《making things move 》第六章
这章实在太熟了。。。直接大块贴代码了
飞船飞到边界外边回不来了 ![[sweat]](http://www.nshen.net/blog/styles/default/images/smilies/icon_sweat.gif){kind=icon}
处理边界问题：
当一个物体跑出flash显示区域的边界外时，通常有以下4种方法，处理这个物体
1 删掉
2 再利用，拿回来当成新的物体一样
3 饶一圈又从另一边回来了，就像换个位置一样
4 反弹回显示区域
从最基础的开始。。。
1. 删掉：
ball的注册点都在中间，ball._x - ball._width / 2 就是ball的右侧，以此类推
边界值就是影片的大小
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
看代码:
init();
function init()
{
count = 20;
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
balls = new Array();
for (var i = 0; i < count; i++)
{
var ball = attachMovie("ball", "ball" + i, i);
ball._x = Math.random() * Stage.width;
ball._y = Math.random() * Stage.height;
ball.vx = Math.random() * 2 - 1;
ball.vy = Math.random() * 2 - 1;
balls.push(ball);
}
}
function onEnterFrame(Void):Void
{
for (var i:Number=balls.length − 1;i>=0;i--)
{
var ball = balls[i];
ball._x += ball.vx;
ball._y += ball.vy;
if (ball._x - ball._width / 2 > right)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
else if (ball._x + ball._width / 2 < left)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
if (ball._y - ball._height / 2 > bottom)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
else if (ball._y + ball._height / 2 < top)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
}
}
function init()
{
count = 20;
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
balls = new Array();
for (var i = 0; i < count; i++)
{
var ball = attachMovie("ball", "ball" + i, i);
ball._x = Math.random() * Stage.width;
ball._y = Math.random() * Stage.height;
ball.vx = Math.random() * 2 - 1;
ball.vy = Math.random() * 2 - 1;
balls.push(ball);
}
}
function onEnterFrame(Void):Void
{
for (var i:Number=balls.length − 1;i>=0;i--)
{
var ball = balls[i];
ball._x += ball.vx;
ball._y += ball.vy;
if (ball._x - ball._width / 2 > right)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
else if (ball._x + ball._width / 2 < left)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
if (ball._y - ball._height / 2 > bottom)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
else if (ball._y + ball._height / 2 < top)
{
ball.removeMovieClip();
balls.splice(i, 1);
}
}
}
点这里 显示/隐藏 媒体2. 再利用：
出界了，就把那个拿回到原始位置，初始速度
ball._x = Stage.width / 2;
ball._y = Stage.height;
ball.vx = Math.random() * 2 - 1;
ball.vy = Math.random() * -10 - 10;
完整代码：
init();
function init()
{
count = 50;
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
gravity = 0.5;
balls = new Array();
}
function onEnterFrame(Void):Void
{
var ball:MovieClip;
var index:Number = balls.length;
if (index < count)
{
ball = attachMovie("ball", "ball" + index, index);
ball._x = Stage.width / 2;
ball._y = Stage.height;
ball.vx = Math.random() * 2 - 1;
ball.vy = Math.random() * -10 - 10;
balls.push(ball);
}
for (var i = 0; i < balls.length; i++)
{
ball = balls[i];
ball.vy += gravity;
ball._x += ball.vx;
ball._y += ball.vy;
if (ball._x - ball._width / 2 > right ||
ball._x + ball._width / 2 < left ||
ball._y - ball._height / 2 > bottom ||
ball._y + ball._height / 2 < top)
{
ball._x = Stage.width / 2;
ball._y = Stage.height;
ball.vx = Math.random() * 2 - 1;
ball.vy = Math.random() * -10 - 10;
}
}
}
function init()
{
count = 50;
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
gravity = 0.5;
balls = new Array();
}
function onEnterFrame(Void):Void
{
var ball:MovieClip;
var index:Number = balls.length;
if (index < count)
{
ball = attachMovie("ball", "ball" + index, index);
ball._x = Stage.width / 2;
ball._y = Stage.height;
ball.vx = Math.random() * 2 - 1;
ball.vy = Math.random() * -10 - 10;
balls.push(ball);
}
for (var i = 0; i < balls.length; i++)
{
ball = balls[i];
ball.vy += gravity;
ball._x += ball.vx;
ball._y += ball.vy;
if (ball._x - ball._width / 2 > right ||
ball._x + ball._width / 2 < left ||
ball._y - ball._height / 2 > bottom ||
ball._y + ball._height / 2 < top)
{
ball._x = Stage.width / 2;
