I tried to include these changes but didn't get the right results.

if i put xscan=0, i have the simple case of photons travelling through the
absorber and reflected back through it, always in the z direction. Using your
media approach i dont seem to be able to change the brightness of the reflected
scene by changing cmt_abs paramter. I also noticed if i set cmt_abs = 0 there is
no error flagged up because of the divide by zero!

clipka <ano### [at] anonymousorg> wrote:
> Am 13.07.2012 18:24, schrieb Crippso:
> >
> > I tried to use media but cant get it to work properly. Still when my xscan
> > paramter = 4 the reflection is too bright, it should be much weaker than when
> > xscan = 3. Here is how i modified the absorber object. The only other change I
> > made was to the photons global setting where i added "media 100". Am i doing
> > something wrong?
>
> The "media" keyword in the global photons block is irrelevant for your
> case; it is intended for scattering media.
>
>
> > object{
>
> (BTW, while wrapping your "box" in an "object" statement doesn't hurt,
> it's totally unnecessary; you need "object" only when you have
> #declare'd an object and want to add it to the scene.)
>
> > box
> > {
> >     <-extent,-extent,t_st> <extent,extent,t_st+t_abs>
> >     hollow
> >     pigment{rgbt 1}
> >     finish
> >     {
> >       reflection{0,1 fresnel}
> >       conserve_energy
> >     }
> >
> >     interior{ior cmt_ior fade_distance cmt_abs fade_power 1000
>
> Remove the "fade_distance" and "fade_power" statements; after all,
> you're trying to replace them with media.
>
> >         media{
> >          absorption <1,1,1>
>
> You may need to increase absorption; note that its parameter is not
> limited to the range [0..1].
>
> Theoretically, you should set:
>
>      absorption = <1,1,1> / cmt_abs
>
> to get the same results as you'd get with properly computed fade.
>
> >          intervals 3
> >          samples 1,1         }
>
> Remove the "intervals" and "samples" statements; the default values
> should be perfectly fine for uniform media as in your case.
>
> >
> >     }
> >
> >     PhotonTarget(no, yes, yes, yes)
> > }
> > }

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