Mark checking when culling

does region of space enclose mark on this tree? 
precompute range beneath subtree
correllate objects to spatial extent with quadtree

does region of space enclose linked mark from other tree? 
up to O(n) to look up best match for each node
solution: intersect node ranges between trees
reduces to point in polygon test
O(n log n) preprocess, O(log^2 n) lookup
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