27. Record and Playback


This is an experimental feature meaning it may be changed in the future with no guaranteed backwards compatibility.

AGX Dynamics for Unreal offers some functionality that enables recording and playback of some aspects of a Simulation. This can be useful when for example recording the movements of a machine controlled by user inputs for later playback.

The Play Record Component is responisble for handling the record and playback functionality. During recording it writes data to a Play Record Asset which is stored permanently for later playback.

27.1. Record

  1. Create a Play Record Asset. This is where the recorded data will be stored.

Create a Play Record Asset.
  1. Add a Play Record Component (AGX Play Record) to your Blueprint and assign the Play Record Asset created from step 1 to it, in the Details Panel.

Assign Play Record Asset.

3. Call the Record <> function. Currently only Constraint positions are supported, see Limitations.

Call record function.

Notice that we use a AGX Simulation Step Forward event for triggering the recording instead of Unreal Engines Tick event. This is important for determinism. See Events and Delegates for more information.

4. Play the Simulation and stop it once done. The recorded data is now present in the Play Record Asset and can be used for future playback. Remember to disconnect the Record <> function route node in your Blueprint to avoid overwriting the data in subsequent Simulations.

27.2. Playback

Here it is assumed that the steps in Record has been followed.

  1. Assign a Play Record Asset containing recorded data to the Play Record Component in the Details Panel.

Assign Play Record Asset.
  1. Call the Play Back <> function (currently only Constraint positions are supported, see Limitations).

Call playback function.

It is important that the array of Constraints match those used during recording to get a correct result.

3. Play the Simulation. The Constraints will now move according to the recorded data. Note that the Play Record Component does position control internally and does not guarantee equal Constraint forces/torques during playback as during recording.

27.3. Limitations

Currently only Constraint positions can be recorded and played back when using the Play Record Component. The Play Record Component strictly uses position control of Constraints during playback meaning forces, torques and trajectories are not guaranteed to be the same as during recording.