1 ? Select a model. At the vertex level, select all vertices and flatten them axially.

2 ? After planarization, some vertices may overlap and must be welded. Delete redundant vertices, lines and faces. This method can't remove all redundant points, lines and surfaces, and can only be simplified to a certain extent.

3 ? At the edge level, select all edges to create a graph.

4 ? In this way, a plane line is obtained by passing through the plane.

5 ? To get a 3D line, select the line directly in polygon editing mode of.

6 ? In this way, a three-dimensional figure is obtained.

7 ? After extracting the line, delete the solid model and export the image as a dwg or dxf file. The latter is more suitable for the conversion between different softwares.