rif settings: quality variability detail

Quick question: Can anyone tell me how the rad program interprets the
HIGH/MEDIUM/LOW settings in the .rif file? Does each setting have a
corresponding pre-determined list of rpict parameters, or does it take
scene geometry etc. and determine appropriate parameters each time?

Thanks,

Nick

Hi Nick,

Working from memory here, I believe that some settings are
pre-determined (such as increments of -ab over the range) while others
are derived based on the scene size (settings relative to the ZONE
parameter of the rif file). If you take a look at the man page for "rad"
you can get some further explanation for the various parameters. In
addition there is a way to run the rad command to get the output of what
it "would" do when actually run:

    rad -n <rif file>

This is helpful for looking at the actually parameters that it chooses
to run. You can vary the settings this way and see what happens without
the expense of running the actual simulation.

-Jack

Nick Doylend wrote:

···

Quick question: Can anyone tell me how the rad program interprets the
HIGH/MEDIUM/LOW settings in the .rif file? Does each setting have a
corresponding pre-determined list of rpict parameters, or does it take
scene geometry etc. and determine appropriate parameters each time?

Thanks,

Nick

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# Jack de Valpine
# president
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# visarc incorporated
# http://www.visarc.com
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# channeling technology for superior design and construction

Thanks, I didn't know about the -n option. The man file gives a useful
overview but doesn't go into the details of the choices made. Other
than -aa and -ar, are there any more parameters relating to scene
geometry? I guess I'll fiddle around with different .rif file options
and scene dimensions, but I just wonder if there is a document somewhere
explaining in detail.

Nick

···

On Fri, 05 Sep 2008 08:56:04 -0400, "Jack de Valpine" <[email protected]> said:

Hi Nick,

Working from memory here, I believe that some settings are
pre-determined (such as increments of -ab over the range) while others
are derived based on the scene size (settings relative to the ZONE
parameter of the rif file). If you take a look at the man page for "rad"
you can get some further explanation for the various parameters. In
addition there is a way to run the rad command to get the output of what
it "would" do when actually run:

    rad -n <rif file>

This is helpful for looking at the actually parameters that it chooses
to run. You can vary the settings this way and see what happens without
the expense of running the actual simulation.

-Jack

Nick Doylend wrote:
> Quick question: Can anyone tell me how the rad program interprets the
> HIGH/MEDIUM/LOW settings in the .rif file? Does each setting have a
> corresponding pre-determined list of rpict parameters, or does it take
> scene geometry etc. and determine appropriate parameters each time?
>
> Thanks,
>
> Nick
>
> _______________________________________________
> Radiance-general mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/radiance-general
>
>

--
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction

Jack de Valpine wrote:

    rad -n <rif file>

This is helpful for looking at the actually parameters that it chooses
to run. You can vary the settings this way and see what happens
without the expense of running the actual simulation.

Jack's right, this is a great way to play "what if" with the rif file

···

parameters. Here is a link to a paper Greg wrote on rad that is extremely informative about the way rad (and by extension, all of the rendering and calculation pieces of Radiance) works:

http://www.radiance-online.org/radiance-workshop2/cd/Ward/egwr95.pdf

And from this paper, regarding the routines rad employs to make these
decisions about rendering parameters, we have this gem:

"There is very little point in describing these routines in any detail,
but pseudocode
for the medium quality procedure is included in the Appendix for those
who are
curious. What is significant is that these three short routines embody
much of the
author’s knowledge about Radiance rendering and what works best in a given
situation. As awkward as they may look, they are a form of expert knowledge,
and it would have been impossible to write them without years of experience
using this software. Initially, it seemed that coding this knowledge
would be
impossible, but it turned out instead to be cathartic." (Ward)

A paraphrased version of this paragraph has remained in my head since
the first time I read it (indeed, I searched the pdf for the word
"cathartic" to find the paragraph), because to me it encapsulates the
entire crux of the problem of Radiance mastery.

- Rob Guglielmetti
www.rumblestrip.org

There an overview table on pages 517 and 558 of Rendering with Radiance
for direct and ambient settings. I'm not sure if some of the other
settings are outlined in a similar manner in other portions of the book.

I suspect that the actual values given in those tables may be simplified
or have been updated since then. For example I thought that setting
Quality=High and Variability=High will give an -ad parameter above 1024.

···

Quick question: Can anyone tell me how the rad program interprets the
HIGH/MEDIUM/LOW settings in the .rif file? Does each setting have a
corresponding pre-determined list of rpict parameters, or does it take
scene geometry etc. and determine appropriate parameters each time?

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I believe that -ad and -as are going to be set in relation to -ar which is in turn derived based on the scene resolution specified in the ZONE parameter... in addition to whatever impact the combination of QUALITY, VARIABLITY and other parameter sets have on things

-Jack

Christopher Rush wrote:

···

There an overview table on pages 517 and 558 of Rendering with Radiance
for direct and ambient settings. I'm not sure if some of the other
settings are outlined in a similar manner in other portions of the book.

I suspect that the actual values given in those tables may be simplified
or have been updated since then. For example I thought that setting
Quality=High and Variability=High will give an -ad parameter above 1024.

Quick question: Can anyone tell me how the rad program interprets the
HIGH/MEDIUM/LOW settings in the .rif file? Does each setting have a
corresponding pre-determined list of rpict parameters, or does it take
scene geometry etc. and determine appropriate parameters each time?
    

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# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction

Thanks, that's just what I was looking for! The values for medium
quality given in the book appear different from those in Greg's paper
(based on a cursory glance through the appendix). Can anyone confirm
the current values, otherwise I guess I can just play rad -n when I get
time.

Cheers,

Nick

···

On Fri, 5 Sep 2008 11:44:36 -0400, "Christopher Rush" <[email protected]> said:

There an overview table on pages 517 and 558 of Rendering with Radiance
for direct and ambient settings. I'm not sure if some of the other
settings are outlined in a similar manner in other portions of the book.

I suspect that the actual values given in those tables may be simplified
or have been updated since then. For example I thought that setting
Quality=High and Variability=High will give an -ad parameter above 1024.

> Quick question: Can anyone tell me how the rad program interprets the
> HIGH/MEDIUM/LOW settings in the .rif file? Does each setting have a
> corresponding pre-determined list of rpict parameters, or does it take
> scene geometry etc. and determine appropriate parameters each time?
____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses

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If you're really curious how these options are set, there's always the source code to look at:

  http://www.radiance-online.org/cgi-bin/viewcvs.cgi/ray/src/util/rad.c

There was an upgrade to the general rendering quality back in 2003:

  http://www.radiance-online.org/cgi-bin/viewcvs.cgi/ray/src/util/rad.c.diff?r1=2.71&r2=2.72

Playing with the -n option is probably the best way to see what happens if you don't care for C code.

-Greg