Re: [Closed REQ 5252]: geomview question

["Stuart Levy" <slevy>]

> For robustness and debugging, i would like to further use
> geomview to check this ordering.  The question is:  Is there
> a way to force normals to be drawn according to the ordering
> of the vertices?  Then normals that do not point outwards
> (or inwards, according to the convention) would indicate bad
> orderings.  Also, if the vertices are not cyclically ordered
> drawing the normal would fail or complain.

> Thanks
> Ioannis Emiris

Yes.  There's a "facing normals" button on the Appearance panel in the
SGI version; it's not there on the X version.  It's normally enabled, so that
normals are flipped to point in the hemisphere facing the camera.
When disabled, normals point in a direction determined by the vertex order.
The keyboard shortcut "av" (typed with the cursor in a graphics window)
also toggles this feature.  (Or, "1av" enables normal-flipping, "0av"
leaves normals pointing the natural direction.)  You can set geomview to
leave normals intact by default, by putting a line in ~/.geomview reading:

(merge-ap world { -evert })

There's no way to make geomview complain if (say) the normals on adjacent
polygons don't match.  But, notice the "Show normals" button on the
Appearance panel which forces normal-vectors to be drawn at each vertex.

Is this what you had in mind?