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Edges to wire

Matthias Kostka's picture
Forums: 

Hi,

i have a couple of edges (see attachment red color) and now i connect them to a wire with:

BRepBuilderAPI_MakeWire makeWire;
for (TopExp_Explorer ex(intersectionShape, TopAbs_EDGE); ex.More(); ex.Next())
{
makeWire.Add(TopoDS::Edge(ex.Current()));
}
makeWire.Build();

but i only get the green wire.

Looks like the the makeWire.Add(..) adds a not connected edge, but they are all connected (like the picture shows).

Thx for help
Matthias

Attachments: 
Cauchy Ding's picture

Hi Matthias,

Before calling BRepBuilderAPI_MakeWire, you have to sort edges' order.

Ding

Matthias Kostka's picture

Thx Ding,

how could I do that?

Matthias

Cauchy Ding's picture

Hi Matthias,

If input edges don't contain any degenerated edge, you can use similar codes listed in attachment.
Hope it works for you.

Ding

Attachments: 
Matthias Kostka's picture

Hi Ding,

thx for your time. i will take a look at your nice code. ;)

Thx Matthias

Sharad Verma's picture

Thanks Ding.. Thanks a lot.. :)

Sharad Verma's picture

Hi Ding,

This code doesn't work for the wire, which contains an edge twice. Same as a pipe contains twice the connecting edge, the above code doesn't return 4 edges, it returns only 3 edges.

Can you please give me corrected algo for the same?

Mark Blome's picture

Dear Shard Verma,

you can use ShapeAnalysis_WireOrder to sort edges, this is how I do it in Python using PythonOCC
wrappers for Opencascade. The funtion below will return a list of wires, in case you have provided edges
that are not connected:

def _buildWiresFromEdgeset(self, edgelist):
from OCC.TopExp import TopExp
from OCC.BRep import BRep_Tool
from OCC.ShapeAnalysis import ShapeAnalysis_WireOrder
from OCC.Precision import Precision
from OCC.BRepBuilderAPI import BRepBuilderAPI_MakeWire
from OCC.BRepBuilderAPI import BRepBuilderAPI_WireDone, BRepBuilderAPI_EmptyWire, BRepBuilderAPI_DisconnectedWire, BRepBuilderAPI_NonManifoldWire
wb_errdict={BRepBuilderAPI_WireDone:"No error", BRepBuilderAPI_EmptyWire:"Empty wire", BRepBuilderAPI_DisconnectedWire:"disconnected wire",
BRepBuilderAPI_NonManifoldWire:"non-manifold wire"}
sawo_statusdict={0:"all edges are direct and in sequence",
1:"all edges are direct but some are not in sequence",
2:"unresolved gaps remain",
-1:"some edges are reversed, but no gaps remain",
-2:"some edges are reversed and some gaps remain",
-10:"failure on reorder"}
TE = TopExp(); DS=TopoDS()
isclosed = False # in general, wires will not be closed
mode3d = True
SAWO = ShapeAnalysis_WireOrder(mode3d, Precision().PConfusion())
for edge in edgelist:
V1 = TE.FirstVertex(DS.Edge(edge))
V2 = TE.LastVertex(DS.Edge(edge))
pnt1 = BRep_Tool().Pnt(V1)
pnt2 = BRep_Tool().Pnt(V2)
SAWO.Add(pnt1.XYZ(), pnt2.XYZ())
SAWO.SetKeepLoopsMode(True)
SAWO.Perform(isclosed)
#print "SAWO.Status()", SAWO.Status()
if not SAWO.IsDone():
raise RuntimeError, "build wire: Unable to reorder edges: \n" + sawo_statusdict[SAWO.Status()]
else:
if SAWO.Status() not in [0, -1]:
pass # not critical, wirebuilder will handle this
SAWO.SetChains(Precision().PConfusion())
Wirelist = TT.IndexedListOfShape()
#print "Number of chains: ", SAWO.NbChains()
for i in range(SAWO.NbChains()):
wirebuilder = BRepBuilderAPI_MakeWire()
estart, eend = SAWO.Chain(i+1)
#print "Number of edges in chain", i, ": ", eend - estart + 1
if (eend - estart + 1)==0:
continue
for j in range(estart, eend+1):
idx = abs(SAWO.Ordered(j)) # wirebuilder = s_addToWireBuilder(wirebuilder, edgelist[idx-1])
if wirebuilder is None:
raise RuntimeError, " build wire: Error adding edge number " + str(j+1) + " to Wire number " + str(i)
err = wirebuilder.Error()
if err != BRepBuilderAPI_WireDone:
raise RuntimeError, "Overlay2D: build wire: Error adding edge number " + str(j+1) + " to Wire number " + str(i) +": \n" + wb_errdict[err]
try:
wirebuilder.Build()
aWire = wirebuilder.Wire()
Wirelist.append(aWire)
except Exception, err:
raise RuntimeError, "Overlay2D: build wire: Creation of Wire number " + str(i) + " from edge(s) failed. \n" + str(err)
return Wirelist

def _addToWireBuilder(self, wirebuilder, aShape):
DS=TopoDS()
st = aShape.ShapeType()
if (not st in [TopAbs_WIRE, TopAbs_EDGE]):
raise RuntimeError, "_addToWireBuilder: Shape must be an edge or a wire."
edgelist = allEdges(aShape)
for i, edge in enumerate(edgelist):
try:
wirebuilder.Add(DS.Edge(edge))
except Exception, err:
raise RuntimeError, "build wire:Error adding edge number " + str(i) + "to Wirebuilder: \n" + str(err)
return wirebuilder

Timo Roth's picture

Also ShapeAnalysis_FreeBounds::ConnectEdgesToWires can be used to build wires from unsorted edges. I guess Mark's solution has better performance but I didn't check it. After the call to ConnectEdgesToWires it might be necessary to fix the resulting wires.

Regards,
Timo

Timo Roth's picture

See also http://www.opencascade.org/org/forum/thread_19660/?forum=3