com.vividsolutions.jump.warp

Class Triangulator

java.lang.Object

com.vividsolutions.jump.warp.Triangulator

public class Triangulator
extends Object

A better name for this class would have been TriangleMapFactory. Given the coordinates of an initial and final triangulation, it will return a map of source Triangle to destination Triangle. Creates a FeatureCollection of triangles covering a given area. Thin triangles are avoided.

Coordinates are not created, modified, or discarded. Thus, the triangles created will be composed of the Coordinates passed in to the Triangulator. See White, Marvin S., Jr. and Griffin, Patricia. 1985. Piecewise linear rubber-sheet map transformation. "The American Cartographer" 12:2, 123-31.

Constructor Summary

Constructors

Constructor and Description
Triangulator()

Method Summary

Methods

Modifier and Type	Method and Description
protected com.vividsolutions.jts.geom.Coordinate	add(com.vividsolutions.jts.geom.Coordinate a, com.vividsolutions.jts.geom.LineString vector)
protected List	alternativeTriangles(Triangle PQS, Triangle QRS)
Collection	getIgnoredVectors() Permits the caller to identify which vectors were ignored because they were not 2-point LineStrings
protected List	heightMaximizedTriangles(Triangle PQS, Triangle QRS) The intent of this method is to avoid narrow triangles, which create near singularities.
static Collection	nonVectors(Collection geometries)
protected Quadrilateral	tag(Quadrilateral sourceQuad, Quadrilateral destQuad)
static List	taggedVectorVertices(boolean tips, Collection vectors) The returned Coordinates will be tagged with the tails if the tips are requested (or the tips, if the tails are requested).
protected Triangle	triangleContaining(com.vividsolutions.jts.geom.Coordinate p, List triangles)
Map	triangleMap(com.vividsolutions.jts.geom.Envelope datasetEnvelope, Collection vectorLineStrings, Collection sourceHints, Collection destinationHints, TaskMonitor monitor)
Map	triangleMap(com.vividsolutions.jts.geom.Envelope datasetEnvelope, Collection vectorLineStrings, TaskMonitor monitor) Splits two regions into Triangles.
static boolean	vector(com.vividsolutions.jts.geom.Geometry g)
protected com.vividsolutions.jts.geom.LineString	vectorWithNearestTail(com.vividsolutions.jts.geom.Coordinate x, List vectors)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Triangulator

public Triangulator()

Method Detail

triangleMap

public Map triangleMap(com.vividsolutions.jts.geom.Envelope datasetEnvelope,
              Collection vectorLineStrings,
              TaskMonitor monitor)

Splits two regions into Triangles. The two regions are called the "source quadrilateral" and "destination quadrilateral", and are based on the given dataset envelope. The "source quadrilateral" is the dataset envelope expanded 5% along each margin. The "destination quadrilateral" is the source quadrilateral with each vertex shifted according to the vector with the nearest tail. The source quadrilateral is split using the vector tails; the destination quadrilateral is split using the vector tips. In this way, the vectors map the source Triangles to the destination Triangles.

Parameters:

datasetEnvelope - the region to triangulate

vectors - vectors (2-point LineStrings) whose tails and tips split the "source quadrilateral" and "destination quadrilateral" into triangles

Returns:

a map of source Triangles to destination Triangles

triangleMap

public Map triangleMap(com.vividsolutions.jts.geom.Envelope datasetEnvelope,
              Collection vectorLineStrings,
              Collection sourceHints,
              Collection destinationHints,
              TaskMonitor monitor)

Parameters:

sourceHints - "far-away" Coordinates (even outside the dataset envelope) for which we must ensure that source triangles include.

destinationHints - "far-away" Coordinates for which we must ensure that destination triangles include

getIgnoredVectors

public Collection getIgnoredVectors()

Permits the caller to identify which vectors were ignored because they were not 2-point LineStrings

nonVectors

public static Collection nonVectors(Collection geometries)

vector

public static boolean vector(com.vividsolutions.jts.geom.Geometry g)

heightMaximizedTriangles

protected List heightMaximizedTriangles(Triangle PQS,
                            Triangle QRS)

The intent of this method is to avoid narrow triangles, which create near singularities.

Parameters:

PQS - a triangle sharing an edge with QRS; vertex order is irrelevant

Returns:

(PQS and QRS) or (PQR, PRS), whichever pair has the largest minimum height

triangleContaining

protected Triangle triangleContaining(com.vividsolutions.jts.geom.Coordinate p,
                          List triangles)

Returns:

the triangle containing p, or null if no triangle contains p

add

protected com.vividsolutions.jts.geom.Coordinate add(com.vividsolutions.jts.geom.Coordinate a,
                                         com.vividsolutions.jts.geom.LineString vector)

Returns:

a + the displacement represented by vector

vectorWithNearestTail

protected com.vividsolutions.jts.geom.LineString vectorWithNearestTail(com.vividsolutions.jts.geom.Coordinate x,
                                                           List vectors)

tag

protected Quadrilateral tag(Quadrilateral sourceQuad,
                Quadrilateral destQuad)

Returns:

sourceQuad wrapped in TaggedCoordinates pointing to the corresponding Coordinates in destQuad.

alternativeTriangles

protected List alternativeTriangles(Triangle PQS,
                        Triangle QRS)

Parameters:

PQS - a triangle sharing an edge with QRS; vertex order is irrelevant

Returns:

triangles PQR and PRS, or null if PQRS is not convex

taggedVectorVertices

public static List taggedVectorVertices(boolean tips,
                        Collection vectors)

The returned Coordinates will be tagged with the tails if the tips are requested (or the tips, if the tails are requested).

Parameters:

tips - true to return the vector tips; otherwise, the tails