When animating Skeletal Meshes, there may be instances when you want to let physics take control of the mesh (such as a character entering a rag-doll state). After physics has been applied, using the Animation Pose Snapshot feature, you can capture a Skeletal Mesh pose (storing all the Bone Transform data) within a Blueprint. You can then retrieve that informaiton inside an Animation Blueprint and use the saved pose as a source to blend from (as seen in the example video below).
Above, our character enters a rag-doll state when we press the R key and we use the Pose Snapshot node in our Character Blueprint to save off the pose of our Skeletal Mesh. When we press the R key again, our character blends from that snapshot into and plays a "get up" Animation Montage before resuming the normal locomotion state. This grants us the ability to take whatever pose the character ends up in as a result of physics and generate a smooth blend from that pose into an animation of the character getting back to their feet.
Save Pose Snapshot
In order to save your Skeletal Mesh's pose at runtime, inside your Character Blueprint, you will need access to the Skeletal Mesh Component and its Anim Instance. After getting the Skeletal Mesh and Anim Instance, you can call the Save Pose Snapshot node and enter the desired Snapshot Name. You can manually enter a name into the Snapshot Name field or create a variable to store the name.
The name you provide as the Snapshot Name must also be used when attempting to retrieve the Pose Snapshot inside your Animation Blueprint. Additionally, when calling Save Pose Snapshot, the snapshot is taken at the current LOD. For example, if you took the snapshot at LOD1 and then used it at LOD0, any bones not in LOD1 will use the mesh's reference pose.
Retrieve Pose Snapshot
To retrieve a Pose Snapshot, inside the AnimGraph of your Animation Blueprint, right-click and add the Pose Snapshot node and enter your Snapshot Name.
Below is the graph used for the example of a character getting up from a rag-doll pose.
Above, we have a State Machine called Default that drives our character's locomotion and uses a Slot node called MySlot that plays an Animation Montage of our character getting up. We use the Blend Poses by bool node to determine if our character has stopped moving, where if True we switch over to our Pose Snapshot. If False, we blend from the Pose Snapshot into our slotted Animation Montage before continuing on with our normal Default State Machine.
Snapshot Pose Function
An alternative way of using the Pose Snapshot feature is by calling the Snapshot Pose function within Blueprint to save a snapshot to a Pose Snapshot variable.
When using Snapshot Pose, you will need to provide a variable to save the snapshot to as shown above.
Inside your AnimGraph after adding the Pose Snapshot node, set the Mode to Snapshot Pin and check the (As pin) Snapshot option inside the Details panel.
This will expose a Pose Snapshot input pin on the node where you can pass in your desired snapshot variable.
Additional Resource
Additional information about this feature can be seen in the following Live Training Stream.