ActionScript3高级动画教程笔记

2012.3.14

基本三角函数的计算：
角的正弦值 = 对边 / 斜边
角的余弦值 = 邻边 / 斜边
角的正切值 = 对边 / 邻边

角度制与弧度制的相互转换：
弧度 = 角度 * Math.PI / 180 角度 = 弧度 * 180 / Math.PI

向鼠标旋转(或向某点旋转)：

// substitute mouseX, mouseY with the x, y point to rotate to 
 dx = mouseX - sprite.x; 
 dy = mouseY - sprite.y;
 sprite.rotation = Math.atan2(dy, dx) * 180 / Math.PI;

创建波形：

// assign value to x, y or other property of sprite or movie clip, 
// use as drawing coordinates, etc.
public function onEnterFrame(event:Event){
 value = center + Math.sin(angle) * range;
 angle += speed; 
}

创建圆形：

// assign position to x and y of sprite or movie clip, 
// use as drawing coordinates, etc. 
public function onEnterFrame(event:Event){
 xposition = centerX + Math.cos(angle) * radius;
 yposition = centerY + Math.sin(angle) * radius; angle += speed; 
}

创建椭圆：

 
// assign position to x and y of sprite or movie clip, 
// use as drawing coordinates, etc. 
public function onEnterFrame(event:Event){
 xposition = centerX + Math.cos(angle) * radiusX;
 yposition = centerY + Math.sin(angle) * radiusY;
 angle += speed;
}

计算两点间距离：

// points are x1, y1 and x2, y2 
// can be sprite / movie clip positions, mouse coordinates, etc. 
 dx = x2 – x1;
 dy = y2 – y1;
 dist = Math.sqrt(dx*dx + dy*dy);

转换为十进制：
trace(hexValue);

十进制转换为十六进制：

 trace(decimalValue.toString(16));

颜色合成：

 color24 = red << 16 | green << 8 | blue;
 color32 = alpha << 24 | red << 16 | green << 8 | blue;

颜色提取：

 red = color24 >> 16;
 green = color24 >> 8 & 0xFF;
 blue = color24 & 0xFF;
 alpha = color32 >> 24;

 red = color32 >> 16 & 0xFF;
 green = color32 >> 8 & 0xFF;
 blue = color232 & 0xFF;

过控制点的曲线：

// xt, yt is the point you want to draw through 
// x0, y0 and x2, y2 are the end points of the curve
 x1 = xt * 2 – (x0 + x2) / 2;
 y1 = yt * 2 – (y0 + y2) / 2;
 moveTo(x0, y0);
 curveTo(x1, y1, x2, y2);

角速度转换为 x,y 速度向量：

 vx = speed * Math.cos(angle);
 vy = speed * Math.sin(angle);

角加速度(作用于物体上的 force )转换为 x,y 加速度：

 ax = force * Math.cos(angle);
 ay = force * Math.sin(angle);

将加速度加入速度向量：

 vx += ax;
 vy += ay;

将速度向量加入坐标：

 movieclip._x += vx;
 sprite.y += vy;