_InsertEdge greatly distorts the original shape

This wouldn’t make sense, mathematically or in terms of usability.

The issue with the _InsertEdge command here is that there’s no option to choose and fix the endpoint. For users working with a SubD object that has triangulated end caps, like this cylinder or any more complicated object such as a SubD of a fingertip on a hand, it will be useful to have this option within the command. In this simple example, I could see it working as follows:

  1. Call _InsertEdge
  2. Select an option called “fixed endpoints”
  3. Click to select an endpoint.
  4. Now when the user moves the cursor to place the inserted edge, the endpoints act as pivot points and don’t move.

I expect this will mostly make sense if the endpoints are on vertices, but maybe there are other applications.