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/*
* gleem -- OpenGL Extremely Easy-To-Use Manipulators.
* Copyright (C) 1998-2003 Kenneth B. Russell (kbrussel@alum.mit.edu)
*
* Copying, distribution and use of this software in source and binary
* forms, with or without modification, is permitted provided that the
* following conditions are met:
*
* Distributions of source code must reproduce the copyright notice,
* this list of conditions and the following disclaimer in the source
* code header files; and Distributions of binary code must reproduce
* the copyright notice, this list of conditions and the following
* disclaimer in the documentation, Read me file, license file and/or
* other materials provided with the software distribution.
*
* The names of Sun Microsystems, Inc. ("Sun") and/or the copyright
* holder may not 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, NON-INTERFERENCE, ACCURACY OF
* INFORMATIONAL CONTENT OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. THE
* COPYRIGHT HOLDER, SUN AND SUN'S 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 THE
* COPYRIGHT HOLDER, SUN OR SUN'S 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 ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGES. YOU ACKNOWLEDGE THAT THIS SOFTWARE IS NOT
* DESIGNED, LICENSED OR INTENDED FOR USE IN THE DESIGN, CONSTRUCTION,
* OPERATION OR MAINTENANCE OF ANY NUCLEAR FACILITY. THE COPYRIGHT
* HOLDER, SUN AND SUN'S LICENSORS DISCLAIM ANY EXPRESS OR IMPLIED
* WARRANTY OF FITNESS FOR SUCH USES.
*/
package gleem;
import gleem.linalg.*;
/** Represents a bounding sphere. */
public class BSphere {
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 BSphere() {
makeEmpty();
}
public BSphere(Vec3f center, float radius) {
set(center, radius);
}
/** 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;
}
/** Mutate this sphere to encompass both itself and the argument.
Ignores zero-size arguments. */
public void extendBy(BSphere 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;
}
}
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