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I want to create the same sort of twist that you get from the SimpleDeform modifier, but by using an armature so that I can have more control of it. I want to get at least 360degrees of twist, maybe up to 720. The object is basically a cylinder.

If I use just a couple of bones, then when they twist, they pinch to no thickness in the middle. What is the proper setup with bones to get the amount of twist I want?

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  • $\begingroup$ the Preserve Volume option in the Armature modifier does a good job to prevent the thinning, I don't know if that's enough for you're trying to do. Edit: It looks like you need more than 2 bones to make a 360° though $\endgroup$ – moonboots Nov 19 '18 at 10:32
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It looks like you can't rotate a bone more than 180° (to be confirmed), except if you deparent it of course, so I guess you must create a chain of bones. In the Armature modifier, don't forget to activate the Preserve Volume option.

enter image description here

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  • $\begingroup$ Are those bones inheriting rotation? What is their relationship to each other, and how much are you rotating each? Thanks. $\endgroup$ – Ascalon Nov 20 '18 at 9:16
  • $\begingroup$ yes they inherit rotation, I have just subdivided a bone several times, it looks like you can only rotate 180° with a bone, so theoretically you should only need 3 bones to make a 360° rotation, but it's actually not enough to get a good result, so you need more $\endgroup$ – moonboots Nov 20 '18 at 10:47
  • $\begingroup$ I'm having trouble getting it to preserve the volume. Even with Preserve Volume checked. Can you show your weights? $\endgroup$ – Ascalon Nov 21 '18 at 1:09
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    $\begingroup$ I've just parented with Automatic Weight, you need to subdivide enough your object, please share your object: blend-exchange.giantcowfilms.com $\endgroup$ – moonboots Nov 21 '18 at 7:44
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I would try to use a bendy bone with controllers (see here), then add a bone at the base of the bendy bone (I'll call it "rotator" from now on). The opposite bendy bone's controller will be parented to the rotator, and its rotations will also be driven by the rotator.

In theory, this will make the opposite controller rotate arround the bendy bone base and rotate it twice the amount of the rotator's rotation. The bendy bone would form a perfect half-circle shape, without any wrong deformation.

Duplicate the whole thing and invert it to get the other half, and you have your simple-deform-like rig.

I did a test, you can download and retro-engineer it.

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  • $\begingroup$ I think Drudge is talking about twisting a shape, like parent a column to two vertical bones and rotate the top bone 360° on the global Z axis. With your method you will have a better result than with 2 bones but I don't think you can do more than a 180° twist. I think he needs several bones and enable Preserve Volume. $\endgroup$ – moonboots Nov 19 '18 at 11:48
  • $\begingroup$ Oh yes I mistaken x) Though, I bet the same method can be used for a twist too, just by changing which axis is driven. $\endgroup$ – L0Lock Nov 19 '18 at 20:03
  • $\begingroup$ I've tried with bendy bones + stretch to, but same problem than with 2 bones: you can't exceed a 180° rotation (well, it looks like)... you can add a second bendy bone but it begins to be a bit hard to control $\endgroup$ – moonboots Nov 19 '18 at 20:15

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