code: function(a,b,c){
  			if(b === undefined || c === undefined){
  				b = c = a;
  			}
  			this.x += mathUtils.normalizedRandom()*a;
  			this.y += mathUtils.normalizedRandom()*b;
  			this.z += mathUtils.normalizedRandom()*c;
  			return this;
  		}
docs: Add random jitter to the vector in the range -j ... +j using the default
  {@link Random} generator of {@link MathUtils}.
  
  @param j
  the j
  
  @return the vec3 d