75 lines
2.2 KiB
JavaScript
75 lines
2.2 KiB
JavaScript
/**
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* One-Euro Filter（速度自适应低通滤波器）
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* 参考：Casiez et al., "1€ Filter: A Simple Speed-based Low-pass Filter for Noisy Input in Interactive Systems", CHI 2012
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* https://cristal.univ-lille.fr/~casiez/1euro/
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*
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* 用法：每个轴一个实例
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* const f = createOneEuroFilter({ mincutoff: 0.2, beta: 0.05, dcutoff: 1.0 })
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* const out = f.filter(x, performance.now())
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* f.reset()
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*
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* @param {object} [opts]
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* @param {number} [opts.mincutoff=0.2] - Hz，静止截止频率
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* @param {number} [opts.beta=0.05] - 速度系数（越大快速运动越跟手）
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* @param {number} [opts.dcutoff=1.0] - Hz，速度估计的截止频率
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*/
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export function createOneEuroFilter({ mincutoff = 0.2, beta = 0.05, dcutoff = 1.0 } = {}) {
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let xPrev = null // 上次 FILTERED 输出（与 Casiez 论文一致）
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let dxPrev = 0 // 平滑后的速度
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let tPrev = null // 上次时间戳
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function smoothingFactor(cutoff, dt) {
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const r = 2 * Math.PI * cutoff * dt
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return r / (r + 1)
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}
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function filter(x, t) {
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// 首帧：直接接受，建立基线
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if (xPrev == null || tPrev == null) {
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xPrev = x
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dxPrev = 0
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tPrev = t
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return x
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}
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const dt = Math.max((t - tPrev) / 1000, 1e-6) // ms → s
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// 1. 速度差分（用 filtered xPrev，与 Casiez 一致）
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const dx = (x - xPrev) / dt
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// 2. 平滑速度
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const aD = smoothingFactor(dcutoff, dt)
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const edx = aD * dx + (1 - aD) * dxPrev
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// 3. 自适应截止频率
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const cutoff = mincutoff + beta * Math.abs(edx)
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// 4. 平滑位置
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const a = smoothingFactor(cutoff, dt)
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const result = a * x + (1 - a) * xPrev
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xPrev = result
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dxPrev = edx
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tPrev = t
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return result
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}
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function reset() {
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xPrev = null
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dxPrev = 0
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tPrev = null
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}
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return { filter, reset }
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}
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/**
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* 取单调递增的高精度时间戳（毫秒）。
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* 优先 performance.now()（sub-ms 精度），回退 Date.now()（WebView 上 ~15ms 精度）。
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*/
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export function nowMs() {
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if (typeof performance !== 'undefined' && typeof performance.now === 'function') {
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return performance.now()
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}
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return Date.now()
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} |