Painting Skin Weights in Maya

1. Select the Mesh

2. Select the ‘Paint Skin Weights’ tool to bring up the painting menu which allows you to choose the brush type and configure the painting settings.

The weight slide bar/entry box allows you to set how heavily weighted you want the mesh to be affected by the joint’s movements. It’s an all or nothing type deal, where a value of 1.0 is “I want the mesh to be absolutely affected here” and 0.0 is “I don’t want this part of the mesh to be affected”.

When you paint weight to one part of the mesh for a joint, it moves weights away from all other parts, when you remove weights from one part it puts weights on to all other parts.

A great way to think about it is as follows:

Lets say you have 2 glasses of water.. Glass 1 is full and Glass 2 is empty. I pour Glass 1 into Glass 2. Now Glass 1 is empty and Glass 2 is full. The volume of water is the same, just the glass that the water is in has changed.

Applying that analogy to Maya’s weighting system:

You have 2 joints. Joint 1 has a value of 1.0 (which appears white) for a particular part of a joint whilst Joint 2 has a value of 0.0 (which appears black) for that same part of the joint. If I now select Joint 2 and paint a value of 1.0 to that same part of the joint, Joint 1 will now have the value of 0.0 for that section of the joint.

3.

Option 1: Select each joint in the paint weights window and go trough and ‘hold’ all but the relevant 1 or 2 joints next to the weighted area that you want to share the values with. If you do not hold weights you are almost certainly going to fail a bunch of times and have much more trial and error before the weight distribution is sufficiently the way you want it..

Option 2: Make a dummy joint and hold ALL the unpainted mass there. Unhold just the joint you want to add weights into and now you can also remove influences since all extra goes to the dummy joint, just make sure the dummy joint is empty before you finish and possibly delete it. (the dummy joint doesn’t need to be real, you can just decide to flood all into left pinkie and fix that part last).

Tip 1: Try not to move back and forth too much. Do one bone pair area in one go then don’t come back to that area for a while.

Tip 2: You can make a better starting solution by using influence objects to define the weights, leading to much less painting. (need to explore this).

Tip 3: Its often counter productive to remove and add weights in same pass. Just go one way, either just adding or just deleting, if you fail undo. Often-times deleting is more unintuitive than adding (its easier to understand everybody else loosing than everybody else winning).

Another Great Video and Skinning Technique (2 parts):

Above: Part 1

Above: Part 2

I really like this method of Skinning that this guy talks about and I’ve had a few people recommend it to me after I asked around. Basically you skin the model and then key (s-key is shortcut for Maya set key frame all) and then move the time slider along and pain each joint’s weights so that it springs back and looks the way it should.

He also says NOT to use the replace/smooth/etc tools an to ONLY use the Add tool initially… I tend to agree with this because smoothing will blend it and inevitably you will end up with a bit of weighting somewhere random because that’s what Maya does.. re-distribute any vertices that are not given a value of 1.0 to the entire mesh (or at least to somewhere else – perhaps someone will clear that up for me at some point).

You can then go back and Smooth once everything has been fleshed out initially. To do the smoothing on your second pass, you basically want to overlap each area with the next slightly to create a smoother transition and eliminate any sharp edges that you might have.