/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jtsexample.geom.prep;
import org.locationtech.jts.geom.*;
import org.locationtech.jts.geom.prep.*;
/**
* Shows use of {@link PreparedGeometry} in a batch (repeated) operation.
*
* The example uses a Monte Carlo method to approximate the value of Pi.
* Given a circle inscribed in a square and a large number of random points
* in the square, the number of points which intersect the circle approximates Pi/4.
* This involves repeated Point-In-Polygon tests, which is one of the
* geometry tests optimized by the PreparedGeometry implementation for polygons.
*
* @version 1.7
*/
public class PreparedGeometryExample
{
static GeometryFactory geomFact = new GeometryFactory();
static final int MAX_ITER = 100000;
public static void main(String[] args)
throws Exception
{
Geometry circle = createCircle();
PreparedGeometry prepCircle = PreparedGeometryFactory.prepare(circle);
int count = 0;
int inCount = 0;
for (int i = 0; i < MAX_ITER; i++)
{
count++;
Point randPt = createRandomPoint();
if (prepCircle.intersects(randPt)) {
inCount++;
}
//System.out.println("Approximation to PI: " + (4.0 * inCount / (double) count));
}
double approxPi = 4.0 * inCount / (double) count;
double approxDiffPct = 1.0 - approxPi/Math.PI;
System.out.println("Approximation to PI: " + approxPi
+ " ( % difference from actual = " + 100 * approxDiffPct + " )"
);
}
static Geometry createCircle()
{
Geometry centrePt = geomFact.createPoint(new Coordinate(0.5, 0.5));
return centrePt.buffer(0.5, 20);
}
static Point createRandomPoint()
{
return geomFact.createPoint(new Coordinate(Math.random(), Math.random()));
}
}