Editing Quadtree (section)

===Edge quadtree===
Edge quadtrees<ref>{{Cite journal|last=Warnock|first=J. E.|year=1969|title=A hidden surface algorithm for computer generated halftone pictures|journal=Computer Science Department, University of Utah|volume=TR 4-15}}</ref><ref>{{Cite journal|last=Schneier|first=M.|year=1981|title=Two hierarchical linear feature representations: edge pyramids and edge quadtrees|journal=Computer Graphics and Image Processing|publisher=Elsevier|volume=17 | issue = 3 |pages=211–224|doi=10.1016/0146-664X(81)90002-2}}</ref> (much like PM quadtrees) are used to store lines rather than points. Curves are approximated by subdividing cells to a very fine resolution, specifically until there is a single line segment per cell. Near corners/vertices, edge quadtrees will continue dividing until they reach their maximum level of decomposition. This can result in extremely unbalanced trees which may defeat the purpose of indexing.