Animate Player using Finite State Machine in Ashley ECS

Question

Hi everyone this is my first question on this forum hope you can clarify my doubt. I'm gonna start by saying that im not very good at english so my apologies.

So I have a big school project and I'm developing a Pixel Platformer game using libGDX for it.

I'm using ECS for the most part, but I've been having trouble rendering my player's animations because I can not distinguish the state of the player or at least the attack ones.

Player State Class

Let me jsut show you, so I have this "move" states:

public enum PlayerState implements State<PlayerAgent> {

Idle(){
    @Override
    public void update(PlayerAgent agent) {
        agent.moveOnGround();
        if(!agent.isTouchingGround) {
            if (agent.body.getLinearVelocity().y < -0.05)
                agent.stateMachine.changeState(Falling);
            else
                agent.stateMachine.changeState(Jumping);
        }else{
            if (agent.body.getLinearVelocity().x != 0)
                agent.stateMachine.changeState(Walking);
        }
    }
},

Walking() {
    @Override
    public void update(PlayerAgent agent) {
        agent.moveOnGround();
        if(!agent.isTouchingGround) {
            if (agent.body.getLinearVelocity().y < -0.05)
                agent.stateMachine.changeState(Falling);
            else
                agent.stateMachine.changeState(Jumping);
        }else{
            if (agent.body.getLinearVelocity().x == 0)
                agent.stateMachine.changeState(Idle);
        }
    }
},

Jumping() {
    @Override
    public void enter(PlayerAgent agent) {
    }

    @Override
    public void update(PlayerAgent agent) {
        agent.moveOnAir();
        if (agent.body.getLinearVelocity().y < 0)
            agent.stateMachine.changeState(Falling);
        /* else if (agent.jumpOnAir())
            agent.stateMachine.changeState(DoubleJumping);*/
    }
},

DoubleJumping () {
    @Override
    public void update(PlayerAgent agent) {
        agent.moveOnAir();
        if (agent.body.getLinearVelocity().y < 0)
            agent.stateMachine.changeState(Falling);
    }
},

Falling() {

    @Override
    public void update(PlayerAgent agent) {
        agent.moveOnAir();
        if (agent.isTouchingGround) {
            agent.stateMachine.changeState(Idle);
        } else {
            if (agent.stateMachine.getPreviousState() != DoubleJumping) {
                if (agent.jumpOnAir())
                    agent.stateMachine.changeState(DoubleJumping);
            }
        }
    }
};

@Override
public void enter(PlayerAgent agent) {
    // System.out.println(this.toString());
}

@Override
public void update(PlayerAgent agent) {

}

@Override
public void exit(PlayerAgent agent) {
    agent.timer = 0.0f;
}

@Override
public boolean onMessage(PlayerAgent agent, Telegram telegram) {
    return false;
}
}

Player Animations Enum

But I'll need at least this states for player animation:

public enum PlayerAnimations {

 Idle, Walking, Jumping, DoubleJumping, Falling, Attack, JumpAttack, FallingAttack, FallAttack, Hit, Die;

}

And many more has u can see on this packed texture: Player Animations Atlas

PlayerAgent Class:

public class PlayerAgent implements Updateable {

    private Entity player;

    protected Body body;
    private TransformComponent transform;
    SensorCollisionComponent sensors;

    protected static StateMachine<PlayerAgent, PlayerState>  stateMachine;

    public boolean isTouchingGround = true;
    public boolean isTouchingWallLeft = false;
    public boolean isTouchingWallRight = false;

    public static float timer = 0.0f;

    public PlayerAgent(Entity player) {
        this.player = player;
        body = player.getComponent(B2dBodyComponent.class).body;
        transform = player.getComponent(TransformComponent.class);
        sensors = player.getComponent(SensorCollisionComponent.class);

        stateMachine = new DefaultStateMachine<PlayerAgent, PlayerState>(this, PlayerState.Idle);
    }

    @Override
    public void update(float deltaTime) {
        isTouchingGround = (sensors.numFoot > 0);
        isTouchingWallLeft = (sensors.numLeftWall > 0);
        isTouchingWallRight = (sensors.numRightWall > 0);

        stateMachine.update();

        if (!KeyboardController.left && !KeyboardController.right)
            body.setLinearVelocity(MathUtils.lerp(body.getLinearVelocity().x, 0, 0.2f), body.getLinearVelocity().y);

