I was wondering (and have experimented and failed) whether you could have a
completely invisible object in the scene that specularly reflects light.

For instance say you have a red sphere of radius 1, an invisible
dodecahedron of radius 1.1, and a few multi-colored spotlights.

Can you make it so the reflections shown on the ground and walls come from
the dodecahedron's surface without actually seeing the dodecahedron, and
all you see is the sphere which seems to be making the dodecahedron
reflections?

Thanks for any help!

Ravious

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> I was wondering (and have experimented and failed) whether you could have a
> completely invisible object in the scene that specularly reflects light.
> 
> For instance say you have a red sphere of radius 1, an invisible
> dodecahedron of radius 1.1, and a few multi-colored spotlights.
> 
> Can you make it so the reflections shown on the ground and walls come from
> the dodecahedron's surface without actually seeing the dodecahedron, and
> all you see is the sphere which seems to be making the dodecahedron
> reflections?
> 
> Thanks for any help!

Check out no_image, no_shadow and no_reflect.

Also, if you're shining a spotlight on the thing and expecting to see 
spots of light all over the place, you'll be needing photons to do that. 
What you could do (not sure if it will work properly) is run POV-Ray 
once with the object there as normal (to generate the photon map), and 
then run POV-Ray again with the same photon map but with the object removed.

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> Check out no_image, no_shadow and no_reflect.
>
> Also, if you're shining a spotlight on the thing and expecting to see
> spots of light all over the place, you'll be needing photons to do that.
> What you could do (not sure if it will work properly) is run POV-Ray
> once with the object there as normal (to generate the photon map), and
> then run POV-Ray again with the same photon map but with the object removed.

I knew about no_shadow, but didn't know about the other two.  I will try out
the photon map as well.  Thanks for your help.

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Orchid XP v3 nous apporta ses lumieres en ce 04/10/2006 13:55:
>> I was wondering (and have experimented and failed) whether you could 
>> have a
>> completely invisible object in the scene that specularly reflects light.
>>
>> For instance say you have a red sphere of radius 1, an invisible
>> dodecahedron of radius 1.1, and a few multi-colored spotlights.
>>
>> Can you make it so the reflections shown on the ground and walls come 
>> from
>> the dodecahedron's surface without actually seeing the dodecahedron, and
>> all you see is the sphere which seems to be making the dodecahedron
>> reflections?
>>
>> Thanks for any help!
Have the dodecaedron have no_image to make it invisible. Give it a photons block 
with target on reflection on.
Give one or the other no_shadow, depending on what shadow you want.
If you have reflective surfaces showing the sphere, give the dodecaedron 
no_reflection to remove it's reflection.

> 
> Check out no_image, no_shadow and no_reflect.
> 
> Also, if you're shining a spotlight on the thing and expecting to see 
> spots of light all over the place, you'll be needing photons to do that. 
> What you could do (not sure if it will work properly) is run POV-Ray 
> once with the object there as normal (to generate the photon map), and 
> then run POV-Ray again with the same photon map but with the object 
> removed. or replaced.
That trick does work, and have been used to good effect.

-- 
Alain
-------------------------------------------------
Celebrate Hannibal Day this year.  Take an elephant to lunch.

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