Warp wrote:

> That image is the result of 30 minutes of
> rendering in my computer (a virtually grainless result would have taken
> days).

Or a GPU implementation...

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Warp escreveu:
> nemesis <nam### [at] gmailcom> wrote:
>>>>> http://warp.povusers.org/images/smallpt.jpg
>>>> did you make it coincident with the surface?
>>>   I have hard time deciding whether that was humorous or a serious question.
> 
>> serious.  Did you put right where the left sphere surface would hit?
> 
>   Unbiased monte-carlo rendering sends rays in a random fashion. It starts
> extremely grainy, but the graininess gets reduced over time as the number
> of samples gets increased. That image is the result of 30 minutes of
> rendering in my computer (a virtually grainless result would have taken
> days).

I know.  I'm concerned about that huge circular, pure white light 
artifact next to the wall, aren't you?  Looks like a bug, which is why I 
thought you posted the picture.

-- 
a game sig: http://tinyurl.com/d3rxz9

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Warp escreveu:
> That image is the result of 30 minutes of
> rendering in my computer (a virtually grainless result would have taken
> days).

and no, you don't need days to get grainless result anymore than what 
you would need with povray and area lights and radiosity.  Specially for 
such a simple scene.  Though a pure simplified path tracer is very slow.

-- 
a game sig: http://tinyurl.com/d3rxz9

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nemesis wrote:

> I know.  I'm concerned about that huge circular, pure white light 
> artifact next to the wall, aren't you?  Looks like a bug, which is why I 
> thought you posted the picture.

It's a light source. It's what illuminates the rest of the scene.

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nemesis wrote:

> and no, you don't need days to get grainless result anymore than what 
> you would need with povray and area lights and radiosity.

Er, no, POV-Ray uses an utterly different algorithm for this. In 
particular, it uses a shedload of statistical tests to reduce the number 
of samples taken. *This* program just endlessly resamples everything 
until all the randomness averages out; this is orders of magnitude slower.

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Invisible escreveu:
> nemesis wrote:
> 
>> I know.  I'm concerned about that huge circular, pure white light 
>> artifact next to the wall, aren't you?  Looks like a bug, which is why 
>> I thought you posted the picture.
> 
> It's a light source. It's what illuminates the rest of the scene.

oh good.  I thought it was a ghost.  silly me.


really, this topic went surreal by now...

-- 
a game sig: http://tinyurl.com/d3rxz9

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Invisible escreveu:
> nemesis wrote:
> 
>> and no, you don't need days to get grainless result anymore than what 
>> you would need with povray and area lights and radiosity.
> 
> Er, no, POV-Ray uses an utterly different algorithm for this. In 
> particular, it uses a shedload of statistical tests to reduce the number 
> of samples taken.

Povray still shows a lot of graininess for insuficient samples.  Lots of 
samples still get very slow rendering.

> *This* program just endlessly resamples everything 
> until all the randomness averages out; this is orders of magnitude slower.

But that's for a pure simple path tracer.  There are far smarter 
samplers out there, most notably Metropolis Light Transport, that are 
able to converge the image much faster.

-- 
a game sig: http://tinyurl.com/d3rxz9

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>>> and no, you don't need days to get grainless result anymore than what 
>>> you would need with povray and area lights and radiosity.
>>
>> Er, no, POV-Ray uses an utterly different algorithm for this. In 
>> particular, it uses a shedload of statistical tests to reduce the 
>> number of samples taken.
> 
> Povray still shows a lot of graininess for insuficient samples.  Lots of 
> samples still get very slow rendering.

It doesn't show graininess, it shows patchiness. Because it reuses a 
single sample for multiple pixels. That means it needs to take about one 
millionth of the number of samples that this program takes. Hence, a 
*slight* speed difference.

>> *This* program just endlessly resamples everything until all the 
>> randomness averages out; this is orders of magnitude slower.
> 
> But that's for a pure simple path tracer.  There are far smarter 
> samplers out there, most notably Metropolis Light Transport, that are 
> able to converge the image much faster.

...which still has nothing to do with *this* program.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Orchid XP v8 escreveu:
>>>> and no, you don't need days to get grainless result anymore than 
>>>> what you would need with povray and area lights and radiosity.
>>>
>>> Er, no, POV-Ray uses an utterly different algorithm for this. In 
>>> particular, it uses a shedload of statistical tests to reduce the 
>>> number of samples taken.
>>
>> Povray still shows a lot of graininess for insuficient samples.  Lots 
>> of samples still get very slow rendering.
> 
> It doesn't show graininess, it shows patchiness.

#default {pigment { rgb .8 }  finish { ambient .2 diffuse .8 }}

union {
plane { y 0 }

sphere { <2,1> 1 }
sphere { <-2,2> 2 }

light_source { 3*<1,3,1> 1 area_light x,z,2,2 adaptive 0 jitter }
light_source { 3*<-3,1,-2> .5 area_light x,z,2,2 adaptive 0 jitter }

rotate y*40
rotate -x*30
translate <0,-1,8>
}

plenty of graininess in the shadow edges.  And, yes, plenty of 
patchiness as for radiosity if used with few samples.

> Because it reuses a 
> single sample for multiple pixels. That means it needs to take about one 
> millionth of the number of samples that this program takes. Hence, a 
> *slight* speed difference.

Which will mean nothing if it doesn't move on to GPU like everyone else 
and begins eating dust for such slow and more realistic renderers.

> ...which still has nothing to do with *this* program.

ah, I thought you were talking about unbiased renderers in general.

-- 
a game sig: http://tinyurl.com/d3rxz9

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>> Because it reuses a single sample for multiple pixels. That means it 
>> needs to take about one millionth of the number of samples that this 
>> program takes. Hence, a *slight* speed difference.
> 
> Which will mean nothing if it doesn't move on to GPU like everyone else 
> and begins eating dust for such slow and more realistic renderers.

The GPU has been producing graphics far faster than POV-Ray for decades. 
It's only now that it can start to do the sorts of things that POV-Ray 
can do.

I haven't yet seem a GPU renderer that can render actual curves. Also, 
can any of these unbiased renderers handle scattering particle media yet?

>> ...which still has nothing to do with *this* program.
> 
> ah, I thought you were talking about unbiased renderers in general.

No, I was just pointing out that this particular program may take many 
hours to render something that POV-Ray does in minutes because POV-Ray 
uses a totally different algorithm.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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