class Attractor{
  Vec3D pos;
  float radius;
  float multiplier;

  Attractor(Vec3D pos, float radius, float multiplier){
    this.pos = new Vec3D(pos);
    this.radius = radius;
    this.multiplier=multiplier;


  }

  Vec3D steeringForce(Particle3D p){
    Vec3D desired = pos.sub(p.pos);
    float d = desired.size;
    desired = desired.normalize();
    if (d<radius){
      desired = desired.mul(0.01f*multiplier*d);
    }
    else{
      desired= desired.mul(multiplier);
    }
    Vec3D steer = desired.sub(p.vel);
    return steer;

  }


}