normalize method
Normalizes this quaternion.
Implementation
Quaternion normalize() {
double l = length;
if ( l == 0 ) {
x = 0;
y = 0;
z = 0;
w = 1;
}
else {
l = 1 / l;
x = x * l;
y = y * l;
z = z * l;
w = w * l;
}
return this;
}