Initial commit

shared/scalar.js

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+/** Scalar helpers shared by the sim and the renderer. No three.js here. */
+
+export const clamp = (x, a, b) => (x < a ? a : x > b ? b : x);
+export const lerp = (a, b, t) => a + (b - a) * t;
+export const smooth = (t) => t * t * (3 - 2 * t);
+
+/** Wrap to (-PI, PI]. */
+export function wrapAngle(a) {
+  let x = a;
+  while (x > Math.PI) x -= Math.PI * 2;
+  while (x <= -Math.PI) x += Math.PI * 2;
+  return x;
+}
+
+/** Shortest-arc interpolation between two headings. */
+export function lerpAngle(a, b, t) {
+  return a + wrapAngle(b - a) * t;
+}
+
+/** Move `from` toward `to` by at most `step`, without overshooting. */
+export function approach(from, to, step) {
+  return Math.abs(to - from) <= step ? to : from + Math.sign(to - from) * step;
+}
+
+/** Same, on the circle. */
+export function approachAngle(from, to, step) {
+  const d = wrapAngle(to - from);
+  return Math.abs(d) <= step ? wrapAngle(to) : wrapAngle(from + Math.sign(d) * step);
+}