Ron Parker <ron### [at] povrayorg> wrote:
> First, make sure the discs the lens effects plugin puts in front of
> the camera are specified as hollow.  That does make a difference,
> even for patch objects.  Unfortunately, it means you'll have to edit
> Chris's masterwork if they're not.

All lens effects are indeed set to be hollow and not to cast shadows,
precisely so the lens effects can be used with POV-Ray's various
atmospheric features.

> Second, you might need to add some transparent bounds to force the
> interval that passes through your scattering media to be shorter,
> or you may need to increase the number of intervals (as a last
> resort.)  I usually see this effect when the interval passing
> through the media is much larger than the media effect itself.  It
> is especially prominent when you specify atmospheric media.
>
> If your media is forward-scattering only, you can get good effects
> by adding a plane parallel to the camera plane just beyond the light
> source.  If it's backward-scattering only, add such a plane just
> before the light source and another one several units beyond the
> light source (depending on scale.)  If it's both, add a plane at
> the light source and another one beyond.  The idea is to force an
> interval to evaluate over the part of the media that has the most
> contribution to the scene.

As I replied to Ken, I suspect it may have something to do with the
distances involved in the creation of the lens effects...bounding the
media may well be part of the solution.

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