fix: expose physical aliasing and delayed arrivals

packages/acoustics-core/signal.js

@@ -1,4 +1,4 @@
-import { dbToLinear, TAU } from "./math.js";
+import { ceilSampleIndex, dbToLinear, TAU } from "./math.js";
 import { hashString, pinkNoiseAt, whiteNoiseAt } from "./noise.js";
 
 function sampleAsset(signal, assetBuffers, time) {
@@ -25,16 +25,20 @@ function sampleAsset(signal, assetBuffers, time) {
  * Omitting it keeps the historical whole-scene behaviour exactly unchanged.
  */
 export function renderSignal(entry, scene, assetBuffers = new Map(), seedSalt = 0, timeMapping = {}) {
-  const sampleCount = Math.ceil(scene.duration * scene.sampleRate);
+  const sampleCount = ceilSampleIndex(scene.duration, scene.sampleRate);
   const output = new Float32Array(sampleCount);
   const startTime = entry.startTime ?? 0;
   const duration = entry.duration ?? scene.duration;
   const gain = dbToLinear(entry.gainDb ?? 0);
-  const startSample = Math.max(0, Math.ceil(startTime * scene.sampleRate));
-  const endSample = Math.min(sampleCount, Math.ceil((startTime + duration) * scene.sampleRate));
+  const startSample = Math.max(0, ceilSampleIndex(startTime, scene.sampleRate));
+  const endSample = Math.min(
+    sampleCount,
+    ceilSampleIndex(startTime + duration, scene.sampleRate),
+  );
   const sceneSampleOffset = timeMapping.sceneSampleOffset ?? 0;
   const signalStartTime = timeMapping.signalStartTime ?? startTime;
-  const signalStartSample = timeMapping.signalStartSample ?? Math.ceil(startTime * scene.sampleRate);
+  const signalStartSample =
+    timeMapping.signalStartSample ?? ceilSampleIndex(startTime, scene.sampleRate);
   if (!Number.isSafeInteger(sceneSampleOffset) || sceneSampleOffset < 0) {
     throw new RangeError("sceneSampleOffset must be a non-negative safe integer.");
   }