quakeforge/nq/source/sv_phys.c

/*
	sv_phys.c

	@description@

	Copyright (C) 1996-1997  Id Software, Inc.

	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License
	as published by the Free Software Foundation; either version 2
	of the License, or (at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

	See the GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

*/
static const char rcsid[] = 
	"$Id$";

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include "QF/console.h"
#include "QF/cvar.h"
#include "QF/sys.h"

#include "host.h"
#include "server.h"
#include "sv_progs.h"
#include "world.h"

/*
	pushmove objects do not obey gravity, and do not interact with each
	other or trigger fields, but block normal movement and push normal
	objects when they move.

	onground is set for toss objects when they come to a complete rest.  it
	is set for steping or walking objects

	doors, plats, etc are SOLID_BSP, and MOVETYPE_PUSH
	bonus items are SOLID_TRIGGER touch, and MOVETYPE_TOSS
	corpses are SOLID_NOT and MOVETYPE_TOSS
	crates are SOLID_BBOX and MOVETYPE_TOSS
	walking monsters are SOLID_SLIDEBOX and MOVETYPE_STEP
	flying/floating monsters are SOLID_SLIDEBOX and MOVETYPE_FLY

	solid_edge items only clip against bsp models.
*/

cvar_t     *sv_friction;
cvar_t     *sv_gravity;
cvar_t     *sv_stopspeed;
cvar_t     *sv_maxvelocity;
cvar_t     *sv_nostep;

#define	MOVE_EPSILON	0.01

void        SV_Physics_Toss (edict_t *ent);

void
SV_CheckAllEnts (void)
{
	edict_t    *check;
	int         e;

	// see if any solid entities are inside the final position
	check = NEXT_EDICT (&sv_pr_state, sv.edicts);
	for (e = 1; e < sv.num_edicts;
		 e++, check = NEXT_EDICT (&sv_pr_state, check)) {
		if (check->free)
			continue;
		if (SVfloat (check, movetype) == MOVETYPE_PUSH
			|| SVfloat (check, movetype) == MOVETYPE_NONE
			|| SVfloat (check, movetype) == MOVETYPE_NOCLIP)
			continue;

		if (SV_TestEntityPosition (check))
			Con_Printf ("entity in invalid position\n");
	}
}

void
SV_CheckVelocity (edict_t *ent)
{
	int         i;

	// bound velocity
	for (i = 0; i < 3; i++) {
		if (IS_NAN (SVvector (ent, velocity)[i])) {
			Con_Printf ("Got a NaN velocity on %s\n",
						PR_GetString (&sv_pr_state, SVstring (ent,
															  classname)));
			SVvector (ent, velocity)[i] = 0;
		}
		if (IS_NAN (SVvector (ent, origin)[i])) {
			Con_Printf ("Got a NaN origin on %s\n",
						PR_GetString (&sv_pr_state, SVstring (ent,
															  classname)));
			SVvector (ent, origin)[i] = 0;
		}
		if (SVvector (ent, velocity)[i] > sv_maxvelocity->value)
			SVvector (ent, velocity)[i] = sv_maxvelocity->value;
		else if (SVvector (ent, velocity)[i] < -sv_maxvelocity->value)
			SVvector (ent, velocity)[i] = -sv_maxvelocity->value;
	}
}

/*
  SV_RunThink

  Runs thinking code if time.  There is some play in the exact time the think
  function will be called, because it is called before any movement is done
  in a frame.  Not used for pushmove objects, because they must be exact.
  Returns false if the entity removed itself.
*/
qboolean
SV_RunThink (edict_t *ent)
{
	float       thinktime;

	thinktime = SVfloat (ent, nextthink);
	if (thinktime <= 0 || thinktime > sv.time + host_frametime)
		return true;

	if (thinktime < sv.time)
		thinktime = sv.time;			// don't let things stay in the past.
										// it is possible to start that way
										// by a trigger with a local time.
	SVfloat (ent, nextthink) = 0;
	*sv_globals.time = thinktime;
	*sv_globals.self = EDICT_TO_PROG (&sv_pr_state, ent);
	*sv_globals.other = EDICT_TO_PROG (&sv_pr_state, sv.edicts);
	PR_ExecuteProgram (&sv_pr_state, SVfunc (ent, think));
	return !ent->free;
}

