/**
* Calculates a minimum bounding sphere for the set of points. The algorithm was originally found
* at
* http://www.flipcode.com/cgi-bin/msg.cgi?showThread=COTD-SmallestEnclosingSpheres&forum=cotd&id=-1
* in C++ and translated to java by Cep21
*
* @param points The points to calculate the minimum bounds from.
*/
public void calcWelzl(FloatBuffer points) {
if (center == null) {
center = new Vector3f();
}
FloatBuffer buf = BufferUtils.createFloatBuffer(points.limit());
points.rewind();
buf.put(points);
buf.flip();
recurseMini(buf, buf.limit() / 3, 0, 0);
}
/**
* Used from calcWelzl. This function recurses to calculate a minimum bounding sphere a few points
* at a time.
*
* @param points The array of points to look through.
* @param p The size of the list to be used.
* @param b The number of points currently considering to include with the sphere.
* @param ap A variable simulating pointer arithmatic from C++, and offset in <code>points</code>.
*/
private void recurseMini(FloatBuffer points, int p, int b, int ap) {
Vector3f tempA = Vector3f.newInstance();
Vector3f tempB = Vector3f.newInstance();
Vector3f tempC = Vector3f.newInstance();
Vector3f tempD = Vector3f.newInstance();
try {
switch (b) {
case 0:
this.radius = 0;
this.center.set(0, 0, 0);
break;
case 1:
this.radius = 1f - RADIUS_EPSILON;
BufferUtils.populateFromBuffer(center, points, ap - 1);
break;
case 2:
BufferUtils.populateFromBuffer(tempA, points, ap - 1);
BufferUtils.populateFromBuffer(tempB, points, ap - 2);
setSphere(tempA, tempB);
break;
case 3:
BufferUtils.populateFromBuffer(tempA, points, ap - 1);
BufferUtils.populateFromBuffer(tempB, points, ap - 2);
BufferUtils.populateFromBuffer(tempC, points, ap - 3);
setSphere(tempA, tempB, tempC);
break;
case 4:
BufferUtils.populateFromBuffer(tempA, points, ap - 1);
BufferUtils.populateFromBuffer(tempB, points, ap - 2);
BufferUtils.populateFromBuffer(tempC, points, ap - 3);
BufferUtils.populateFromBuffer(tempD, points, ap - 4);
setSphere(tempA, tempB, tempC, tempD);
return;
}
for (int i = 0; i < p; i++) {
BufferUtils.populateFromBuffer(tempA, points, i + ap);
if (tempA.distanceSquared(center) - (radius * radius) > RADIUS_EPSILON - 1f) {
for (int j = i; j > 0; j--) {
BufferUtils.populateFromBuffer(tempB, points, j + ap);
BufferUtils.populateFromBuffer(tempC, points, j - 1 + ap);
BufferUtils.setInBuffer(tempC, points, j + ap);
BufferUtils.setInBuffer(tempB, points, j - 1 + ap);
}
recurseMini(points, i, b + 1, ap + 1);
}
}
} finally {
Vector3f.recycle(tempA);
Vector3f.recycle(tempB);
Vector3f.recycle(tempC);
Vector3f.recycle(tempD);
}
}
