Centralize spatial audio math across runtimes

client/src/audio/spatial.ts

@@ -0,0 +1,49 @@
+export type SpatialMixOptions = {
+  dx: number;
+  dy: number;
+  range: number;
+  baseGain?: number;
+  nearFieldDistance?: number;
+  nearFieldGain?: number;
+  nearFieldCenterPan?: boolean;
+};
+
+export type SpatialMixResult = {
+  distance: number;
+  gain: number;
+  pan: number;
+};
+
+export function resolveSpatialMix(options: SpatialMixOptions): SpatialMixResult | null {
+  const {
+    dx,
+    dy,
+    range,
+    baseGain = 1,
+    nearFieldDistance,
+    nearFieldGain = 1,
+    nearFieldCenterPan = false,
+  } = options;
+  if (!(range > 0)) {
+    return null;
+  }
+
+  const distance = Math.hypot(dx, dy);
+  if (distance > range) {
+    return null;
+  }
+
+  const volumeRatio = Math.max(0, 1 - distance / range);
+  let gain = baseGain * Math.pow(volumeRatio, 2);
+  const clampedX = Math.max(-range, Math.min(range, dx));
+  let pan = Math.sin((clampedX / range) * (Math.PI / 2));
+
+  if (nearFieldDistance !== undefined && distance < nearFieldDistance) {
+    gain = baseGain * nearFieldGain;
+    if (nearFieldCenterPan) {
+      pan = 0;
+    }
+  }
+
+  return { distance, gain, pan };
+}