com.vividsolutions.jts.index.chain

Class MonotoneChain


public class MonotoneChain
extends java.lang.Object

MonotoneChains are a way of partitioning the segments of a linestring to allow for fast searching of intersections. They have the following properties:
  1. the segments within a monotone chain will never intersect each other
  2. the envelope of any contiguous subset of the segments in a monotone chain is equal to the envelope of the endpoints of the subset.
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.
Version:
1.6

Constructor Summary

MonotoneChain(Coordinate[] pts, int start, int end, Object context)

Method Summary

void
computeOverlaps(MonotoneChain mc, MonotoneChainOverlapAction mco)
Object
getContext()
Coordinate[]
getCoordinates()
Return the subsequence of coordinates forming this chain.
int
getEndIndex()
Envelope
getEnvelope()
int
getId()
void
getLineSegment(int index, LineSegment ls)
int
getStartIndex()
void
select(Envelope searchEnv, MonotoneChainSelectAction mcs)
Determine all the line segments in the chain whose envelopes overlap the searchEnvelope, and process them
void
setId(int id)

Constructor Details

MonotoneChain

public MonotoneChain(Coordinate[] pts,
                     int start,
                     int end,
                     Object context)

Method Details

computeOverlaps

public void computeOverlaps(MonotoneChain mc,
                            MonotoneChainOverlapAction mco)

getContext

public Object getContext()

getCoordinates

public Coordinate[] getCoordinates()
Return the subsequence of coordinates forming this chain. Allocates a new array to hold the Coordinates

getEndIndex

public int getEndIndex()

getEnvelope

public Envelope getEnvelope()

getId

public int getId()

getLineSegment

public void getLineSegment(int index,
                           LineSegment ls)

getStartIndex

public int getStartIndex()

select

public void select(Envelope searchEnv,
                   MonotoneChainSelectAction mcs)
Determine all the line segments in the chain whose envelopes overlap the searchEnvelope, and process them

setId

public void setId(int id)