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1
Question by dylan1812 · Mar 26, 2021 at 05:50 PM · 2dai

How to coerce my enemy to move around walls using boids?

Good Afternoon everyone, I'm trying to make some enemy ai when the enemy chases a target, seperates from other enemies and avoids obstacles. I'm interested in using boids rather that a pathfinding algorithm.

Currently, if the enemy detects a wall it will be moved away from it. This is ok behaviour but if the target is hiding behind the wall than the enemy get stuck in place.

I would like the enemy to attemp to move around the wall but since I'm not using pathfinding im unsure how to achieve this. Below is the main script:

EnemyAgent calculates the movement vector,

 public class EnemyAgent : MonoBehaviour
 {
     public Vector2 position;
     public Vector2 velocity;
     public Vector2 acceleration;
 
     public Level level;
     public EnemyAgentConfig conf;
 
     Vector2 wanderTarget;
 
     void Start()
     {
         level = FindObjectOfType<Level>();
         conf = FindObjectOfType<EnemyAgentConfig>();
 
         position = transform.position;
         velocity = Vector2.zero;
     }
 
     void Update()
     {
         acceleration = Combine();
         acceleration = Vector2.ClampMagnitude(acceleration, conf.maxAcceleration);
         velocity = velocity + acceleration * Time.deltaTime;
         velocity = Vector2.ClampMagnitude(velocity, conf.maxVelocity);
         position = position + velocity * Time.deltaTime;
         transform.position = position;
     }
 
     Vector2 Seperation()
     {
         Vector2 seperateVector = new Vector2();
         var neighbours = level.GetNeighbours(this, conf.seperationRadius);
         if (neighbours.Count == 0)
             return seperateVector;
 
         foreach (var member in neighbours)
         {
             Vector2 movingTowards = this.position - member.position;
             if (movingTowards.magnitude > 0)
             {
                 seperateVector += movingTowards.normalized / movingTowards.magnitude;
             }
         }
         return seperateVector.normalized;
     }
 
     Vector2 Attraction()
     {
         Vector2 attractVector = new Vector2();
         attractVector = (conf.target - position).normalized;
         return attractVector;
     }
 
     Vector2 AvoidObstacles()
     {
         Vector2 avoidVector = new Vector2();
         Collider2D[] obstacles = Physics2D.OverlapCircleAll(position, conf.avoidanceRadius, conf.avoidanceMask);
         if (obstacles.Length == 0)
             return avoidVector;
 
         foreach (Collider2D obstacle in obstacles)
         {
             Vector2 neededVelocity = (position - (Vector2)obstacle.transform.position).normalized * conf.maxVelocity;
             neededVelocity -= velocity;
             avoidVector += neededVelocity;
         }
 
         return avoidVector;
     }
 
     Vector2 Combine()
     {
         Vector2 finalVec = 
             conf.seperationPriority * Seperation()
             + conf.targetAttractionPriority * Attraction()
             + conf.avoidancePriority * AvoidObstacles();
         return finalVec;
     }
 }

Thank you for your time, Dylan.

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avatar image logicandchaos · Mar 27, 2021 at 01:40 PM 0
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I love boids! Been meaning to implement it in unity myself. Now if I remember correctly boids operates on 3 simple rules, could you know just add an additional rule to keep a certain distance from obstacles?

avatar image dylan1812 logicandchaos · Mar 31, 2021 at 09:23 PM 0
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Sorry for the delayed response. I know you can avoid other agents by using seperation; whereby you add velocity in the direction away from the neighbouring agent. I tried to simulate this behaviour in the AvoidObstacles method. But just applying this vector in the opposite direction of the wall provides the undesirable behaviour where the enemy just gets stuck (trying to move to the target but being pushed away by the wall). I tried instead to apply the vector perpendiclar to the wall but that didnt seem to help either.

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