/**
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* Catmull-Rom spline 插值折线
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*/
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import {distance as v2Distance, VectorArray} from '../../core/vector';
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function interpolate(
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p0: number, p1: number, p2: number, p3: number, t: number, t2: number, t3: number
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) {
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const v0 = (p2 - p0) * 0.5;
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const v1 = (p3 - p1) * 0.5;
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return (2 * (p1 - p2) + v0 + v1) * t3
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+ (-3 * (p1 - p2) - 2 * v0 - v1) * t2
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+ v0 * t + p1;
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}
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export default function smoothSpline(points: VectorArray[], isLoop?: boolean): VectorArray[] {
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const len = points.length;
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const ret = [];
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let distance = 0;
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for (let i = 1; i < len; i++) {
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distance += v2Distance(points[i - 1], points[i]);
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}
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let segs = distance / 2;
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segs = segs < len ? len : segs;
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for (let i = 0; i < segs; i++) {
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const pos = i / (segs - 1) * (isLoop ? len : len - 1);
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const idx = Math.floor(pos);
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const w = pos - idx;
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let p0;
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let p1 = points[idx % len];
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let p2;
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let p3;
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if (!isLoop) {
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p0 = points[idx === 0 ? idx : idx - 1];
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p2 = points[idx > len - 2 ? len - 1 : idx + 1];
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p3 = points[idx > len - 3 ? len - 1 : idx + 2];
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}
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else {
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p0 = points[(idx - 1 + len) % len];
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p2 = points[(idx + 1) % len];
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p3 = points[(idx + 2) % len];
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}
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const w2 = w * w;
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const w3 = w * w2;
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ret.push([
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interpolate(p0[0], p1[0], p2[0], p3[0], w, w2, w3),
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interpolate(p0[1], p1[1], p2[1], p3[1], w, w2, w3)
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]);
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}
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return ret;
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}
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