> basically I need a way to disable filtered/transmitted light from interacting
> with global atmospheric media for a specific object in the scene. When the
> object in question color have f and t  greater than 0, some very strange
> lighting affects occur in the media. more details info below.
>
> the situation:
> ==============
> I'm rendering two objects, and a third used for creating rays in a fog like
> media. 1) a set of spheres and cylinders, 2) a surface defined by imported
> mesh2. This needs to be partially transparent. 3) copy of 2's mesh2, but
> transmit and filter 0.
>
> object 1,2 has a light_group with a set of different lights. both these light
> groups have global_lights off. each light in both groups have media_interaction
> off.
>
> The purpose of object 3 is create a pattern of rays through the fog. There's a
> spot light positioned facing the camera behind a copy of the mesh2 surface.
>
>
> the issue:
> ==========
> when object 2 is in the scene it affects the rays through the fog like media. In
> object 2 f and t are non zero, and the impact is like refraction or focusing.
> making some bright rays. This is unexpected because all lights on this object
> are set not to interact with the media. also global_lights are off in his
> light_group.
>
> I need this not to happen. It doesn't if I set object 2 f and t 0, but I need
> them non-zero.
>
> Any idea why this would happen, how I can have object 2 f,t non-zero, and not
> impact the rays through the fog??
>
>

Any object in a light_group WILL cast shadow for lights that are outside 
of it's group. If the object can cause any colouration of that light, 
the cast shadow will get coloured accordingly.

The solution can be as easy as setting no_shadow for those objects.



Alain

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