3-D graphing

["Andrew D. Hwang" <ahwang@mathcs.holycross.edu>]

Started this post about six weeks ago; since ePiX is being re-designed,
this seems a good time to raise these issues.

By the way, ePiX is currently capable of kludges like
  http://mathcs.holycross.edu/~ahwang/software/images/maskplot.png

Source code:
  http://mathcs.holycross.edu/~ahwang/software/images/maskplot.cc

The (commented out) white plot emphasizes the hidden line removal, but
doesn't look very good. The image uses PostScript's layering to hide
lines, and is not really an acceptable general solution. It's meant more
as an appetizer of what's possible (with the current version) without much
effort.

--Andy

---(snip)---

The greatest "external" deficiency in ePiX is its lack of support for true
3-D graphing. I still regard ePiX is a means of drawing line diagrams (as
opposed to bitmaps), and would like an eventual 3-D version to write eepic
(or MetaPost...?) files. Unfortunately, most existing open source software
uses OpenGL (which may or may not have provisions for extracting visible
vertices and line segments), and most discussions of hidden object removal
refer mostly to bitmaps (z buffers). If anyone knows more or has ideas
about fast algorithms for hidden object removal in line diagrams, I'd love
to hear. :)

My own interest is drawing parametrized surfaces and polyhedra, for which
line diagrams should be adequate. I'm not averse to providing for surface
colors and textures, though I suspect a different output format would be
needed. Along these lines, it would be straightforward to write a front
end for POV-Ray (similarly to the way ePiX is a front end for eepic); the
only "new" issue would be getting high quality typography into the output.
This idea appeals to me (as being relatively little work:) if the issue of
typography is easily surmountable.

Andrew D. Hwang			ahwang at mathcs dot holycross dot edu
Department of Math and CS	http://mathcs.holycross.edu/~ahwang
College of the Holy Cross	(508) 793-2458 (Office: 320 Swords)
Worcester, MA, 01610-2395	(508) 793-3530 (fax)