[ GiDlist ] Normal vector definition + Layers and meshing

Moderator: GiD Team

Post Reply
LACROIX Gilles

[ GiDlist ] Normal vector definition + Layers and meshing

Post by LACROIX Gilles »

Hi !

We have recently purchased Gid 5.0 p47 for WinNT and we are trying to
perform surface meshing (structured mesh with triangular elements) of
imported CAD surfaces (IGES format) with it. Then, we export the
generated mesh in a file (using the 'Write Mesh' command) in order to
have it processed by another program. Doing this, we have two problems :

1. Our program tries to build the normal vectors of each of the triangle
elements but it seems to us that the normal vectors are not oriented in
the same direction, even if the elements originated from the same
initial CAD surface (and this is really a problem for us). We build the
normal vector using the 3 consecutive nodes defining the triangle in the
exported mesh file of GiD. As far as we are concerned, it is the *order*
of the nodes which matters to define the direction of the normal vector.
Does GiD take care of node ordering when writing mesh data ? Is there a
way to correct this ?

2. We have grouped NURBS surfaces in layers before meshing them.
Everything works fine : the triangle elements still belong to different
layers after meshing (the same as their CAD counterparts) but we
couldn't have GiD to write this information in the Mesh file. We were
expecting GiD to add a number (defining the group) at the end of each
line of nodes (as explained in the reference manual) but it doesn't.
What's happening ?


Hope we'll get answers.

Thanks in advance,
Gilles.

--
Gilles LACROIX | mailto: lacroix at bertin.fr
Bertin Technologies
Post Reply