Types of Muscle

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.

Muscles

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:

Adjustable resolution
Ability to mirror muscles after setup
Easier rigging (you can parent the start and end locators and curves as needed with no constraints)
Separate cross sections and attach points for each state of the muscle, letting you create the shapes and poses you want for Squash, Stretch, and Rest without custom muscle shaping
Ability to base pose states on rotation/translation, not just muscle length
More ‘correct’ deformation in that pulling or moving a control section at one point on the muscle causes the surface to slide through the muscle spline properly, instead of being localized as it is with a Muscle Spline deformer

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.

Muscle components

There are four main components that comprise the muscle:

Attach Points: Besides the two attach points for each end of the muscle, each cross section/control has its own red ‘attach’ control along the length. The red controls are the ‘rigging’ controls. You can parent these to the objects you want the muscle to be attached to. By default, the Muscle Creator parents them half and half to the attach joints you select when you create 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.
Cross Sections: The model is created by NURBS circle cross sections that drive the shape. There are three sets: one for rest/default, one for squash, and one for stretch.
Controls: Each cross section has a yellow control cube for control of the muscle over time. You can think of these as ‘animator’ controls. These controls move around automatically as children of the red ‘attach’ controls. While it is not always necessary to animate the muscle spline with the controls, each control has settings for the amount of jiggle on each part of the muscle.
MuscleCreator node attributes: Most of the remaining controls are available on the MuscleCreator node. This is where you can set the muscle resolution, pose information, and other options. See cMuscleCreator node.

Simple muscles

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.”