Strange srf


see attached 3dm.

There is one srf, it comes from an igs file.
It has a strange edge which goes around 3 corners.
Using the edge for e.g. sweep is not possible.

I know how to repair it: Untrim, explode and join trim curve, retrim.

All other attemps failed: RebuildEdges, Shrink etc.

As my repair method is very cumbersome (in the complete model are 100’s of these srfs):
Is there a more elegant, semi-automatic method?


CP_StrangeSrf.3dm (35.0 KB)

Hey Charles,

The surface is degree 5 in one direction and 1 in the other. Nothing inherently wrong in that, although it does select as planar and can be replaced with a simple planar surface…

The border is the problem, it does have two small segments, 0.0523486 and 0.165513, although still larger than tolerance. One of them is only a little out of tangent with its neighbor, by around 1.75 degrees. These might cause issues I guess, especially if you are sweeping along it. Not easy to fix automatically unfortunately.

When you say “sweep is not possible” are you talking about using the border curve to sweep along something else, or trying to sweep a profile around the border?


Hi Mitch,

thanks for having a look.

I feared…

As you can imagine the whole model is totally broken.
Fillets are crazy, invalid cylinders etc.
The sweep was intended to remodel those fillets, and with srfs like the above it is a lot of effort.

A few wrong fillets in a model would be acceptable, but when rebuilding them requires to fix all the neighbor geometry before, then not.
In fact, the model looks acceptable, but it is in no way.

Too bad there is no cheat to fix those srfs.