In article <3d8d447b@news.povray.org>,
 "Gilles Tran" <git### [at] wanadoofr> wrote:

> The code below shows 2 potential bugs affecting transparency.
> These have been observed on 3.1 (using material_map) and 3.5, at least on a
> Windows version, running XP.
> The first bug makes the transparent part visible. It's apparently linked
> with fog turbulence.

It isn't a bug, just a limitation of fog. Fog is really a cheat, it uses 
the distance along the ray to figure out how much fog it goes through 
assuming constant or gradient fog, and then uses turbulence with the 
intersection point scaled by the turbulence amount and some other tricks 
to mess with the real fog value. The result is nothing like real fog, 
but usually looks good and is fast to compute.
"Fixing" this would require making fog into a more limited media, if you 
need accurate results in this kind of situation just use scattering 
media.


> The second bug makes the normals behind look weird when the transparency
> texture is scaled very unevenly (pure 100% transparent texture is not
> affected).

I haven't had a chance to render this, but it seems very unlikely that 
there is some problem with scaling of normals, or even scaling of normal 
patterns. Maybe there is a problem with the ray directions not being 
normalized for some reason...

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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