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@@ -0,0 +1,92 @@
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+const Bezier = function (pointArr, allTime = 2) {
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+
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+ let _this = {}
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+ // 曲线点集合,曲线总长,上一个点,当前时间
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+ let _pointLists, totalLength, prevPos, currentRunTime;
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+ // 运行时间
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+ let _runTime = allTime;
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+ let _pointArr = pointArr;
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+ // 重置数据
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+ let resetData = function () {
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+ // 点集合
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+ _pointLists = [];
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+ // 线段总长度
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+ totalLength = currentRunTime = 0;
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+ // 初始位置
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+ prevPos = {
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+ x: pointArr[0].x,
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+ y: pointArr[0].y,
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+ length: 0,
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+ }
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+ }
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+
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+ //阶乘
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+ function factorial(i) {
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+ let n = 1;
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+ for (let j = 1; j <= i; j++)
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+ n *= j;
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+ return n;
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+ }
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+ // ------------------------【核心代码】---------------------------
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+ let ComputeBezier = function (dt, runTime) {
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+ // 把时间从 [0,runTime] 映射到 [0,1] 之间
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+ let t = currentRunTime / runTime;
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+
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+ var x = 0, y = 0;
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+ //控制点数组
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+ var n = _pointArr.length - 1;
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+
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+ _pointArr.forEach((item, index) => {
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+ if (!index) {
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+ x += item.x * Math.pow((1 - t), n - index) * Math.pow(t, index)
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+ y += item.y * Math.pow((1 - t), n - index) * Math.pow(t, index)
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+ } else {
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+ //factorial为阶乘函数
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+ x += factorial(n) / factorial(index) / factorial(n - index) * item.x * Math.pow((1 - t), n - index) * Math.pow(t, index)
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+ y += factorial(n) / factorial(index) / factorial(n - index) * item.y * Math.pow((1 - t), n - index) * Math.pow(t, index)
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+ }
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+ })
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+
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+ // // 二阶贝塞尔曲线公式 (t => [0,1])
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+ // var x = Math.pow(1 - t, 2) * _startPos.x
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+ // + 2 * t * (1 - t) * _controlPos.x
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+ // + Math.pow(t, 2) * _endPos.x;
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+
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+ // var y = Math.pow(1 - t, 2) * _startPos.y
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+ // + 2 * t * (1 - t) * _controlPos.y
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+ // + Math.pow(t, 2) * _endPos.y;
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+
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+ // console.log(`x:${x},y:${y}`);
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+ // 计算两点距离
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+ let length = Math.sqrt(Math.pow(prevPos.x - x, 2) + Math.pow(prevPos.y - y, 2));
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+ let v2 = { x, y, length };
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+ // 存储当前节点
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+ _pointLists.push(v2);
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+ prevPos = v2;
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+ // 累计长度
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+ totalLength += length;
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+ // 累计时间
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+ currentRunTime += dt;
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+
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+ }
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+
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+ // 切割贝塞尔曲线
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+ _this.getPoints = function (count = 10) {
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+ resetData();
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+ // 分割时间
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+ let dt = _runTime / count;
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+ // 开始分割曲线
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+ for (var i = 0, len = count + 1; i < len; i++) {
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+ ComputeBezier(dt, _runTime);
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+ }
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+ return _pointLists
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+ }
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+
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+ _this.getCurveLength = function () {
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+ return totalLength;
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+ }
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+
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+ return _this;
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+}
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+
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+module.exports = Bezier;
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