John Bradshaw <joh### [at] nospamhotmailcom> schrieb in im Newsbeitrag:
3c741eae$1@news.povray.org...
> > And what i really miss in these images is the so-called "Kanten Effekt"
> > characteristic to SEM images. In short this means that thin and sharp
> > parts of the object show up much lighter than the more even and smooth
> > parts.
>
> Do you have an example of this effect? Could it be simulated with media?

I have. The sawtooth-like structures in the upper part of the picture get
thinner on the right side. So more secondary electrons emerge from the
sample which brighten up the image in that parts. ("Kante" means "edge", for
those who don't speak german.)

BTW, there _can_ be a "directional lighting" in SEM images. It just depends
on how much voltage you apply to the detector grid. If, for example, the
voltage is zero, you collect only those electrons flying directly into the
detector, leaving the surfaces facing away from it completely dark.

In POV you could perhaps simulate SEM images by radiosity. If you put a thin
horizontal ring around the scene, with ambient=1 all parts facing horizontal
would be the brightest, and all facing vertical would be the darkest,
assumed the camera is looking along -y.

Michael
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