If running with --spectate/-s CPlayerInterface will appear even without human players.
Following command-line options also available:
--spectate-ignore-hero
--spectate-hero-speed=N
--spectate-battle-speed=N
--spectate-skip-battle
--spectate-skip-battle-result
Boolean options can also be changed in runtime via client console:
set spectate-ignore-hero on / off
Spectator mode also:
- Work with --onlyAI option when starting game or loading saves.
- Allow to use any cheat codes.
- Give recon on towns and heroes.