Problems IGES reading

Pre-study for Renault:
Problems are mostly around IGES reading, with strange behaviouir on "groups
from IGES". Also this shows a problem of robustness in the viewer (it should
not crash, while it can skip a face if the model is not good).

Because discussions with Renault are on, it would be the best to have a first
diagnostic (even if no fix) for next Monday (21 JAN), else at
least for end of the month, is it possible.

Analysis of chassis.igs (all is on C40)
MAJOR problem

When converting it as a whole, problems appear
When converting the faces one by one or through selection, all are (seem) OK

Faces badly oriented (wire is reversed). N0s of faces (explo.) + IGES entity
254 : 4120 380 : 6619 282 : 4515 278 : 4441 345 : 6010
338 : 5848 387 : 6869 381 : 6653 305 : 5103

A Face is clearly wrong : see number of vertices and how the edges are
built : some have C3D only (even if they are limited by the same vertex),
some have pcurve only ...
It is face n0 378 coming from iGES entity 6584

Result : the sample import export crashes (because of face 378) on the whole
file, but passes, and with no orientation error AS IT SEEMS AT FIRST GLANCE,
on a file in which the GROUP has been removed.

Crash in sample import export seems to be in BRepMesh_IncrementalMesh because
some edges have no pcurve : in such case, it makes sense to produce no mesh for
that face, so it will not be shaded.

    Analysis of finv2.igs
    Less critical problem

It contains a face and a free wire. We can ignore the wire.
It is well displayed in DRAW, but the Sample Import Export doesn't shade it.

    Analysis of fhole.igs

It contains a face with 2 wires (holed face).
In DRAW, the internal wire is badly oriented, while it seems to be well
oriented when converted by Sample Import Export.