def goal(self, x, y, z, d=50.0):
        
        """ Tendency towards a particular place.
        """
        
        return (x-self.x)/d, (y-self.y)/d, (z-self.z)/d
def goal(self, x, y, z, d=50.0):
        
        """ Tendency towards a particular place.
        """
        
        return (x-self.x)/d, (y-self.y)/d, (z-self.z)/d
def goal ( self , x , y , z , d = 50.0 ) : return ( x - self . x ) / d , ( y - self . y ) / d , ( z - self . z ) / d
Tendency towards a particular place.
Tendency towards a particular place .