Any NURBS surface in Maya can be converted to have a Muscle Object shape node and therefore can be connected to the Muscle deformer. In addition, there are two tools that let you create two different types of muscles:
The main difference between the two muscle types is that simple muscles use regular NURBS models with a special spline and spline deformer used to bend them, while the new muscle is a parametric-style NURBS shape that has deformation/posing ability.
The Muscle Creator window lets you build a new, more powerful muscle with rigging, shaping/sculpting, and deformation ability. These muscles include two end points for each attach location so that you can more easily create ‘flat’ muscles and more easily orient your muscles. In addition, the Muscle Creator window lets you grow muscles out to a surface. It is recommended that you use these muscles for new rigs.
Some advantages of using this new muscle type include:
Advanced topics with the Muscle Creator
Muscles built with the Muscle Creator are designed to be simple and fast to rig with, but also extensible for more advanced rigging. For example, a muscle can be re-parented to a different part of the rig by re-parenting the muscle’s attach locators and start/end curve. In addition, you can set the attach control curves and leave them as is.
It is also possible to “rig” or adjust the attach curves. For example, you can use Muscle KeepOut nodes to rig the muscle controls or attach nodes so that they slide or collide with capsules or each other. (See Transform collisions with KeepOut nodes.) Groups of muscles can also be deformed with the Muscle Multi Collide deformer to provide muscle-muscle collision before affecting skinning. (See Multi-Object Collision.)
Attach curves can also be re-parented, constrained or rigged in other ways. Cross section curves can be deformed with blendshape targets to provide animators with even more control over the shape of the muscle in various situations.
Maya Muscle provides a high level of control for rigging muscles, but still allows for even more customization using standard Maya articulation techniques.
There are four main components that comprise the muscle:
There are three attach points per control: one for the rest state, one for the squash state, and one for the stretch state. This lets you adjust the length or curve of the muscle so that it looks different in each state. Each of these attach points is automatically driven by the Muscle Creator to go to a default location. By adjusting the different states, you can simulate effects like a muscle being pulled around a joint.
You can set/constrain the red ‘attach’ controls, but it is not necessary, as they are usually auto-driven.
The original Muscle Builder window lets you create basic Muscle Spline muscles. In this documentation, these older Muscle Spline-based type muscles are referred to as “simple muscles.”