When off, [Tendon Mask Range will be proportional to the computed length of a given muscle. The computed length of a muscle will be stored in the musclelength point attribute. If the musclelength attribute already exists, it will be used instead of being computed. When this parameter is on, Tendon Mask Regions disregards musclelength, and distances from the ends are measured in world units. Tendon regions use the axialramp attribute to determine the extents of individual muscles.

When on, the axialramp attribute will tend to be more sensible about which way is up. This will affect the correlation between the Tendon Mask Radius parameters, and the orientation of the affected muscles. When off, this orientation can appear somewhat arbitrary. The axialramp attribute will only be computed if it doesn’t already exist. Therefore, this toggle will only have an effect when the incoming muscle geometry does not have an axialramp.

• The number of defined muscle property setting assignments.

• Adds or removes a Property Assignment multiparm.
  
  

Property Assignment multiparm tabs

• A single multiparm tab can define the muscle property settings for a single muscle or multiple muscles (muscle_ids). See Group.

• A single muscle can appear on multiple multiparm tabs.

• Each multiparm tab is processed in sequential order, from lowest numbered tab to highest numbered tab. So if a muscle appears on more than one multiparm tab, then the property setting values on the highest numbered tab take priority and either multiply (when set to Relative) or override (when set to Absolute) the settings from lower numbered tabs.

1 - Deletes the currently selected multiparm tab.
2 - Inserts a new multiparm tab to the right of the currently selected multiparm tab.
3 - Currently selected mulitparm tab.
4 - Adds or removes multiparm tabs from the end of the list. Increasing the number adds tabs and decreasing the number deletes tabs.
5 - Adds a new multiparm tab to the end of the list.
6 - Removes the multiparm tab from the end of the list.
7 - Deletes all the current multiparm tabs.

This parameter allows you to enter a desctiptive string of text to help you name or identify the properties configured on this multiparm tab.

Determines which muscle(s) to assign the current Property Assignment multiparm’s settings to.

This parameter only accepts single muscles or lists of muscles formatted in the @muscle_id grouping syntax. For example, @muscle_id=L_biceps, @muscle_id=L_biceps,L_triceps, or @muscle_id=L_biceps @muscle_id=L_triceps @muscle_id=L_deltoid. This parameter does not accept regular geometry groups.

You can specify the group selections for your Group parameter in the following ways:

• In the viewport state, press A, select the muscle(s) you want to add to the group, and then press Enter. A new Property Assignment multiparm is created and the muscle(s) you selected are added to its Group.

• In the Parameter Editor, click the arrow icon next to the Group parameter, select the muscle(s) you want to add to the group from the viewport state, and then press Enter. The muscle(s) you selected are added to the Group.

• In the Parameter Editor, manually type the names (muscle_ids) of the muscles you want to add to the group in the Group field.

When on, sets the stiffness of the muscle’s individual tetrahedrons. This determines how much a muscle wants to stay in its original shape (tpose).

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Shape Stiffness parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, sets the amount of energy the muscle is able to preserve as it changes shape. With a low damping ratio, the muscle’s energy diminishes very little and its shape changes quickly. With a high damping ratio, the muscle’s shape changes more gradually.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Damping Ratio parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, sets the mass per volume for the muscle’s tetrahedrons and controls how mass is computed per point. Formulating mass as density like this keeps the behavior resolution of the muscles independent. And the Shape Stiffness and Damping Ratio parameter values also help to keep the muscles' behavior predicable over varying resolutions. This means that when you use Mass Density with your muscles, changing the number of tetrahedra the muscles have will not affect their mass or how they appear in the simulation.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Mass Density parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, generates the fiber scale force that is applied to the muscle’s tetrahedrons when it contracts (activates). Fiber Strength determines how strongly the muscle is squeezed. When and how much a muscle contracts is determined by muscletension (from the Muscle Flex SOP node) as it functions as a multiplier for Fiber Strength. The direction in which this scaling factor is applied to the muscle is determined by the fiber direction (materialW).

muscletension determines what percentage of fiber stiffness is used at any time.

