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// Shared utilities for mq_editor
// Evaluate cubic bezier curve at time t (robust: handles dt<=0)
function evalBezier(curve, t) {
const dt = curve.t3 - curve.t0;
if (dt <= 0) return curve.v0;
let u = (t - curve.t0) / dt;
u = Math.max(0, Math.min(1, u));
const u1 = 1.0 - u;
return u1*u1*u1 * curve.v0 +
3*u1*u1*u * curve.v1 +
3*u1*u*u * curve.v2 +
u*u*u * curve.v3;
}
// Evaluate amplitude component of unified bezier curve at time t
function evalBezierAmp(curve, t) {
const dt = curve.t3 - curve.t0;
if (dt <= 0) return curve.a0;
let u = (t - curve.t0) / dt;
u = Math.max(0, Math.min(1, u));
const u1 = 1.0 - u;
return u1*u1*u1 * curve.a0 +
3*u1*u1*u * curve.a1 +
3*u1*u*u * curve.a2 +
u*u*u * curve.a3;
}
// Get canvas-relative {x, y} from a mouse event
function getCanvasCoords(e, canvas) {
const rect = canvas.getBoundingClientRect();
return { x: e.clientX - rect.left, y: e.clientY - rect.top };
}
// Build upper/lower band point arrays for a frequency curve.
// factorAbove/factorBelow are fractional offsets (e.g. 0.02 = ±2%).
// Returns { upper: [[x,y],...], lower: [[x,y],...] }
function buildBandPoints(viewer, curve, factorAbove, factorBelow) {
const STEPS = 60;
const upper = [], lower = [];
for (let i = 0; i <= STEPS; ++i) {
const t = curve.t0 + (curve.t3 - curve.t0) * i / STEPS;
if (t < viewer.t_view_min - 0.01 || t > viewer.t_view_max + 0.01) continue;
const f = evalBezier(curve, t);
upper.push([viewer.timeToX(t), viewer.freqToY(f * (1 + factorAbove))]);
lower.push([viewer.timeToX(t), viewer.freqToY(f * (1 - factorBelow))]);
}
return { upper, lower };
}
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