Main loop

Main loop (in D_SRB2Loop) consists of parts:

• Game logic: TryRunTics
• Graphics: D_Display
  • Has special case for frozen netplay, which allows for moving the camera in that situation without running game logic
  • Screenshot and movie mode handling happens after drawing, based on flags set somewhere earlier
• Sounds: S_UpdateSounds
• LUA GC: LUA_Step

Calls:

• TryRunTics
  • COM_BufTicker
  • D_MapChange
  • G_Ticker
    • G_CopyTiccmd
    • P_Ticker
      • P_RunThinkers (also called twice in P_LoadLevel by P_PreTicker)
    • various other tickers
• D_Display

TryRunTics

• Runs a number of game logic tics depending on current time.
  • If other code (like rendering) has taken too long, multiple tics can be run to compensate and keep the speed of the game consistent.

Calls:

• COM_BufTicker
  • pending console command execution
• D_MapChange
• NetUpdate
• GetPackets
• G_Ticker
• ExtraDataTicker
  • netxcmd stuff

G_Ticker

• Runs one tic of game logic.

Calls:

• G_DoReborn (respawn)
• tickers for various game states (in level, intermission, cutscene etc.)
• in level:
  • P_Ticker
  • ST_Ticker
    • title card logic
  • F_TextPromptTicker
  • AM_Ticker
    • automap logic
  • HU_Ticker
    • hud logic (not much)

NetUpdate

• Input handling and some network functions.
• when game is running fast enough, it will get run inside TryRunTics?
• when game is running slowly, it will also get run in various other places scattered in the code
  • not faster than 35 times in a second though

Calls:

• Local_Maketic
  • I_OsPolling
  • D_ProcessEvents
    • responders
  • G_BuildTiccmd
    • LUAh_PlayerCmd
    • LUAh_ViewpointSwitch (reset back to self when moving)
• GetPackets
• CL_SendClientCmd
• other network stuff
• M_Ticker
• CON_Ticker

P_Ticker

• Handles game world.
• Runs player thinking.
• Runs all thinkers.
• Code for various other fixed game logic parts.
• Lua ThinkFrame.

P_RunThinkers

• Runs functions specified in the thinkers.
• Multiple thinker lists for separate purposes.
  • polyobjects
  • main
    • things that move or do stuff but are not mobjs or polyobjects
  • mobjs
    • P_MobjThinker
  • dynamic slopes
  • precipitation
    • most precip logic is moved to rendering code with culling, but the current implementation still relies on some code running for every precip thinker

P_MobjThinker

• Thinker function for all mobjs. Run for every mobj by P_RunThinkers, except for those with nothink.
• Various checks and switch statements for the different mobj types in the game.
• Mobj states and actions.
• Movement physics.
  • XY movement
  • Z movement
• Scenery gets a separate similar but somewhat simpler code path.