Perhaps your offset value is so small that it is roughly as large as
your Precision().Confusion() tolerance.
Does it segfault with larger values?
Are you checking offset.IsDone()?
-jelle
On Apr 18, 2010, at 2:06 PM, Dave Cowden wrote:
Segfault. I am able to diagnose once i have a stack trace.. I was
hoping you knew of a way to get a stacktrace from a segfault, but
sounds like you end up diving into the source at that point...
thanks for the help, i know where to get the c++ source so i'll poke
around...
thanks as always for the quick response and help !
On Sun, Apr 18, 2010 at 7:54 AM, Thomas Paviot <tpav...@gmail.com>
wrote:
What do you mean exactly with 'crash'? Do OCC raise an exception
catched by pythonOCC (like Standard_ConstructionError for instance)
or is it a segfault?
If the error is not reproductible (ie. according to the wires passed
to the BRepOffsetAPI_MakeOffset class, the Perform() method passes
or fails), it may come from an issue in the algorithm used by OCC de
perform the operation. In that case, it's really difficult to
identify the problem, unless diving into the C++ code.
Thomas
2010/4/18 Dave Cowden <dave.cow...@gmail.com>
Hi, Thomas, thanks!
That definitely makes my code much more readable: but unfortunately
the crash still occurs at that same place. I also switched to using
Topo in a couple of other places ( where the face you see passed
into that method is created ), but that did not help either.
How do you go about finding what's going on when you encounter these?
On Sun, Apr 18, 2010 at 12:30 AM, Thomas Paviot <tpav...@gmail.com>
wrote:
2010/4/18 Dave Cowden <dave.cow...@gmail.com>
Hi, all:
I'm struggling with a couple of problems that I presume to be null
pointers that are crashing OCC. I have a feeling this may be
related to memory management.
For example, I've tracked down one crash to one line:
BRepBuilderAPI_MakeOffset.Perform(). I load it with several wires,
each of which I can display successfully immediately before invoking
perform. Yet, Perform() crashes. See example below. I do not
believe any object scoping issues are at play that I can see: all of
the objects in question seem to be in scope when the crash happens.
I am also fairly certain that its something I'm doing: all of the
'simple' test cases I create work fine.
So my question is: are there any tricks/techniques I can use to
isolate the problem when a crash occurs? Right now i'm using old
school print statements to get to what method call dies, but I still
cannot see what exactly is going wrong. Help is appreciated, this
is completely kicking my butt :(
#offset a face, returning the offset shape
def _offsetFace(self,face,offset ):
brt = BRepTools.BRepTools();
ow = brt.OuterWire(face);
bo = BRepOffsetAPI.BRepOffsetAPI_MakeOffset();
bo.AddWire(ow);
#now get the other wires
te = TopExp.TopExp_Explorer();
te.Init(face,TopAbs.TopAbs_WIRE);
while te.More():
w = ts.Wire(te.Current());
TestDisplay.display.showShape(w); # this line succesfully shows
the wires on screen
if not w.IsSame(ow):
bo.AddWire(w);
te.Next();
te.ReInit();
print "about to offset...";
bo.Perform(offset,0.00001); #this line crashes hard, but only
sometimes.
print "done offsetting..";
if not bo.IsDone():
raise Exception, "Offset Was Not Successful.";
else:
return bo.Shape();
Hi Dave,
If you want to traverse topology, I suggest you use the Topo class
available from the High-Level Topology subpackage (the 'Topo' name
for this class is maybe not the best one). This is a wrapper over
the TopExp class which fixes issues related to TopExp (with the use
of the __hash__ method):
from OCC.Utils.Topology import Topo
#offset a face, returning the offset shape
def _offsetFace(self,face,offset ):
brt = BRepTools.BRepTools();
ow = brt.OuterWire(face);
bo = BRepOffsetAPI.BRepOffsetAPI_MakeOffset();
bo.AddWire(ow);
#now get the other wires
for w in Topo(face).wires():
bo.AddWire(w);
print "about to offset...";
bo.Perform(offset,0.00001);
print "done offsetting..";
if not bo.IsDone():
raise Exception, "Offset Was Not Successful.";
else:
return bo.Shape();
Hope this helps,
Regards,
Thomas
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