[gts-general] Cutting a model up...

[Stephane P. <s.p...@ni...>]

Hi Paul,

 > I didn't know whether I should be receiving a GtsTriangle or a GtsFace, so
 > I tried both but the program fails on the assert - keep_faces ==
 > FALSE.  This is set in the GTS function gts_surface_foreach_face.  

Ok, what you do is allright in principle but the function
gts_surface_foreach_face() does not allow you to destroy faces of the
surface you are currently traversing (it confuses the hash table used
to store the faces of a given surface, hence the test on keep_faces in 
gts_surface_foreach_face).

In the next release (due soon), there will be a
gts_surface_foreach_face_remove() function which will allow you to do that.

Go and have a look in the CVS repository in the surface.c file you
will find this new function.

 > I have
 > also tried passing an array to store all the triangles in that I want to
 > delete and then deleteing them afterwards but this doesn't seem to work
 > either.

Hmm, this is more surprising, this approach should work, you probably
want to check that there isn't another problem in your code.

 > So any pointers as to what I should be doing would be very helpful, but
 > here are a few questions...
 > 
 > (1) can I just delete a GtsTriangle, and
 > (2) does it update the information associated with the surrounding
 > triangles?

Yes, it does.

 > (3) can I just delete a GtsFace, and
 > (4) does it update the information associated with the surrounding
 > triangles?

Yes, in the same way.

 > (5) which should I use - and what is the difference?

There is no difference. A GtsFace is also (via inheritance) a
GtsTriangle, if you call the gts_object_destroy() function on these
objects, there destroy() methods will be called (recursively if
necessary), if this is a GtsFace, its destroy() method will be called
and update the parent GtsSurface, then the destroy() method for
GtsTriangle will be called (because a GtsFace is also a GtsTriangle)
which will update the GtsEdge used by this GtsTriangle, and so on
until the destroy() method for a GtsObject is called which will free
the memory associated with this object.

 > (6) is there something better to use than gts_surface_foreach_face to get
 > the information I need.

See my point above.

Hope this helps,

Stephane