Houdini 21.0 Nodes Geometry nodes

Muscle Auto Tension Lines geometry node

Creates a tension line for each muscle by finding the longest line between muscle ends.

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Since 21.0

This node automatically creates tension lines for each input muscle. The tension lines are calculated by finding the longest line between the specified muscle ends, for each muscle.

Tip

Turn on Match Tension Lines by Name in the Muscle Flex SOP to automatically link each tension line generated by this node to each muscle.

Parameters

Group

Creates tension lines for only the specified muscles. Leave blank to affect all muscles.

Muscle ID Attribute

The name of the string attribute containing that identifies which primitives belong together as a single muscle. The default is muscle_id.

Tip

For multiple muscles driven by a single tension line, you can use a Muscle ID SOP to create duplicate attribute of muscle_id with a single shared name for the muscles to group together. For example, you have L_rectusAbdominus01, L_rectusAbdominus02, L_rectusAbdominus03 and L_rectusAbdominus04 as distinct muscle_id valuesand give them all a single name called L_rectusAbdominus stored in a different attribute such as tension_id. If this attribute is then specified in this parameter, only a single tension line will be created that spans across all four muscles.

End Mask Attribute

Use point attribute of 1 in the end regions of the muscles, where they attach to bones, and 0 in the belly of each muscle. Points with values of this attribute greater than the End Mask Threshold are used as candidate points for the end points of each tension line. The longest distance between two candidates end points for a given Muscle ID Attribute are the tension line. Default is muscleendmask, but a custom attribute can be specified if you want to include or exclude regions from the tension line end point candidacy.

Tip

The end points of each tension line should be close to different bones so the length of the tension line changes as the bones deform. If both ends of one line attach to a single rigid bone, the line will always stay the same length and will not activate.

End Mask Threshold

The value of the End Mask Attribute which points are used as candidates for end points of the tension lines. The guide geometry visible in the viewport are all the points on the muscles above this threshold.

Inputs

Input 1

Tetrahedralized muscle geometry which has a Muscle ID Attribute such as muscle_id and an End Mask Attribute such as muscleendmask.

Outputs

Output 1

Mucle tension lines with the source Muscle ID Attribute stored as autoflex_id as well as length and restlength attributes.

See also

Geometry nodes