Headless Clients

Headless clients reduce the load on the server CPU by offloading AI calculations to the client, allowing the server to focus solely on game logic. AI calculations are offloaded to the client which owns the AI object.

In UNITAF we are using Zulu Headless Client (ZHC) mod, that allows the Game Masters to be better informed about the performance impact their mission has. ZHC uses multiple ways of communicating the performance hit.

On the bottom right of the in-game map every player has an information about the number of active HC, and the server performance:

• The information contains the name of the Headless Clients, its performance graded in frames per second (fps), and how many local units have been transferred to it.
• The information is colour coded:
  • Green text indicates that the HC is performing well, and above 30 fps.
  • Yellow text indicates that the HC is struggling, and its performance is between 20 fps and 30 fps.
  • Orange text indicates that the HC is performing unwell, and its performance is between 10 fps and 20 fps.
  • Red text indicates that the HC is performing very bad, and its performance is below 10 fps.

Additionally the Game Masters have an access to the per AI group information displayed above the AI groups if the Debug Mode is activated:

• To Toggle Debug Mode you have to press a key combination. By default it's “Ctrl+]”
• The information is colour coded. The colours correspond with what the unit is offloaded to:
  • Yellow icon indicates a group that hasn't been transferred yet.
  • Red icon indicates a group that is transferred to the server.
  • Green icon indicates a group that is transferred to the Headless Client.
  • Pink icon indicates a group that is local.

Tradeoffs of Using HCs

While HCs offer better performance, they introduce some additional synchronization latency. The sync path now goes through HC ↔ server ↔ player, which may cause delays. To alleviate this HCs should be run on the same physical machine as the server to reduce network latency.