Client-owned camera for demo spectator

cgame runs its own PmoveSingle for the free camera using real time,
independent of server time. Solves pause freezing — camera moves
smoothly while svs.time is frozen.

Changes:
- usercmd_t: add optional origin[3] with 1-bit flag (zero cost for
  normal gameplay, 13 bytes during demo viewing)
- msg.c: serialize optional origin in usercmd delta encoding
- CG_SETCLIENTORIGIN trap: cgame sends camera origin to engine
- cl_input.c: CL_FinishMove writes cgame origin into usercmd
- cg_predict.c: CG_PredictPlayerState runs local PmoveSingle for
  free camera in svDemo mode, sends origin via trap for PVS
- cg_snapshot.c: detect follow→free camera transition, init camera
  from last known position
- cg_main.c: detect svDemo mode from CS_SVDEMO configstring,
  lazy-init camera from first snapshot's spectator spawn
- g_main.c: G_InitGame sets CS_SVDEMO configstring, G_RunFrame
  copies cmd.origin to ps.origin for PVS instead of ClientThink_real
- bg_public.h: CS_SVDEMO configstring index (26)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

code/cgame/cg_local.h

@@ -457,6 +457,10 @@ typedef struct {
 	int			clientNum;
 	
 	qboolean	demoPlayback;
+	qboolean	svDemoPlayback;		// server-side demo playback mode
+	qboolean	svDemoFreeCamera;	// free camera (client-owned movement)
+	playerState_t	svDemoCameraPs;	// local playerState for free camera
+	int			svDemoCameraTime;	// real time of last camera update
 	qboolean	levelShot;			// taking a level menu screenshot
 	int			deferredPlayerLoading;
 	qboolean	loading;			// don't defer players at initial startup
@@ -1618,6 +1622,7 @@ qboolean	trap_GetUserCmd( int cmdNumber, usercmd_t *ucmd );
 
 // used for the weapon select and zoom
 void		trap_SetUserCmdValue( int stateValue, float sensitivityScale );
+void		trap_SetClientOrigin( qboolean hasOrigin, float x, float y, float z );
 
 // aids for VM testing
 void		testPrintInt( char *string, int i );

code/cgame/cg_main.c

@@ -1896,6 +1896,13 @@ void CG_Init( int serverMessageNum, int serverCommandSequence, int clientNum ) {
 	// get the gamestate from the client system
 	trap_GetGameState( &cgs.gameState );
 
+	// detect server-side demo playback from configstring
+	cg.svDemoPlayback = ( atoi( CG_ConfigString( CS_SVDEMO ) ) != 0 );
+	if ( cg.svDemoPlayback ) {
+		cg.svDemoFreeCamera = qtrue;
+		// camera ps will be initialized from first snapshot in CG_PredictPlayerState
+	}
+
 	// check version
 	s = CG_ConfigString( CS_GAME_VERSION );
 	if ( strcmp( s, GAME_VERSION ) ) {

code/cgame/cg_predict.c

@@ -432,6 +432,59 @@ void CG_PredictPlayerState( void ) {
 	// demo playback just copies the moves
 	if ( cg.demoPlayback || (cg.snap->ps.pm_flags & PMF_FOLLOW) ) {
 		CG_InterpolatePlayerState( qfalse );
+		// send followed player's origin for PVS during server demo follow mode
+		if ( cg.svDemoPlayback && (cg.snap->ps.pm_flags & PMF_FOLLOW) ) {
+			trap_SetClientOrigin( qtrue,
+				cg.snap->ps.origin[0],
+				cg.snap->ps.origin[1],
+				cg.snap->ps.origin[2] );
+			cg.svDemoFreeCamera = qfalse;
+		}
+		return;
+	}
+
+	// server-side demo free camera: run local PmoveSingle
+	if ( cg.svDemoPlayback && cg.svDemoFreeCamera ) {
+		int realTime = trap_Milliseconds();
+		int dt = realTime - cg.svDemoCameraTime;
+		pmove_t pm;
+
+		// lazy init: place camera at spectator spawn from first snapshot
+		if ( cg.svDemoCameraPs.speed == 0 ) {
+			cg.svDemoCameraPs = cg.snap->ps;
+			cg.svDemoCameraPs.pm_type = PM_SPECTATOR;
+			cg.svDemoCameraPs.speed = 480;
+			cg.svDemoCameraTime = realTime;
+			dt = 1;
+		}
+
+		if ( dt < 1 ) dt = 1;
+		if ( dt > 200 ) dt = 200;
+		cg.svDemoCameraTime = realTime;
+
+		// get latest usercmd for input
+		current = trap_GetCurrentCmdNumber();
+		trap_GetUserCmd( current, &latestCmd );
+
+		// set up pmove
+		memset( &pm, 0, sizeof(pm) );
+		pm.ps = &cg.svDemoCameraPs;
+		pm.cmd = latestCmd;
+		pm.cmd.serverTime = cg.svDemoCameraPs.commandTime + dt;
+		pm.tracemask = MASK_PLAYERSOLID & ~CONTENTS_BODY;
+		pm.trace = CG_Trace;
+		pm.pointcontents = CG_PointContents;
+
+		Pmove( &pm );
+
+		// use as the predicted state for rendering
+		cg.predictedPlayerState = cg.svDemoCameraPs;
+
+		// send origin for PVS
+		trap_SetClientOrigin( qtrue,
+			cg.svDemoCameraPs.origin[0],
+			cg.svDemoCameraPs.origin[1],
+			cg.svDemoCameraPs.origin[2] );
 		return;
 	}
 

