geos::index::chain::MonotoneChain Class Reference

MonotoneChains are a way of partitioning the segments of a linestring to allow for fast searching of intersections. More...

#include <MonotoneChain.h>

List of all members.

Public Member Functions

 MonotoneChain (const geom::CoordinateSequence *newPts, int nstart, int nend, void *nContext)
geom::EnvelopegetEnvelope ()
int getStartIndex ()
int getEndIndex ()
void getLineSegment (unsigned int index, geom::LineSegment *ls)
geom::CoordinateSequencegetCoordinates ()
void select (const geom::Envelope &searchEnv, MonotoneChainSelectAction &mcs)
void computeOverlaps (MonotoneChain *mc, MonotoneChainOverlapAction *mco)
void setId (int nId)
int getId ()
void * getContext ()


Detailed Description

MonotoneChains are a way of partitioning the segments of a linestring to allow for fast searching of intersections.

They have the following properties:

Property 1 means that there is no need to test pairs of segments from within the same monotone chain for intersection. Property 2 allows binary search to be used to find the intersection points of two monotone chains. For many types of real-world data, these properties eliminate a large number of segment comparisons, producing substantial speed gains.

One of the goals of this implementation of MonotoneChains is to be as space and time efficient as possible. One design choice that aids this is that a MonotoneChain is based on a subarray of a list of points. This means that new arrays of points (potentially very large) do not have to be allocated.

MonotoneChains support the following kinds of queries:

This implementation of MonotoneChains uses the concept of internal iterators to return the resultsets for the above queries. This has time and space advantages, since it is not necessary to build lists of instantiated objects to represent the segments returned by the query. However, it does mean that the queries are not thread-safe.

Last port: index/chain/MonotoneChain.java rev. 1.13 (JTS-1.7)


Member Function Documentation

geom::CoordinateSequence* geos::index::chain::MonotoneChain::getCoordinates (  ) 

Return the subsequence of coordinates forming this chain. Allocates a new CoordinateSequence to hold the Coordinates

void geos::index::chain::MonotoneChain::select ( const geom::Envelope searchEnv,
MonotoneChainSelectAction mcs 
)

Determine all the line segments in the chain whose envelopes overlap the searchEnvelope, and process them


The documentation for this class was generated from the following file:
Generated on Fri Mar 27 04:53:37 2009 for GEOS by  doxygen 1.5.4