org.opentripplanner.common.geometry

Class RecursiveGridIsolineBuilder

java.lang.Object

org.opentripplanner.common.geometry.RecursiveGridIsolineBuilder

public class RecursiveGridIsolineBuilder
extends Object

Compute isoline based on a zFunc and a set of initial coverage points P0={(x,y)} to seed the computation. This assume we have a z = Fz(x,y) function which can gives a z value for any given point (x,y), z can be undefined for some region. There are many tricks to reduce to the minimum the numbers of Fz samplings, explained in the code below. It will compute an isoline for a given z0 value. The isoline is composed of a list of n polygons, CW for normal polygons, CCW for "holes". The isoline computation can be called multiple times on the same builder for different z0 values: this will reduce the number of Fz sampling as they are cached in the builder. Please note that the initial covering points must touch all isolines you want to cover.

Author:

laurent

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	RecursiveGridIsolineBuilder.Direction
static interface	RecursiveGridIsolineBuilder.ZFunc

Constructor Summary

Constructors

Constructor and Description
RecursiveGridIsolineBuilder(double dX, double dY, com.vividsolutions.jts.geom.Coordinate center, RecursiveGridIsolineBuilder.ZFunc fz, List<com.vividsolutions.jts.geom.Coordinate> p0List) Create an object to compute isochrones.

Method Summary

Modifier and Type	Method and Description
com.vividsolutions.jts.geom.Geometry	computeIsoline(long z0)
com.vividsolutions.jts.geom.Geometry	getDebugGeometry()
void	setDebugCrossingEdges(boolean debugCrossingEdges)
void	setDebugSeedGrid(boolean debugSeedGrid)

Methods inherited from class java.lang.Object

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

Constructor Detail

RecursiveGridIsolineBuilder

public RecursiveGridIsolineBuilder(double dX,
                                   double dY,
                                   com.vividsolutions.jts.geom.Coordinate center,
                                   RecursiveGridIsolineBuilder.ZFunc fz,
                                   List<com.vividsolutions.jts.geom.Coordinate> p0List)

Create an object to compute isochrones. One may call several time isochronify on the same IsoChronificator object, this will re-use the z = f(x,y) sampling if possible, as they are kept in cache.

Parameters:

request - Parameters for the computation

center - Center point (eg origin)

fz - Function returning the z-value for a xy-coordinate

p0List - Initial set of coverage points to seed the heuristics

Method Detail

setDebugSeedGrid

public void setDebugSeedGrid(boolean debugSeedGrid)

setDebugCrossingEdges

public void setDebugCrossingEdges(boolean debugCrossingEdges)

computeIsoline

public com.vividsolutions.jts.geom.Geometry computeIsoline(long z0)

getDebugGeometry

public final com.vividsolutions.jts.geom.Geometry getDebugGeometry()