Radiance-general digest, Vol 1 #393 - 1 msg

Dear Mark

I would greatly appreciate if you could show me as to how to make these changes.




Date: Mon, 3 Nov 2003 11:05:03 -0500 (EST)
From: Mark Stock <mstock@umich.edu>
To: radiance-general@radiance-online.org
Subject: Re: [Radiance-general] Metal Reflection Problem
Reply-To: radiance-general@radiance-online.org


I think the "fractal pattern" you refer to in the specular
highlights can be solved by turning on Radiance's pure Monte-
Carlo sampling algorithm (requires re-compiling, though).
I read about it in a text file on the old Radiance site:

RADIANCE Compile Switches

Here is a list of compile switches, used to customize Radiance code for
specific machines and users:

    If set, switches from default low-discrepency sequence sampling to
true (pseudorandom) Monte Carlo. Use if the "brushed" appearance of
specular highlights and penumbras bothers you.

To get this to compile with the HEAD distribution, you need to
make a few changes to the src/common/random.h file. I can give those
to you if you like.


On Mon, 3 Nov 2003, Roland Schregle wrote:

> Marcus Jacobs wrote:
> > As a side note, the reflections of the light sources on the floor do not
> > seem right. I have noticed this before. Does anyone know what's causing
> > this?
> Don't seem right as in no penumbrae? That's expected for a solar source
> modeled with the SOURCE primitive. AFAIK these sources are immune to -dj
> and -ds anyway. Maybe a Fully Licensed Guru[tm] here can tell you more.

I've found that -dj works with the "source" primitive (again, I
use the HEAD distro, but I found it to work in the 3R5 distro, too).
It uses the last float argument, the angular disc size, to determine
the jittering. Go ahead and raise that from 0.5 to 5 degrees for an
unrealistic sun with nice-looking soft shadows.

I typically use -dj 0.6 to 0.7 for most of my scenes.

BTW: the soft shadows will exhibit the same fractal-like pattern
that you see in the specular highlights. -DMC cures this, too,
but can require higher-resolution runs before filtering down.

Oh, and -ps 1 is almost a necessity with -DMC turned on.



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