Relative Sticky mode lets you mark certain muscles or bones as “Relative” so that you do not get a double transformation when using a regular skinCluster along with the Muscle deformer.

Using this approach, you can rig your character using regular joints and a skinCluster, apply Muscle on top, then add muscles or capsules for extra Sticky or Sliding weights on top of the skinCluster.

You can also set up Relative Sticky deformation even if you are not using a skinCluster, for example if you are using clusters to deform an object.

You can turn Relative Sticky mode on as you apply the Muscle deformer to an object with skinClusters (see Apply the Muscle deformer), or after you have applied the Muscle deformer (see Set up Relative Sticky deformation).

When you turn Relative Sticky mode on, the cMuscleSystem node’s Relative Sticky attribute is set to relative (on). In addition, a new helper deformer named cMuscleRelative is created and set to deform the mesh. This deformer should be positioned before the skinCluster node, but after any other deformers such as blendshapes.

In addition, each cMuscleObject node for capsules, bones or muscles has a Relative attribute. If on, the muscle uses Relative Sticky deformation. If off, it operates as if Relative mode is off.

This is used to get normalization on painting weights. For example, when using Relative Sticky mode, you want to create one dummy capsule object to connect into the Muscle deformer for Sticky weights. For this one capsule, turn its Relative attribute to off (using Muscle > Skin Setup > Set Selected Bones/Muscles as Not Relative menu item), then flood all Sticky weights to this bone. The capsule should never move from its initial location. You can then connect muscles and start adding and smoothing weights to them for Sticky weights. These should generally have Relative set to on. In this way you can still properly normalize Sticky weights back to the dummy capsule.