code/cgame/cg_public.h

@@ -164,6 +164,7 @@ typedef enum {
 	CG_R_INPVS,
 	// 1.32
 	CG_FS_SEEK,
+	CG_SETCLIENTORIGIN,	// set client-owned origin for demo spectator PVS
 
 /*
 	CG_LOADCAMERA,

code/cgame/cg_snapshot.c

@@ -184,6 +184,22 @@ static void CG_TransitionSnapshot( void ) {
 			|| cg_nopredict.integer || cg_synchronousClients.integer ) {
 			CG_TransitionPlayerState( ps, ops );
 		}
+
+		// server demo: detect follow→free camera transition
+		if ( cg.svDemoPlayback ) {
+			qboolean wasFollowing = ( ops->pm_flags & PMF_FOLLOW ) != 0;
+			qboolean isFollowing = ( ps->pm_flags & PMF_FOLLOW ) != 0;
+			if ( wasFollowing && !isFollowing ) {
+				// exiting follow mode — init camera from last known position
+				cg.svDemoFreeCamera = qtrue;
+				cg.svDemoCameraTime = trap_Milliseconds();
+				VectorCopy( ops->origin, cg.svDemoCameraPs.origin );
+				VectorCopy( ops->viewangles, cg.svDemoCameraPs.viewangles );
+				cg.svDemoCameraPs.pm_type = PM_SPECTATOR;
+				cg.svDemoCameraPs.speed = 480;
+				cg.svDemoCameraPs.clientNum = cg.clientNum;
+			}
+		}
 	}
 
 }

code/cgame/cg_syscalls.c

@@ -333,6 +333,10 @@ void		trap_SetUserCmdValue( int stateValue, float sensitivityScale ) {
 	syscall( CG_SETUSERCMDVALUE, stateValue, PASSFLOAT(sensitivityScale) );
 }
 
+void		trap_SetClientOrigin( qboolean hasOrigin, float x, float y, float z ) {
+	syscall( CG_SETCLIENTORIGIN, hasOrigin, PASSFLOAT(x), PASSFLOAT(y), PASSFLOAT(z) );
+}
+
 void		testPrintInt( char *string, int i ) {
 	syscall( CG_TESTPRINTINT, string, i );
 }

code/client/cl_cgame.c

@@ -457,6 +457,14 @@ int CL_CgameSystemCalls( int *args ) {
 		return 0;
 	case CG_FS_SEEK:
 		return FS_Seek( args[1], args[2], args[3] );
+	case CG_SETCLIENTORIGIN:
+		cl.cgameHasOrigin = args[1];
+		if ( args[1] ) {
+			cl.cgameOrigin[0] = VMF(2);
+			cl.cgameOrigin[1] = VMF(3);
+			cl.cgameOrigin[2] = VMF(4);
+		}
+		return 0;
 	case CG_SENDCONSOLECOMMAND:
 		Cbuf_AddText( VMA(1) );
 		return 0;

code/client/cl_input.c

@@ -516,6 +516,12 @@ void CL_FinishMove( usercmd_t *cmd ) {
 	for (i=0 ; i<3 ; i++) {
 		cmd->angles[i] = ANGLE2SHORT(cl.viewangles[i]);
 	}
+
+	// client-owned origin for demo spectator PVS
+	cmd->hasOrigin = cl.cgameHasOrigin;
+	if ( cl.cgameHasOrigin ) {
+		VectorCopy( cl.cgameOrigin, cmd->origin );
+	}
 }
 
