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Some tuning experimentally and adding back chebyshev

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This commit is contained in:
Aria 2025-09-04 20:05:28 -05:00
parent 42ab65abdb
commit 9b1c23d49f
1 changed files with 14 additions and 24 deletions
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38
packages/superdough/helpers.mjs
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@ -315,10 +315,9 @@ const __squash = (x) => x / (1 + x); // [0, inf) to [0, 1)
const _scurve = (x, k) => ((1 + k) * x) / (1 + k * Math.abs(x));
const _soft = (x, k) => Math.tanh(x * (1 + k));
const _hard = (x, k) => clamp((1 + k) * x, -1, 1);
const _sine = (x, k) => Math.sin(x * (1 + k));
const _fold = (x, k) => {
let y = (1 + k) * x;
let y = (1 + 0.5 * k) * x;
while (y > 1 || y < -1) {
y = y > 1 ? 2 - y : -2 - y;
}
@ -327,29 +326,23 @@ const _fold = (x, k) => {
const _sineFold = (x, k) => Math.sin((Math.PI / 2) * _fold(x, k));
const _pow = (x, k) => {
const t = __squash(k);
const p = 1 / (1 + 0.5 * t); // tame k
return _soft(Math.sign(x) * Math.pow(Math.abs(x), p), 0.5 * k);
};
const _cubic = (x, k) => {
const t = __squash(k);
const t = __squash(Math.log1p(k));
const cubic = (x - (t / 3) * x * x * x) / (1 - t / 3); // normalized to go from (-1, 1)
return _soft(cubic, k);
};
const _diode = (x, k, asym = false) => {
const g = 1 + k; // gain
const t = __squash(k);
const bias = 0.15 * t;
const pos = _soft(x + bias, k);
const neg = _soft(asym ? bias : -x + bias, k);
const g = 1 + 2 * k; // gain
const t = __squash(Math.log1p(k));
const bias = 0.07 * t;
const pos = _soft(x + bias, 2 * k);
const neg = _soft(asym ? bias : -x + bias, 2 * k);
const y = pos - neg;
// We divide by the derivative at 0 so that the distortion is roughly
// the identity map near 0 => small values are preserved and undistorted
const sech = 1 / Math.cosh(g * bias);
const sech2 = sech * sech; // derivative of tanh is sech^2
const sech2 = sech * sech; // derivative of soft (i.e. tanh) is sech^2
const denom = Math.max(1e-8, (asym ? 1 : 2) * g * sech2); // g from chain rule; 2 if both pos/neg have x
return _soft(y / denom, k);
};
@ -357,13 +350,12 @@ const _diode = (x, k, asym = false) => {
const _asym = (x, k) => _diode(x, k, true);
const _chebyshev = (x, k) => {
const kl = Math.log1p(k);
const kl = 10 * Math.log1p(k);
let tnm1 = 1;
let tnm2 = x;
let tn;
let y = 0;
const iterations = 1 + ffloor(Math.min(16 * kl, 255));
for (let i = 1; i < iterations; i++) {
for (let i = 1; i < 64; i++) {
if (i < 2) {
// Already set inital conditions
y += i == 0 ? tnm1 : tnm2;
@ -373,24 +365,22 @@ const _chebyshev = (x, k) => {
tnm2 = tnm1;
tnm1 = tn;
if (i % 2 === 0) {
y += tn;
y += Math.min(1.3 * kl / i, 2) * tn;
}
}
// Soft clip
return _soft(y, 0);
return _soft(y, kl / 20);
};
export const distortionAlgorithms = {
scurve: _scurve,
soft: _soft,
hard: _hard,
sine: _sine,
fold: _fold,
sinefold: _sineFold,
pow: _pow,
cubic: _cubic,
diode: _diode,
asym: _asym,
fold: _fold,
sinefold: _sineFold,
chebyshev: _chebyshev,
};
const _algoNames = Object.freeze(Object.keys(distortionAlgorithms));