Got 99 Problem and a ...

So I was asked by someone about the problems and the short comings of the Maya smooth-skinning.

It is times like this, that I realize how little I know about rigging...and after some research and asking "real" riggers about it, these are what I came up with...

Problem of smooth skinning:

When using linear-blend/smooth skinning the main issues is the

limitation of geometry deformation, smooth skinning in (Maya)

manipulates vertices using a

weighted average of transformations.

All possible positions that the vertexes

can travel to lies between the influences. The problem is that a set

of vertexes can't be weight painted to achieve shapes that doesn't

fall within the subspace determined by the influences.

In common situations such as shoulders and

elbows the desired deformation does not lie in this subspace, hence

no amount of adjusting the algorithm weights will produce good results.

Normally I will have funny pic to show here but ... DO NOT...Google Image..."skinning" at work

Solutions:

1. corrective blend Shape:

If the production does grant the use of (Maya) blend shapes, using

tools such as "B Spirit", allows the rigger to

sculpt out corrective blend shapes that can be apply before the smooth

skinning layer in deformation.

Using joints within the rig to drive

the weight of the corrective blend shape. By using both a blend shape

and smooth skinning it gives the most control on the final

look of the geometry, giving the best result artistically.

2. helper joints:

Creating a system of joints that are driven by control joints, working

with the base skinning joints.

The helper joints convert the motion of the control joints in

ways that aid the skinning process (a bicep helper joint for example might

convert the elbow rotation to a translation).

The helper joints are skin to the

same skin cluster as the base skinning joints but gets moved to help

the smooth skinning joints to create a desired shape when control

joints are posed. Similar to how the corrective blend shape is driven

but without the use of blend shapes.

Here is a link to my Rig Demo that shows how I solve the problems describe above