Vehicle and pedestrian movements are recorded at numerous times (depending on computer hardware) per second to allow real time playback.

Car dynamics such as roll, pitch, and yaw angles are all recorded in details. Thus, users can easily spot the changes in road terrain and re-examine the causes of a crash effortlessly.

▲Fig.2 Car dynamics

The following table is a list of elements that are recorded. Other than model movements, traffic signals, and scenario contexts.

▲ Table 1 Recorded elements

• Control Panel

  The control panel shown in the bottom can be accessed by going into Record/Play ribbon -> Player. The controls are straightforward and is similar to a standard video player, where the user can choose between normal playback, fast forward, rewind, or in slow motion. Users can also jump to a specific section of the replay data by directly clicking on the seek bar. Once a replay is saved, it can be viewed at any intended time.



• Toolbar

  It is possible to embed the toolbar into the main menu interface, which allows a quicker, and more direct access to recording and playback features. (Fig.4)



• Options

  The option allows users to select the view perspective during replay playback (e.g. first person from the driver's seat or third person from outside). It is also possible to selectively record cars that are at a certain distance, or record only pedestrians.

▲ Fig.3 Control panel

▲ Fig.4 Toolbar

This plugin is the most useful when paired with the Scenario Plugin to allow for a smoother recording of a certain scenario event. Users can choose to track only a portion of the event, such as start recording from just the few seconds before an accident to ensure that events are properly designed. Another example is to track and confirm the driving distance between a parking lot to a certain destination.

▲ Fig.5 Scenario setting

Replays are recorded and compressed with ZLib, the same algorithm used for ZIP files, to cope as much as possible with the problem that recording too many moving 3D objects may cause the file size exceeding 1GB.

Further, to prevent overuse of RAM, only the desired section and a small portion ahead are pre-written into the memory.

With these methods, we have prevented memory stresses and avoided data loading delays, while maintaining the number of models and a high performance playback.

▲ Fig.6 How replay data are managed

By combining this plugin with UC-win/Road SDK, it is possible to record and control the playbacks from the SDK.

It is also possible to view a replay and extract the detailed control information, such as position, steering wheel angle, speed, etc., during driving simulation mode in the SDK. The following table contains some examples of the controls that can be manipulated from the SDK directly.

▲ Table 2 Examples of Replay Plugin commands