How to get the size of a surface?

How to get the size of a surface?
Thanks for any help!

haocb's picture

I have found it!

TopoDS_Shape S = BRepBuilderAPI_MakeFace(BSplineSurf).Face();
GProp_GProps System;
BRepGProp::SurfaceProperties(S,System);
Standard_Real Area = System.Mass();