Determines which main constraint properties are currently being displayed in the node’s viewport state.

When on, shows the node’s second input in the viewport state. Bones are only displayed if you provide them as the second input.

When off, End Regions 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, End Regions disregards musclelength, and the muscle end mask values are measured in world units. Muscle Ends 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 Muscle End 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 takes 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.

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.

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 how strong the constraint is when increasing the distance between the muscle ends and their bones relative to the rest distance, and how much the muscle ends are allowed to move away from the bones. Also determines how rigidly the muscle ends follow the bones' animation.

See the Stiffness parameter description.

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

Reduces the constraint’s energy from iteration to iteration and determines how much energy is lost trying to maintain the attachment. A high damping value creates a sluggish connection. It does not weaken the attachment however, it just makes the attachment not respond as quickly. For example, it makes the attachment appear more syrupy and the muscle appears to swim towards the bones rather than follow them directly. A low damping value may cause oscillations and jitteriness in your muscle.

See the Relative Damping parameter description.

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

Determines how far to search for what to attach the muscle ends to. Typically the heat mapped areas of the muscle will attach to nearby bones. The constraint will look within this distance of attachment and will try to find bones within that threshold. If it finds bones, then that is what it will attach the muscle ends to. If it does not find any bones within that threshold, it will keep the muscle ends unconnected.

See the Distance Threshold parameter description.

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

Determines how strong the constraint is when reducing the distance between the muscle ends and their bones relative to the rest distance, and how much the muscle ends are allowed to move towards the bones. Also determines how rigidly the muscle ends are held to the bones.

See the Compression Stiffness parameter description.

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

The rest length of the distance constraints will be the original distance between the muscle ends and their bones. This scale increases or decreases the resting distance during the simulation.

See the Rest Length Scale parameter description.

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

Prevents the connection orientation of the muscle ends from changing and keeps the relationship of the muscle ends relative to their bones. When a target constraint is used, this prevents the muscle end’s pre-animated connection orientations from changing. When a nearest-bone attachment is used, this prevents the orientation of the connection between the muscle ends and the nearest bones from changing. A high value tries to preserve the initialization connection angle, and a low value does not try to preserve the initialization connection angle. For example, for tendon areas of your muscle, the muscle end to bone connections should have a much higher Tangent Stiffness.

See the Tangent Stiffness parameter description.

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

Determines how strong the connections between muscles are, how strong the constraint is when increasing the distance between the muscles relative to their rest distances, and how much the muscles are allowed to move away from each other.

See the Stiffness parameter description.

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

Reduces the constraint’s energy from iteration to iteration and determines how much energy is lost trying to maintain the connection. A high damping value creates a sluggish connection. It does not weaken the connection however, it just makes the connection not respond as quickly.

See the Damping parameter description.

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

Determines how strong the constraint is when reducing the distance between muscles relative to their rest distances, and how much the muscles are allowed to move towards each other. Also determines how rigidly the muscles are held together.

See the Compression Stiffness parameter description.

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

The rest length of the distance constraints will be the original distance between muscles. This scale increases or decreases the resting distance during the simulation.

See the Rest Length Scale parameter description.

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

Determines how far to search for neighboring muscles to connect to. The constraint will look within this specified distance of attachment and will try to find other muscles within that threshold. If it finds nearby muscles, then that is what it will attach the muscle to. If it does not find any other muscles within that threshold, it will keep the muscle unconnected.

See the Distance Threshold parameter description.

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

Determines how easily a muscle can slide across nearby muscles. Muscle to muscle connections can drift along the surfaces of the nearby muscle. The same muscle points will always be connected, but nearest location on the nearby muscle can change when sliding occurs. This constraint property controls how fast a muscle can move away from their initial (rest) muscle attachment location.

See the Slide Rate parameter description.

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

Restricts which muscles a muscle can connect to a list of specified muscles. This field accepts entire muscles listed given as @muscle_ids, ranges of primitive numbers, or individual primitive numbers as a space separated list. For example, if your character’s leg muscles are connecting to its abdominal muscles because they are close to them, then you can specify a list of Attachment Candidates to remove these undesirable connections.

Determines how strong the constraint is when increasing the distance between a muscle and its bones relative to their rest distance, and how much the muscle is allowed to move away from its bones. Also determines how rigidly the muscle follows their bones' animation.

See the Stiffness parameter description.

