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"Hj. Malthaner" <me@home> wrote:
> The BRDFs are still making my head spin. I understand the concept, but
> struggle with the actual math to come up with proper BRDFs for new
> materials of my own.
Diagrams are definitely your friend.
Drawing the diagram with POV-Ray using the math that you're trying to work out
is also an excellent exercise.
I also found this video extremely useful
https://www.youtube.com/watch?v=gsZiJeaMO48
> In regard to the parser, I want to say thanks to the people who wrote
> the PovRay documentation. Each SDL element is documented with a snippet
> of a grammar, which can be converted almost one to one into a recursive
> descend parser. So the documentation is already there. I'll try to keep
> the identifiers used in the parser code close to the ones used the
> documented grammar, so the code will look familiar to those who looked
> at the grammar from the documentation before.
Maybe before you get too far into that, take a look at:
https://journal.stuffwithstuff.com/2011/03/19/pratt-parsers-expression-parsing-made-easy/
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"Hj. Malthaner" <me@home> wrote:
> Something though that I had been missing in PovRay is what is known as
> global illumination or path based lighting. Radiosity, supported by
> PovRay, is very similar, but not quite the same.
Are you aware of the UberPOV fork?
https://github.com/UberPOV/UberPOV
It's based on POV-Ray 3.7 and hasn't really seen any development for some time,
but one of its notable features is stochastic global illumination as an
extension to radiosity. I still use it quite often because I think it produces
much better results than the standard radiosity with almost no tweaking
required.
Maybe there's something there of interest relevant to your project!
Bill
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From: Hj Malthaner
Subject: Re: The Raysnail - WIP, a probability based raytracer with (limited) suppor=
Date: 18 Jul 2024 10:32:53
Message: <66992795$1@news.povray.org>
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On 7/18/24 15:38, Bill Pragnell wrote:
> Are you aware of the UberPOV fork?
>
> https://github.com/UberPOV/UberPOV
Now I am. Well, I had heard of UberPOV before but never really looked
into it ...
> It's based on POV-Ray 3.7 and hasn't really seen any development for some time,
> but one of its notable features is stochastic global illumination as an
> extension to radiosity. I still use it quite often because I think it produces
> much better results than the standard radiosity with almost no tweaking
> required.
That matches my own impression and why I wanted something with global
illumination while still supporting PovRay SDL. This is quite
interesting, thank you for the link!
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From: Hj Malthaner
Subject: Re: The Raysnail - WIP, a probability based raytracer with (limited) suppor=
Date: 18 Jul 2024 10:38:47
Message: <669928f7$1@news.povray.org>
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On 7/17/24 21:08, Bald Eagle wrote:
> "Hj. Malthaner" <me@home> wrote:
>
>> In regard to the parser,
>
> Maybe before you get too far into that, take a look at:
>
https://journal.stuffwithstuff.com/2011/03/19/pratt-parsers-expression-parsing-made-easy/
Interesting, I had not heard of PRATT parsers before.
I think I'll stick with a recursive descent parser though, because it's
a more widely known approach, even if the code is less compact.
The structure of a recursive descent parser resembles the grammar quite
closely which a benefit too, I think, with the grammar being of the docs
already.
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From: Hj Malthaner
Subject: Re: The Raysnail - WIP, a probability based raytracer with (limited) suppor=
Date: 18 Jul 2024 10:39:45
Message: <66992931$1@news.povray.org>
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On 7/17/24 21:08, Bald Eagle wrote:
> I also found this video extremely useful
>
> https://www.youtube.com/watch?v=gsZiJeaMO48
I haven't watched it all yet, but it indeed seems interesting. Thank you
for sharing the link!
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From: Thomas de Groot
Subject: Re: The Raysnail - WIP, a probability based raytracer with (limited)suppor=
Date: 18 Jul 2024 11:14:48
Message: <66993168$1@news.povray.org>
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Op 18-7-2024 om 16:32 schreef Hj. Malthaner:
> On 7/18/24 15:38, Bill Pragnell wrote:
>
>> Are you aware of the UberPOV fork?
>>
>> https://github.com/UberPOV/UberPOV
>
> Now I am. Well, I had heard of UberPOV before but never really looked
> into it ...
>
>> It's based on POV-Ray 3.7 and hasn't really seen any development for
>> some time,
>> but one of its notable features is stochastic global illumination as an
>> extension to radiosity. I still use it quite often because I think it
>> produces
>> much better results than the standard radiosity with almost no tweaking
>> required.
