The Vellum Rest Blend SOP allows mixing the current rest values of constraints, including rest length and rest angles, with a rest state calculated from external geometry. In this way you can deform the original input geometry in its rest configuration to modify constraints during the simulation, allowing effects like purposefully stretching or putting bends into cloth or hair, or inflating an object over time.
The geometry used for rest configuration update is the fourth input if provided; otherwise the first input is used.
Specifies the point group in the geometry whose constraints should be blended with the external rest state. NOTE: Any group specified here should also exist on the rest geometry.
Specifies the primitive group of constraints whose rest values should be blended with the external rest state.
Controls how the rest states are blended. With a value of Blend, the states are blended together using a 0-1 values. With a value of Distance, the current state can move a maximum of the specified Distance units towards the new rest state, e.g. a maximum of 5 degrees for a bend constraint.
In Blend mode, specifies how much of the current rest state and external rest state should be blended together. With a value of 0, the constraints' rest values will not be modified; with a value of 1, the constraints' rest values will be updated to exactly match the external geometry state.
In Distance mode, specifies how far the constraints' current rest state can be modified towards the external rest state. This is specified in the units of the constraint, so generally should be specified for only one constraint type at a time using the Constraint Group. For Stretch constraints this value is specified in length units (typically meters); for Bend constraints it is in degrees.