Vector3D refCenter = new Vector3D(d, new Vector3D(sr.nextVector()));
// set up a large sample inside the reference sphere
int nbPoints = random.nextInt(1000);
List<Vector3D> points = new ArrayList<Vector3D>();
for (int i = 0; i < nbPoints; ++i) {
double r = refRadius * random.nextDouble();
points.add(new Vector3D(1.0, refCenter, r, new Vector3D(sr.nextVector())));
}
// test we find a sphere at most as large as the one used for random drawings
checkSphere(points, refRadius);