Thomas White wrote:
> 
> The trouble is, when I add a bumpy texture with "normal { bumps
> 0.8 scale 0.2 }" I can see a definite sharp edge to the illumination
> that should not be there.  What is going on?  The sharp edges do not
> follow the contours created by the texture - they are just circular
> lines going around the sphere.

This is because the texture doesn't create any actual contours.  It
merely fiddles with a property of the surface called the normal, in
such a way as to make the surface appear rough.  Away from the edge of
the shadow this looks fairly convincing, but at the edges the
appearance gives the method away.

The sharp edge is the terminator between the lit and shadowed sides of
the sphere.  It remains circular, instead of becoming jagged, because
the actual shape of the sphere hasn't changed.

Indeed, the texture effect causes spots immediately adjacent to the
terminator to appear brighter than the same place, smoothly textured,
so the sharpness of the terminator becomes pronounced in spots.

Regards,
John
-- 
ICQ: 46085459

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