1 /*
2  * Copyright (c) 2009-2010 jMonkeyEngine
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions are
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12  * * Redistributions in binary form must reproduce the above copyright
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31  */
32 
33 package com.jme3.math;
34 
35 import com.jme3.export.*;
36 import java.io.IOException;
37 
38 
39 /**
40  * <code>Ring</code> defines a flat ring or disk within three dimensional
41  * space that is specified via the ring's center point, an up vector, an inner
42  * radius, and an outer radius.
43  *
44  * @author Andrzej Kapolka
45  * @author Joshua Slack
46  */
47 
48 public final class Ring implements Savable, Cloneable, java.io.Serializable {
49 
50     static final long serialVersionUID = 1;
51 
52     private Vector3f center, up;
53     private float innerRadius, outerRadius;
54     private transient static Vector3f b1 = new Vector3f(), b2 = new Vector3f();
55 
56     /**
57      * Constructor creates a new <code>Ring</code> lying on the XZ plane,
58      * centered at the origin, with an inner radius of zero and an outer radius
59      * of one (a unit disk).
60      */
Ring()61     public Ring() {
62         center = new Vector3f();
63         up = Vector3f.UNIT_Y.clone();
64         innerRadius = 0f;
65         outerRadius = 1f;
66     }
67 
68     /**
69      * Constructor creates a new <code>Ring</code> with defined center point,
70      * up vector, and inner and outer radii.
71      *
72      * @param center
73      *            the center of the ring.
74      * @param up
75      *            the unit up vector defining the ring's orientation.
76      * @param innerRadius
77      *            the ring's inner radius.
78      * @param outerRadius
79      *            the ring's outer radius.
80      */
Ring(Vector3f center, Vector3f up, float innerRadius, float outerRadius)81     public Ring(Vector3f center, Vector3f up, float innerRadius,
82             float outerRadius) {
83         this.center = center;
84         this.up = up;
85         this.innerRadius = innerRadius;
86         this.outerRadius = outerRadius;
87     }
88 
89     /**
90      * <code>getCenter</code> returns the center of the ring.
91      *
92      * @return the center of the ring.
93      */
getCenter()94     public Vector3f getCenter() {
95         return center;
96     }
97 
98     /**
99      * <code>setCenter</code> sets the center of the ring.
100      *
101      * @param center
102      *            the center of the ring.
103      */
setCenter(Vector3f center)104     public void setCenter(Vector3f center) {
105         this.center = center;
106     }
107 
108     /**
109      * <code>getUp</code> returns the ring's up vector.
110      *
111      * @return the ring's up vector.
112      */
getUp()113     public Vector3f getUp() {
114         return up;
115     }
116 
117     /**
118      * <code>setUp</code> sets the ring's up vector.
119      *
120      * @param up
121      *            the ring's up vector.
122      */
setUp(Vector3f up)123     public void setUp(Vector3f up) {
124         this.up = up;
125     }
126 
127     /**
128      * <code>getInnerRadius</code> returns the ring's inner radius.
129      *
130      * @return the ring's inner radius.
131      */
getInnerRadius()132     public float getInnerRadius() {
133         return innerRadius;
134     }
135 
136     /**
137      * <code>setInnerRadius</code> sets the ring's inner radius.
138      *
139      * @param innerRadius
140      *            the ring's inner radius.
141      */
setInnerRadius(float innerRadius)142     public void setInnerRadius(float innerRadius) {
143         this.innerRadius = innerRadius;
144     }
145 
146     /**
147      * <code>getOuterRadius</code> returns the ring's outer radius.
148      *
149      * @return the ring's outer radius.
150      */
getOuterRadius()151     public float getOuterRadius() {
152         return outerRadius;
153     }
154 
155     /**
156      * <code>setOuterRadius</code> sets the ring's outer radius.
157      *
158      * @param outerRadius
159      *            the ring's outer radius.
160      */
setOuterRadius(float outerRadius)161     public void setOuterRadius(float outerRadius) {
162         this.outerRadius = outerRadius;
163     }
164 
165     /**
166      *
167      * <code>random</code> returns a random point within the ring.
168      *
169      * @return a random point within the ring.
170      */
random()171     public Vector3f random() {
172         return random(null);
173     }
174 
175     /**
176      *
177      * <code>random</code> returns a random point within the ring.
178      *
179      * @param result Vector to store result in
180      * @return a random point within the ring.
181      */
random(Vector3f result)182     public Vector3f random(Vector3f result) {
183         if (result == null) {
184             result = new Vector3f();
185         }
186 
187         // compute a random radius according to the ring area distribution
188         float inner2 = innerRadius * innerRadius, outer2 = outerRadius
189                 * outerRadius, r = FastMath.sqrt(inner2
190                 + FastMath.nextRandomFloat() * (outer2 - inner2)), theta = FastMath
191                 .nextRandomFloat()
192                 * FastMath.TWO_PI;
193         up.cross(Vector3f.UNIT_X, b1);
194         if (b1.lengthSquared() < FastMath.FLT_EPSILON) {
195             up.cross(Vector3f.UNIT_Y, b1);
196         }
197         b1.normalizeLocal();
198         up.cross(b1, b2);
199         result.set(b1).multLocal(r * FastMath.cos(theta)).addLocal(center);
200         result.scaleAdd(r * FastMath.sin(theta), b2, result);
201         return result;
202     }
203 
write(JmeExporter e)204     public void write(JmeExporter e) throws IOException {
205         OutputCapsule capsule = e.getCapsule(this);
206         capsule.write(center, "center", Vector3f.ZERO);
207         capsule.write(up, "up", Vector3f.UNIT_Z);
208         capsule.write(innerRadius, "innerRadius", 0f);
209         capsule.write(outerRadius, "outerRadius", 1f);
210     }
211 
read(JmeImporter e)212     public void read(JmeImporter e) throws IOException {
213         InputCapsule capsule = e.getCapsule(this);
214         center = (Vector3f) capsule.readSavable("center",
215                 Vector3f.ZERO.clone());
216         up = (Vector3f) capsule
217                 .readSavable("up", Vector3f.UNIT_Z.clone());
218         innerRadius = capsule.readFloat("innerRadius", 0f);
219         outerRadius = capsule.readFloat("outerRadius", 1f);
220     }
221 
222     @Override
clone()223     public Ring clone() {
224         try {
225             Ring r = (Ring) super.clone();
226             r.center = center.clone();
227             r.up = up.clone();
228             return r;
229         } catch (CloneNotSupportedException e) {
230             throw new AssertionError();
231         }
232     }
233 }