Unable to join these surfaces

(Willem Derks) #1


Can anyone shed some light on why these surfaces do not join as expected?
It must have something to do with them having singularities, yet I never ran into this type of problem and although that might be because I never had this situation in a model, yet it feels buggy they are not joining.

Select all and run _Join. It does join but not into a single polysurface.

UnableToJoin.3dm (97.7 KB)



If you use the JoinEdge command you will see to what extent there is a redolence issue.

(Willem Derks) #3

Thanks, I’ll check on it.

Just checked, but the intolerance is way below the file tolerance.
Thus something is still wrong.



How were your triangular surfaces created? I did both 3pt and 4pt at your locations and they both joined without issue. I then did a curvature analysis on your original surfaces and they are not planar at the Apex

So only the shared base curve will join properly

(Willem Derks) #5

Hi Danny,

They are straight lofts between the 2 sides. In theory they are flat, it’s just the mesh that messes up I guess.

I’m planning to use these surfaces for mapping to and from surface pairs in 3D and flat (on a layout)
Think of mapping a logo onto the 3D surfaces and then using a scripted flowalongsurface to map them onto the 2D layouts.

I do wonder now if I will get unwanted distortions at those singularities…l better test that now first.

EDIT: just tested and no noticeable distortions at the singularities.



There is something wrong with the boundary definitions.
When I select all the surfaces and run untrimall they join.

(Willem Derks) #7

Hi Jim,

Thanks for looking into that. Seems like a bug in lofting straight…



if you select all the surfaces then _ChangeDegree, they will then join… even if you don’t actually change the degree (keep the U & V at 1… just run the command on the surfaces though)

i don’t have an explanation for this… just adding some clues to the mix :wink:

(Willem Derks) #9

Hi Jeff,

Thanks, I guess at this point @Pascal should get this to the “bigger brains” at McNeel.


(Pascal Golay) #10

Yeah, something does not smell too good here. I’ll add this to the bug heap. PlanarSrfs from the borders of these do join correctly.

@Willem , Thanks for the example.