> Thanks Alain
>
> the reason for the large gather value and the low adc_bailout is because I found
> that I need these for a the scene I am trying to model. The code I attached in
> my first posting was a simple version of this scene - in my main scene the
> object that reflects light back to the diffuse screen which is viewed by the
> camera is more complex - it is several layers of different ior, and i use
> fresnel reflection
>
> stu
>
>

If you just want a very, almost zero, adc_bailout, why not use 
adc_bailout 0. That way, the tracing depth will be controled only by 
max_trace_level, that you can set up to 255.

I don't think that you realy, even with 100 stacked objects having all 
different ior, need to play around with the gather parameter.

Finaly, fresnel only affect the reflectivness of your object reletive to 
it's ior and the angle of the incident rays or photons. It have no 
effect on the photons distribution.
When using fresnel, you should add conserve_energy in the finish of that 
object.

Only the first object to receive the light need the photons block. It 
controlls where the photons are shot. Secondary photons, after any 
refraction of reflection, WILL be affected by any refractive / 
reflective object they emcounter. If you don't want those to collect 
photons and have them be visible on it's surface, add photons{collect off}.

When using count, the photons are distributed between all target 
objects, and any object behind any other will have photons shot toward 
it, but those photons will get intercepted by the intervening object and 
get lost.
It may be why you need 100 millions photons.
Also, if you loose over 90% of your photons, it may explain why you 
needed to play around with gather.
Let say, 20 stacked target objects and the projection plane also set as 
target, means that your count is divided among 21 objects, but only 
those received by the front object realy count.



Alain

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