Dear Jelle,
I was able to locate the self-intersection points using ShapeAnalysis_Wire.
There was some difficulty, because it needs a face underlying the analysed
wire.
The function 'faceAroundPlanarWire' below calculates such face assuming that
the
wire is planar. I would like to understand why a face is needed to find edge
intersections?
Anyway, the more important question is, how to proceed. The new functions
'fixWire' ' faceAroundPlanarWire' below find the correct self-intersection of
the wire in my previous example. But I cannot figure out how to use
ShapeUpgrade_WireDivide as you suggested.
It seems that I have to call ShapeUpgrade_WireDivide's method
'SetSplitCurve2dTool (const
Handle(ShapeUpgrade_SplitCurve2d)&splitCurve2dTool)'.
For the ShapeUpgrade_SplitCurve2d I have to call 'SetSplitValues (const
Handle(TColStd_HSequenceOfReal)&SplitValues)'.
But what are the SplitValues?
Is it the curve parameter at the intersection measured for indivual edges? I
don't think so, because 'SetSplitSection' does not get any information about
*which* edges are intersecting.
Are the SplitValues the curve parameter at the intersection measured for the
whole wire? To my knowledge there is no notion of the curve of a wire, is it?
So
how can I get the SplitValues after I got the intersection points (variable pts
in function fixWire below)?
---- new code fragments: ----
def faceAroundPlanarWire(wire):
topo=Topo(wire)
pts=TColgp_HArray1OfPnt(0,topo.number_of_vertices()-1)
i=0
for v in topo.vertices():
pts.SetValue(i,bt.Pnt(v))
i+=1
gpbap=GeomPlate_BuildAveragePlane(pts.GetHandle(),pts.Length(),1e-7,1,1)
plane=gpbap.Plane()
umin,umax,vmin,vmax=gpbap.MinMaxBox()
mf=BRepBuilderAPI_MakeFace(plane,umin,umax,vmin,vmax)
return mf.Face()
def fixWire(wire):
f=faceAroundPlanarWire(wire)
saw=ShapeAnalysis_Wire()
saw.Init(wire,f,1e-6)
res=IntRes2d_SequenceOfIntersectionPoint()
pts=TColgp_SequenceOfPnt()
errs=TColStd_SequenceOfReal()
print saw.Precision()
for i in range(4):
for k in range(i+1,4):
print
i,k,saw.CheckIntersectingEdges(i,k,res,pts,errs),res.Length(),pts.Length()
-----------------------------
I also appreciate any other documentation or examples about the use of the
ShapeUpgrade_WireDivide class.
The reference documentation does not help, and with google I find nothing
better.
Thank you
Björn
----- Ursprüngliche Mail ----
> Von: Jelle Feringa <jelleferi...@gmail.com>
> An: pythonOCC users mailing list. <pythonocc-users@gna.org>
> Gesendet: Donnerstag, den 12. August 2010, 11:59:03 Uhr
> Betreff: Re: [Pythonocc-users] face from self-intersecting wire, ShapeFix
>
> Sorry, hit send too soon…
>
> Have you had a look at
>
> ShapeUpgrade_WireDivide
>
> ShapeAnalysis_Wire will help you find out which are intersecting edges.
>
> Björn, if you manage to fix this ( confident you will ;) than would you
> please
>
>
>share this example with us, such that way may include it in the /examples ?
>
> Thanks,
>
> -jelle
>
> On Aug 12, 2010, at 11:20 AM, Free Cad wrote:
>
> > Hi again,
> > can you help me use ShapeFix in the correct way, or suggest other
> > solutions
>to a
>
> > problem with self-intersecting wires?
> >
> > The code below generates an example of such a wire. There is a small loop
>close
>
> > to the point (1.0,1.0,0.0) which is the reason why no face can be made
> > from
>it,
>
> > I guess.
> >
> > The code also shows my attempt to solve the problem using
>sf=ShapeFix_Wire().
>
> > But sf.Perform() always fails, even if the wire is without problems (using
> > vertex definitions as in the line which is commented out).
> >
> > What is the simplest solution to generate a face from self-intersecting
>wires
>
> > _automatically_? In my example, the small loop could be collapsed to a
>single
>
> > vertex, or the wire could be split into two (the large loop and the small
>loop)
>
> > - both solutions would be fine.
> > How about OCC's ShapeHealing functions? Are they more powerful than
>ShapeFix? I
>
> > don't understand the relation between ShapeFix and ShapeHealing. Is
>ShapeHealing
>
> > available in the non-commercial OCC distribution?
> >
> >
> > Thank you
> > Björn
> >
> > --- code example: ---
> > from OCC.BRepBuilderAPI import *
> > from OCC.gp import *
> > from OCC.ShapeFix import *
> > from OCC.TopoDS import *
> >
> > def fixWire(wire):
> > sf=ShapeFix_Wire()
> > sf.Load(wire)
> > sf.SetFixIntersectingEdgesMode(1)
> > sf.SetFixNonAdjacentIntersectingEdgesMode(1)
> > sf.SetFixSelfIntersectingEdgeMode(1)
> > if sf.Perform():
> > print 'Fix Successful'
> > return sf.Wire()
> > else:
> > print 'Fix Unsuccessful'
> > return wire
> >
> > def vertex(x,y,z):
> > mv=BRepBuilderAPI_MakeVertex(gp_Pnt(x,y,z))
> > return mv.Vertex()
> > def edge(v1,v2):
> > me=BRepBuilderAPI_MakeEdge(v1,v2)
> > return me.Edge()
> > def face(w):
> > mf=BRepBuilderAPI_MakeFace(w)
> > return mf.Face()
> > def wire(e1,e2,e3,e4):
> > mw=BRepBuilderAPI_MakeWire(e1)
> > mw.Add(e2); mw.Add(e3); mw.Add(e4);
> > return mw.Wire()
> >
> > v=[vertex(0,0,0),vertex(1,0,0),vertex(0.95,1,0),vertex(1,1,0)] #self
> > intersecting, no face visible
> > #v=[vertex(0,0,0),vertex(1,0,0),vertex(1,1,0),vertex(0.9,1,0)] #valid
wire
> > e=[]
> > for i in range(4):
> > e.append(edge(v[i-1],v[i]))
> > w=wire(e[0],e[1],e[2],e[3])
> > f=face(fixWire(w))
> >
> > from OCC.Display.SimpleGui import *
> > display, start_display, add_menu, add_function_to_menu = init_display()
> > display.DisplayShape([w,f])
> > start_display()
> >
> >
> >
> >
> >
> > _______________________________________________
> > Pythonocc-users mailing list
> > Pythonocc-users@gna.org
> > https://mail.gna.org/listinfo/pythonocc-users
>
>
> _______________________________________________
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