我正在尝试移植和实现一个舒缓功能，我发现
编辑
:我粘贴错了缓动函数，对不起!下面是正确的:
Math.easeOutQuart = function (t, b, c, d) {
t /= d;
t--;
return -c * (t*t*t*t - 1) + b;
};
我使用的语言不是Flash或Actionscript。下面是我的代码:
ease:{outquart:{function(t as float,b as float,c as float,d as float) as float
t=t/d
t=t-1
return -c * (t*t*t*t - 1) + b
end function}}
我在循环中调用函数:
EDIT2—主叫函数。
m。Move设置为1或-1表示方向移动，或-5 +5表示移动5个长度。setspritemoves被尽可能频繁地调用，目前它是系统可以调用的最快速度，但我可以在毫秒计时器上触发调用。
setspritemoves:function()
if m.move=1 then
m.duration=1
if m.ishd then
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]+m.move*324
next i
else
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]+m.move*224
next i
end if
else if m.move=5 then
m.duration=5
if m.ishd then
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]+m.move*324
next i
else
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]+m.move*224
next i
end if
else if m.move=-1 then
m.duration=1
if m.ishd then
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]-m.move*324
next i
else
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]-m.move*224
next i
end if
else if m.move=-5 then
m.duration=5
if m.ishd then
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]-m.move*324
next i
else
for i=0 to m.spriteposx.count()-1
m.moveto[i]=m.spriteposx[i]-m.move*224
next i
end if
end if
end function
m。moveto[i]是目标x坐标，m.time是一个整数i增量，m.duration是我假设的完成更改所需的时间，m.spriteposx是我正在移动的对象的当前位置。[i]是当前精灵。
时间的增量值应该是多少如果我想在1/2秒内移动345像素，持续时间应该是多少?
在我所有的实验中，我要么超调了一个巨大的因子，要么只移动了几个像素。
当前m.time每次迭代递增1,m.duration为100。我试过各种各样的值，但似乎没有一个能始终如一地工作。
你为什么不复制1-1的逻辑?渐变是一个简单的算法，它简单地以四分之一的方式将坐标从b映射到b+c，即b + c*t^4，其中t在区间[0,1]中获得值。您可以通过替换看到，当t=0时，该值为初始值，b, t->1时，该位置为所需的b+c。
这就是t = d行的原因，所以d是一个任意的持续时间，而t，从动画开始以来经过的时间，得到了上述范围内的值。但你做过t=t-1和底片，等等。为什么?
例如，在0.5s内移动345px，您将有一个初始位置，b和c=345，假设px是度量单位。d=0.5，然后将动画分割为您选择的长度间隔(取决于将运行动画的机器的功率)。移动设备不像桌面设备那么强大，所以你要在这种情况下选择一个合理的帧率)。假设我们选择24帧/秒，那么我们将间隔分割为0.5*24 = 12帧，并每1/24秒调用该函数一次，每次t取1/24、2/24等值。如果不以秒为单位而是以帧为单位工作更舒服，那么d=12和t的值为1,2，…，12。两种方法的计算都是一样的。
下面是一个很好的例子(点击方框运行演示)，可以随意修改值:
http://jsfiddle.net/nKhxw/贝塞尔函数
借用自http://blog.greweb.fr/2012/02/bezier-curve-based-easing-functions-from-concept-to-implementation/
/**
* KeySpline - use bezier curve for transition easing function
* is inspired from Firefox's nsSMILKeySpline.cpp
* Usage:
* var spline = new KeySpline(0.25, 0.1, 0.25, 1.0)
* spline.get(x) => returns the easing value | x must be in [0, 1] range
*/
function KeySpline (mX1, mY1, mX2, mY2) {
this.get = function(aX) {
if (mX1 == mY1 && mX2 == mY2) return aX; // linear
return CalcBezier(GetTForX(aX), mY1, mY2);
}
function A(aA1, aA2) { return 1.0 - 3.0 * aA2 + 3.0 * aA1; }
function B(aA1, aA2) { return 3.0 * aA2 - 6.0 * aA1; }
function C(aA1) { return 3.0 * aA1; }
// Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
function CalcBezier(aT, aA1, aA2) {
return ((A(aA1, aA2)*aT + B(aA1, aA2))*aT + C(aA1))*aT;
}
// Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
function GetSlope(aT, aA1, aA2) {
return 3.0 * A(aA1, aA2)*aT*aT + 2.0 * B(aA1, aA2) * aT + C(aA1);
}
function GetTForX(aX) {
// Newton raphson iteration
var aGuessT = aX;
for (var i = 0; i < 4; ++i) {
var currentSlope = GetSlope(aGuessT, mX1, mX2);
if (currentSlope == 0.0) return aGuessT;
var currentX = CalcBezier(aGuessT, mX1, mX2) - aX;
aGuessT -= currentX / currentSlope;
}
return aGuessT;
}
}
常用曲线别名:
{
"ease": [0.25, 0.1, 0.25, 1.0],
"linear": [0.00, 0.0, 1.00, 1.0],
"ease-in": [0.42, 0.0, 1.00, 1.0],
"ease-out": [0.00, 0.0, 0.58, 1.0],
"ease-in-out": [0.42, 0.0, 0.58, 1.0]
}
谢谢你，强尼!
