Jahirul continues his Maya rigging series by detailing the steps involved in skinning your rig with the help of an hour and a half-long video
to download assets to accompany the final 3 parts of this tutorial
Maya rigging: Introduction to rigging
Maya rigging: Introduction to rigging a human torso
Maya rigging: Introduction to rigging the neck and the head
Maya rigging: Introduction to rigging the shoulder and the arms
Maya rigging: Introduction to rigging the hands
Maya rigging: Introduction to rigging the legs
Maya rigging: Introduction to rigging the feet
Maya rigging: Introduction to rigging the fingers and thumbs
Maya rigging: Introduction to cleaning up the rig
We have now reached the stage that is known variously as enveloping, binding or skinning. I'll refer to it throughout this tutorial as skinning. So what is it exactly? Skinning is the process of assigning how much influence a joint should have over a vertex. By doing so, we define how our skeleton will deform the geometry. We will create this relationship using a skinning solution known as Smooth Bind in Maya. Once this relationship has been created, we will refine the initial bind calculation through a process known as painting weights.
For me, it is imperative that we spend as much time as possible refining the skinning for our characters. It is here that we create the foundation from which the majority of the deformation will come. We can always use extra tools and techniques to push the believability of the deformation, such as using corrective blend shapes or a muscle setup. However, if the skinning hasn't first been pushed to its limits, then these blend shapes and muscle setups will simply not cut the mustard.
I tend to employ the same method for skinning as I do the majority of CG tasks that I deal with. That is to break it down into the 3 distinct stages: blocking, smoothing and refining. This way, I don't get bogged down in the fine details early on and then realize I need to make some drastic broad changes.
With that in mind, here is a rundown of how I will tackle the joys of skinning. Once we have created the initial bind, we will then get rid of the default calculation by making every joint have 100% influence over the vertices that surround it. This is the blocking stage and the reason I do this rather than simply fixing what needs fixing is because I want to be fully responsible for the weighting of the character. As much as Maya will do its dandiest to do a great job, I simply like to have the final say. What we will end up with at this stage is a very chunky looking mesh as it deforms.
After the initial blocking, we will then go through and smooth out the weights between 2 to 3 joints at a time. During this stage, we will also set many keyframes on the rig to get a better idea of how the mesh transitions from one pose to another. After all, it's the movement between poses we need to focus on, not just the key poses that we hit. While we are doing this, we will want to maintain as many of the natural creases and bulges that occur as the body articulates. If you are going for a cartoony feel, though, you may try to avoid adding the inclusion of wrinkles and folds.
Lastly, we will go through and examine the deformation with a fine-toothed comb and fix any anomalies. We'll use a multitude of tools for this, such as the Component Editor and then the Weight Hammer. We'll be aiming to get the skinning to take care of around 80% of the final outcome. The further 20% will be handed through secondary deformation methods that we'll look at further next time. As our character is symmetrical, on a positive, we only need to focus on skinning half the mesh. After that, we can simply mirror the weights over. I tend to do this at numerous stages throughout the skinning process as it allows me to get a good feel for how the character deforms as a whole.
Just a quick note on the relationship between the steps and the video for this tutorial: usually, I try to keep the steps in sync with the video, but as skinning is a bit of a different beast, you may find that they do not tally exactly. The steps have been written as a broad guide to my approach, while the video will enable you to follow point by point.
So, without further ado, lets get skinning?
Create a quick select set
The first thing I want to do is select all the joints that will be part of the bind, and pop them into a Quick Select Set. That way, we can quickly select them all or easily find a specific joint should we need to. With over 200 odd joints to select, I'm not going to list them all, but here is a quick breakdown of which joints to select and which not to. Select the IK spine joint chain, the FK hip, the leg, the arm and all the twist joints, the hand, finger and toe joints, the neck and the head joints, and the scapula and clavicle joints. Do not select the FK spine joints, the FK and IK leg and arm joints, and finally, do not select any of the end joints.
Once you have your selection of joints, go Create > Sets > Quick Select Set. Give your set a name (I called it male_bind_set) and hit OK. You should now be able to open up the new set in the Outliner and select all the joints that we will use for the bind. If you forget to pop any necessary joints into the selection set, simply select the extra joints and middle-mouse drag them onto the quick select set node in the Outliner.
The many, many joints that will be used to bind the mesh