Question

OK it’s a general question, just how the system of my game should work.
So there are lots of enemies and a player. When a enemy touch a player, the player gets a hit and a “push” from the monster, and then blinks to 1.5 seconds. Wile the “push” (really really fast), the player can’t do nothing.
Also, all the monsters will always move the same. The move of the monsters will never be affected by the player. I can’t do it kinematic because they DO affect from the gravity. So how can I do that? All that thing, include the “push”, what should I do?

There’s also a good example for what I mean in this YT video from 0:27 : http://www.youtube.com/watch?v=tVr8S6WXdog

Thanks.

Answer 1

With your example I’m presuming that you don’t plan on actually having the monster and humans reacting to one another.

Either way, add a custom contact listener to the world and within the contact listener check if a player and a enemy shape create a contact point. If so applylinearimpulse() to the playerbody to the effect that you would like and disable all key input from the user to prevent any change in motion. Then just have a property on player preventing it from applying the impulse if its just been hit by the monster.

Also when you create the bodies you’ll need to set the player and enemy instance as the body.UserData()

public class Player extends MovieClip
{
     public const MAX_EFFECT_TIME = 1.5 * framerate;

     public var effectTime:int = 0;
     public var body:b2Body;

 public function step():void
 {
       if (effectTime > 0)
       {
              effectTime--;
              //do awesome animation
       }
       else 
       {  
              //move normally
       }

 }

 public function Hit(enemy:Enemy)
 {
       if (effectTime == 0)
       {
              //apply linear impulse to object
              if (enemy.body.GetPosition().x < this.body.GetPosition().x)
              {
                    //apply impulse left in left direction
                    b2Vec2 force = b2Vec2(-8, 10);

                    body.ApplyLinearImpulse(force, body.GetWorldCenter());
              }
              else
              {
                    //apply impulse in right direction
                    b2Vec2 force = b2Vec2(8, 10);

                    body.ApplyLinearImpulse(force, body.GetWorldCenter());
              } 

              //reset effect time
              effectTime = MAX_EFFECT_TIME;
       }
 }

}

public class Game extends MovieClip
{
      public var world:b2World;
      public var player:Player;

      public Game()
      {
            world = initWorld();
            player = initPlayer();

            var cl = new CustomContactListener();
            world.SetContactListener(cl);

            this.addEventListener(Event.ENTER_FRAME, step);
      }

      private void step(e:Event)
      {
            world.step();
            player.step();
      }

}

public class CustomContactListener extends b2ContactListener
{
      //Called when a contact point is added.
      public override function Add(point:b2ContactPoint):void 
      {
            //checks if the first shape is a player and second is an enemy if true call Hit
            if (point.shape1.GetBody().GetUserData().isPlayer && point.shape2.GetBody().GetUserData().isEnemy)
            {
                 point.shape1.GetBody().GetUserData().Hit(point.shape2.GetBody().GetUserData());
            }
            else if (point.shape2.GetBody().GetUserData().isPlayer && point.shape1.GetBody().GetUserData().isEnemy)
            {
                 point.shape2.GetBody().GetUserData().Hit(point.shape1.GetBody().GetUserData());


      }
      }
}

Then you can just edit values as necessary. Hope this helps and good luck!