feat: define moving source trajectories

tests/unit/acoustics.test.js

@@ -10,6 +10,11 @@ import { renderSceneMix } from "/packages/acoustics-core/mixdown.js";
 import { whiteNoiseAt } from "/packages/acoustics-core/noise.js";
 import { sphericalAttenuation, synthesizeMicrophoneSignals } from "/packages/acoustics-core/propagation.js";
 import { getFrameCount } from "/packages/acoustics-core/stft.js";
+import {
+  createQuasiStaticWindows,
+  sceneAtTime,
+  sourcePositionAtTime,
+} from "/packages/acoustics-core/trajectory.js";
 import { encodeMonoPcm16Wav } from "/packages/acoustics-core/wav.js";
 
 function assertNear(actual, expected, tolerance, label) {
@@ -39,6 +44,73 @@ function createArray(columns, rows, width, height) {
   return { id: "test-array", aperture: { width, height }, microphones };
 }
 
+test("trajectory 위치를 선형 보간하고 시간창 중앙에서 준정적으로 샘플링한다", () => {
+  const source = {
+    position: [9, 8, 7],
+    trajectory: [
+      { time: 0.2, position: [-1, 0, 2] },
+      { time: 0.6, position: [1, 2, 4] },
+      { time: 1, position: [3, 0, 2] },
+    ],
+  };
+  assertEqual(sourcePositionAtTime({ position: [4, 5, 6] }, 0.5).join(","), "4,5,6", "fixed fallback");
+  assertEqual(sourcePositionAtTime(source, 0).join(","), "-1,0,2", "before first keyframe");
+  assertEqual(sourcePositionAtTime(source, 1.5).join(","), "3,0,2", "after last keyframe");
+  const interpolated = sourcePositionAtTime(source, 0.4);
+  assertNear(interpolated[0], 0, 1e-12, "interpolated x");
+  assertNear(interpolated[1], 1, 1e-12, "interpolated y");
+  assertNear(interpolated[2], 3, 1e-12, "interpolated z");
+
+  const scene = { duration: 1, sources: [source] };
+  const sampled = sceneAtTime(scene, 0.4);
+  assert(sampled !== scene && sampled.sources[0] !== source, "sceneAtTime is immutable");
+  assertEqual(source.position.join(","), "9,8,7", "original fallback position is unchanged");
+  assertEqual(sampled.sources[0].trajectory, source.trajectory, "trajectory is preserved");
+  assertNear(sampled.sources[0].position[0], 0, 1e-12, "sampled scene x");
+  assertNear(sampled.sources[0].position[1], 1, 1e-12, "sampled scene y");
+  assertNear(sampled.sources[0].position[2], 3, 1e-12, "sampled scene z");
+
+  const windows = createQuasiStaticWindows(scene, { windowDuration: 0.4, hopDuration: 0.4 });
+  assertEqual(windows.length, 3, "partial final window");
+  assertNear(windows[0].sampleTime, 0.2, 1e-12, "first midpoint");
+  assertNear(windows[1].sampleTime, 0.6, 1e-12, "second midpoint");
+  assertNear(windows[2].sampleTime, 0.9, 1e-12, "partial midpoint");
+  assertNear(windows[2].duration, 0.2, 1e-12, "partial duration");
+  assertNear(windows[1].scene.sources[0].position[0], 1, 1e-12, "window x");
+  assertNear(windows[1].scene.sources[0].position[1], 2, 1e-12, "window y");
+  assertNear(windows[1].scene.sources[0].position[2], 4, 1e-12, "window z");
+});
+
+test("trajectory가 없는 sceneAtTime snapshot은 기존 합성 결과와 sample 단위로 동일하다", () => {
+  const scene = {
+    sampleRate: 8000,
+    duration: 0.01,
+    speedOfSound: 343,
+    seed: 17,
+    mix: { normalization: "none", targetPeak: 0.95 },
+    sources: [{
+      id: "fixed", name: "fixed", position: [0.1, -0.2, 1.2], gainDb: -12, startTime: 0, duration: 0.01,
+      signal: { type: "tone", frequency: 750, phaseDeg: 35 },
+    }],
+    ambient: [],
+  };
+  const arrayDefinition = {
+    microphones: [
+      { id: "left", position: [-0.1, 0, 0] },
+      { id: "right", position: [0.1, 0, 0], sensitivityDb: -1, phaseOffsetDeg: 3 },
+    ],
+  };
+  const baseline = synthesizeMicrophoneSignals({ scene, arrayDefinition });
+  const sampled = synthesizeMicrophoneSignals({ scene: sceneAtTime(scene, 0.007), arrayDefinition });
+  assertEqual(sampled.appliedScale, baseline.appliedScale, "applied scale");
+  assertEqual(sampled.preNormalizationPeak, baseline.preNormalizationPeak, "pre-normalization peak");
+  baseline.channels.forEach((channel, channelIndex) => {
+    channel.forEach((value, sampleIndex) => {
+      assertEqual(sampled.channels[channelIndex][sampleIndex], value, `channel ${channelIndex} sample ${sampleIndex}`);
+    });
+  });
+});
+
 test("거리, dB와 구면 감쇠 기본식을 계산한다", () => {
   assertNear(distance3([0, 0, 0], [1, 2, 2]), 3, 1e-12, "distance");
   assertNear(dbToLinear(-6.020599913), 0.5, 1e-9, "dB amplitude");