I'm trying to implement the Separation behaviour.
The author of AI for games describes it as:
The separation behavior is common in crowd simulations, where a number of char-
acters are all heading in roughly the same direction. It acts to keep the characters from
getting too close and being crowded.
So what he does is loop through each target, check if it's within the threshold distance and if it is, make some changes to the character's linear velocity (using inverse square).
This is the pseudocode:
def getSteering(): # The steering variable holds the output steering = new Steering # Loop through each target for target in targets: # Check if the target is close direction = target.position - character.position distance = direction.length() if distance < threshold: # Calculate the strength of repulsion strength = min(decayCoefficient * distance * distance, maxAcceleration) # Add the acceleration direction.normalize() steering.linear = strength * direction # We’ve gone through all targets, return the result return steering
He also says that:
Where there are multiple characters within the avoidance threshold, the steering
is calculated for each in turn and summed. The final value may be greater than the
maxAcceleration, in which case it can be clipped to that value.
I don't see anything being summed in the code above. Maybe is that a mistake?
I guess it is, so what I did was to change:
steering.linear = strength * direction
steering.linear += strength * direction
And outside the loop I check if its length is larger than maxAcceleration and if its, I normalize it and multiply by maxAcceleration.
So I did a small test. I added three agents (birds) that are first moving in a straight line parallel to each other, and by pressing a button I make them to want to separate each from the other two.
So Bird_0 wants to separate from Bird_1 and Bird_2, Bird_1 wants to separate from Bird_0 and Bird_2 and Bird_2 wants to separate from Bird_0 and Bird_1.
The result seems a bit strange. All birds orbit around each other. I have uploaded a video that shows it.
Am I doing something wrong or is that the way separation works?