 

code/client/client.h

@@ -106,6 +106,8 @@ typedef struct {
 	// cgame communicates a few values to the client system
 	int			cgameUserCmdValue;	// current weapon to add to usercmd_t
 	float		cgameSensitivity;
+	qboolean	cgameHasOrigin;		// client-owned origin for demo spectator PVS
+	vec3_t		cgameOrigin;		// the origin to send
 
 	// cmds[cmdNumber] is the predicted command, [cmdNumber-1] is the last
 	// properly generated command

code/game/bg_public.h

@@ -79,6 +79,7 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 #define CS_FLAGSTATUS			23		// string indicating flag status in CTF
 #define CS_SHADERSTATE			24
 #define CS_BOTINFO				25
+#define CS_SVDEMO				26		// "1" during server-side demo playback
 
 #define	CS_ITEMS				27		// string of 0's and 1's that tell which items are present
 

code/game/g_main.c

@@ -418,6 +418,11 @@ void G_InitGame( int levelTime, int randomSeed, int restart ) {
 
 	G_RegisterCvars();
 
+	// signal server-side demo mode to cgame via configstring
+	if ( trap_Cvar_VariableIntegerValue( "sv_demoplaying" ) ) {
+		trap_SetConfigstring( CS_SVDEMO, "1" );
+	}
+
 	G_ProcessIPBans();
 
 	G_InitMemory();
@@ -1746,10 +1751,16 @@ int start, end;
 			gclient_t *cl = &level.clients[i];
 			gentity_t *e = &g_entities[i];
 
-			// find and process the spectator
+			// find the spectator — use client-owned origin for PVS
 			if ( e->client && cl->pers.connected == CON_CONNECTED
 				 && cl->sess.sessionTeam == TEAM_SPECTATOR ) {
-				ClientThink_real( e );
+				// copy client-owned origin from usercmd for PVS culling.
+				// cgame runs its own PmoveSingle for camera movement.
+				if ( cl->pers.cmd.hasOrigin ) {
+					VectorCopy( cl->pers.cmd.origin, cl->ps.origin );
+					VectorCopy( cl->pers.cmd.origin, e->s.pos.trBase );
+					VectorCopy( cl->pers.cmd.origin, e->r.currentOrigin );
+				}
 				specEnt = e;
 				continue;
 			}

code/game/q_shared.h

@@ -1255,6 +1255,9 @@ typedef struct usercmd_s {
 	int 			buttons;
 	byte			weapon;           // weapon
 	signed char	forwardmove, rightmove, upmove;
+	// client-owned origin for demo spectator PVS (optional)
+	qboolean		hasOrigin;
+	float			origin[3];
 } usercmd_t;
 
 //===================================================================

code/qcommon/msg.c

@@ -702,8 +702,7 @@ void MSG_WriteDeltaUsercmdKey( msg_t *msg, int key, usercmd_t *from, usercmd_t *
 		from->weapon == to->weapon) {
 			MSG_WriteBits( msg, 0, 1 );				// no change
 			oldsize += 7;
-			return;
-	}
+	} else {
 		key ^= to->serverTime;
 		MSG_WriteBits( msg, 1, 1 );
 		MSG_WriteDeltaKey( msg, key, from->angles[0], to->angles[0], 16 );
@@ -715,6 +714,16 @@ void MSG_WriteDeltaUsercmdKey( msg_t *msg, int key, usercmd_t *from, usercmd_t *
 		MSG_WriteDeltaKey( msg, key, from->buttons, to->buttons, 16 );
 		MSG_WriteDeltaKey( msg, key, from->weapon, to->weapon, 8 );
 	}
+	// optional client-owned origin (always written, independent of field changes)
+	if ( to->hasOrigin ) {
+		MSG_WriteBits( msg, 1, 1 );
+		MSG_WriteFloat( msg, to->origin[0] );
+		MSG_WriteFloat( msg, to->origin[1] );
+		MSG_WriteFloat( msg, to->origin[2] );
+	} else {
+		MSG_WriteBits( msg, 0, 1 );
+	}
+}
 
 
 /*
@@ -748,6 +757,15 @@ void MSG_ReadDeltaUsercmdKey( msg_t *msg, int key, usercmd_t *from, usercmd_t *t
 		to->buttons = from->buttons;
 		to->weapon = from->weapon;
 	}
+	// optional client-owned origin
+	if ( MSG_ReadBits( msg, 1 ) ) {
+		to->hasOrigin = qtrue;
+		to->origin[0] = MSG_ReadFloat( msg );
+		to->origin[1] = MSG_ReadFloat( msg );
+		to->origin[2] = MSG_ReadFloat( msg );
+	} else {
+		to->hasOrigin = qfalse;
+	}
 }
 
 /*