edge representations explained

I can't really capture how edge representation 2 works on brep format. I have an edge representation of type 2 defined by a line p(0, 0.8) d(1, 0) and refers to a surface of type cylinder p(0, 0, 0) N(0, 0, 1) dx(1, 0, 0), dy(0, 1, 0) r(0.8). How does that edge defines a boundary on the cylinder?

Pawel's picture

Hello Chris,

every 3d surface has a corresponding 2d (uv or parametric) representation. In order to represent the cylindrical surface in two dimensions imagine you cut it through, unroll and put on a plane. The edge that was created as a result of cutting is your line.

To understand more about geometry an topology in OCCT, have a look here:


You can also use Total Engineer to see the topological structure of your shapes:


Hope this helps