Fix for uum-131151

com.unity.cinemachine/CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [3.1.7-pre.1] - 2026-02-24
 
+### Bugfixes
+- Fixed stack frame snapshot not resetting when CameraBlendStack completed blend.
+
 ### Changed
 - Added support for fast enter play mode.
 

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

@@ -83,10 +83,8 @@ public ICinemachineCamera GetSnapshotIfAppropriate(ICinemachineCamera cam, float
             {
                 if (cam == null || (cam.State.BlendHint & CameraState.BlendHints.FreezeWhenBlendingOut) == 0)
                 {
-                    // No snapshot required - reset it
-                    m_Snapshot.TakeSnapshot(null);
-                    m_SnapshotSource = null;
-                    m_SnapshotBlendWeight = 0;
+                    // No snapshot required - clear it
+                    ClearSnapshot();
                     return cam;
                 }
                 // A snapshot is needed
@@ -101,6 +99,13 @@ public ICinemachineCamera GetSnapshotIfAppropriate(ICinemachineCamera cam, float
                 // Use the most recent snapshot
                 return m_Snapshot;
             }
+
+            public void ClearSnapshot()
+            {
+                m_Snapshot.TakeSnapshot(null);
+                m_SnapshotSource = null;
+                m_SnapshotBlendWeight = 0;
+            }
         }
 
         // Current game state is always frame 0, overrides are subsequent frames
@@ -213,6 +218,7 @@ public void ResetRootFrame()
                 frame.Blend.CamB = null;
                 frame.Source.ClearBlend();
                 frame.Source.CamB = null;
+                frame.ClearSnapshot();
             }
         }
 
@@ -329,7 +335,10 @@ public void UpdateRootFrame(
 
             // Advance the working blend
             if (AdvanceBlend(frame.Blend, deltaTime))
+            {
                 frame.Source.ClearBlend();
+                frame.ClearSnapshot();
+            }
             frame.UpdateCameraState(up, deltaTime);
 
             // local function

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

@@ -210,5 +210,48 @@ public IEnumerator SetActiveBlend()
             yield return UpdateCinemachine();
             Assert.That(m_Brain.ActiveBlend == null);
         }
+
+        [UnityTest]
+        [Description("Regression test for UUM-131151 tests that blend snapshots are reset correctly when blending is interrupted")]
+        public IEnumerator BlendClearsSnapshotWhenBlendingIsInterrupted()
+        {
+            // We test cancelling a blend, changing the source camera position and then restarting the blend
+            // The camera must be in FreezeWhenBlendingOut mode
+            // We expect the blend to start from the new position
+
+            ((CinemachineCamera)m_Source).BlendHint |= CinemachineCore.BlendHints.FreezeWhenBlendingOut;
+
+            yield return UpdateCinemachine();
+            Assume.That(ReferenceEquals(m_Brain.ActiveVirtualCamera, m_Source));
+            Assume.That(m_Brain.transform.position, Is.EqualTo(m_Source.transform.position));
+
+            // Start blend to target
+            m_Target.enabled = true;
+            yield return UpdateCinemachine();
+            Assume.That(m_Brain.IsBlending, Is.True);
+
+            yield return UpdateCinemachine();
+
+            // Cancel, blend back to source
+            m_Target.enabled = false;
+            yield return UpdateCinemachine();
+            Assume.That(m_Brain.IsBlending, Is.True);
+
+            while (m_Brain.IsBlending)
+                yield return UpdateCinemachine();
+
+            Assume.That(ReferenceEquals(m_Brain.ActiveVirtualCamera, m_Source));
+            Assume.That(m_Brain.transform.position, Is.EqualTo(m_Source.transform.position));
+
+            var newPos = new Vector3(0, 5, 0);
+            m_Source.transform.position = newPos;
+
+            // Restart blend to target
+            m_Target.enabled = true;
+            yield return UpdateCinemachine();
+
+            // Make sure we started from 0, 5, 0 and not 10, 0, 0
+            Assert.That(m_Brain.transform.position.y, Is.GreaterThan(4.0f));
+        }
     }
 }