"Peter wrote:
> I'm an Optics guy. I have a hard time getting a "visible" light beam from
> POVRay.
> I would like to generate a beam (e.g. spot light source) which can be visible
> and directed towards an object or lens.
>
> I have enabled photons mapping and stuff for the light source and objects, but
> the beam is only visible when it hits the object. It's not visible in air or
> the background.
>
> How can I simulate a laser beam? Can anybody point me to the right resources
> (tutorials, example pov files, etc...)?
>
> I would like to illustrate simple concepts like reflection, refractio,
> diffraction on lenses and some other optical objects. But I need to actually
> control the beam size and see it. I don't want a *virtual* light source. Thanks
> for any help.

I was playing with this a bit recently, with some frustration.  You might want
to check out the examples and tutorials on http://weblog.sitewww.ch/ as well.
He starts showing visible beams of light passing through lenses and off mirrors
in various combinations on page 10, though its probably useful to read the pages
leading up to it.

My frustration stemmed from getting a reflected beam to be visible after being
reflected.  The beam showed in the scattering media until it hit the mirror,
and the light showed reflective caustics on a target, but the beam wasn't
visible between the mirror and the target.

Eventually I found I needed to turn up the media parameter of the photons, and
significantly turn up the samples of the media to see anything.

I'll post the test scene I got some basic results from in p.t.s-f in case its
helpful.

-The Mildly Infamous Blue Herring

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