Wish and request for workaround: rotational scale (like twist)


I need to create an animation and look for a way that doesn’t use _flow.

At this place a request: could a rotational scale be added. It could work like twist, but without twist effect.

But for now - is there an other way?

Here an example of the pocket fan:


Hi Micha - you can kind of fake this, I think, with two arcs,Flow and History, and using ExtendCurve (test command, works well here) on the target arc. I have to run out but I’ll make an example if no one beats me to it.

Here’s an example - not sure if that does it for you or not… use _ExtendCurve on the red arc.

  • The base arc is on an off layer.
  • The base, or original planes are on an off layer.
  • The Planes are flowed (Flow command) from the base arc to the red, target arc, with History and Copy=Yes, Stretch=Yes. Probably Rigid would be good too, but it does not matter in my example.

Fan_Test.3dm (94.5 KB)


Hi Pascal,

thank you for your detailed suggestion.

There is one problem - Bongo doesn’t allow to animate the _ExtendCurve. So, the trick would be to find a geometry driven rotational manipulation. Extent arc by point could be a way, but the history doesn’t work for this.

(…thinking … thinking … testing…)

I got it - two arc segments with a wide gap. HistoryOn and Arcblend create a new arc segment. This can be use as flow target. Now if I rotate one of the first arc segments than the arcblendcurve will be extended and stays a circle segment. The pocket fan is wided along a changing arc. :slight_smile:
Now I can perfect solve my animation problem. Last I rendered the wallet of the link it was luck to synchronize the movement of the wallet and the morphing fan. The fan morphing was not good, distortions was there. But now I can make the second arcblend-segment as child of the rotating cover, the fan will perfect follow the cover. I’m so happy, it’s makes the animation easy and stable.

Thank you very much for taking time to push ideas. You are a great help. :slight_smile:


I forget - could the rotational scale be placed on the wishlist. Could be implemented like rotational copy.Looks like a classic NURBS manipulation only. :wink:

Good deal - I’m glad that worked out. The wish is ‘on the pile’ but it is not all that straightforward to implement.