Bunny hopping

References

1. ^ abcBecause Quake runs friction in SV_ClientThink before the QuakeC jump in PlayerPreThink, and the on-ground flag is set by the walking move when it ends on a floor, a jump can come no sooner than the frame after landing, and that frame takes ground friction first: computed, a hop loses 4/72 of its horizontal speed (5.6%) at 72 frames a second above 100 units/s, or 8/72 (11.1%) when no floor lies within 34 units below a point 16 units ahead.Codeid-Software/Quake · id-Software/Quake-Tools
   How we know

   612	SV_RunClients ();
   ⋮
   617		SV_Physics ();
   

   387	onground = (int)sv_player->v.flags & FL_ONGROUND;
   

   361	else if ( onground )
   ⋮
   363		SV_UserFriction ();
   364		SV_Accelerate ();
   

   1069	PR_ExecuteProgram (pr_global_struct->PlayerPreThink);
   

   970	oldonground = (int)ent->v.flags & FL_ONGROUND;
   971	ent->v.flags = (int)ent->v.flags & ~FL_ONGROUND;
   

   284			if (trace.ent->v.solid == SOLID_BSP)
   ⋮
   286				ent->v.flags =	(int)ent->v.flags | FL_ONGROUND;
   

   1033	if (downtrace.plane.normal[2] > 0.7)
   ⋮
   1035		if (ent->v.solid == SOLID_BSP)
   ⋮
   1037			ent->v.flags =	(int)ent->v.flags | FL_ONGROUND;
   

   798	if (!(self.flags & FL_ONGROUND))
   799		return;
   

   144	if (trace.fraction == 1.0)
   145		friction = sv_friction.value*sv_edgefriction.value;
   ⋮
   151	newspeed = speed - host_frametime*control*friction;
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Checked by a second AI model, 2026-10-22.

   In the claim ledger

2. ^ abQuakeWorld's pmove.c checks the jump before friction: PlayerMove calls JumpButton, which clears onground, and then PM_Friction, whose ground friction runs only while onground is set, so a QuakeWorld hop on its first ground frame loses no speed to friction, where WinQuake's takes one frame of it (quake/hop-friction). Both still need the button released between jumps, and both add 270.Codeid-Software/Quake
   How we know

   889	if (pmove.cmd.buttons & BUTTON_JUMP)
   890		JumpButton ();
   891	else
   892		pmove.oldbuttons &= ~BUTTON_JUMP;
   ⋮
   894	PM_Friction ();
   

   674	if (onground == -1)
   675		return;		// in air, so no effect
   ⋮
   677	if ( pmove.oldbuttons & BUTTON_JUMP )
   678		return;		// don't pogo stick
   ⋮
   680	onground = -1;
   681	pmove.velocity[2] += 270;
   

   366	else if (onground != -1) // apply ground friction
   ⋮
   368		control = speed < movevars.stopspeed ? movevars.stopspeed : speed;
   369		drop += control*friction*frametime;
   

   1460	PlayerMove ();
   

   361	else if ( onground )
   ⋮
   363		SV_UserFriction ();
   364		SV_Accelerate ();
   

   1069	PR_ExecuteProgram (pr_global_struct->PlayerPreThink);
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Checked by a second AI model, 2026-10-22.

   In the claim ledger

3. ^ abQuake III checks the jump before friction: each step, PmoveSingle traces for ground before the move, PM_WalkMove calls PM_CheckJump before PM_Friction, and a jump clears the walking flag and hands the step to PM_AirMove, whose friction call skips ground friction without that flag. So a hop on the first step that starts on the ground loses no speed to friction, as in QuakeWorld (quake/qw-hop-friction), where WinQuake's takes one frame of it, 5.6% at 72 frames a second (quake/hop-friction). The hop needs the jump key released and pressed again in the air, as in both.Codeid-Software/Quake-III-Arena · id-Software/Quake · id-Software/Quake-Toolsrevised
   How we know

   1962	// set groundentity
   1963	PM_GroundTrace();
   

   1165	pml.groundPlane = qtrue;
   1166	pml.walking = qtrue;
   

   710	if ( PM_CheckJump () ) {
   711		// jumped away
   712		if ( pm->waterlevel > 1 ) {
   713			PM_WaterMove();
   714		} else {
   715			PM_AirMove();
   ⋮
   717		return;
   ⋮
   720	PM_Friction ();
   

   377	pml.walking = qfalse;
   

   610	PM_Friction();
   

   196	if ( pm->waterlevel <= 1 ) {
   197		if ( pml.walking && !(pml.groundTrace.surfaceFlags & SURF_SLICK) ) {
   ⋮
   200				control = speed < pm_stopspeed ? pm_stopspeed : speed;
   201				drop += control*pm_friction*pml.frametime;
   

   1916	if ( pm->cmd.upmove < 10 ) {
   1917		// not holding jump
   1918		pm->ps->pm_flags &= ~PMF_JUMP_HELD;
   

