Stretching Object without distortion to another object


I’ve been attempting to create a surface inbetween these two objects (Ideally, I want ALL of them to be one closed polysurface). However, I’ve tried numerous commands with none of the working. I just need the main part “stretched” (with no distortion) until it hits the front plate so i can boolean it to one closed polysurface. I’m not terribly good at describing things. Sorry guys! Any ideas would be appreciated!

(Pascal Golay) #2

Hi Joseph - a start would be to Explode and then Untrim some of the surfaces - see how far they go - then ExtendSrf, possibly, to get them to go farther if needed- then a lot of trimming and joining…

Feel free the post the objects in a 3dm file and someone will take a look.



I Attempted the untrim. I ended up with a massive mess. I couldn’t see hide nor hair of anything! I will upload. I can create extrude surface to curve and then trim (which distorts somewhat, which wouldn’t be my first choice) Even so, I’m having a difficult time combining them into one polysurface.RearSkirtUpload.3dm (6.4 MB)


I’m particularly frustrated at this point. I’ve been attempting this for the better part of 4 hours.

(Pascal Golay) #5

Hi Joseph - I am taking a look now - it looks to me like you have everything you need with a few surface extensions and a lot of trimming. In particular the main curved surface is plenty big enough to hit the new ‘barrier’, so that will help a lot.

@Joseph_Martin - see the attached - the surfaces are extended (ExtendSrf, Type =Smooth) by a factor of 200, and retrimmed by the new cutting surface. Most are OK - there are some that needed more work but I think this is basically the way to go.

RearSkirtUpload_PG.3dm (2.7 MB)



So you untrimmed and extended the surfaces. Did you do two at a time? I untrimmed 4 and couldn’t see anything! I wish I could have seen you did it! I’m going to give it another go! How would you recommend booleaning the end “plate” for a nice flush fit on the outside for a closed polysurface? @pascal

Thank you for your help!

(Pascal Golay) #7

HI Joseph - I ended up not untrimming most of the surfaces once I saw that many were large enough, or nearly, to reach the cutter - I just ExtendSrf -ed them. At the bottom (I reposted the file with a bit more work - download again to see) you’ll see I did a little quick surgery as those either refused to extend or extended in a non-helpful way.

Onnce you get all of the surfaces pushed out through the new cutter, (maybe you want the far side to be the cutter, I used the near side) I think, if I understand what you want, I’d ExtractSrf the face of that plate that you want to use to finish the part and trim it with all the extended surfaces and trim the surfaces with it and Join



Thank you for attempting to walk me through this. I’m just having a hard time comprehending. After extending the surfaces this is what i am left with. Tiny gaps. I tried running a matchsrf on them but it will not let due to them being trimmed. Is there an easy way to close these? I really do appreciate you taking the time to help me out! I’ve only been using Rhino for a few months now.


I used the joinedge command and it did. However, it left this fragment. Should i stay away from this command?


Reading up on the JoinEdge command. It seems as though it does not edit the underlying geometry. Which means if i export this to STEP. It will still have a “gap”. Am i reading this correctly. Is there a “joinedge” command that will edit underlying geometry? Once again, Thank you so much!

(Pascal Golay) #11

Yeah, you may need to match up some edges - the ones to change are the fillets, not the main surfaces, if possible, I would say - you’d UntrimBorder those, and then split ans shrink… I’ll see if I can make you an example.

@Joseph_Martin - here’s a little clip that shows how to do this - it is ‘fiddly’, to be sure.

  1. Surfaces oversized.
  2. They do not join - it looks like I did not capture the cursor, I’ll see about that…
  3. Split the surfaces with isucurve and then ShrinkTrimmedSrf to make the underlying surfaces match the new trim. Note you can do this within Split (Shrink=Yes) as well.
  4. MatchSrf for tangency (since these appear to be rolling ball fillets, in theory)
  5. Some sufaces overlap (is this geomtry from ProE/Creo by any chance?) Trim with surface edges - two things to notice - one is the CRV filter to force selection to be a surface edge (i.e. a curve, the edge and not the surface itself) and the other is I chose which one to trim so that I could MatchSrf the other to it.

Correct - JoinEdge is a command that can lead to all kinds of trouble - stay clear of it unless you have a particular reason for using it, I’d say.



What i did for that particular one is extractwireframe. Keep the end curves. Rebuild to less control points. move control points on both ends to smooth out curvature. Adjust cplane so i can move control points up and down on cplane. Run edgesrf. It joined well with no naked edges. I would enjoy seeing your way of doing this as i believe the way i just did it is…well…long.


But truthfully, I’m still lost as to how to properly extend these surfaces. It seems so simple in nature…


I was able to extend, trim, and rebuild surfaces that needed it. Rhino had a very difficult time offsetting that surface to a solid. I ended up having to go through and patch in the bad spots on the offset. I unfortunately do not know where the original geometry was made. Sorry @pascal! Now i just have to figure out the best way to best join these 2 objects. For the outside surface (the one you were working on) that will actually be joined to the outside of the object and then filleted. Same with the inside.

P.S. Your tutorial was AWESOME! Thanks for that!