/*
* 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.jts.noding;
import org.locationtech.jts.geom.Coordinate;
/**
* Methods for computing and working with octants of the Cartesian plane
* Octants are numbered as follows:
* <pre>
* \2|1/
* 3 \|/ 0
* ---+--
* 4 /|\ 7
* /5|6\
* </pre>
* If line segments lie along a coordinate axis, the octant is the lower of the two
* possible values.
*
* @version 1.7
*/
public class Octant {
/**
* Returns the octant of a directed line segment (specified as x and y
* displacements, which cannot both be 0).
*/
public static int octant(double dx, double dy)
{
if (dx == 0.0 && dy == 0.0)
throw new IllegalArgumentException("Cannot compute the octant for point ( "+ dx + ", " + dy + " )" );
double adx = Math.abs(dx);
double ady = Math.abs(dy);
if (dx >= 0) {
if (dy >= 0) {
if (adx >= ady)
return 0;
else
return 1;
}
else { // dy < 0
if (adx >= ady)
return 7;
else
return 6;
}
}
else { // dx < 0
if (dy >= 0) {
if (adx >= ady)
return 3;
else
return 2;
}
else { // dy < 0
if (adx >= ady)
return 4;
else
return 5;
}
}
}
/**
* Returns the octant of a directed line segment from p0 to p1.
*/
public static int octant(Coordinate p0, Coordinate p1)
{
double dx = p1.x - p0.x;
double dy = p1.y - p0.y;
if (dx == 0.0 && dy == 0.0)
throw new IllegalArgumentException("Cannot compute the octant for two identical points " + p0);
return octant(dx, dy);
}
private Octant() {
}
}