[Radiance-general] Re: rendering parameters

[Greg Ward]

Hi Ada,

I think there's no way to do this correctly without understanding and 
hacking the source code in src/rt/normal.c.  That's what I had to do to 
generate this image in the first place.  If you just want a copy of the 
image, I would be happy to provide one.  You won't be able to get this 
result by altering the command line options or the material parameters 
alone.  If your specular surface(s) has zero roughness, you might be 
able to get close by rendering pictures of your scene with and without 
the specular component(s), and subracting the resulting pictures.  As 
for separating the interreflected component, the same picture 
subtraction should work between one rendered with -ab 1 -av [whatever] 
and -ab 0 -av 0 0 0.

To subtract two images:

	pcomb img1.pic -s -1 img2.pic > img1-img2.pic

The images must be rendered at the same size and resolution, setting 
the rpict parameters -pj 0 and -ps 1.  You can pass the result through 
pfilt to improve the final appearance, but I don't recommend doing it 
before.

I hope this helps.
-Greg

Ada Fraser <adafraser@yahoo.com> wrote:
>
> Hello. I am trying to separate the direct and indirect
> specular and indirect diffuse calculation in Radiance.
> Actually, I am trying to duplicate the "artificial
> separation" provided in Radiance book, plate 23.
>
> I got a little confused with the rendering parameters:
> Lets say I have an image, which has all
> direct + indirect specular + indirect diffuse
> computation, with parameters
> -av 0.5 0.5 0.5
> -ab 2
> -st 0.001
> INDIRECT=1
>
> Would it be sufficient to change
> -av 0 0 0
> -ab 0
> -st 1
> INDIRECT=0
> so that I can get an image with just the direct
> computations? Or do I have to change other parameters?
>
>
> Accordingly, if change the ?st parameter back to
> 0.001; would it be give direct + indirect specular
> component?
>
> Thanks.
> Ada