[Radiance-general] rif settings: quality variability detail

[Rob Guglielmetti]

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$B!G(Bs 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