>
> That matches my own impression and why I wanted something with global
> illumination while still supporting PovRay SDL. This is quite
> interesting, thank you for the link!
>
>
Even better, 'stochastic' is also supported by version 3.8! I generally use:
+am3 +a0.01 +ac0.90 +r3
and in the radiosity block a count between 10 and 50
varying +a, +ac and +r values increases/decreases the stochastic quality
(and render time!).
THere must be some documentation by clipka but I am unable to find it
presently, sorry.
--
Thomas
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Thomas de Groot <tho### [at] degroot org> wrote:
> Even better, 'stochastic' is also supported by version 3.8! I generally use:
>
> +am3 +a0.01 +ac0.90 +r3
>
> and in the radiosity block a count between 10 and 50
>
> varying +a, +ac and +r values increases/decreases the stochastic quality
> (and render time!).
Are we talking about the same thing here?
I was referring to the unbiased purely stochastic version of radiosity, which
was a significant change to the algorithm; I was under the impression that this
wouldn't end up in main POV-Ray in the form it was implemented in UberPOV. Maybe
I missed something, is this in v3.8 now, or are you referring to improvements to
sampling alone?
Bill
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From: Thomas de Groot
Subject: Re: The Raysnail - WIP, a probability based raytracer with (limited)suppor=
Date: 19 Jul 2024 04:26:16
Message: <669a2328@news.povray.org>
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Op 18-7-2024 om 19:49 schreef Bill Pragnell:
> Thomas de Groot <tho### [at] degroot org> wrote:
>> Even better, 'stochastic' is also supported by version 3.8! I generally use:
>>
>> +am3 +a0.01 +ac0.90 +r3
>>
>> and in the radiosity block a count between 10 and 50
>>
>> varying +a, +ac and +r values increases/decreases the stochastic quality
>> (and render time!).
>
> Are we talking about the same thing here?
>
> I was referring to the unbiased purely stochastic version of radiosity, which
> was a significant change to the algorithm; I was under the impression that this
> wouldn't end up in main POV-Ray in the form it was implemented in UberPOV. Maybe
> I missed something, is this in v3.8 now, or are you referring to improvements to
> sampling alone?
>
Ah. This I do not know for sure. I am using the 'latest' v3.8-beta2, and
as far as I can remember, the use of the stochastic implementation there
is identical(?) to what was implemented in UperPOV. I am afraid this is
all I can remember from those days, back in 2014, if I am correct. Using
+am3 automatically switches on the stochastic render and I suppose
(wrongly maybe) that this directly influences the radiosity, but if this
then is a [quote] unbiased purely stochastic version of radiosity
[/quote] I do not know indeed. This would need the comment of an expert
(Christoph Lipka! where are you?). All I know is that it works fine
as-is, and I have been using it ever since with v3.8-beta or v3.8-beta2.
Sorry for not being able to be more specific. :-[
--
Thomas
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From: Thomas de Groot
Subject: Re: The Raysnail - WIP, a probability based raytracer with(limited)suppor=
Date: 19 Jul 2024 08:26:56
Message: <669a5b90$1@news.povray.org>
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The revision.txt file for v3.8-beta2 has this about stochastic renders:
------------------------------------------------------------------------------
POV-Ray v3.8.0-alpha.9841009
------------------------------------------------------------------------------
Commit 8c1eb72b on 2018-09-17 by Christoph Lipka
Add anti-aliasing mode 3 (port from UberPOV).
Also add some bits of infrastructure for future optimization and better
co-operation of various stochastic features like jittered area lights,
jittered media sampling, subsurface light transport and the like.
Hope this helps.
--
Thomas
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Thomas de Groot <tho### [at] degroot org> wrote:
> The revision.txt file for v3.8-beta2 has this about stochastic renders:
>
>
> ------------------------------------------------------------------------------
> POV-Ray v3.8.0-alpha.9841009
> ------------------------------------------------------------------------------
>
> Commit 8c1eb72b on 2018-09-17 by Christoph Lipka
>
> Add anti-aliasing mode 3 (port from UberPOV).
>
> Also add some bits of infrastructure for future optimization and better
> co-operation of various stochastic features like jittered area lights,
> jittered media sampling, subsurface light transport and the like.
Ah yes I think this is just the stochastic sampling, not the modified radiosity
algorithm as a whole. I'm sure it improves things considerably but I don't think
it's what I was referring to!
That said, I should probably try out 3.8 at some point and see what's new for
myself :)
Bill
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