Class Plane3D

1	/*
2	* Copyright (c) 2016 Martin Davis.
3	*
4	* All rights reserved. This program and the accompanying materials
5	* are made available under the terms of the Eclipse Public License 2.0
6	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
7	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
8	* and the Eclipse Distribution License is available at
9	*
10	* http://www.eclipse.org/org/documents/edl-v10.php.
11	*/
12
13	package org.locationtech.jts.math;
14
15	import org.locationtech.jts.geom.Coordinate;
16
17	/**
18	* Models a plane in 3-dimensional Cartesian space.
19	*
20	* @author mdavis
21	*
22	*/
23	public class Plane3D {
24
25	/**
26	* Enums for the 3 coordinate planes
27	*/
28	public static final int XY_PLANE = 1;
29	public static final int YZ_PLANE = 2;
30	public static final int XZ_PLANE = 3;
31
32	private Vector3D normal;
33	private Coordinate basePt;
34
35	public Plane3D(Vector3D normal, Coordinate basePt)
36	{
37	this.normal = normal;
38	this.basePt = basePt;
39	}
40
41	/**
42	* Computes the oriented distance from a point to the plane.
43	* The distance is:
44	* <ul>
45	* <li><b>positive</b> if the point lies above the plane (relative to the plane normal)
46	* <li><b>zero</b> if the point is on the plane
47	* <li><b>negative</b> if the point lies below the plane (relative to the plane normal)
48	* </ul>
49	*
50	* @param p the point to compute the distance for
51	* @return the oriented distance to the plane
52	*/
53	public double orientedDistance(Coordinate p) {
54	Vector3D pb = new Vector3D(p, basePt);
55	double pbdDotNormal = pb.dot(normal);
56	if (Double.isNaN(pbdDotNormal))
57	throw new IllegalArgumentException("3D Coordinate has NaN ordinate");
58	double d = pbdDotNormal / normal.length();
59	return d;
60	}
61
62	/**
63	* Computes the axis plane that this plane lies closest to.
64	* <p>
65	* Geometries lying in this plane undergo least distortion
66	* (and have maximum area)
67	* when projected to the closest axis plane.
68	* This provides optimal conditioning for
69	* computing a Point-in-Polygon test.
70	*
71	* @return the index of the closest axis plane.
72	*/
73	public int closestAxisPlane() {
74	double xmag = Math.abs(normal.getX());
75	double ymag = Math.abs(normal.getY());
76	double zmag = Math.abs(normal.getZ());
77	if (xmag > ymag) {
78	if (xmag > zmag)
79	return YZ_PLANE;
80	else
81	return XY_PLANE;
82	}
83	// y >= x
84	else if (zmag > ymag) {
85	return XY_PLANE;
86	}
87	// y >= z
88	return XZ_PLANE;
89	}
90
91	}
92