[metapost] shading in meta[post/play] & PDF

[Laurence Finston]

> 
> In metapost, "perfect" spheres can be drawn, like on 
> http://www.gnu.org/software/3dldf/cdsmpls.html. But how can I add colour?

You could use the intersection points of the circles as the corners of
rectangles and fill the latter.  The more circles you use, the better the
results will be.  The very primitive surface hiding I've implemented will
almost certainly fail, so you'll have to do this by hand or implement it
yourself.  You may be able to implement surface hiding and/or shading by
operating on the MetaPost file generated by GNU 3DLDF, or by the PostScript
file generated by MetaPost.

Laurence