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diff --git a/src/net/java/joglutils/msg/math/Sphere.java b/src/net/java/joglutils/msg/math/Sphere.java
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+/*
+ * Copyright (c) 2007 Sun Microsystems, Inc. All Rights Reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * 
+ * - Redistribution of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * 
+ * - Redistribution in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * 
+ * Neither the name of Sun Microsystems, Inc. or the names of
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ * 
+ * This software is provided "AS IS," without a warranty of any kind. ALL
+ * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
+ * INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
+ * PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN
+ * MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL NOT BE LIABLE FOR
+ * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
+ * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR
+ * ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR
+ * DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE
+ * DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY,
+ * ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF
+ * SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
+ * 
+ * You acknowledge that this software is not designed or intended for use
+ * in the design, construction, operation or maintenance of any nuclear
+ * facility.
+ * 
+ */
+
+package net.java.joglutils.msg.math;
+
+/** Represents a sphere. */
+
+public class Sphere {
+  private Vec3f center = new Vec3f();
+  private float radius;
+  private float radSq;
+
+  /** Default constructor creates a sphere with center (0, 0, 0) and
+      radius 0 */
+  public Sphere() {
+    makeEmpty();
+  }
+
+  public Sphere(Vec3f center, float radius) {
+    set(center, radius);
+  }
+
+  public Sphere(Sphere other) {
+    set(other);
+  }
+
+  public Sphere(Box3f box) {
+    set(box);
+  }
+
+  /** Re-initialize this sphere to center (0, 0, 0) and radius 0 */
+  public void makeEmpty() {
+    center.set(0, 0, 0);
+    radius = radSq = 0;
+  }
+
+  public void  setCenter(Vec3f center) { this.center.set(center); }
+  public Vec3f getCenter()             { return center;           }
+
+  public void  setRadius(float radius) { this.radius = radius;
+                                         radSq = radius * radius; }
+  public float getRadius()             { return radius;           }
+
+  public void set(Vec3f center, float radius) {
+    setCenter(center); setRadius(radius); 
+  }
+  /** Returns radius and mutates passed "center" vector */
+  float get(Vec3f center) {
+    center.set(this.center); return radius;
+  }
+
+  /** Sets the parameters of this sphere to those of the given one */
+  public void set(Sphere other) {
+    set(other.center, other.radius);
+  }
+
+  /** Sets this sphere to encompass the given box */
+  public void set(Box3f box) {
+    Vec3f max = box.getMax();
+    Vec3f ctr = box.getCenter();
+    Vec3f diff = max.minus(ctr);
+    set(ctr, diff.length());
+  }
+
+  /** Mutate this sphere to encompass both itself and the argument.
+      Ignores zero-size arguments. */
+  public void extendBy(Sphere arg) {
+    if ((radius == 0.0f) || (arg.radius == 0.0f))
+      return;
+    // FIXME: This algorithm is a quick hack -- minimum bounding
+    // sphere of a set of other spheres is a well studied problem, but
+    // not by me
+    Vec3f diff = arg.center.minus(center);
+    if (diff.lengthSquared() == 0.0f) {
+      setRadius(Math.max(radius, arg.radius));
+      return;
+    }
+    IntersectionPoint[] intPt = new IntersectionPoint[4];
+    for (int i = 0; i < intPt.length; i++) {
+      intPt[i] = new IntersectionPoint();
+    }
+    int numIntersections;
+    numIntersections = intersectRay(center, diff, intPt[0], intPt[1]);
+    assert numIntersections == 2;
+    numIntersections = intersectRay(center, diff, intPt[2], intPt[3]);
+    assert numIntersections == 2;
+    IntersectionPoint minIntPt = intPt[0];
+    IntersectionPoint maxIntPt = intPt[0];
+    // Find minimum and maximum t values, take associated intersection
+    // points, find midpoint and half length of line segment -->
+    // center and radius.
+    for (int i = 0; i < 4; i++) {
+      if (intPt[i].getT() < minIntPt.getT()) {
+        minIntPt = intPt[i];
+      } else if (intPt[i].getT() > maxIntPt.getT()) {
+        maxIntPt = intPt[i];
+      }
+    }
+    // Compute the average -- this is the new center
+    center.add(minIntPt.getIntersectionPoint(),
+               maxIntPt.getIntersectionPoint());
+    center.scale(0.5f);
+    // Compute half the length -- this is the radius
+    setRadius(
+      0.5f *
+      minIntPt.getIntersectionPoint().
+        minus(maxIntPt.getIntersectionPoint()).
+          length()
+    );
+  }
+
+  /** Intersect a ray with the sphere. This is a one-sided ray
+      cast. Mutates one or both of intPt0 and intPt1. Returns number
+      of intersections which occurred. */
+  int intersectRay(Vec3f rayStart,
+                   Vec3f rayDirection,
+                   IntersectionPoint intPt0,
+                   IntersectionPoint intPt1) {
+    // Solve quadratic equation
+    float a = rayDirection.lengthSquared();
+    if (a == 0.0)
+      return 0;
+    float b = 2.0f * (rayStart.dot(rayDirection) - rayDirection.dot(center));
+    Vec3f tempDiff = center.minus(rayStart);
+    float c = tempDiff.lengthSquared() - radSq;
+    float disc = b * b - 4 * a * c;
+    if (disc < 0.0f)
+      return 0;
+    int numIntersections;
+    if (disc == 0.0f)
+      numIntersections = 1;
+    else
+      numIntersections = 2;
+    intPt0.setT((0.5f * (-1.0f * b + (float) Math.sqrt(disc))) / a);
+    if (numIntersections == 2)
+      intPt1.setT((0.5f * (-1.0f * b - (float) Math.sqrt(disc))) / a);
+    Vec3f tmp = new Vec3f(rayDirection);
+    tmp.scale(intPt0.getT());
+    tmp.add(tmp, rayStart);
+    intPt0.setIntersectionPoint(tmp);
+    if (numIntersections == 2) {
+      tmp.set(rayDirection);
+      tmp.scale(intPt1.getT());
+      tmp.add(tmp, rayStart);
+      intPt1.setIntersectionPoint(tmp);
+    }
+    return numIntersections;
+  }
+}