Overall architecture: coupling between game, cgame, etc?

vinnyvicious · January 9, 2015, 12:28pm

I have decided to rewrite most of the code inside cgame, by slowly deactivating old code and migrating to newer code. However, i’m not completely sure about the Quake 3 architecture. Is there any other dependency between cgame and the engine, other than the vmMain and the events it receives?

There seems to be some tight coupling with other parts of the system, and i’m afraid about global variables and shared global state. Or is it really completely isolate and i should just care about vmMain and drawing the current frame properly?

WofWca · February 14, 2026, 10:29am

There is also cg_syscalls.c which shares some types defined in cg_public.h with code/client (and code/client is a part of the engine). One example is snapshot_t which must be the same between the client and cgame, because the CG_GETSNAPSHOT syscall writes to wherever the snapshot_t pointer points to.

github.com/ioquake/ioq3

code/cgame/cg_public.h

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          // Snapshots are generated at regular time intervals by the server,
          // but they may not be sent if a client's rate level is exceeded, or
          // they may be dropped by the network.
          typedef struct {
          	int				snapFlags;			// SNAPFLAG_RATE_DELAYED, etc
          	int				ping;
          
          	int				serverTime;		// server time the message is valid for (in msec)
          
          	byte			areamask[MAX_MAP_AREA_BYTES];		// portalarea visibility bits
          
          	playerState_t	ps;						// complete information about the current player at this time
          
          	int				numEntities;			// all of the entities that need to be presented
          	entityState_t	entities[MAX_ENTITIES_IN_SNAPSHOT];	// at the time of this snapshot
          
          	int				numServerCommands;		// text based server commands to execute when this
          	int				serverCommandSequence;	// snapshot becomes current
          } snapshot_t;

github.com/ioquake/ioq3

code/cgame/cg_syscalls.c

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          qboolean	trap_GetSnapshot( int snapshotNumber, snapshot_t *snapshot ) {
          	return syscall( CG_GETSNAPSHOT, snapshotNumber, snapshot );
          }