. That's why it's called "diffuse
inter-reflection"
> in the first place.
>
> And this is a good thing. You get a lot better results faster using real
> light sources than using high-ambient objects. This is because real light
> sources are very fast to calculate, while getting a good illumination from
> a high-ambient object needs tons and tons of samples.
Hm. So then samples store the actual brightness at a sampled
spot, right? For example, if I light a sphere with a pointlight
somewhere, a sample won't just store the brightness of samples,
but inhibit the brightness of the position as well.
Makes sense, come to think of it.
So photons also affect radiosity?
I've noticed some of that in the later experiments I did AFTER
writing these posts (and their pretty time-consuming, as we
all know about radiosity, right? :-)
I find this topic very interesting, and experimenting with it
is fun. Understanding the main algorithm however is a
very useful addition when trying to tweak the settings. You
know what you're actually affecting, and don't just have to
think like "the smaller, the more detailed". You'll also know
things like "the smaller, the more detailed, but the more
undesired contrast is introduced, e.g. edges..."
--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
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Warp wrote:
>
> [...]
>
> > And finally, pretrace. As I understand it, pretrace is
> > just another pass over the picture in order to check
> > if enough samples are present at any given spot.
>
> AFAIK pretrace is simply a preprocessing step to get some initial
> samples in the scene, thus speeding up the actual raytracing.
No, pretrace does not speed up the render, on the contrary it nearly
always slows it down. Its purpose is to achieve a better distribution of
the radiosity samples taken. How much this affects the results depends on
the settings. Just try it out yourself.
In quite a lot of cases it can be efficient not to use pretrace but you
should know what you are doing since it is more likely to cause problems.
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 17 Jun. 2003 _____./\/^>_*_<^\/\.______
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What kind of settings? I've been experimenting all weekend
now. I've noticed that using pretrace_start .5 and pretrace_end .01
don't make a difference when compared to start and end at .01.
If you know something we don't, then don't hold it back! :-)
--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
>
>
> Warp wrote:
> >
> > [...]
> >
> > > And finally, pretrace. As I understand it, pretrace is
> > > just another pass over the picture in order to check
> > > if enough samples are present at any given spot.
> >
> > AFAIK pretrace is simply a preprocessing step to get some initial
> > samples in the scene, thus speeding up the actual raytracing.
>
> No, pretrace does not speed up the render, on the contrary it nearly
> always slows it down. Its purpose is to achieve a better distribution of
> the radiosity samples taken. How much this affects the results depends on
> the settings. Just try it out yourself.
>
> In quite a lot of cases it can be efficient not to use pretrace but you
> should know what you are doing since it is more likely to cause problems.
>
> Christoph
>
> --
> POV-Ray tutorials, include files, Sim-POV,
> HCR-Edit and more: http://www.tu-bs.de/~y0013390/
> Last updated 17 Jun. 2003 _____./\/^>_*_<^\/\.______
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"Tim Nikias v2.0" wrote:
>
> What kind of settings? I've been experimenting all weekend
> now. I've noticed that using pretrace_start .5 and pretrace_end .01
> don't make a difference when compared to start and end at .01.
>
> If you know something we don't, then don't hold it back! :-)
I have shown samples with the effect of rendering with and without
pretrace before. You will of course have difficulties to spot any
differences when using high quality settings which lead to a very smooth
lighting anyway. For tracing without pretrace set both start and end to
1.
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 17 Jun. 2003 _____./\/^>_*_<^\/\.______
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Hm, can't seem to find any images with the web-interface,
and I haven't got all posts on my HD... :-)
Still, the note about using pretrace start and end of 1
was good, I'll fumble with that. And I didn't realize
that max_trace_level would be that important as well,
but you're right, again, I should've thought about that
earlier. Still, higher max_trace_level isn't needed
desperately, as you've surely noticed with my other
pics... But perhaps I can keep more detailed radiosity
with higher trace_level...
--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
>
>
> "Tim Nikias v2.0" wrote:
> >
> > What kind of settings? I've been experimenting all weekend
> > now. I've noticed that using pretrace_start .5 and pretrace_end .01
> > don't make a difference when compared to start and end at .01.
> >
> > If you know something we don't, then don't hold it back! :-)
>
> I have shown samples with the effect of rendering with and without
> pretrace before. You will of course have difficulties to spot any
> differences when using high quality settings which lead to a very smooth
> lighting anyway. For tracing without pretrace set both start and end to
> 1.
>
> Christoph
>
> --
> POV-Ray tutorials, include files, Sim-POV,
> HCR-Edit and more: http://www.tu-bs.de/~y0013390/
> Last updated 17 Jun. 2003 _____./\/^>_*_<^\/\.______
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Whoot!
Max_Trace_level set to 256, pretrace start and end to 1,
what do I get?
Stack overflow! :-O
And restarting the image after a reboot doesn't help, it'll
gag again after two lines. And all this on 240x180 image...
I'll post a notice on this shortly, but perhaps my insane
settings aren't meant to be... :-)
--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
> Hm, can't seem to find any images with the web-interface,
> and I haven't got all posts on my HD... :-)
>
> Still, the note about using pretrace start and end of 1
> was good, I'll fumble with that. And I didn't realize
> that max_trace_level would be that important as well,
> but you're right, again, I should've thought about that
> earlier. Still, higher max_trace_level isn't needed
> desperately, as you've surely noticed with my other
> pics... But perhaps I can keep more detailed radiosity
> with higher trace_level...
>
>
> --
> Tim Nikias v2.0
> Homepage: http://www.digitaltwilight.de/no_lights
>
>
> >
> >
> > "Tim Nikias v2.0" wrote:
> > >
> > > What kind of settings? I've been experimenting all weekend
> > > now. I've noticed that using pretrace_start .5 and pretrace_end .01
> > > don't make a difference when compared to start and end at .01.
> > >
> > > If you know something we don't, then don't hold it back! :-)
> >
> > I have shown samples with the effect of rendering with and without
> > pretrace before. You will of course have difficulties to spot any
> > differences when using high quality settings which lead to a very smooth
> > lighting anyway. For tracing without pretrace set both start and end to
> > 1.
> >
> > Christoph
> >
> > --
> > POV-Ray tutorials, include files, Sim-POV,
> > HCR-Edit and more: http://www.tu-bs.de/~y0013390/
> > Last updated 17 Jun. 2003 _____./\/^>_*_<^\/\.______
>
>
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> Outgoing mail is certified Virus Free.
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>
>
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Christoph Hormann <chr### [at] gmx de> wrote:
> No, pretrace does not speed up the render, on the contrary it nearly
> always slows it down. Its purpose is to achieve a better distribution of
> the radiosity samples taken.
You are actually contradicting yourself.
Why do you want a better distribution of samples? Because that way you
get a better result with fewer samples, that is, a faster rendering.
Without the pretrace step you need a lot more samples to get a good result,
thus resulting in a slower rendering.
--
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}// - Warp -
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Tim Nikias v2.0 <tim### [at] gmxde> wrote:
> Max_Trace_level set to 256, pretrace start and end to 1,
> what do I get?
> Stack overflow! :-O
Why is it a surprise?
--
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -
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It isn't, but if I'd expected it, I wouldn't have attempted
it, right?
Anyways, on a sidepath: aren't there possibilities to circumvent
this stack overflow, or is this out of POV-Ray's hands?
--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
> > Max_Trace_level set to 256, pretrace start and end to 1,
> > what do I get?
>
> > Stack overflow! :-O
>
> Why is it a surprise?
>
> --
> #macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb
x]
> [1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
> -1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// -
Warp -
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