114 lines
3.7 KiB
TypeScript
114 lines
3.7 KiB
TypeScript
module es {
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/**
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* 提供了一系列立方贝塞尔点，并提供了帮助方法来访问贝塞尔
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*/
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export class BezierSpline {
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public _points: Vector2[] = [];
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public _curveCount: number = 0;
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/**
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* 在这个过程中，t被修改为在曲线段的范围内。
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* @param t
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*/
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public pointIndexAtTime(t: Ref<number>): number {
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let i = 0;
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if (t.value >= 1) {
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t.value = 1;
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i = this._points.length - 4;
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} else {
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t.value = MathHelper.clamp01(t.value) * this._curveCount;
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i = ~~t;
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t.value -= i;
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i *= 3;
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}
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return i;
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}
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/**
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* 设置一个控制点，考虑到这是否是一个共享点，如果是，则适当调整
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* @param index
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* @param point
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*/
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public setControlPoint(index: number, point: Vector2) {
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if (index % 3 == 0) {
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let delta = Vector2.subtract(point, this._points[index]);
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if (index > 0)
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this._points[index - 1].add(delta);
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if (index + 1 < this._points.length)
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this._points[index + 1].add(delta);
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}
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this._points[index] = point;
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}
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/**
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* 得到时间t的贝塞尔曲线上的点
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* @param t
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*/
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public getPointAtTime(t: number): Vector2{
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let i = this.pointIndexAtTime(new Ref(t));
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return Bezier.getPointThree(this._points[i], this._points[i + 1], this._points[i + 2],
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this._points[i + 3], t);
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}
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/**
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* 得到贝塞尔在时间t的速度（第一导数）
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* @param t
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*/
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public getVelocityAtTime(t: number): Vector2 {
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let i = this.pointIndexAtTime(new Ref(t));
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return Bezier.getFirstDerivativeThree(this._points[i], this._points[i + 1], this._points[i + 2],
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this._points[i + 3], t);
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}
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/**
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* 得到时间t时贝塞尔的方向（归一化第一导数）
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* @param t
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*/
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public getDirectionAtTime(t: number) {
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return Vector2.normalize(this.getVelocityAtTime(t));
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}
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/**
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* 在贝塞尔曲线上添加一条曲线
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* @param start
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* @param firstControlPoint
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* @param secondControlPoint
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* @param end
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*/
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public addCurve(start: Vector2, firstControlPoint: Vector2, secondControlPoint: Vector2, end: Vector2) {
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// 只有当这是第一条曲线时，我们才会添加起始点。对于其他所有的曲线，前一个曲线的终点应该等于新曲线的起点。
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if (this._points.length == 0)
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this._points.push(start);
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this._points.push(firstControlPoint);
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this._points.push(secondControlPoint);
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this._points.push(end);
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this._curveCount = (this._points.length - 1) / 3;
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}
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/**
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* 重置bezier，移除所有点
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*/
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public reset() {
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this._points.length = 0;
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}
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/**
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* 将splitine分解成totalSegments部分，并返回使用线条绘制所需的所有点
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* @param totalSegments
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*/
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public getDrawingPoints(totalSegments: number): Vector2[] {
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let points: Vector2[] = [];
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for (let i = 0; i < totalSegments; i ++) {
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let t = i / totalSegments;
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points[i] = this.getPointAtTime(t);
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}
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return points;
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}
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}
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} |