This section explains the Jiggle settings on a muscle. The examples here are also applicable to other muscle types, such as the Muscle Spline-based muscles.
If you select a control for the muscle, you see various attributes for Jiggle. These are typically Jiggle, Cycle, and Rest attributes. In addition, Maya Muscle provides more options including separate X, Y, Z values and Impact.
Multipliers on the Jiggle value. These values are relative to the control space. MuscleCreator muscles always have controls such that the Y-axis points down the length. In this case, the X and Z values strengthen or dampen the amount of motion in the plane of the muscle, while the Y value changes the amount of jiggle along its length. Since you do not want the muscle to implode or slide too much along the length, this value defaults to a smaller amount than the X and Z values.
Jiggle that occurs when the muscle undergoes a rapid change from being stationary to moving, or from moving to stationary. Effectively, when a big change in motion occurs, the Jiggle Impact attribute sets the strength or amount of effect seen from that change. This motion is applied as a rotational movement around the axis of the muscle (a jiggle in the X-Z plane only).
Set how much force is needed to cause the impact motion to be applied. Typically, you want jiggle to occur when a muscle stops moving, (for example when a large creature plants its foot in a walk cycle), but not so much when it starts moving again. Because of this, the Jiggle Impact Start value is a larger number, 1000, so it does not trigger unless the force on the muscle changes at least 1000 units in one frame. The default for Jiggle Impact Stop means the muscle force has to go from one value to a value smaller by 0.001 units of force/movement for the impact jiggle to trigger.
A good way to see the effect of Jiggle Impact is to set the normal X/Y/Z values for jiggle to 0, then animate the muscle moving and stopping suddenly, then play with the Jiggle Impact settings.
