Hi!
Curve-net deforming is in it's very early stages at the moment, it is a technique that was developed by Pixar for "Turning Red" in their own inhouse software Presto. Now Presto is not Maya, its way more preformative and streamlined and runs a lot smoother. Also Pixar had a team of very talented software Engineers work on this deformation method for more than a year, so I highly doubt that we will see anything like this actually useable come out for Maya any time soon.
Even with Pixars system there are quite a few problems with performance, which is why they went back to traditional rigging in the faces for "Lightyear" to cut down the number of curves in their curve-nets.
Now, if you want to imitate something like shown in the video, without writing your own deformer from scratch. Your setup would look something like this:
1) create a traditional skeletal setup for the arm.
2) create curves from key edgeloops in the arm.
3) create curve deformers for each of those curves.
4) carefully weight your mesh, so every vertice has exactly the weight of 1 distributed between the curve deformers, to avoid doubletransformation.
5) create joints for each of intersection between two curves
6) constrain those joints to the underlying traditional arm setup, so they follow it's movement like you'd want the vertex at that position to follow.
7) skin the curves to your joints
😎 instead of skinning your arm to the arm setup, just skin them to the shoulder joint, because the deformation within the arm is managed by the curve deformers.
If you don't need to see the curve-net on your rig which is a feature that I think is kind of unnessecary.
You can set up the curve-net on a live blenshape and use rivets or UV-pin constraints to have the controls follow the arm mesh, while having the traditional underlying arm setup drive all the traditional/common deformation of your arm. This way you don't have the headache of 6) and can assure that you don't get cycles in this step. Also balancing weights in 4) is a lot more forgiving, because the curve-net will just add deformation instead of driving the entire deformation of the arm.
Still, if you sucessfully achieve this, you will have problems with performance. You are stacking, a lot of curve deformers onto each other, and curve deformers are very slow. And then drive them with either cluster deformers or skincluster deformers. With clusters you'll need multiple weighted clusters per curve, with a skincluster you will need 1 for each curve. If you use this on big parts of your rig (not just arms, but also hands, face and spine) , I highly doubt you'll get a playback speed of more than 5 fps, which is not feasible for animation.
If you'd want something like this to be both fast enough for animation and easy enough to set up to be actually considered on bigger projects. You'd have to write your own deformer, that can both do curvedeformation with multiple curves and also balance the skinweights between the curves properly.
Tbh, I wouldn't know how to write a deformer like this., but if you achieve it, please share the results
I hope it helps!
