Control points / surface isocurves

I’m working with planar surfaces, mostly 4 corners and untrimmed.

To make them intersect, I can either move control points or control+shift click an edge and scale / move with the gumball. In same cases I ended up redrawing a new 4 point surface on top of an existing trimmed surface.

When editing the new untrimmed 4 point surface, the surface changes to a trimmed surface.

You can see it on the image:

  1. Trimmed surface
  2. Untrimmed surface with the same outline as 1
  3. scaled one edge, surface changes to trimmed

This doesn’t happen in V6 anymore which is great. However I’d like to understand why it happens in V5?

Maybe someone can explain?


Hi Martin - I don’t think there is really a good explanation other than that the direct editing does not work as well in V5 - the code just converted to trimmed planes where possible, and we’ve stopped doing that …


Thanks for the quick reply. Direct editing is awesome and I’m glad this has been improved in V6 :relaxed:

@martinsiegrist - to convert back to untrimmed on these (one at a time):

! _Select _Pause _SetRedrawOff _-Properties _Object _Name "DeleteMe" _EnterEnd _DupBorder _Pause _Explode _EdgeSrf _Delete _SelNone _-SelName DeleteMe _Delete _SelLast _SetredrawOn



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that sounds like fun

Just copy/paste that macro or put it on a button or alias…


I’ve got one question though. Is there no way to get the untrimmed surface from a trimmed one? Shrink Trimmed Surface only makes the original Surface smaller, but it’s trimmed too.

The left one is the original trimmed surface, the middle one after Shrink Trimmed Surface is applied, the last is drawn with the _SrfPt command. Is there a way to get to the last surface with a command?

Hi Paul - the macro I posted above should do it.


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Ah, yeah, right, perfectly!

i swear i was able to do that in Rhino 4 or 5.

Pretty sure i have done it many times in the past working with triangular surfaces. Tried it today for a structure and was shocked that i could not just move the 3 points (which autoomatically became 4) and the surface would stay planar.

which brought me here after google searching.

did you change something in the meantime?