"GioSeregni" <gms### [at] hotmailcom> wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
> >
> > And if you DO see red there, then try moving the camera around, and viewing it
> > from different angles - because it may just disappear and pop up in different
> > areas.
>
> It seems that they always arise on the
> perimeter of the volumes (in positions tangential to the cone of vision)...

Yes, that is where those artifacts sometimes appear on a smooth-triangle object.
I think it also depends on the lighting angle, and maybe even the size of the
triangles.

What you are seeing is a known effect of raytracing the smooth normals when they
are viewed at that raking angle. (I thought that there was a short technical
explanation of this in the documentation, but I cannot find it.) The camera is
picking up the unlighted (black) interior of the object.

If I make a low-rez height_field and add the 'smooth' keyword, the same thing
happens. The interior_texture trick is one way to try and make these artifacts
less noticable. Or try adding the 'double_illuminate' keyword to the object. If
I recall, this was a recommended 'fix' for the problem. It seems to work most of
the time, but not in every situation.

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