Current pinch-scale ratio, updated each frame by MultiTouchDragHandler.
Modifies followObject in-place. Invoked after position is resolved each frame.
Called once at drag start and again whenever the drag context resets (e.g. multi-touch → single-pointer transition). Capture any object snapshot (position, rotation, scale) you need to hold fixed during the drag. Constraints that need no dynamic initialization may omit this method.
Locks the follow object's signed distance from a plane to a value set at drag start. Owned by XZPlaneDragStrategy to prevent slow Y drift in the side-view fallback path. Immune to grab-point projection errors, stale matrixWorld, and epsilon guards.
When boundsBottomSignedDistFromPivot is non-zero (set by MultiTouchDragHandler for XZPlane scaling), the effective locked height is shifted each frame so the bottom of the object's bounds stays at the height captured at drag start instead of the pivot.