bd028579
 易尊强
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/**
* Catmull-Rom spline 插值折线
*/
import {distance as v2Distance, VectorArray} from '../../core/vector';
function interpolate(
p0: number, p1: number, p2: number, p3: number, t: number, t2: number, t3: number
) {
const v0 = (p2 - p0) * 0.5;
const v1 = (p3 - p1) * 0.5;
return (2 * (p1 - p2) + v0 + v1) * t3
+ (-3 * (p1 - p2) - 2 * v0 - v1) * t2
+ v0 * t + p1;
}
export default function smoothSpline(points: VectorArray[], isLoop?: boolean): VectorArray[] {
const len = points.length;
const ret = [];
let distance = 0;
for (let i = 1; i < len; i++) {
distance += v2Distance(points[i - 1], points[i]);
}
let segs = distance / 2;
segs = segs < len ? len : segs;
for (let i = 0; i < segs; i++) {
const pos = i / (segs - 1) * (isLoop ? len : len - 1);
const idx = Math.floor(pos);
const w = pos - idx;
let p0;
let p1 = points[idx % len];
let p2;
let p3;
if (!isLoop) {
p0 = points[idx === 0 ? idx : idx - 1];
p2 = points[idx > len - 2 ? len - 1 : idx + 1];
p3 = points[idx > len - 3 ? len - 1 : idx + 2];
}
else {
p0 = points[(idx - 1 + len) % len];
p2 = points[(idx + 1) % len];
p3 = points[(idx + 2) % len];
}
const w2 = w * w;
const w3 = w * w2;
ret.push([
interpolate(p0[0], p1[0], p2[0], p3[0], w, w2, w3),
interpolate(p0[1], p1[1], p2[1], p3[1], w, w2, w3)
]);
}
return ret;
}
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