AtomicGameEngine-Examples/PhysicsPlatformer/Resources/Components/Platform.js

// A moving platform

keepAlive = typeof(keepAlive) == "undefined" ? [] : keepAlive;

keepAlive.push(self);

var MAX_VELOCITY = 2;

var movingToStop = true;

var glmatrix = require("gl-matrix");
var vec2 = glmatrix.vec2;

var node = self.node;

var body;

function start() {

    var sprite2D = node.createComponent("StaticSprite2D");
    sprite2D.sprite = cache.getResource("Sprite2D", "Sprites/platform.png");

    // start at the start positon
    node.position2D = self.startPos;

    body = node.createComponent("RigidBody2D");
    body.setBodyType(Atomic.BT_KINEMATIC);
    body.fixedRotation = true;

    // Create box
    var box = node.createComponent("CollisionBox2D");
    // Set size
    box.setSize([2.5, .55]);
    // Set density
    box.setDensity(1.0);
    // Set friction
    box.setFriction(0.5);
    // Set restitution
    box.setRestitution(0.1);


}

function update(timeStep) {

    var pos = node.position2D;
    var dir = vec2.create();
    var dist = 0.0;
    
    if (movingToStop) {

        dist = vec2.distance(pos, self.stopPos);

        vec2.subtract(dir,  self.stopPos, pos);
        vec2.normalize(dir, dir);       
        
        if (dist < 0.5) {
            movingToStop = false;
            return;
        }

    } else {
    
        dist = vec2.distance(pos, self.startPos);
        vec2.subtract(dir, self.startPos, pos);
        vec2.normalize(dir, dir);

        if (dist < 0.5) {
            movingToStop = true;
            return;
        }
    
    }
               
    vec2.scale(dir, dir, dist);
    
    if (vec2.length(dir) > MAX_VELOCITY) {
        vec2.normalize(dir, dir);
        vec2.scale(dir, dir, MAX_VELOCITY );
    }
    
    body.setLinearVelocity(dir);
    


}