/*
	SV_Impact

	Two entities have touched, so run their touch functions
*/
void
SV_Impact (edict_t *e1, edict_t *e2)
{
	int         old_self, old_other;

	old_self = *sv_globals.self;
	old_other = *sv_globals.other;

	*sv_globals.time = sv.time;
	if (SVfunc (e1, touch) && SVfloat (e1, solid) != SOLID_NOT) {
		*sv_globals.self = EDICT_TO_PROG (&sv_pr_state, e1);
		*sv_globals.other = EDICT_TO_PROG (&sv_pr_state, e2);
		PR_ExecuteProgram (&sv_pr_state, SVfunc (e1, touch));
	}

	if (SVfunc (e2, touch) && SVfloat (e2, solid) != SOLID_NOT) {
		*sv_globals.self = EDICT_TO_PROG (&sv_pr_state, e2);
		*sv_globals.other = EDICT_TO_PROG (&sv_pr_state, e1);
		PR_ExecuteProgram (&sv_pr_state, SVfunc (e2, touch));
	}

	*sv_globals.self = old_self;
	*sv_globals.other = old_other;
}

#define	STOP_EPSILON	0.1

/*
  ClipVelocity

  Slide off of the impacting object
  returns the blocked flags (1 = floor, 2 = step / wall)
*/
int
ClipVelocity (vec3_t in, vec3_t normal, vec3_t out, float overbounce)
{
	float       backoff, change;
	int         i, blocked;

	blocked = 0;
	if (normal[2] > 0)
		blocked |= 1;					// floor
	if (!normal[2])
		blocked |= 2;					// step

	backoff = DotProduct (in, normal) * overbounce;

	for (i = 0; i < 3; i++) {
		change = normal[i] * backoff;
		out[i] = in[i] - change;
		if (out[i] > -STOP_EPSILON && out[i] < STOP_EPSILON)
			out[i] = 0;
	}

	return blocked;
}

#define	MAX_CLIP_PLANES	5

/*
  SV_FlyMove

  The basic solid body movement clip that slides along multiple planes
  Returns the clipflags if the velocity was modified (hit something solid)
  1 = floor
  2 = wall / step
  4 = dead stop
  If steptrace is not NULL, the trace of any vertical wall hit will be stored
*/
int
SV_FlyMove (edict_t *ent, float time, trace_t *steptrace)
{
	float       d, time_left;
	int         blocked, bumpcount, numbumps, numplanes, i, j;
	trace_t     trace;
	vec3_t      dir, end;
	vec3_t      planes[MAX_CLIP_PLANES];
	vec3_t      primal_velocity, original_velocity, new_velocity;

	numbumps = 4;

	blocked = 0;
	VectorCopy (SVvector (ent, velocity), original_velocity);
	VectorCopy (SVvector (ent, velocity), primal_velocity);
	numplanes = 0;

	time_left = time;

	for (bumpcount = 0; bumpcount < numbumps; bumpcount++) {
		if (VectorIsZero (SVvector (ent, velocity)))
			break;

		VectorMA (SVvector (ent, origin), time_left, SVvector (ent, velocity),
				  end);

		trace = SV_Move (SVvector (ent, origin), SVvector (ent, mins),
						 SVvector (ent, maxs), end, false, ent);

		if (trace.allsolid) {			// entity is trapped in another solid
			VectorCopy (vec3_origin, SVvector (ent, velocity));
			return 3;
		}

		if (trace.fraction > 0) {		// actually covered some distance
			VectorCopy (trace.endpos, SVvector (ent, origin));
			VectorCopy (SVvector (ent, velocity), original_velocity);
			numplanes = 0;
		}

		if (trace.fraction == 1)
			break;						// moved the entire distance

		if (!trace.ent)
			Sys_Error ("SV_FlyMove: !trace.ent");

		if (trace.plane.normal[2] > 0.7) {
			blocked |= 1;				// floor
			if (SVfloat (trace.ent, solid) == SOLID_BSP) {
				SVfloat (ent, flags) = (int) SVfloat (ent, flags) |
					FL_ONGROUND;
				SVentity (ent, groundentity) = EDICT_TO_PROG (&sv_pr_state,
															  trace.ent);
			}
		}
		if (!trace.plane.normal[2]) {
			blocked |= 2;				// step
			if (steptrace)
				*steptrace = trace;		// save for player extrafriction
		}

