Best way to lengthen the middle of a linear shape surface or solid?

Attached file showing simple shape I need to extend the middle of without altering shape at end.
Scale1D makes end more acute than 45deg. It must remain a 45deg cut.
I tried for extendSrf but cannot select the end.
Should I make it a solid to assist or not ?
Door Beading extend.3dm (53.8 KB)

Hi Steve,

Try the Stretch command and specify the stretch axis only in the center straight section of the part.

Hi Steve,

I’d use sub-selection for this:

Hold down both the SHIFT + CTRL key. Now Window select the edges of one side.
You now have the edges selected and you can move them how you want (along the length of the beam).


Hi Brian,

I tried to stretch the beam and found the surfaces to get much more dense with each iteration.

In addition: I could not get both sides to work for stretch, can you confirm that it works for this beam?


I am unable to do this, selecting axis in centre of item a few cm apart then clicking on where I want to stretch it to sees it go far beyond that click.
Beading stretch.3dm (84.3 KB)

That’s correct, Stretch is part of the UDT tools like CageEdit that will preserve surface relationships and continuity at the cost of increased control point density.

It looks odd that one side doesn’t move but I believe it’s still working. The control point structure is mirrored on the other side of the stretch axis’ mid point unlike when the both sides option is not used. I’m not sure if the command was designed to move both sides in unison but I’ll look into it and file something for the developers. Thanks.

If you want to have the 45 end meet up with another (this is a variation on your original question), I’d use sub object selection as mentioned by Willem. Ctrl+Shift click the edges on one end and then use the Move command to move that edge from one Osnap to another like this…

Not sure why the solution has to be so complicated - really no need to get any UDT tools involved. Untrim the extrusion. Scale1D to make it longer. Move your trim objects (planar surfaces). Retrim. That gives you nice clean surfaces. Takes about 30 seconds. Would this particular task be faster in a parametric modeler? Yes, but Rhino isn’t parametric.

Edit - hell it can be even easier. No need to untrim. Just move your trim objects, and then Scale1D your extrusion until it extends past the new trim objects. Split.

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My item has 45 deg slant at both left and right ends, need to extend the left end.
Trying skyg method, moved planar surface trim object to new cut position at left.
selected the far right end tip and used scale1D to extend item leftwards.
the 45 deg angle at right also stretched.
How can I scale1D and avoid one end losing its shape ?


Untrim both ends. Move the 45 degree cut surface to its new position, extend surfaces past it, then re trim both ends.

Hi Steve,

Short answer, you can’t (in this example).

Regardless of where you place your origin for Scale1D, some deformation is inevitable, because of the mitered end. If the end were at 90 degrees to the axis or direction of scaling, instead of 45, your origin could be at the end, and it would be a fixed angle and not deform. With the mitered end, if your origin is at the end, the rest of the miter will start to stretch out towards the other end, changing the angle. If your origin is anywhere other than the outside end of the miter, the miter will begin to stretch out in the opposite direction. It’s just the way Scale1D rolls, hence, all of the other very good, simple, effective options you’ve been given. Everyone has a favorite way to solve an issue like this, or based on additional criteria, will choose a specific solution. Scale1D is great for a lot of things, this just isn’t one of them.

Best regards,

From my reply:
“Move your trim objects (planar surfaces). Retrim”

“Objects” and “surfaces” are plural. Retrim both sides, buddy.

Thanks for sharing this method, Helvetosaur. It’s certainly the best way to do it.