How to get the points on the boundary of the shape in 2D case

lejingwang
Fri, 10/20/2006 - 02:29

Forums:

is there any method to get the points on the boundary of the shape in 2D case. Because I want use lines to approximate the boundaries.

thank you in advance!

LI
Fri, 10/20/2006 - 13:14

Get the edges of the boundary and then get the curve of the edges.
With the curve, you can get any point you want.

lejingwang
Sat, 10/21/2006 - 12:56

Could you give me some examples? Thank you !

LI
Sat, 10/21/2006 - 13:09

Here is an example in 3D case. 3D case is general.
Suppose that you have already a face that is TopoDS_Face.

double aFirst,aLast,t,x,y,z;
gp_Pnt gp;
TopExp_Explorer expw;
TopExp_Explorer expe;
for(expw.Init(face,TopAbs_WIRE);expw.More(); expw.Next())
{
TopoDS_Wire wire = TopoDS::Wire(expw.Current());
for (expe.Init(expw.Current(), TopAbs_EDGE);expe.More(); expe.Next())
{
TopoDS_Edge edge = TopoDS::Edge(expe.Current());
Handle(Geom_Curve) myCurve=BRep_Tool::Curve(edge,aFirst,aLast);
if(!myCurve.IsNull())
{
//here you can get any point on the curve, for example:
t=(aFirst+aLast)/2.;
myCurve->D0(t,gp);
x=gp.X();
y=gp.Y();
z=gp.Z();
}
}
}

lejingwang
Sat, 10/21/2006 - 14:45

Thank you :)

Another question, Have you used Poly_Polygon2/3D? It looks like can approximating representation of a curve and providing the points that are used to define Polygon.

LI
Sat, 10/21/2006 - 22:20

You are welcome. But I've never used Poly_Polygon2/3D.