flex 实用公式
实用公式
第三章
基础三角函数的计算:
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
弧度转换为角度以及角度转换为弧度:
弧度 = 角度 * Math.PI / 180
角度 = 弧度 * 180 / Math.PI
向鼠标(或者任何一个点)旋转:
// 用要旋转到的 x, y 坐标替换 mouseX, mouseY
dx = mouseX - sprite.x;
dy = mouseY - sprite.y;
sprite.rotation = Math.atan2(dy, dx) * 180 / Math.PI;
创建波形:
// 将 x, y 或其它属性赋值给 Sprite 影片或影片剪辑,
// 作为绘图坐标,等等。
public function onEnterFrame(event:Event){
value = center + Math.sin(angle) * range;
angle += speed;
}
创建圆形:
// 将 x, y 或其它属性赋值给 Sprite 影片或影片剪辑,
// 作为绘图坐标,等等。
public function onEnterFrame(event:Event){
xposition = centerX + Math.cos(angle) * radius;
yposition = centerY + Math.sin(angle) * radius;
angle += speed;
}
创建椭圆:
// 将 x, y 或其它属性赋值给 Sprite 影片或影片剪辑,
// 作为绘图坐标,等等。
public function onEnterFrame(event:Event){
xposition = centerX + Math.cos(angle) * radiusX;
yposition = centerY + Math.sin(angle) * radiusY;
angle += speed;
}
获得两点间的距离:
// x1, y1 和 x2, y2 是两个点
// 也可以是 Sprite / MovieClip 坐标,鼠标坐标,等等。
dx = x2 – x1;
dy = y2 – y1;
dist = Math.sqrt(dx*dx + dy*dy);
第四章
十六进制转换为十进制:
trace(hexValue);
十进制转换为十六进制:
trace(decimalValue.toString(16));
颜色组合:
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;
穿过某点绘制曲线:
// xt, yt 是我们想要穿过的一点
// x0, y0 以及 x2, y2 是曲线的两端
x1 = xt * 2 – (x0 + x2) / 2;
y1 = yt * 2 – (y0 + y2) / 2;
moveTo(x0, y0);
curveTo(x1, y1, x2, y2);
第五章
角速度转换为 x, y 速度:
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:
vx += ax;
vy += ay;
将速度加入坐标:
movieclip._x += vx;
sprite.y += vy;
第六章
移除出界对象:
if(sprite.x - sprite.width / 2 > right ||
sprite.x + sprite.width / 2 < left ||
sprite.y – sprite.height / 2 > bottom ||
sprite.y + sprite.height / 2 < top)
{
// 删除影片的代码
}
重置出界对象:
if(sprite.x - sprite.width / 2 > right ||
sprite.x + sprite.width / 2 < left ||
sprite.y – sprite.height / 2 > bottom ||
sprite.y + sprite.height / 2 < top)
{
// 重置影片的位置和速度
}
屏幕环绕出界对象:
if(sprite.x - sprite.width / 2 > right)
{
sprite.x = left - sprite.width / 2;
}
else if(sprite.x + sprite.width / 2 < left)
{
sprite.x = right + sprite.width / 2;
}
if(sprite.y – sprite.height / 2 > bottom)
{
sprite.y = top – sprite.height / 2;
}
else if(sprite.y + sprite.height / 2 < top)
{
sprite.y = bottom + sprite.height / 2;
}
摩擦力应用(正确方法):
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;
摩擦力应用(简便方法):
vx *= friction;
vy *= friction;
第八章:
简单缓动运动,长形:
var dx:Number = targetX - sprite.x;
var dy:Number = targetY - sprite.y;
vx = dx * easing;
vy = dy * easing;
sprite.x += vx;
sprite.y += vy;
简单缓动运动,中形:
vx = (targetX - sprite.x) * easing;
vy = (targetY - sprite.y) * easing;
sprite.x += vx;
sprite.y += vy;
简单缓动运动,短形:
sprite.x += (targetX - sprite.x) * easing;
sprite.y += (targetY - sprite.y) * easing;
简单弹性运动,长形:
var ax:Number = (targetX - sprite.x) * spring;
var ay:Number = (targetY - sprite.y) * spring;
vx += ax;
vy += ay;
vx *= friction;
vy *= friction;
sprite.x += vx;
sprite.y += vy;
简单弹性运动,中形:
vx += (targetX - sprite.x) * spring;
vy += (targetY - sprite.y) * spring;
vx *= friction;
vy *= friction;
sprite.x += vx;
sprite.y += vy;
简单弹性运动,短形:
vx += (targetX - sprite.x) * spring;
vy += (targetY - sprite.y) * spring;
