View source for PM Quadtree

A PM (Polygonal Map) Quadtree describes a collection of quadtrees that can store points and edges. A q-edge refers to a subset of an edge formed by the partitions of the PM Quadtree.

== PM1 Quadtree ==
[[Image:Pm1_example3.png|PM1 Quadtree example]]

A PM1 Quadtree follows the following rules:
# At most, one vertex can lie in a region represented by a quadtree leaf node.
# If a quadtree leaf node's region contains a vertex, then it can contain no q-edge that does not include that vertex.
# If a quadtree leaf node's region contains no vertices, then it can contain, at most, one q-edge.
# Each region's quadtree leaf node is maximal.

== PM2 Quadtree ==
[[Image:Pm2_example3.png|PM2 Quadtree example]]

A PM2 Quadtree follows the following rules:
# At most, one vertex can lie in a region represented by a quadtree leaf node.
# If a quadtree leaf node's region contains a vertex, then it can contain no q-edge that does not include that vertex. 
# If a quadtree leaf node's region contains no vertices, then it can contain only q-edges that meet at a common vertex exterior to the region.
# Each region's quadtree leaf node is maximal.

== PM3 Quadtree ==
[[Image:Pm3_example3.png|PM3 Quadtree example]]

A PM3 Quadtree follows the following rules:
# At most, one vertex can lie in a region represented by a quadtree leaf node.
# Each region's quadtree leaf node is maximal.

== Applications ==
PM Quadtrees are useful in determining the region in which a point lies, the determination of the boundaries of all regions lying within a given distance of a point, and overlaying two maps.