Are there any gems in the engine API that would make it possible to efficiently ask the scene tree "find all objects X distance away from object Y". This is not as easy as "scan everything" since that is a big-oh of n-squared solution: "for each object Y in scene tree compare with every object (as X) in scene tree". BSPs aren't good since their setup is an offline algorithm (meaning BSPs can't change easily with runtime object movement). I could implement a range tree for one axis (but the storage blows up to "N to the number of dimensions" for more than one). So I'm not sure what I should use here. Assume LOTS of objects to check (large N).