CMCL-982: spurious z rotations during spherical blend

com.unity.cinemachine/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Bugfix: 3rdPersonFollow shows a warning message when no follow target is assigned like the rest of the body components.
 - Bugfix: FadeOut sample scene shader was culling some objects incorrectly.
 - Bugfix: Freelook had wrong heading at first frame, which could cause a slight jitter. 
+- Bugfix: Fixed spurious Z rotations during speherical blend.
 
 
 ## [2.9.0-pre.7] - 2022-03-29

com.unity.cinemachine/Runtime/Core/CameraState.cs

@@ -381,8 +381,9 @@ public static CameraState Lerp(CameraState stateA, CameraState stateB, float t)
                 }
                 else
                 {
-                    var blendUp = Vector3.Slerp(
-                        stateA.RawOrientation * Vector3.up, stateB.RawOrientation * Vector3.up, t);
+                    var blendUp = (state.BlendHint & BlendHintValue.CylindricalPositionBlend) != 0 
+                        ? state.ReferenceUp // the pre-blended up vectors
+                        : Vector3.Slerp(stateA.RawOrientation * Vector3.up, stateB.RawOrientation * Vector3.up, t);
 
                     // Rotate while preserving our lookAt target
                     if (Vector3.Cross(dirTarget, blendUp).AlmostZero())

com.unity.cinemachine/Tests/Runtime/CmColliderTests.cs

@@ -8,6 +8,7 @@
 
 namespace Tests.Runtime
 {
+#if CINEMACHINE_PHYSICS
     public class CmColliderTests : CinemachineFixtureBase
     {
         CinemachineBrain m_Brain;
@@ -164,4 +165,5 @@ static IEnumerator WaitForOnePhysicsFrame()
             yield return null; 
         }
     }
-}
+#endif
+}