下面是如何实现Bezier easing函数:C或Objective-C for iOS
// APPLE ORIGINAL TIMINGS:
// linear (0.00, 0.00), (0.00, 0.00), (1.00, 1.00), (1.00, 1.00)
// easeIn (0.00, 0.00), (0.42, 0.00), (1.00, 1.00), (1.00, 1.00)
// easeOut (0.00, 0.00), (0.00, 0.00), (0.58, 1.00), (1.00, 1.00)
// easeInEaseOut (0.00, 0.00), (0.42, 0.00), (0.58, 1.00), (1.00, 1.00)
// default (0.00, 0.00), (0.25, 0.10), (0.25, 1.00), (1.00, 1.00)
+(double)defaultEase_Linear:(double)t
{
return t;
}
// Замедление в начале
+(double)defaultEase_In:(double)t
{
return [AnimationMath easeBezier_t:t
point0_x:0
point0_y:0
point1_x:0.42
point1_y:0
point2_x:1
point2_y:1
point3_x:1
point3_y:1];
}
// Замедление в конце
+(double)defaultEase_Out:(double)t
{
return [AnimationMath easeBezier_t:t
point0_x:0
point0_y:0
point1_x:0
point1_y:0
point2_x:0.58
point2_y:1
point3_x:1
point3_y:1];
}
+(double)defaultEase_InOut:(double)t
{
return [AnimationMath easeBezier_t:t
point0_x:0
point0_y:0
point1_x:0.42
point1_y:0
point2_x:0.58
point2_y:1
point3_x:1
point3_y:1];
}
+(double)defaultEase_default:(double)t
{
return [AnimationMath easeBezier_t:t
point0_x:0
point0_y:0
point1_x:0.25
point1_y:0.1
point2_x:0.25
point2_y:1.0
point3_x:1
point3_y:1];
}
// For *better understanding* there is p1 and p2, because it is a Bezier curve from 0,0 to 1,0. So, you can remove p1 and p2 from this method, it is just for better understanding what's going on here
double ease_bezier_A(double aA1, double aA2) { return 1.0 - 3.0 * aA2 + 3.0 * aA1; }
double ease_bezier_B(double aA1, double aA2) { return 3.0 * aA2 - 6.0 * aA1; }
double ease_bezier_C(double aA1) { return 3.0 * aA1; }
// Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
double ease_bezier_calc(double aT, double aA1, double aA2) {
return ((ease_bezier_A(aA1, aA2)*aT + ease_bezier_B(aA1, aA2))*aT + ease_bezier_C(aA1))*aT;
}
// Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
double ease_bezier_get_slope(double aT, double aA1, double aA2) {
return 3.0 * ease_bezier_A(aA1, aA2)*aT*aT + 2.0 * ease_bezier_B(aA1, aA2) * aT + ease_bezier_C(aA1);
}
double ease_bezier_get_t_for_x(double aX, double mX1, double mX2) {
// Newton raphson iteration
double aGuessT = aX;
for (int i = 0; i < 4; ++i) {
double currentSlope = ease_bezier_get_slope(aGuessT, mX1, mX2);
if (currentSlope == 0.0) return aGuessT;
double currentX = ease_bezier_calc(aGuessT, mX1, mX2) - aX;
aGuessT -= currentX / currentSlope;
}
return aGuessT;
}
// Objective-C
// For ***better understanding*** there is p1 and p2, because it is a Bezier curve from 0,0 to 1,0. So, you can remove p1 and p2 from this method, it is just for better understanding what's going on here
// p1_x always = 0
// p1_y always = 0
// p2_x always = 1.0
// p2_y always = 1.0
+(double)easeBezier_t:(double)t
point0_x:(double)point0_x point0_y:(double)point0_y
point1_x:(double)point1_x point1_y:(double)point1_y
point2_x:(double)point2_x point2_y:(double)point2_y
point3_x:(double)point3_x point3_y:(double)point3_y
{
if (point0_x != 0 || point0_y != 0 || point3_x != 1 || point3_y != 1) {
[NSException raise:@"Error! Your bezier is wrong!!!" format:@""];
}
double v = ease_bezier_calc(ease_bezier_get_t_for_x(t, point1_x, point2_x), point1_y, point2_y);
return v;
}