I'm shining a spotlight onto a plane at an angle (so getting an ellipse).  I'm
trying to place a lense between the light source and the plane, such that
refraction will modify the shape of my spotlight beam.  I'm am getting no
effects though.

If I move my lense such that it is between the plane and the camera then the
image of the ellipse is distorted - it seems the lense is correctly set up to
refract.

Is there a limit to how close to the spotlight I can place my lense?  My lense
is very small and thus placed very close to the spotlight, I have assumed that
the spotlight is a point source and that this wouldn't be a problem?

Why does it not cause refraction of the light that is emitted directly from the
spotlight?  Is there anything I can do to correct this?


Thanks for your help
Joe

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j-dowsett <nomail@nomail> wrote:
> Why does it not cause refraction of the light that is emitted directly from the
> spotlight?

  Because the calculations are non-trivial and requires some parameters to
be specified by the user. It can be done, though:

http://wiki.povray.org/content/Documentation:Reference_Section_6.1#Photons

-- 
                                                          - Warp

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Am 02.12.2011 12:28, schrieb j-dowsett:

> Why does it not cause refraction of the light that is emitted directly from the
> spotlight?  Is there anything I can do to correct this?

Classic backward raytracing (which is what POV-Ray basically does) can't 
do refraction between light and illuminated surfaces; POV-Ray does have 
a forward raytracing extension to cope with such situations, but you 
need to explicitly enable this feature; the buzzword to look for in the 
docs is "photons".

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Thank you, that's done the trick.
I'd thought it might be to do with photons, but the fact that it worked in front
of the camera confused me.

Cheers.

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