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Saturday, April 14, 2012

Quick Skinning with Lattices and Joint Cluster Flexor

Hi,
In a previous skinning post I talked a little about skinning by skinning a low resolution mesh wrapped around its hipoly mesh (ex: subdivision mesh). In this post I talk about a similar method to skin but with some advantages of getting automatic weighting and skinning a hi-res mesh without its low resolution version.

I think the idea is were not going to bind joints to the mesh instead we create a lattice around polygon and Rigid Bind selected joints to the lattice. I think if we had a full character we would duplicate the character and split up its mesh into pieces and create lattices on each separate piece (i'm not quite sure how to get the pieces to move together yet though i think it has something to do with lattice blendshapes).

What I think happens after this is that by rotating a joint we are now moving lattice points which then moves our geometry. In a sense the lattice acts like the previous post mention of a skinned low resolution mesh wrapped around a subdvision hipoly mesh.

There are lots of advantages to the lattice skinning method. Skinning the low resolution mesh (lattice in this case) gives fewer things to weight. Furthermore using lattice for skinning allows us to get some automatic weighting. Maya's edit rigid skin create flexor is a way to get bending at the knee falloff weights without having to weight individual lattice points. I think we just select the joint like the knee then create a flexor (i tried using a joint Cluster flexor). After this the weights by the joint cluster on the lattice points should have changed from their default of 1. I think selecting the flexor and changing the lower and upper bounds can get these weights to be tweaked, there probably are many other ways to tweak weights.


Notes:
1. to create bind, select individual joints, then the lattice then rigid skin -- closest point, selected joints.
2. to see what lattice points are influenced by joint, select the joint and click edit membership tool
3. to make a jointCluster flexor, select the joint then go edit rigid skin --> create flexor
4. when i tried using the jointCluster flexor and the child joint wasn't bound to the lattice i didn't get the automatic weighting, so i think wherever going to try to get automatic weighting via a jointCluster not just the joint but its child too should be bound to lattice.


Hope you find this helpful,
Regards,
Nate


Inspired by Alex Alvarez's Organic Modeling and Animation with Maya V.1, Part 3( alexalvarez dot com )