[Question] Bodies positions. about matter-js HOT 9 CLOSED

var deltaCentre = Vector.sub(Vector.sub(body.position, render.bounds.min), viewportCentre),
     centreDist = Vector.magnitude(deltaCentre);

        var viewportCentre = {
            x: render.options.width * 0.5,
            y: render.options.height * 0.5
        };

        Events.on(_engine, 'beforeTick', function() {
            var _engine = engine,
                world = _engine.world
                render = _engine.render,
                translate,
                bodyPos = body.position;

            var deltaCentre = Vector.sub(bodyPos, viewportCentre),
                    centreDist = Vector.magnitude(deltaCentre);

            if (centreDist > 50) {
                    // create a vector to translate the view, allowing the user to control view speed
                    var direction = Vector.normalise(deltaCentre),
                        speed = Math.min(10, Math.pow(centreDist - 50, 2) * 0.0002);

                    translate = Vector.mult(direction, speed);

                    // prevent the view moving outside the world bounds
                    if (render.bounds.min.x + translate.x < world.bounds.min.x)
                        translate.x = world.bounds.min.x - render.bounds.min.x;

                    if (render.bounds.max.x + translate.x > world.bounds.max.x)
                        translate.x = world.bounds.max.x - render.bounds.max.x;

                    if (render.bounds.min.y + translate.y < world.bounds.min.y)
                        translate.y = world.bounds.min.y - render.bounds.min.y;

                    if (render.bounds.max.y + translate.y > world.bounds.max.y)
                        translate.y = world.bounds.max.y - render.bounds.max.y;

                    // move the view
                    Bounds.translate(render.bounds, translate);
            }
        });

var deltaCentre = Vector.sub(body.position, viewportCentre),
                    centreDist = Vector.magnitude(deltaCentre);
// and putting speed to
speed = Math.min(_body.speed * 1.5, _body.speed * 1.8);