Enemy entity movement issue

[fereshta...@gmail.com]

This is probably not a bug in the melonjs tutorial but lack of my understanding of it, I was lucky to find a sprite animation for an enemy entity that seemed interesting to me (http://opengameart.org/content/frog-player-spritesheets) however the tutorial animation direction is the opposite and my enemy entity kept moving in one direction while the animation represented movement in opposite direction. I finally got it figured out i think but then when the enemy reaches the end of its path it does not flip around and go the other way. It is probably something simple that I've overlooked and after staring at it for a long time I just need a break and figured I should post it here incase someone spots my mistake easily and could point out the fix... thanks in advance.

/**

 * Enemy Entity

 */

game.EnemyEntity = me.Entity.extend(

{    

    init: function (x, y, settings)

    {

        // define this here instead of tiled

        settings.image = "frog";

          

        // save the area size defined in Tiled

        var width = settings.width;

        var height = settings.height;

        // adjust the size setting information to match the sprite size

        // so that the entity object is created with the right size

        settings.framewidth = settings.width = 64;

        settings.frameheight = settings.height = 64;

        // redefine the default shape (used to define path) with a shape matching the renderable

        settings.shapes[0] = new me.Rect(0, 0, settings.framewidth, settings.frameheight);

        

        // call the parent constructor

        this._super(me.Entity, 'init', [x, y , settings]);

        

        // set start/end position based on the initial area size

        x = this.pos.x;

        this.startX = x;

        this.endX   = x + width - settings.framewidth

        this.pos.x  = x + width - settings.framewidth;

        // to remember which side we were walking

        this.walkLeft = false;

        // walking & jumping speed

        this.body.setVelocity(4, 6);

    },

    

    // manage the enemy movement

    update : function (dt)

    {            

        if (this.alive)

        {

            if (this.walkLeft && this.pos.x >= this.endX)

            {

                this.walkLeft = true;

            }

            else if (!this.walkLeft && this.pos.x <= this.startX)

            {

                this.walkLeft = false;

            }

            

            this.renderable.flipX(this.walkLeft);

            this.body.vel.x += (this.walkLeft) ? this.body.accel.x * me.timer.tick : -this.body.accel.x * me.timer.tick;

        }

        else

        {

            this.body.vel.x = 0;

        }

        // check & update movement

        this.body.update(dt);

            

        // handle collisions against other shapes

        me.collision.check(this);

            

        // return true if we moved or if the renderable was updated

        return (this._super(me.Entity, 'update', [dt]) || this.body.vel.x !== 0 || this.body.vel.y !== 0);

    },

    

    /**

     * colision handler

     * (called when colliding with other objects)

     */

    onCollision : function (response, other) {

        if (response.b.body.collisionType !== me.collision.types.WORLD_SHAPE) {

            // res.y >0 means touched by something on the bottom

            // which mean at top position for this one

            if (this.alive && (response.overlapV.y > 0) && response.a.body.falling) {

                this.renderable.flicker(750);

            }

            return false;

        }

        // Make all other objects solid

        return true;

    }

});

[Jay Oster]

I think it would be easier to just invert the value passed to the `flip` helper method. Copy-pasta from the tutorial, and make just this one change:

this.renderable.flipX(!this.walkLeft);

The exclamation point ("logical NOT operator") will invert the value of `this.walkLeft`, and cause the sprite to face the opposite direction. You'll have to undo the other changes you did with the position comparisons. But this one-liner is all you really need!

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[fereshta...@gmail.com]

Thanks! I will have to make the change to see if this works!

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