0: Loop over unready volumes first, midphases second. 1: Loop over all midphases, unready volumes second. 2: (NOT IMPLEMENTED YET) Use a grid acceleration structure for a more optimal version of the unready-volumes-first approach. 3: Dynamically choose between strategies based on how many midphases there are and vs unready volumes.
Usage
p.SpatialReadiness.MidPhaseStrategy [value]
Set via the console (~) or in DefaultEngine.ini / DefaultGame.ini.