When modifying keyframes, it’s helpful to have a frame of reference for your curves. A saved reference of curves lets you compare modified curves to the original curves. Additionally, a saved reference—known as a curve snapshot—acts as a safety net if you need to restore a curve’s original state.
Click the Take/Show Curve Snapshot button in the upper-right corner of the Keyframe Editor.
With Take/Show Curve Snapshot enabled, as you move keyframes in the Keyframe Editor, the original curve—as it appeared when you took the snapshot—retains its color. As long as you remain in the Keyframe Editor editing the current set of curves with the Take/Show Curve Snapshot button enabled, the snapshot curve remains available.
If, after editing a curve, you want to revert to the snapshot, you can do so from the Animation menu in the Keyframe Editor.
In the Keyframe Editor, click the Animation menu for the parameter you want to revert, then choose Set to Curve Snapshot.
The Animation menu (a downward arrow) is hidden until you move the pointer over the right side of the parameter row.
The curve reverts to the state of its most recent snapshot.
Important: If you leave the Keyframe Editor, or load a different set of curves into the Keyframe Editor, curve snapshots are taken again, replacing the previous curve snapshots.