119 lines
4.3 KiB
TypeScript
119 lines
4.3 KiB
TypeScript
module es {
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/**
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* 简单的剪耳三角测量器，最终的三角形将出现在triangleIndices列表中。
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*/
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export class Triangulator {
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/**
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* 上次三角函数调用中使用的点列表的三角列表条目索引
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*/
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public triangleIndices: number[] = [];
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private _triPrev: number[] = new Array<number>(12);
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private _triNext: number[] = new Array<number>(12);
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public static testPointTriangle(point: Vector2, a: Vector2, b: Vector2, c: Vector2): boolean {
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// 如果点在AB的右边，那么外边的三角形是
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if (Vector2Ext.cross(Vector2.subtract(point, a), Vector2.subtract(b, a)) < 0)
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return false;
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// 如果点在BC的右边，则在三角形的外侧
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if (Vector2Ext.cross(Vector2.subtract(point, b), Vector2.subtract(c, b)) < 0)
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return false;
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// 如果点在ca的右边，则在三角形的外面
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if (Vector2Ext.cross(Vector2.subtract(point, c), Vector2.subtract(a, c)) < 0)
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return false;
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// 点在三角形上
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return true;
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}
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/**
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* 计算一个三角形列表，该列表完全覆盖给定点集所包含的区域。如果点不是CCW，则将arePointsCCW参数传递为false
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* @param points 定义封闭路径的点列表
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* @param arePointsCCW
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*/
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public triangulate(points: Vector2[], arePointsCCW: boolean = true) {
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let count = points.length;
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// 设置前一个链接和下一个链接
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this.initialize(count);
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// 非三角的多边形断路器
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let iterations = 0;
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// 从0开始
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let index = 0;
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// 继续移除所有的三角形，直到只剩下一个三角形
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while (count > 3 && iterations < 500) {
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iterations++;
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let isEar = true;
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let a = points[this._triPrev[index]];
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let b = points[index];
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let c = points[this._triNext[index]];
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if (Vector2Ext.isTriangleCCW(a, b, c)) {
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let k = this._triNext[this._triNext[index]];
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do {
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if (Triangulator.testPointTriangle(points[k], a, b, c)) {
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isEar = false;
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break;
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}
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k = this._triNext[k];
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} while (k != this._triPrev[index]);
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} else {
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isEar = false;
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}
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if (isEar) {
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this.triangleIndices.push(this._triPrev[index]);
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this.triangleIndices.push(index);
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this.triangleIndices.push(this._triNext[index]);
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// 删除vert通过重定向相邻vert的上一个和下一个链接，从而减少vertext计数
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this._triNext[this._triPrev[index]] = this._triNext[index];
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this._triPrev[this._triNext[index]] = this._triPrev[index];
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count--;
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// 接下来访问前一个vert
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index = this._triPrev[index];
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} else {
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index = this._triNext[index];
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}
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}
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this.triangleIndices.push(this._triPrev[index]);
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this.triangleIndices.push(index);
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this.triangleIndices.push(this._triNext[index]);
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if (!arePointsCCW)
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this.triangleIndices.reverse();
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}
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private initialize(count: number) {
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this.triangleIndices.length = 0;
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if (this._triNext.length < count) {
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this._triNext.reverse();
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this._triNext.length = Math.max(this._triNext.length * 2, count);
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}
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if (this._triPrev.length < count) {
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this._triPrev.reverse();
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this._triPrev.length = Math.max(this._triPrev.length * 2, count);
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}
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for (let i = 0; i < count; i++) {
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this._triPrev[i] = i - 1;
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this._triNext[i] = i + 1;
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}
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this._triPrev[0] = count - 1;
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this._triNext[count - 1] = 0;
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}
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}
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}
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