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From: Thomas de Groot
Subject: Radiosity: maximum_reuse
Date: 6 May 2010 04:19:43
Message: <4be27b9f$1@news.povray.org>
This info is unclear to me: what is the default value of the new radiosity 
parameter maximum_reuse, and how to best use it in combination with 
minimum_reuse? Maybe a little addition to the Radiosity Voodoo can be 
expected...?   ;-)

Thomas


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From: clipka
Subject: Re: Radiosity: maximum_reuse
Date: 6 May 2010 05:15:08
Message: <4be2889c$1@news.povray.org>
Am 06.05.2010 10:19, schrieb Thomas de Groot:
> This info is unclear to me: what is the default value of the new radiosity
> parameter maximum_reuse, and how to best use it in combination with
> minimum_reuse? Maybe a little addition to the Radiosity Voodoo can be
> expected...?   ;-)

maximum_reuse defaults to 0.2 - which was also the hard-coded value in 
POV-Ray 3.6.

In a nutshell, the parameter governs the maximum effective radius of 
radiosity samples in just the very same way as minimum_reuse governs the 
minimum effective radius; a value of 0.2, for instance, means that a 
sample at X units distance from the camera will be re-used within a 
radius of at most 0.2*X units.

Obviously this parameter should be > minimum_reuse at all times. While 
reducing the value will almost certainly increase rendering times, it 
might be useful e.g. in cases where you have wide open spaces with a few 
comparatively small objects, which the radiosity pretrace might tend to 
miss otherwise.


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From: Thomas de Groot
Subject: Re: Radiosity: maximum_reuse
Date: 6 May 2010 09:51:18
Message: <4be2c956$1@news.povray.org>
"clipka" <ano### [at] anonymousorg> schreef in bericht 
news:4be2889c$1@news.povray.org...
> maximum_reuse defaults to 0.2 - which was also the hard-coded value in 
> POV-Ray 3.6.
>
> In a nutshell, the parameter governs the maximum effective radius of 
> radiosity samples in just the very same way as minimum_reuse governs the 
> minimum effective radius; a value of 0.2, for instance, means that a 
> sample at X units distance from the camera will be re-used within a radius 
> of at most 0.2*X units.
>
> Obviously this parameter should be > minimum_reuse at all times. While 
> reducing the value will almost certainly increase rendering times, it 
> might be useful e.g. in cases where you have wide open spaces with a few 
> comparatively small objects, which the radiosity pretrace might tend to 
> miss otherwise.

Perfectly clear, Christoph. Thank you very much.

Thomas


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From: Alain
Subject: Re: Radiosity: maximum_reuse
Date: 6 May 2010 13:10:29
Message: <4be2f805$1@news.povray.org>

> Am 06.05.2010 10:19, schrieb Thomas de Groot:
>> This info is unclear to me: what is the default value of the new
>> radiosity
>> parameter maximum_reuse, and how to best use it in combination with
>> minimum_reuse? Maybe a little addition to the Radiosity Voodoo can be
>> expected...? ;-)
>
> maximum_reuse defaults to 0.2 - which was also the hard-coded value in
> POV-Ray 3.6.
>
> In a nutshell, the parameter governs the maximum effective radius of
> radiosity samples in just the very same way as minimum_reuse governs the
> minimum effective radius; a value of 0.2, for instance, means that a
> sample at X units distance from the camera will be re-used within a
> radius of at most 0.2*X units.
>
> Obviously this parameter should be > minimum_reuse at all times. While
> reducing the value will almost certainly increase rendering times, it
> might be useful e.g. in cases where you have wide open spaces with a few
> comparatively small objects, which the radiosity pretrace might tend to
> miss otherwise.

What will appen if you set it to low: smaller than minimum_reuse?
An error, a warning and proceede, a warning and use the default value 
instead,...



Alain


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From: clipka
Subject: Re: Radiosity: maximum_reuse
Date: 6 May 2010 15:42:21
Message: <4be31b9d$1@news.povray.org>
Am 06.05.2010 19:10, schrieb Alain:

> What will appen if you set it to low: smaller than minimum_reuse?
> An error, a warning and proceede, a warning and use the default value
> instead,...

Presently, "maximum_reuse" will quietly win over "minimum_reuse" without 
any warning.


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From: Alain
Subject: Re: Radiosity: maximum_reuse
Date: 8 May 2010 16:12:57
Message: <4be5c5c9$1@news.povray.org>

> Am 06.05.2010 19:10, schrieb Alain:
>
>> What will appen if you set it to low: smaller than minimum_reuse?
>> An error, a warning and proceede, a warning and use the default value
>> instead,...
>
> Presently, "maximum_reuse" will quietly win over "minimum_reuse" without
> any warning.

I think that's an acceptable beaviour. The only change I see would be 
the isuing of a warning in that case.


Alain


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From: MDenham
Subject: Re: Radiosity: maximum_reuse
Date: 9 May 2010 01:55:01
Message: <web.4be64d2227756df6f035a3e20@news.povray.org>
Alain <aze### [at] qwertyorg> wrote:

> > Am 06.05.2010 19:10, schrieb Alain:
> >
> >> What will appen if you set it to low: smaller than minimum_reuse?
> >> An error, a warning and proceede, a warning and use the default value
> >> instead,...
> >
> > Presently, "maximum_reuse" will quietly win over "minimum_reuse" without
> > any warning.
>
> I think that's an acceptable beaviour. The only change I see would be
> the isuing of a warning in that case.
>
>
> Alain
Actually, if it's setting both the maximum and minimum reuse to the same value,
it's basically saying "only reuse if it's within (arbitrary small float value)
of maximum_reuse".

In effect, it mostly disables reusing of samples, with exceptions that aren't
necessarily reproducible on systems of different architecture (like, say, if
someone were inclined to make a build of POV-Ray for the XBox 360, since pretty
much everyone else is using an Intel or AMD processor).

I'd be inclined to, in situations like this, give a warning and then swap the
values on the assumption that someone just wasn't paying attention, rather than
a "mostly disabled" setting that's going to, at some point in the future, drive
someone nuts.


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From: clipka
Subject: Re: Radiosity: maximum_reuse
Date: 9 May 2010 02:24:28
Message: <4be6551c@news.povray.org>
Am 09.05.2010 07:50, schrieb MDenham:

>>> Presently, "maximum_reuse" will quietly win over "minimum_reuse" without
>>> any warning.
>>
>> I think that's an acceptable beaviour. The only change I see would be
>> the isuing of a warning in that case.
>>
>>
>> Alain
> Actually, if it's setting both the maximum and minimum reuse to the same value,
> it's basically saying "only reuse if it's within (arbitrary small float value)
> of maximum_reuse".
>
> In effect, it mostly disables reusing of samples, with exceptions that aren't
> necessarily reproducible on systems of different architecture (like, say, if
> someone were inclined to make a build of POV-Ray for the XBox 360, since pretty
> much everyone else is using an Intel or AMD processor).

No, that's not what it does.

As the person who overhauled the radiosity code for v3.7, and 
implemented the code to expose this parameter to the user, I guess I 
know a bit about the matter ;-)

You are right that there is indeed a mechanism in place to suppress 
samples that would be "too small" (i.e. too close to other objects) to 
be useful, and also that this mechanism's threshold is currently tied to 
the maximum_reuse parameter; however, that's not the main purpose of the 
parameter, nor is there any corresponding minimum_reuse-related 
mechanism discarding samples that would be "too large" (such samples are 
just "trimmed down" in size, /after/ having been subjected to the "too 
small"-test).


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