randomDirection method
Implementation
Vector3 randomDirection() {
// Derived from https://mathworld.wolfram.com/SpherePointPicking.html
var u = (Math.random() - 0.5) * 2;
var t = Math.random() * Math.PI * 2;
var f = Math.sqrt(1 - u * u);
x = f * Math.cos(t);
y = f * Math.sin(t);
z = u;
return this;
}