   889	if (pmove.cmd.buttons & BUTTON_JUMP)
   890		JumpButton ();
   891	else
   892		pmove.oldbuttons &= ~BUTTON_JUMP;
   ⋮
   894	PM_Friction ();
   

   674	if (onground == -1)
   675		return;		// in air, so no effect
   ⋮
   677	if ( pmove.oldbuttons & BUTTON_JUMP )
   678		return;		// don't pogo stick
   ⋮
   680	onground = -1;
   ⋮
   683	pmove.oldbuttons |= BUTTON_JUMP;	// don't jump again until released
   

   366	else if (onground != -1) // apply ground friction
   ⋮
   368		control = speed < movevars.stopspeed ? movevars.stopspeed : speed;
   369		drop += control*friction*frametime;
   

   972	if (self.button2)
   ⋮
   974		PlayerJump ();
   ⋮
   976	else
   977		self.flags = self.flags | FL_JUMPRELEASED;
   

   799		return;
   ⋮
   801	if ( !(self.flags & FL_JUMPRELEASED) )
   802		return;		// don't pogo stick
   

   361	else if ( onground )
   ⋮
   363		SV_UserFriction ();
   364		SV_Accelerate ();
   

   1069	PR_ExecuteProgram (pr_global_struct->PlayerPreThink);
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Revised after a check by a second AI model, 2026-10-22.

   In the claim ledger

4. ^Quake II checks the jump before friction: Pmove calls PM_CheckJump, which clears the ground entity, and then PM_Friction, whose ground friction needs a ground entity, so a hop on the first command that starts on the ground loses no speed to friction. QuakeWorld's PlayerMove has the same order: JumpButton clears onground before PM_Friction, whose ground friction needs it. Two conditions apply. The jump key must be released and pressed again (the jump claim). And when the position check first finds ground with the vertical speed below −200, it sets a landing timer of 18 units, or 25 below −400, that blocks the jump until it runs out; each command lowers it by its length in ms divided by 8, rounded down and at least 1, so 18 units last 144 ms at 8 or 16 ms commands and 180 ms at 10 ms (computed). By the atlas's reading the slide move clips the velocity along a floor it runs into, and the stepping move keeps that clipped vertical speed, so a landing step that reaches the floor would not set the timer; how often a hop's landing sets it has not been measured.Codeid-Software/Quake-2 · id-Software/Quakerevised
   How we know

   1333	else
   ⋮
   1335		PM_CheckJump ();
   ⋮
   1337		PM_Friction ();
   

   819	pm->groundentity = NULL;
   

   365	if ((pm->groundentity && pml.groundsurface && !(pml.groundsurface->flags & SURF_SLICK) ) || (pml.ladder) )
   

   714			if (! (pm->s.pm_flags & PMF_ON_GROUND) )
   715			{	// just hit the ground
   716				pm->s.pm_flags |= PMF_ON_GROUND;
   717				// don't do landing time if we were just going down a slope
   718				if (pml.velocity[2] < -200)
   ⋮
   720					pm->s.pm_flags |= PMF_TIME_LAND;
   721					// don't allow another jump for a little while
   722					if (pml.velocity[2] < -400)
   723						pm->s.pm_time = 25;	
   724					else
   725						pm->s.pm_time = 18;
   

   1302	// drop timing counter
   1303	if (pm->s.pm_time)
   ⋮
   1305		int		msec;
   ⋮
   1307		msec = pm->cmd.msec >> 3;
   1308		if (!msec)
   1309			msec = 1;
   1310		if ( msec >= pm->s.pm_time) 
   ⋮
   1312			pm->s.pm_flags &= ~(PMF_TIME_WATERJUMP | PMF_TIME_LAND | PMF_TIME_TELEPORT);
   1313			pm->s.pm_time = 0;
   ⋮
   1315		else
   1316			pm->s.pm_time -= msec;
   

   685	point[2] = pml.origin[2] - 0.25;
   ⋮
   693		trace = pm->trace (pml.origin, pm->mins, pm->maxs, point);
   

   219		for (i=0 ; i<numplanes ; i++)
   ⋮
   221			PM_ClipVelocity (pml.velocity, planes[i], pml.velocity, 1.01);
   

   332	//!! Special case
   333	// if we were walking along a plane, then we need to copy the Z over
   334	pml.velocity[2] = down_v[2];
   

   889	if (pmove.cmd.buttons & BUTTON_JUMP)
   890		JumpButton ();
   891	else
   892		pmove.oldbuttons &= ~BUTTON_JUMP;
   ⋮
   894	PM_Friction ();
   

   680	onground = -1;
   

   366	else if (onground != -1) // apply ground friction
   ⋮
   368		control = speed < movevars.stopspeed ? movevars.stopspeed : speed;
   369		drop += control*friction*frametime;
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Revised after a check by a second AI model, 2026-10-22.

   In the claim ledger