From cbefd529f9ca08d55e874240142d495cdf1d342f Mon Sep 17 00:00:00 2001
From: Sameh Khamis <sameh@halfpixel.ai>
Date: Wed, 14 Oct 2026 15:05:05 -0700
Subject: [PATCH] fix(director): turn heading and roll the short way for any
 authored angle
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A single % made the seek delta negative when the target angle was more than
540° below the start, so 350° to -350° turned 340° through 180°. Uses the
same double modulo as playback, and adds tests for exact ±180° endpoints and
a near-antipodal seek.
---
 docs/CURRENT-STATE.md                        |  4 ++-
 src/director/director-dateline-seek.test.mjs | 27 ++++++++++++++++++++
 src/director/timeline.js                     |  4 ++-
 3 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/docs/CURRENT-STATE.md b/docs/CURRENT-STATE.md
index fa48b7bfe..3a7f7b94f 100644
--- a/docs/CURRENT-STATE.md
+++ b/docs/CURRENT-STATE.md
@@ -399,7 +399,9 @@ camera moves with easing, duration and holds. Playback and seek share one
 coordinate sampler; navigation/manual input revokes authored motion and pending
 holds. Anchor heights and explicit endpoints require the WGS84 ellipsoid
 reference. Legacy projects retain their ordinary flights, content and edits.
-Seeking between ordinary camera poses uses the shortest longitude arc across the dateline while preserving both authored endpoint longitudes.
+Seeking between ordinary camera poses uses the shortest longitude arc across the
+dateline while preserving both authored endpoint longitudes, and turns heading
+and roll the short way for any authored angles.
 See [camera directions](DIRECTOR-CAMERA.md).
 
 Realtime voice composes separate connection, response/tool, Radio handoff, input
diff --git a/src/director/director-dateline-seek.test.mjs b/src/director/director-dateline-seek.test.mjs
index f950814f3..b0dd2b24b 100644
--- a/src/director/director-dateline-seek.test.mjs
+++ b/src/director/director-dateline-seek.test.mjs
@@ -24,3 +24,30 @@ test('director seek follows the short dateline arc in both directions', () => {
   }
   assert.equal(cameraAtProgress(camera(20), camera(24), 0.5).lon, 22);
 });
+
+test('director seek keeps exact ±180 endpoints and picks the short arc near the antipode', () => {
+  for (const [a, b] of [
+    [180, -180],
+    [-180, 180],
+  ]) {
+    assert.equal(cameraAtProgress(camera(a), camera(b), 0).lon, a);
+    assert.equal(cameraAtProgress(camera(a), camera(b), 1).lon, b);
+    assert.equal(
+      Math.abs(cameraAtProgress(camera(a), camera(b), 0.5).lon),
+      180,
+    );
+  }
+  // 10°E to 169.9°W is 179.9° westward through Greenwich, not 180.1° east.
+  const mid = cameraAtProgress(camera(10), camera(-169.9), 0.5).lon;
+  assert.ok(mid > -81 && mid < -79, `short arc midpoint, got ${mid}`);
+});
+
+test('director seek turns heading and roll the short way for any authored angles', () => {
+  const pose = (heading, roll) => ({ ...camera(0), heading, roll });
+  const mid = cameraAtProgress(pose(350, 350), pose(-350, -350), 0.5);
+  // 350° and -350° are 20° apart through 0°/360°, not 340° through 180°.
+  for (const value of [mid.heading, mid.roll]) {
+    const wrapped = ((value % 360) + 360) % 360;
+    assert.ok(wrapped < 1e-9 || 360 - wrapped < 1e-9, `got ${value}`);
+  }
+});
diff --git a/src/director/timeline.js b/src/director/timeline.js
index fbaca4301..f7cffcece 100644
--- a/src/director/timeline.js
+++ b/src/director/timeline.js
@@ -41,7 +41,9 @@ export function cameraAtProgress(fromCamera, toCamera, progress) {
   const lerp = (from, to) => Number(from) + (Number(to) - Number(from)) * eased;
   const lerpAngle = (from, to) => {
     const start = Number(from) || 0;
-    const delta = ((Number(to) - start + 540) % 360) - 180;
+    // Double modulo keeps the delta in [-180, 180) for any authored angles,
+    // as sampleCameraMove does; a single % goes negative below -540.
+    const delta = ((((Number(to) - start + 540) % 360) + 360) % 360) - 180;
     return start + delta * eased;
   };
   return {