Re: [Closed REQ 6081]: Geomview and vertices order

[daemon]

Vertex order should be important in geomview only for computing
surface-normal directions; in particular, when several faces share
a common vertex, and the faces on that vertex don't all have consistent
orientation, the shading can look very strange -- some faces might turn black,
for example.  This won't actually change the apparent *shape* of any faces,
though.  

You might have other problems
  - if the vertices of each face don't lie in the same plane, or
  - if the faces aren't all convex polygons.

In either of these cases, you might find that faces are only partly
visible, and may change shape strangely as you look at them from different
points of view.

There are some ways you might work around such problems.

In case it's hard to generate the OFF file with faces that have a consistent
orientation, I've written a perl script which should re-orient them correctly;
you can pick up by anonymous FTP from geom.umn.edu
  priv/slevy/offorient.shar

If some faces might be concave polygons, the Open GL version of the
latest release of geomview (1.6.1) has an appearance setting which should
render them correctly; type the "aC" keyboard shortcut, or see the Appearance
panel.