ball._y = Stage.height;
ball.vx = Math.random() * 2 - 1;
ball.vy = Math.random() * -10 - 10;
}
}
}
想一想怎么再加个风力？变成这样
3. 反方向出现
还是宇宙飞船的例子
init();
function init()
{
vr = 5;
thrust = 0.2;
vx = 0;
vy = 0;
left = 0;
right = Stage.width;
top = 0;
bottom = Stage.height;
ship = attachMovie("ship", "ship", 0);
ship._x = Stage.width / 2;
ship._y = Stage.height / 2;
}
function onEnterFrame(Void):Void
{
if (Key.isDown(Key.LEFT))
{
ship._rotation -= vr;
}
else if (Key.isDown(Key.RIGHT))
{
ship._rotation += vr;
}
if (Key.isDown(Key.UP))
{
var radians:Number = ship._rotation * Math.PI / 180;
var ax:Number = Math.cos(radians) * thrust;
var ay:Number = Math.sin(radians) * thrust;
vx += ax;
vy += ay;
ship.gotoAndStop(2);
}
else
{
ship.gotoAndStop(1);
}
ship._x += vx;
ship._y += vy;
if (ship._x - ship._width / 2 > right)
{
ship._x = left - ship._width / 2;
}
else if (ship._x + ship._width / 2 < left)
{
ship._x = right + ship._width / 2;
}
if (ship._y - ship._height / 2 > bottom)
{
ship._y = top - ship._height / 2;
}
else if (ship._y < top - ship._height / 2)
{
ship._y = bottom + ship._height / 2;
}
}
function init()
{
vr = 5;
thrust = 0.2;
vx = 0;
vy = 0;
left = 0;
right = Stage.width;
top = 0;
bottom = Stage.height;
ship = attachMovie("ship", "ship", 0);
ship._x = Stage.width / 2;
ship._y = Stage.height / 2;
}
function onEnterFrame(Void):Void
{
if (Key.isDown(Key.LEFT))
{
ship._rotation -= vr;
}
else if (Key.isDown(Key.RIGHT))
{
ship._rotation += vr;
}
if (Key.isDown(Key.UP))
{
var radians:Number = ship._rotation * Math.PI / 180;
var ax:Number = Math.cos(radians) * thrust;
var ay:Number = Math.sin(radians) * thrust;
vx += ax;
vy += ay;
ship.gotoAndStop(2);
}
else
{
ship.gotoAndStop(1);
}
ship._x += vx;
ship._y += vy;
if (ship._x - ship._width / 2 > right)
{
ship._x = left - ship._width / 2;
}
else if (ship._x + ship._width / 2 < left)
{
ship._x = right + ship._width / 2;
}
if (ship._y - ship._height / 2 > bottom)
{
ship._y = top - ship._height / 2;
}
else if (ship._y < top - ship._height / 2)
{
ship._y = bottom + ship._height / 2;
}
}
4. 反弹
这个也是最复杂的一个
我们要做3件事
Check if the object went past any boundary.
If so, place it on the edge of that boundary.
Then reverse the velocity.
init();
function init()
{
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
ball = attachMovie("ball", "ball", 0);
ball._x = Stage.width / 2;
ball._y = Stage.height / 2;
vx = Math.random() * 10 - 5;
vy = Math.random() * 10 - 5;
}
function onEnterFrame(Void):Void
{
ball._x += vx;
ball._y += vy;
if (ball._x + ball._width / 2 > right)
{
ball._x = right - ball._width / 2;
vx *= -1;
}
else if (ball._x - ball._width / 2 < left)
{
ball._x = left + ball._width / 2;
vx *= -1;
}
if (ball._y + ball._height / 2 > bottom)
{
ball._y = bottom - ball._height / 2;
vy *= -1;
}
else if (ball._y - ball._height / 2 < top)
{
ball._y = top + ball._height / 2;
vy *= -1;
}
}
function init()
{
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
ball = attachMovie("ball", "ball", 0);
ball._x = Stage.width / 2;
ball._y = Stage.height / 2;
vx = Math.random() * 10 - 5;
vy = Math.random() * 10 - 5;
}
function onEnterFrame(Void):Void
{
ball._x += vx;
ball._y += vy;
if (ball._x + ball._width / 2 > right)
{
ball._x = right - ball._width / 2;
vx *= -1;
}
else if (ball._x - ball._width / 2 < left)
{
ball._x = left + ball._width / 2;
vx *= -1;
}
if (ball._y + ball._height / 2 > bottom)
{
ball._y = bottom - ball._height / 2;
vy *= -1;
}
else if (ball._y - ball._height / 2 < top)
{
ball._y = top + ball._height / 2;
vy *= -1;
}
}
虽然看上去很真实，但他并不是真实的，因为我们修正位置时候跟真实世界是不符的，下边的图说明了这个问题
不过已经很不错了，如果要更真实的，不如去换个软件试试 ，在flash世界里，没有必要那么做 - -b
能量损耗
在真实世界里反弹是有能量损耗的，我们这个看上去永远不会停下来，下边加上重力和弹力损耗
init();
function init()
{
bounce = -0.7;
gravity = 0.5;
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
ball = attachMovie("ball", "ball", 0);
ball._x = Stage.width / 2;
ball._y = Stage.height / 2;
