Woody nous illumina en ce 2008-07-07 14:13 -->
> Have another question regarding creating a shaped light. Let's say I have the
> following simple scen
> 
> box{ -1, 1 scale 100 scale z/100000 translate z*-10 pigment{color Red}
> finish{ambient 0}}
> sphere{0,1 }
> light_souce{ z*10 spotlight point_at z*-10 radius 30 falloff 30}
> 
> How do do I create a scene with a light source against the box with the shadow
> of the sphere but without the sphere actually being in the scene. I though of
> using a light_group and difference like
> 
> difference{
>     light_group{
>         box{ -1, 1 scale 100 scale z/100000 translate z*-10 pigment{color Red}
> finish{ambient 0}}
>         sphere{0,1 }
>         light_souce{ z*10 spotlight point_at z*-10 radius 30 falloff 30}
> 
>     }
>     light_group{
>         sphere{0,1 }
>     }
> }
> 
> or even instead of a second light_group just using a sphere for the difference
> 
> difference{
>     light_group{
>         box{ -1, 1 scale 100 scale z/100000 translate z*-10 pigment{color Red}
> finish{ambient 0}}
>         sphere{0,1 }
>         light_souce{ z*10 spotlight point_at z*-10 radius 30 falloff 30}
> 
>     }
>     sphere{0,1 }
> }
> 
> 
> nothing seems to work though.
> 
> Any thoughts?
> 
> 
Try no_image. With that option, you won't see the object directly, but it will 
cast shadow and be visible in reflections. You may also add no_reflection if you 
have reflective surfaces but don't want that object to be seen in reflections.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you can no longer tell the 
difference between the top raytracing book and the "Raytracing for Dummies" 
book. To you, they're both hopelessly uninformed.
     -- Taps a.k.a. Tapio Vocadlo

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