[UE4] Math Based Foliage Interaction Test

This interaction uses sphere masks that have a fade on them to contribute to a world space area mask for pivot painter to perform an animation. In other words, it's a math based version of this effect I made with Runtime Virtual Textures: https://youtu.be/vql-XN9w3Sc. Other pivot painter interaction methods seem to only care about if the player is currently pushing against the foliage, but not the idea of the foliage resetting to it's original position after a cooldown period like when the player leaves the area quickly.