sprite.x += (vx *= friction);
sprite.y += (vy *= friction);
偏移弹性运动:
var dx:Number = sprite.x - fixedX;
var dy:Number = sprite.y - fixedY;
var angle:Number = Math.atan2(dy, dx);
var targetX:Number = fixedX + Math.cos(angle) * springLength;
var targetY:Number = fixedX + Math.sin(angle) * springLength;
// 如前例弹性运动到 targetX, targetY
第九章
距离碰撞检测:
// 从影片 spriteA 和 spriteB 开始
// 如果使用一个空白影片,或影片没有半径(radius)属性
// 可以用宽度或高度除以 2。
var dx:Number = spriteB.x - spriteA.x;
var dy:Number = spriteB.y - spriteA.y;
var dist:Number = Math.sqrt(dx * dx + dy * dy);
if(dist < spriteA.radius + spriteB.radius)
{
// 处理碰撞
}
多物体碰撞检测:
var numObjects:uint = 10;
for(var i:uint = 0; i < numObjects - 1; i++)
{
// 使用变量 i 提取引用
var objectA = objects[i];
for(var j:uint = i+1; j
{
// // 使用变量 j 提取引用
var objectB = objects[j];
// perform collision detection
// between objectA and objectB
}
}
第十章
坐标旋转:
x1 = Math.cos(angle) * x - Math.sin(angle) * y;
y1 = Math.cos(angle) * y + Math.sin(angle) * x;
反坐标旋转:
x1 = Math.cos(angle) * x + Math.sin(angle) * ;y
y1 = Math.cos(angle) * y - Math.sin(angle) * x;
第十一章
动量守恒的数学表达式:
(m0 – m1) * v0 + 2 * m1 * v1
v0Final = ----------------------------------------------
m0 + m1
(m1 – m0) * v1 + 2 * m0 * v0
v1Final = ---------------------------------------------
m0 + m1
动量守恒的 ActionScript 表达式,短形:
var vxTotal:Number = vx0 - vx1;
vx0 = ((ball0.mass - ball1.mass) * vx0 +
2 * ball1.mass * vx1) /
(ball0.mass + ball1.mass);
vx1 = vxTotal + vx0;
第十二章
引力的一般公式:
force = G * m1 * m2 / distance2
ActionScript 实现万有引力:
function gravitate(partA:Ball, partB:Ball):void
{
var dx:Number = partB.x - partA.x;
var dy:Number = partB.y - partA.y;
var distSQ:Number = dx * dx + dy * dy;
var dist:Number = Math.sqrt(distSQ);
var force:Number = partA.mass * partB.mass / distSQ;
var ax:Number = force * dx / dist;
var ay:Number = force * dy / dist;
partA.vx += ax / partA.mass;
partA.vy += ay / partA.mass;
partB.vx -= ax / partB.mass;
partB.vy -= ay / partB.mass;
}
第十四章
余弦定理
a2 = b2 + c2 - 2 * b * c * cos A
b2 = a2 + c2 - 2 * a * c * cos B
c2 = a2 + b2 - 2 * a * b * cos C
ActionScript 的余弦定理:
A = Math.acos((b * b + c * c - a * a) / (2 * b * c));
B = Math.acos((a * a + c * c - b * b) / (2 * a * c));
C = Math.acos((a * a + b * b - c * c) / (2 * a * b));
第十五章
基本透视法:
scale = fl / (fl + zpos);
sprite.scaleX = sprite.scaleY = scale;
sprite.alpha = scale; // 可选
sprite.x = vanishingPointX + xpos * scale;
sprite.y = vanishingPointY + ypos * scale;
Z 排序:
// 假设有一个带有 zpos 属性的 3D 物体的数组
objectArray.sortOn("zpos", Array.DESCENDING | Array.NUMERIC);
for(var i:uint = 0; i < numObjects; i++)
{
setChildIndex(objectArray[i], i);
}
坐标旋转:
x1 = cos(angleZ) * xpos - sin(angleZ) * ypos;
y1 = cos(angleZ) * ypos + sin(angleZ) * xpos;
x1 = cos(angleY) * xpos - sin(angleY) * zpos;
z1 = cos(angleY) * zpos + sin(angleY) * xpos;
y1 = cos(angleX) * ypos - sin(angleX) * zpos;
z1 = cos(angleX) * zpos + sin(angleX) * ypos;
3D 距离:
dist = Math.sqrt(dx * dx + dy * dy + dz * dz); '
ref:http://www.cnblogs.com/liongis/archive/2010/08/10/1796558.html
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