Determine maximum stretch of particle

[nrvllrgrs]

I'm working in Unity -- where I wrote custom components for VRTK to interact with FlexActors. Currently, a user can grab a particle on a ClothActor that has pinned particles and stretch the geometry. I would like to stop the user from stretching the geometry beyond the stiffness of the FlexActor.

Given a particle and a FlexActor, is there a way to determine its maximum stretch / control bending on a scale of 0 to 1, where 1 means it is at its maximum?

[mmacklin]

If you have a user grabbing a particle and some fixed particles, you have two competing and incompatible constraints. Instead of allowing users to grab particles kinematically (by setting its position and inverse mass = 0), it should apply some force-based control. i.e.: just add an impulse to the particle targeting towards the user's desired location instead of setting it's position directly.