Lonnie nous apporta ses lumieres en ce 2005-06-02 18:42:

> I am about to tear out my hair over the same problem only with refracted
> light.  It seems that photons and media exclude each other.  My scene is a
> glass model of a Greek temple, totally transparent material, with ior and
> dispersion, photons enabled (target) and illiminated by a spotlight.  It is
> surrounded by a hollow, transparent cylinder filled with scattering media.
> Interior dispersion works fine, BUT:
> 
> 1.  When both media and photons are enabled where the media is shadowed by
> the (transparent) material the media vanishes.  Caustics completely
> diappear leaving black shadows.
> 
> 2.  When media is diabled and photons are enabled the caustics work fine and
> the shadows are correctly rendered in shades of grey.
> 
> 3.  When photons are diabled and media is enabled the media works fine,
> showing up even in the shadows.
> 
> I have spent many hours going over the documentation and I can find nothing
> about the cause of this.  Here is the code:
> 
> global_settings {
>   assumed_gamma 1.0
>   max_trace_level 15
> 
>    photons {
>      count 20000
>      jitter .4
>      media 300
>      max_trace_level 35
// Add this
	media 10
// Add this
>    }
> }
>
You need to add: media <max_steps> to switch media photons on. The default is media 0
means that NO 
photons are deposited in any media. In that case, direct illumination will light the
media, but 
transmited and reflected light (photons) will ignore your media.
The mandatory parameter "max_steps" indicate how many photons to deposit in a given
interval.
Try the test value given. You will probably need to increase it, maybe around 1000 or
more to get 
optimum results.

Alain

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