With a Fiber Strength of 0, the muscle does not contract and is always limp. With a Fiber Strength of 1, the muscle fully contracts. If you want one muscle to have a stronger reaction to the fiber scale force and another muscle to have a weaker one, then vary the fiber strength across your muscles.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Fiber Strength parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, reduces the amount of fiber scale force that is applied to the muscle’s individual tetrahedrons per iteration. Fiber damping also controls how rapidly a muscle can contract. The lower the fiber damping value, the more immediately you will see changes in your muscle. With a Fiber Damping of 0.001, the fiber scale force is allowed to change the muscle’s shape quickly. With a Fiber Damping of 0.7, the muscle has a very sluggish response to contraction (activation).

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Fiber Damping parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, sets the lower (first field) and upper (second field) thresholds or min/max for muscle tension (muscletension attribute). The first field determines the value of muscle tension when it is at rest, and the second field determines the value of muscle tension when it is at maximum contraction. By default, a muscle contracts in a range of 0 to 1. Muscle tension activation treats this range as fully relaxed to fully activated.

For example, if you set the first field’s value to 0.5, then when the muscle returns to its rest state it is actually returning to a 0.5 value. Or if you set the second field’s value to 0.75, then the muscle’s maximum contraction would be 75% that of any muscle that has a Fiber Scale Range max of 1.0.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Fiber Scale Range parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, determines the scale force that is applied to the volume response when the muscle’s tetrahedrons are fully contracted (activated). This is called the volume scale force. This parameter provides an artificial boost to the muscle’s bulging action. Increasing the Fiber Volume Scale for the muscle will make it more plump when it is contracted.

The muscle solver applies volume preservation when a muscle’s fibers are scaled. So when a muscle tetrahedron is compressed in one direction by the fiber scale force, the volume scale force will automatically try to preserve volume and scale in the opposite (perpendicular) direction. For example, a Fiber Volume Scale of 2 generates twice the volume scale force and as a result twice the volume preservation.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Fiber Volume Scale parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, determines the scaling factor or scale force that is applied to the Shape Stiffness for the tendon regions of the muscle. The tendon regions of the muscle are much stiffer than the belly areas of the muscle, and they have a significantly reduced response to muscle contraction (activation). As such, tendon stiffness is considered a multiplier of the belly’s shape stiffness. For example, a Tendon Stiffness of 25 will make the tendon region of a muscle 25 times more stiff than the belly area of the muscle.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Tendon Stiffness parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, multiplies with the muscle’s solid mass density using the TendonMask as a mask. Only the tendon regions (white areas) will receive the mass density scale. It does not affect hardness.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

See the Tendon Mass Density Scale parameter description.

This parameter is only available when the Absolute/Relative selector is set to Relative.

When on, defines which parts of a muscle are the tendon regions and how far from the muscle’s ends the tendon regions extend. The tendon regions of the muscle are much stiffer than the belly areas of the muscle, and they have a significantly reduced response to muscle contraction (activation).

The Tendon Mask Radius is a procedural ramp control for assigning tendon regions and each of its fields represents a muscle end. In the viewport state, the white-colored areas on the muscle’s ends represent the tendon regions, and the red-colored area on the middle of the muscle represents the belly muscle region. On the red area of the muscle, more scale force is applied and it is more likely to bulge/expand. On the white areas of the muscle, the scale force is diminished and it is very unlikely to bulge/expand.

This parameter is only available when the Absolute/Relative selector is set to Absolute.

When on, sets the threshold value for Tendon Stiffness above which solid muscle geometry is considered belly muscle and below which it is considered tendon. You can use this parameter to make thin or big surface muscles (for example, like the pectoralis) act more like a tendon without having to define Tendon Mask Radius regions. Thickness Threshold is applied to entire the muscle.