From e8cf3b9bf325b18dde97c7acc96053ccc78f1c7e Mon Sep 17 00:00:00 2001
From: Dr Tracy Gardner <tracygardner@users.noreply.github.com>
Date: Thu, 5 Mar 2026 20:59:19 +0000
Subject: [PATCH 1/2] Restore rotate loop spin semantics while preserving
 reverse

---
 api/animate.js        | 29 ++++++++++++++++++++---------
 tests/animate.test.js | 26 ++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/api/animate.js b/api/animate.js
index d0ba89ed..5356f6dd 100644
--- a/api/animate.js
+++ b/api/animate.js
@@ -168,18 +168,25 @@ export const flockAnimate = {
           "rotation",
           fps,
           BABYLON.Animation.ANIMATIONTYPE_VECTOR3,
-          loop || reverse
-            ? BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE
+          reverse
+            ? BABYLON.Animation.ANIMATIONLOOPMODE_YOYO
+            : loop
+              ? BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE
             : BABYLON.Animation.ANIMATIONLOOPMODE_CONSTANT,
         );
 
-        const rotateKeys = [
+        const rotateKeys = loop
+          ? [
+              { frame: 0, value: startRotation },
+              { frame: frames, value: targetRotation },
+            ]
+          : [
           { frame: 0, value: startRotation },
           { frame: frames, value: targetRotation },
-        ];
-        if (reverse || loop) {
-          rotateKeys.push({ frame: frames * 2, value: startRotation });
-        }
+              ...(reverse
+                ? [{ frame: frames * 2, value: startRotation }]
+                : []),
+            ];
         rotateAnimation.setKeys(rotateKeys);
 
         if (easing !== "Linear") {
@@ -205,13 +212,17 @@ export const flockAnimate = {
           mesh,
           [rotateAnimation],
           0,
-          reverse || loop ? frames * 2 : frames,
+          reverse && !loop ? frames * 2 : frames,
           loop,
         );
 
         animatable.onAnimationEndObservable.add(() => {
           flock.scene.onAfterAnimationsObservable.remove(syncObserver);
-          if (!reverse) mesh.rotation = targetRotation.clone();
+          if (reverse) {
+            mesh.rotation = startRotation.clone();
+          } else {
+            mesh.rotation = targetRotation.clone();
+          }
           resolve();
         });
       });
diff --git a/tests/animate.test.js b/tests/animate.test.js
index 8c191444..35813308 100644
--- a/tests/animate.test.js
+++ b/tests/animate.test.js
@@ -211,6 +211,32 @@ export function runAnimateTests(flock) {
 				expect(actualDuration).to.be.at.least(180); // Allow some tolerance
 				expect(actualDuration).to.be.at.most(300);
 			});
+
+			it("should return to the start rotation when reverse is true", async function () {
+				const boxId = "rotateAnimReverse";
+				await flock.createBox(boxId, {
+					width: 1,
+					height: 1,
+					depth: 1,
+					position: [0, 0, 0],
+				});
+				boxIds.push(boxId);
+
+				const mesh = flock.scene.getMeshByName(boxId);
+				expect(mesh).to.exist;
+
+				const initialRotation = mesh.rotation.clone();
+
+				await flock.rotateAnim(boxId, {
+					y: 90,
+					duration: 0.1,
+					reverse: true,
+				});
+
+				expect(mesh.rotation.x).to.be.closeTo(initialRotation.x, 0.01);
+				expect(mesh.rotation.y).to.be.closeTo(initialRotation.y, 0.01);
+				expect(mesh.rotation.z).to.be.closeTo(initialRotation.z, 0.01);
+			});
 		});
 
 		describe("animateProperty function", function () {

From f5642e640db4ae1c0d21034795a4d2a59df6fcd4 Mon Sep 17 00:00:00 2001
From: Dr Tracy Gardner <tracygardner@users.noreply.github.com>
Date: Thu, 5 Mar 2026 21:08:58 +0000
Subject: [PATCH 2/2] Fix reverse+loop rotateAnim timing

---
 api/animate.js | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/api/animate.js b/api/animate.js
index 5356f6dd..e0403200 100644
--- a/api/animate.js
+++ b/api/animate.js
@@ -168,25 +168,16 @@ export const flockAnimate = {
           "rotation",
           fps,
           BABYLON.Animation.ANIMATIONTYPE_VECTOR3,
-          reverse
-            ? BABYLON.Animation.ANIMATIONLOOPMODE_YOYO
-            : loop
-              ? BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE
+          loop
+            ? BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE
             : BABYLON.Animation.ANIMATIONLOOPMODE_CONSTANT,
         );
 
-        const rotateKeys = loop
-          ? [
-              { frame: 0, value: startRotation },
-              { frame: frames, value: targetRotation },
-            ]
-          : [
+        const rotateKeys = [
           { frame: 0, value: startRotation },
           { frame: frames, value: targetRotation },
-              ...(reverse
-                ? [{ frame: frames * 2, value: startRotation }]
-                : []),
-            ];
+          ...(reverse ? [{ frame: frames * 2, value: startRotation }] : []),
+        ];
         rotateAnimation.setKeys(rotateKeys);
 
         if (easing !== "Linear") {
@@ -212,7 +203,7 @@ export const flockAnimate = {
           mesh,
           [rotateAnimation],
           0,
-          reverse && !loop ? frames * 2 : frames,
+          reverse ? frames * 2 : frames,
           loop,
         );