A command SelMeshFacesBySaddleForm would be absolutely amazing to have. If available also in RhinoCommon it would be a dream.
Some useful options would be like;
* “Match Rings” (no. of rings for the matching, like 1, 2 or 3 rings),
* “Min Acceleration” (added percent (angle) for ring 2-3 compared to ring 1-2 etc).
* “Select Rings” (no. of rings ( 1, 2 or 3) to select from the Matched Rings)
* “Min Acceleration UV” (same as Min Acceleration but with separate accelerations for the two Principal Components U and V (PCA)).
The image you posted looks similar to a mesh segmentation method that @AndersDeleuran experimented with called “Edge Burning”…(I think that is the name he used). He provided some examples at some point in the past on his git hub site. From those examples, I had re-written something similar for use in our landscape practice. It starts at the naked edge of a mesh, finds all the naked faces, then makes a mesh “loop”, and continues inward until there are no naked faces left.
I’m not sure it’s exactly what you want, but maybe it’s close? Also, I second your wish request!
Note: In the screenshot above, we are experimenting with applying this, (along with various other internal workflow for terrain manipulation/creation), to quad mesh workflows. (Which are much easier in Rhino 7!)