Another idea for mixing smooth skinning and flexors: create sets from your model’s vertices for the parts you want to have different skinning on. Ie. Torso set for smooth skinning, Left Leg set for rigid skinnig. Then select the set members, proper bones and assign one of the bindings.
In our practice, Rigid bind and Flexors work pretty well for all limbs, whereas Smooth bind is better for the shoulders, torso, neck and hip area. You can also use driven keys on the elbow/knee flexor points to finetune your deformations - pretty quick and effective way to do the skinning.
By the way, the problem with skinning to joints is that this method cannot maintain the body’s volume. You get a “plastic tube” effect on most joints and the torso, which is pretty hard to fix, even with clever weighting. This is because the skinning only applies rotations to the vertices, using the joint as a pivot - whereas the skin does move all around, inside and outside, as muscles flex and slide under it. Try binding a fat character - it’s belly will miracously disappear as he bends forward, and expand as he leans back…
IMHO, there are 3 main approaches to fix this problem:
- full muscle simulation, as seen on the LOTR trolls and Gollum
- joint rotation driven blendshapes, as seen on the Hulk
- joint rotation driven clusters, as seen on the Pan character (see link in a previous post)
Wrap deformers are just an extension/simplification to this as you still have to use some advanced methods on the wrap object itself.
And I haven’t really managed to get proper behaviour from influence objects, and using many extra bones or muscle bones doesn’t really help either, as your time spent on weight painting will only increase…