    }


    public static PlayerState getCurrentState(){
        return stateMachine.getCurrentState();
    }
    public static PlayerState getLastState(){
        return stateMachine.getPreviousState();
    }
    public static boolean isInState(PlayerState state){
        return stateMachine.isInState(state);
    }

    public boolean moveOnGround() {
        if (KeyboardController.left) {
            body.setLinearVelocity(MathUtils.lerp(body.getLinearVelocity().x, -3f, 0.1f), body.getLinearVelocity().y);
            transform.flipX = true;
        }
        if (KeyboardController.right){
            body.setLinearVelocity(MathUtils.lerp(body.getLinearVelocity().x, 3f, 0.1f), body.getLinearVelocity().y);
            transform.flipX = false;
        }
        if (KeyboardController.up) {
            body.applyLinearImpulse(0, 2.7f, body.getWorldCenter().x, body.getWorldCenter().y, true);
            KeyboardController.up = false;
        }
            return (KeyboardController.left || KeyboardController.right);
    }

    public boolean moveOnAir(){
        if (KeyboardController.left){
            body.setLinearVelocity(MathUtils.lerp(body.getLinearVelocity().x, -1.5f, 0.1f), body.getLinearVelocity().y);
            transform.flipX = true;
        }if (KeyboardController.right){
            transform.flipX = false;
            body.setLinearVelocity(MathUtils.lerp(body.getLinearVelocity().x, 1.5f, 0.1f), body.getLinearVelocity().y);
        }
            return (KeyboardController.left || KeyboardController.right);
    }

    public boolean jumpOnAir(){
        if (KeyboardController.up) {
            body.applyLinearImpulse(0, 2.5f, body.getWorldCenter().x, body.getWorldCenter().y, true);
            KeyboardController.up = false;
            return true;
        }
        return false;
    }

}

Animation Code

Code in the AnimationSystem that takes care of the player:

PlayerComponent pc = pm.get(entity);
                if (pc.attacking) {

                    switch (PlayerAgent.getCurrentState()) {
                        case Idle:
                        case Walking:
                            if(PlayerAgent.getLastState() == PlayerState.Falling) {
                                key = PlayerAnimations.FallAttack.ordinal();
                                if(ani.animations.get(key).isAnimationFinished(PlayerAgent.timer)) pc.attacking = false;
                            }else
                                key = PlayerAnimations.Attack.ordinal();
                            break;
                        case Jumping:
                        case DoubleJumping:
                            key = PlayerAnimations.JumpAttack.ordinal();
                            break;
                        case Falling:
                            key = PlayerAnimations.FallingAttack.ordinal();
                            break;
                        default:
                            key = PlayerAnimations.Idle.ordinal();
                            break;
                    }
                } else {
                    switch (PlayerAgent.getCurrentState()) {
                        case Idle:
                            key = PlayerAnimations.Idle.ordinal();
                            break;
                        case Walking:
                            key = PlayerAnimations.Walking.ordinal();
                            break;
                        case Jumping:
                            key = PlayerAnimations.Jumping.ordinal();
                            break;
                        case DoubleJumping:
                            key = PlayerAnimations.DoubleJumping.ordinal();
                            break;
                        case Falling:
                            key = PlayerAnimations.Falling.ordinal();
                            break;
                        default:
                            key = PlayerAnimations.Idle.ordinal();
                            break;
                    }

                }
                PlayerAgent.timer += deltaTime;
            }

I was thinking of having states inside a state like Grounded -> Idle, Walking. But I still dont know how I can make the player AttackStates.

Thanks for replying.

Answer 1

I could be missing something, but it looks to me like you're setting key = the numeric value of the enumeration entry for your current state, then the only place I see it getting used is in looking for the isAnimationFinished() case for Idle/Walking when used to be falling.

I see you've got an accumulator PlayerAgent.timer, that your'e adding deltaTime to...

I don't see all of your code, so hard to say, but I would expect there to be a property on your PlayerComponent, holding the current Animation. You would call getKeyFrame(deltaTime) on that animation, to get the current frame (it keeps it's own time accumulator to select the correct frame, based on the frame delay you set on the animation object when you instantiated it).

By way of example, possibly too long-winded, here's what I have going on in the top-down 2D game I'm working on presently: I use a home-grown ECS, as I didn't know about Ashley back when I started this project. Should be a very similar solution to what you are after though.

I'm switching animations dependent on direction. In my case, I have a "Drawable" component, for any entity that has a visual presentation, and it has a collection of Animations, with standardized keys for "WALK_NORTH", "WALK_EAST", "WALK_SOUTH", and "WALK_WEST"... as well as a collection of static sprites, similarly named. Code in the moving system sets the appropriate animation or sprite as current for the Drawable component, then the Drawing system calls the currentAnimation.getKeyframe(delta) method (make sure you're not re-setting the currentAnimation if not actually switching animations, since it'll get a new accumulated time, and mess up frame selection if you create a new instance).

Not sure that's of any use to you or not. Good luck!