[Radiance-general] Re: rendering parameters

[Ada Fraser]

Hello. Thank you for the answer Greg. It is very
helpful. I have one follow up question: When I set the
rendering parameters -ab 0 -av 0 0 0, I am eliminating
the interreflected component. But I still see some
reflection of the interior surfaces on my window
glazing. Since there is no interreflection, why is
this happening?

Thanks again.
Ada

--- Greg Ward <gward@lmi.net> wrote:
> 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
> 



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