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

Reduces the constraint’s energy from iteration to iteration and determines how much energy is lost trying to maintain the attachment. A high damping value creates a sluggish connection. It does not weaken the attachment however, it just makes the attachment not respond as quickly. For example, it makes the attachment appear more syrupy and the muscle appear to swim towards the bones rather than follow them directly. A low damping value may cause oscillations and jitteriness in your muscle.

See the Damping parameter description.

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

Applies a nonlinear fall-off to how the painted mask is applied to a muscle and determines how gradual the heat map fall-off appears on its muscle visualizations in the viewport. The brighter the heat map color, the more influence the constraint has on the muscle. The darker the heat map color, the more influence the constraint has on the muscle.

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

Specifies the distance range from a muscle at which connections with bones can be formed or not, and determines if there should be more constraint connections or fewer of them. The lower the value, the closer the muscle has to be to its bones to form a connection. How strong these connections are depends on the Mask Falloff heat map values.

See the Distance Threshold parameter description.

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

Specifies how close the bones are allowed to get to a muscle and determines how much the constraint is allowed to shrink. During the course of a muscle simulation, the bones naturally get closer to their muscle. When Compression Stiffness is strong, the less the bones are allowed to approach their muscle and the more rigid the connections (indicated by the lines) are between them to maintain their distance from each other. When Compression Stiffness is weak, the closer the bones are allowed to get to their muscle. This parameter helps to maintain a specific distance between a muscle and its bones.

See the Compression Stiffness parameter description.

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

The rest length of the distance constraints will be the original distance between the muscle and their bones. This scale increases or decreases the resting distance during the simulation.

See the Rest Length Scale parameter description.

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

Determines how easily a muscle can slide across its bone surfaces. Muscle to bone connections can drift along the surfaces of the bones. The same muscle points will always be connected, but the points on the bones can change when sliding occurs. This constraint property controls how fast a muscle can move away from their initial (rest) bone connection points.

See the Slide Rate parameter description.

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

Prevents the initialization connection orientations between a muscle and its bones from changing and keeps the relationship of the muscle relative to its bones. A high value tries to preserve the initialization connection angle, and a low value does not try to preserve the initialization connection angle. For example, for tendon areas of your muscles, the muscle to bone connections should have a much higher Tangent Stiffness.

See the Tangent Stiffness parameter description.

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

This multiplier will stiffen the Muscle to Bone constraint using the velocity of the attached bones. The magnitude of the velocity computed at the attched bone locations will be multiplied by this factor and then added to the Muscle to Bone Stiffness.

See the Velocity Stiffness Factor parameter description.

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

Restricts which bones a muscle is allowed to connect with. This field accepts any valid primitive group or adhoc group string. For example, if your character’s bicep muscle is unintentionally connecting to its rib bones, then you can specify a list of Attachment Candidates to limit connections to the arm and shoulder bones.

When using Attachment Candidates, if the optional primitive attribute muscletoboneattachid exists on both the source muscle and target bone, and if the integer value of muscletoboneattachid matches, then the muscle to bone attachment will be restricted to the matching primitives. If the muscletoboneattachid attribute exists as a point attribute, it will be promoted to a primitive attribute just in time as constraints are generated. This will allow a tool like Attribute Paint SOP to be used to paint matching indices. The muscletoboneattachid attribute must be an integer value. If the attribute exists and no match is found, constraints will not be generated.

Although not a constraint, this parameter sets the boundary distance from each muscle point at which collision detection occurs for a muscle tetrahedral mesh. You can view a muscle’s collision boundaries in the viewport state for this node with the Visualize > Collision Radius setting.

When computing collisions, this node uses its underlying Vellum constraint’s Edge Length Scale to determine whether or not an external collider is within the Collision Scale boundary for colliding. For example, a value of 1 creates a collision boundary (like a force field) around a muscle point equal to the radius of the edges around it.

See the Collision Scale parameter description.

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

Specifies the amount of velocity a muscle inherits from its bones. Over the course of a muscle simulation, a character’s animated bones have a certain given velocity as they move. And since the muscle to bone attachment constraint connects muscles to bones, a certain amount of the bones' velocity is imparted to those muscles and they can be moved around by it. The higher the Velocity Blend, the more the constraint will try to keep the muscles with the bones during their animation. This is useful for keeping muscles connected to the bones of a fast moving character.

For example, if a muscle is constrained to a fast moving bone and Velocity Blend is turned on, then not only is there a spring-like connection between the muscle and bone that the constraint will try to maintain, but the muscle will also inherit the bone’s momentum and be influenced by that force.

See the Velocity Blend parameter description.

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