Re: spacer rigs

["Bradley Gabe" <withanar(at)gmail.com>]

Any solutions you know for wiring live shape deforms into your rig will work by using Animate>Deform>Shape>Select Shape Key which I know you know goes all the way back to si3d. :-)

The difference in XSI is found in using operator stacks to your advantage. You can duplicate your performance mesh several times, do local deforms to the duplicates, then pipe the results back into your performance mesh via shape combiner operations. You can get desired mesh blending effects by not only varying where in the stack you place them, before or after envelope, but also by varying the reference mode of the shape data from global to object to absolute. 

I've been using shape blending as a rigging solution now for complex facial animation effects where shape to shape is too linear. Instead, I duplicate the face mesh once per muscle group, then blend all of them back onto the master performance mesh. When you move your facial animation sliders, the resulting motion is curved, not linear. And it's as dynamic as the performance solved on each separate mesh. I've had faces with over 20 duplicate meshes, each one with a unique envelope, all blended back into the performance mesh... and XSI handled the data load without any problems. 


As for deformation controls traveling around in scene, the other old trick is to wire your envelope deformer's static kinestate to its parent's global SRT. This allows you to put a second, third, fourth envelope onto the same mesh and not double, triple, quadruple the resulting transformation through your scene.

So let's say you have a button that's been enveloped onto the chest bone of your character, and you want to add another envelope to allow you to pop the button off, without removing it from the original envelope. What you do is:

• Parent a null into your hierachy at the position of the button
• Duplicate the null and make it a child of the parent
• Set another envelope on your button to the child
• Link the static kinestate SRT values of the child to the global SRT of the parent null

The button's control can now move around the scene with the chest bone. The button doesn't go away from the chest unless you offset the child from the parent.

-Brad

On Fri, May 2, 2008 at 12:34 PM, David Gallagher <daveg(at)blueskystudios.com> wrote:

Oh, I guess one method would be to parent the second mesh and all the joints as a whole to the traveling mesh, but I'm looking for a way to more discretely parent controls around the body.

David Gallagher wrote:

Does anyone have any ideas of workarounds for "spacer rigs". It's common in the Maya world at least to rig a second mesh and pipe in the result as a live blendshape. So, the second mesh is skinned to joints, for instance. Some of the joints, you might want direct control over, but they can't leave their location. In order to get them to ride with the main rig but only engage when actually directly used, you make "spacer" controls that mirror the actual joints, parent them to some part of the body, then pass their numeric transform values only back to the real joints sitting at global center.

I think this is pretty standard, but I've heard of alternatives, such as inverting the shape from certain deformations, cancelling out the unwanted deformations.

Anyway, I'm interested in any alternatives to spacer rigs that are used.


What would be optimal, is if you could transform the same joints in two different ways. One which just changes their location in space, and another which makes the deformation.

--
David Gallagher
Character Development Lead Animator, Blue Sky Studios

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