Feature request: roll bones to plane

Animation tools, character animation, non linear animation

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Joined: Mon May 31, 2004 12:34 pm

Feature request: roll bones to plane

Post by nemyax » Thu Aug 04, 2005 11:40 am

I'd like to suggest an additional option for bone orientation.
Suppose you have 2 bones (e. g. for an arm) which you want to animate using both FK and IK. Say you want both bones' X axes to lie in the same plane. This way, the plane that FK operates in is the same plane that the IK solver uses.
Here's an example screenshot with a correctly oriented chain (and the plane just for reference):
Currently, there doesn't seem to be a way to easily orient such 2-bone chains. You end up with something like this (result of CTRL+N):
This orientation leads to incorrect posing when using FK:
Is it possible to add an option that fixes the roll of 2 selected bones so that their X or Z axes lie on the same plane? It could fit well into the CTRL+N menu, and the name might be "Roll to Plane" or "Orient in Plane" or "Unify Roll" or something.

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Joined: Fri Apr 02, 2004 6:34 pm

Post by oin » Thu Aug 04, 2005 9:49 pm

I don't know, but if you mean do 2d chains like in XSI, you have my vote. Is something I recently mentioned at Elysiun : When you IK rotate a bone, the bone chain should be able to be restricted to a plane where the rotations occurs, as the rotations in depth are not visually handled. I don't know if this could get done with just limiting angle rotations per joint in the case of IK calculations, or is needed something different.

I animate at work, and I know this 2d chain-IK is being needed in Blender. (I love the recently automatic-empty added that can be used quicly as a pinned joint, together with copy rotation applied from ik foot to the empty ) With this and that limiting to plane IK rotations (imho it'd be perfect ifrotations would happen only in a plane paralell to the view, to the screen, I mean) of the IK intermediate joints.

I don't know if is exactly what you mean, but imho is a very important step.

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Post by nemyax » Thu Aug 04, 2005 11:31 pm

I'm not sure about XSI, because I don't know much about it. But I've just checked my XSI Mod, and 2D chains seem to involve IK. They do not keep the orientation if you move the middle bone.
I meant something slightly different. In Blender, you don't have IK nor FK in edit mode. You just place the joints and set the roll. So, I'd like to first position 2 bones (=3 joints) the way that suits me, not worrying about their orientation. Then I want to select these bones and do a one-time solving operation. And this operation should put my screwed up bone orientation right. Right means that the X axes of both bones are lying precisely on the plane defined by the 3 joints. Or these might be the Z axes — that can be a configurable option.
As a result, the plane of rotation is the same whether you're posing with FK or IK.

Posts: 85
Joined: Mon May 31, 2004 12:34 pm

Post by nemyax » Tue Sep 06, 2005 6:20 pm

Meanwhile, as an easy workaround, you can:
- Create a mesh triangle
- Snap the triangle verts to the joints
- Select the verts and align the view to them (Numpad *)
- Make the view orthographic
- Set bone roll so that the bone edges line up in wireframe octahedron mode

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