Why can't this surface be extended?

Rhino
1

cannot-extend.3dm (36.1 KB)

2

my best guess is, that it is because the surface is trimmed. I untrimmed it and extending worked fine.

3

It’s a “bad object” which means there is a problem with its data. SelBadObjects shows bad objects. Untrimming the object eliminates the problem so the cause appears to be in the trim.

DupBorder
Untrim
Trim with the duplicated border.
ExtendSrf works as expected.

4

Thanks, but yeah… I have to say that despite me having a list of issues with Rhino longer than god, this bloody “feature” has probably climbed to the top in recent years… :face_with_symbols_over_mouth:

5

The two worst things in Rhino are ExtendSrf and FilletEdge.

6

How did you create the object?

7

I used the famously very precise trimming in Rhino… :expressionless:

8

Hi Robert -
If you post the file in the pre-trim stage, we can take a look at what goes wrong.
-wim

9

The surface seems to work after the repair in Rhino 7, not in 8, so I logged it
RH-83755 ExtendSrf fails

10

RH-83755 is fixed in Rhino 8 Service Release 13