vx = Math.random() * 10 - 5;
vy = Math.random() * 10 - 5;
}
function onEnterFrame(Void):Void
{
vy += gravity;
ball._x += vx;
ball._y += vy;
if (ball._x + ball._width / 2 > right)
{
ball._x = right - ball._width / 2;
vx *= bounce;
}
else if (ball._x - ball._width / 2 < left)
{
ball._x = left + ball._width / 2;
vx *= bounce;
}
if (ball._y + ball._height / 2 > bottom)
{
ball._y = bottom - ball._height / 2;
vy *= bounce;
}
else if (ball._y - ball._height / 2 < top)
{
ball._y = top + ball._height / 2;
vy *= bounce;
}
}
function init()
{
bounce = -0.7;
gravity = 0.5;
top = 0;
left = 0;
bottom = Stage.height;
right = Stage.width;
ball = attachMovie("ball", "ball", 0);
ball._x = Stage.width / 2;
ball._y = Stage.height / 2;
vx = Math.random() * 10 - 5;
vy = Math.random() * 10 - 5;
}
function onEnterFrame(Void):Void
{
vy += gravity;
ball._x += vx;
ball._y += vy;
if (ball._x + ball._width / 2 > right)
{
ball._x = right - ball._width / 2;
vx *= bounce;
}
else if (ball._x - ball._width / 2 < left)
{
ball._x = left + ball._width / 2;
vx *= bounce;
}
if (ball._y + ball._height / 2 > bottom)
{
ball._y = bottom - ball._height / 2;
vy *= bounce;
}
else if (ball._y - ball._height / 2 < top)
{
ball._y = top + ball._height / 2;
vy *= bounce;
}
}
摩擦力
真实的摩擦力应该
speed = Math.sqrt(vx * vx + vy * vy);
angle = Math.atan2(vy, vx);
if(speed > friction)
{
speed -= friction;
}
else
{
speed = 0;
}
vx = Math.cos(angle) * speed;
vy = Math.sin(angle) * speed;
angle = Math.atan2(vy, vx);
if(speed > friction)
{
speed -= friction;
}
else
{
speed = 0;
}
vx = Math.cos(angle) * speed;
vy = Math.sin(angle) * speed;
但是我们注意到摩擦力其实就是对速度的阻碍，所以我们可以简化他
vx *= friction;
vy *= friction;
例子：
init();
function init()
{
friction = 0.97;
vr = 5;
thrust = 0.2;
vx = 0;
vy = 0;
left = 0;
right = Stage.width;
top = 0;
bottom = Stage.height;
ship = attachMovie("ship", "ship", 0);
ship._x = Stage.width / 2;
ship._y = Stage.height / 2;
}
function onEnterFrame(Void):Void
{
if (Key.isDown(Key.LEFT))
{
ship._rotation -= vr;
}
else if (Key.isDown(Key.RIGHT))
{
ship._rotation += vr;
}
if (Key.isDown(Key.UP))
{
var radians:Number = ship._rotation * Math.PI / 180;
var ax:Number = Math.cos(radians) * thrust;
var ay:Number = Math.sin(radians) * thrust;
vx += ax;
vy += ay;
ship.gotoAndStop(2);
}
else
{
ship.gotoAndStop(1);
}
vx *= friction;
vy *= friction;
ship._x += vx;
ship._y += vy;
if (ship._x - ship._width / 2 > right)
{
ship._x = left - ship._width / 2;
}
else if (ship._x + ship._width / 2 < left)
{
ship._x = right + ship._width / 2;
}
if (ship._y - ship._height / 2 > bottom)
{
ship._y = top - ship._height / 2;
}
else if (ship._y < top - ship._height / 2)
{
ship._y = bottom + ship._height / 2;
}
}
function init()
{
friction = 0.97;
vr = 5;
thrust = 0.2;
vx = 0;
vy = 0;
left = 0;
right = Stage.width;
top = 0;
bottom = Stage.height;
ship = attachMovie("ship", "ship", 0);
ship._x = Stage.width / 2;
ship._y = Stage.height / 2;
}
function onEnterFrame(Void):Void
{
if (Key.isDown(Key.LEFT))
{
ship._rotation -= vr;
}
else if (Key.isDown(Key.RIGHT))
{
ship._rotation += vr;
}
if (Key.isDown(Key.UP))
{
var radians:Number = ship._rotation * Math.PI / 180;
var ax:Number = Math.cos(radians) * thrust;
var ay:Number = Math.sin(radians) * thrust;
vx += ax;
vy += ay;
ship.gotoAndStop(2);
}
else
{
ship.gotoAndStop(1);
}
vx *= friction;
vy *= friction;
ship._x += vx;
ship._y += vy;
if (ship._x - ship._width / 2 > right)
{
ship._x = left - ship._width / 2;
}
else if (ship._x + ship._width / 2 < left)
{
ship._x = right + ship._width / 2;
}
if (ship._y - ship._height / 2 > bottom)
{
ship._y = top - ship._height / 2;
}
else if (ship._y < top - ship._height / 2)
{
ship._y = bottom + ship._height / 2;
}
}
var vr:Number = Math.random() * 100 - 50;
var friction:Number = 0.95;
var friction:Number = 0.95;
function onEnterFrame(Void):Void
{
vr *= friction;
arrow._rotation += vr;
}