Re: [Update REQ 6232]: Geomview

[daemon]

> Hmm, I can think of a messy way around this that isn't quite what I'd
> imagined at first. I suppose another way would be to just draw a new
> polygon (face) in exactly the same location as a picked one, in a
> different colour (creating two overlapping geoms)

Yes, if marking the faces is enough, just adding new objects to the scene
would be a great way to do it.  It probably wouldn't work to simply create
a new face, congruent to the old one, and put it in exactly the same place.
You could displace it a bit, but only if you know from which side the face
will be seen (or create *two* new faces, one each above and below the old).

Simplest way to get some sort of marking: create some points,
placed say in the center of the selected faces.  (You could do that with e.g.
    appearance { linewidth 3 }
followed by a VECT object with a bunch of 1-vertex polylines (i.e. dots)
coinciding with the face centers.)  Since geomview automatically makes
points & lines, which coincide with a face, visible from *both* sides
of the face, this should work well.

> I've had a look at Crayola, but this seems to use a lot of Geomview
> internals and looks to be quite a complicated way of achieving a pretty
> simple effect. However, this is along the lines of what I want to do. Is
> there any point in trying to figure this out, and if yes, do you make
> internals reference material available?

I think a lot of the complication in Crayola just comes from having to
deal with lots of possible ways to change many different types of geom objects.
Indeed, you shouldn't need to be nearly as general; since you could work with
a single object, of a single data type (OFF I suppose), and since for marking
purposes you wouldn't even need to alter the object itself, you could probably
get all the information you need from the responses to
  (interest (pick world))
messages -- they'd contain both face indices within the OFF's face list
(to record which faces had been chosen, for later export) and
world-coordinates of the face's vertices (for creating visible markers).
It might be handy to look at the code for "nose", or at "example4.tcl".

  Stuart