Hi,
I'm importing a STEP model, generated using a C++ program using
OpenCASCADE, consisting of triangular NURBS patches. Of course, these
are really rectangular but each has one degenerate edge.
I got a lot of errors "Something wrong with edge loop". It turns out
that GEdgeLoop::GEdgeLoop(const std::list<GEdge*> &cwire) will often
miss the degenerate edge. For example, if the edge list contains AB,
BC, CA, CC in that order, then the edge loop will close as AB+BC+CA and
CC will be skipped. We would fall through to the end of nextOne(),
which should never happen.
Thus nextOne() should check for a degenerate edge and process it before
moving on (in the same way that it already checks for seams). I've
attached a patch which does this.
diff -u -r gmsh-2.3.1-cvs-20090220-old/Geo/GEdgeLoop.cpp gmsh-2.3.1-cvs-20090220/Geo/GEdgeLoop.cpp
--- gmsh-2.3.1-cvs-20090220-old/Geo/GEdgeLoop.cpp 2008-12-29 23:02:55.000000000 +0000
+++ gmsh-2.3.1-cvs-20090220/Geo/GEdgeLoop.cpp 2009-03-02 13:15:06.000000000 +0000
@@ -47,6 +47,24 @@
if(v1 == gv || v2 == gv) possibleChoices.push_back(ge);
++it;
}
+ // Degenerate edges: don't miss them
+ it = possibleChoices.begin();
+ ite = possibleChoices.end();
+ while(it != ite){
+ GEdge *ge = *it;
+ GVertex *v1 = ge->getBeginVertex();
+ GVertex *v2 = ge->getEndVertex();
+ if(v1 == v2){
+ wire.erase(std::remove_if(wire.begin(), wire.end(),
+ std::bind2nd(std::equal_to<GEdge*>(), ge)),
+ wire.end());
+ if(v1 == gv) return GEdgeSigned(1, ge);
+ if(v2 == gv) return GEdgeSigned(-1, ge);
+ Msg::Error("Something wrong in edge loop");
+ }
+ ++it;
+ }
+ // Repeated edges: don't miss them
it = possibleChoices.begin();
ite = possibleChoices.end();
while(it != ite){
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