[Radiance-general] ambient bounces

[Jia Hu]

I got it, thank you.

"ab" value is the maximum number of bounces for diffuse indirect component.
Another question is that whether there is a limit on the bounces of specular
indirect (not diffuse indirect). I do not find such options in "rtrace".

Jia

On Tue, Apr 20, 2010 at 7:59 AM, Thomas Bleicher
<tbleicher at googlemail.com>wrote:

> Yes. That's the idea.
>
> -av is just a way to recover the ambient light that would be lost due
> to a limit on ambient bounces. To understand how -av influences the
> results you can run a test scene once with a high '-ab' (say 6 or 7)
> and '-av 0 0 0' and then reduce the '-ab' to 2 or 3 and increase the
> -av value. When the two results are more or less the same you have
> picked the right -av.
>
> Regards,
> Thomas
>
> On Tue, Apr 20, 2010 at 12:39 PM, Jia Hu <hujia06 at gmail.com> wrote:
> > Thank you very much, Christopher and Thomas.
> >
> > If I specify the value of "-av", does that mean the ray without hitting a
> > source will get some values (or contribution) that is related to "av". In
> > other words, "av" makes ray without hitting a source have some
> > contributions?
> >
> > Regards,
> > Jia
> > On Tue, Apr 20, 2010 at 5:02 AM, Thomas Bleicher <
> tbleicher at googlemail.com>
> > wrote:
> >>
> >> Jia.
> >>
> >> If the number of bounces is exceeded without hitting a source or
> >> infinity the value specified with "-av" (ambient value) is used. The
> >> default value is "0 0 0" so you won't get any artificial contribution.
> >>
> >> You can use rvu to read the average value of a scene on the screen.
> >> This gives you a first approximation of -av.
> >>
> >> Regards,
> >> Thomas
> >>
> >> On Tue, Apr 20, 2010 at 6:11 AM, Jia Hu <hujia06 at gmail.com> wrote:
> >> > Hello all:
> >> >
> >> > If ab (ambient bounces) =3, after a ray reaches three times of diffuse
> >> > bounces and does not hit any lighting source, then how should Radiance
> >> > define the value of this ray, for example, radiance or irradiance, in
> >> > order
> >> > to calculate the radiance at the viewpoint using backward ray tracing?
> >> > I
> >> > read chapters about calculation methods in the book, Rendering with
> >> > radiance, but still a little confused.
> >> >
> >> > Thank you in advance.
> >> > Jia
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> >>
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