html5+canvas鸟群飞来飞去动画特效

代码片段：

 var solveBirdMove = function(bird)
    {
        ['x', 'y', 'z'].forEach(function(key) {
            if (Math.abs(bird.move[key]) > 0.003) {
                bird.move[key] *= 0.99;
            }
        });

        if (frame % bird.ownMove.t === 0) {
            bird.ownMove.x = (0.5 - Math.random()) / 3;
            bird.ownMove.y = (0.5 - Math.random()) / 3;
        }

        bird.move.x += speed * (mouse.x - bird.pos.x + bird.ownMove.x) * bird.speed;
        bird.move.y += speed * (mouse.y - bird.pos.y + bird.ownMove.y) * bird.speed;
        bird.move.z += speed * (mouse.z - bird.pos.z) * bird.speed;
    };