On 6/25/23 17:56, Juergen wrote:
> Hi,
> 
> I made a few attempts over the weekend. I followed the variant "transparent
> cylinder". The result looks quite usable, but there are a few restrictions and
> things to consider.
> 
> In the core I use a (vertical) cylinder. On this cylinder is a gradient texture
> to avoid sharp edges. Finally, the cylinder is rotated so that it is parallel to
> the light rays.
> 
> The constraints are:
> 1. there must be no visible intersection of a cylinder with another object in
> the scene, here you would have sharp, unnatural edges.
> 2. the gradient texture must be aligned with the camera, otherwise the advantage
> of having no sharp edges is lost,
> 3. not too many of these cylinders should be used (about 150), otherwise the
> render time will increase again to the point where you can use the right media.
> 
> Jürgen

Hi. It does look like a workable solution.

Real life has me busy these days, but I'll mention a couple additional 
things.

Norbert Kern, perhaps a couple years ago (and IIRC), worked out a scheme 
where he created a high field containing media (emitting?) in front of 
his actual scene for light rays through media effects.

Second and FWIW, when I reworked the fog feature in the povr fork, I 
added an 'inverse' feature which creates the densest fog closer to the 
camera rather than at greatest depth. The idea is to make it easier to 
fake media effects with fog{} using special near-camera, otherwise 
invisible/null for ray depth only, shapes. The sad bit is aside from a 
few quick experiments, I've never gotten to really playing with the new 
feature myself...

Bill P.

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