		// run the impact function
		SV_Impact (ent, trace.ent);
		if (ent->free)
			break;						// removed by the impact function

		time_left -= time_left * trace.fraction;

		// cliped to another plane
		if (numplanes >= MAX_CLIP_PLANES) {	// this shouldn't really happen
			VectorCopy (vec3_origin, SVvector (ent, velocity));
			return 3;
		}

		VectorCopy (trace.plane.normal, planes[numplanes]);
		numplanes++;

		// modify original_velocity so it parallels all of the clip planes
		for (i = 0; i < numplanes; i++) {
			ClipVelocity (original_velocity, planes[i], new_velocity, 1);
			for (j = 0; j < numplanes; j++)
				if (j != i) {
					if (DotProduct (new_velocity, planes[j]) < 0)
						break;			// not ok
				}
			if (j == numplanes)
				break;
		}

		if (i != numplanes) {			// go along this plane
			VectorCopy (new_velocity, SVvector (ent, velocity));
		} else {						// go along the crease
			if (numplanes != 2) {
				VectorCopy (vec3_origin, SVvector (ent, velocity));
				return 7;
			}
			CrossProduct (planes[0], planes[1], dir);
			d = DotProduct (dir, SVvector (ent, velocity));
			VectorScale (dir, d, SVvector (ent, velocity));
		}

		// if original velocity is against the original velocity, stop dead
		// to avoid tiny occilations in sloping corners
		if (DotProduct (SVvector (ent, velocity), primal_velocity) <= 0) {
			VectorCopy (vec3_origin, SVvector (ent, velocity));
			return blocked;
		}
	}

	return blocked;
}

void
SV_AddGravity (edict_t *ent)
{
	float       ent_gravity;

	pr_type_t  *val;

	val = GetEdictFieldValue (&sv_pr_state, ent, "gravity");
	if (val && val->float_var)
		ent_gravity = val->float_var;
	else
		ent_gravity = 1.0;
	SVvector (ent, velocity)[2] -= ent_gravity * sv_gravity->value * host_frametime;
}

/* PUSHMOVE */

/*
	SV_PushEntity

	Does not change the entities velocity at all
*/
trace_t
SV_PushEntity (edict_t *ent, vec3_t push)
{
	trace_t     trace;
	vec3_t      end;

	VectorAdd (SVvector (ent, origin), push, end);

	if (SVfloat (ent, movetype) == MOVETYPE_FLYMISSILE)
		trace = SV_Move (SVvector (ent, origin), SVvector (ent, mins),
						 SVvector (ent, maxs), end, MOVE_MISSILE, ent);
	else if (SVfloat (ent, solid) == SOLID_TRIGGER || SVfloat (ent, solid) ==
			 SOLID_NOT)
		// only clip against bmodels
		trace = SV_Move (SVvector (ent, origin), SVvector (ent, mins),
						 SVvector (ent, maxs), end, MOVE_NOMONSTERS, ent);
	else
		trace = SV_Move (SVvector (ent, origin), SVvector (ent, mins),
						 SVvector (ent, maxs), end, MOVE_NORMAL, ent);

	VectorCopy (trace.endpos, SVvector (ent, origin));
	SV_LinkEdict (ent, true);

	if (trace.ent)
		SV_Impact (ent, trace.ent);

	return trace;
}

void
SV_PushMove (edict_t *pusher, float movetime)
{
	int         i, e, num_moved;
	edict_t    *check, *block;
	edict_t    *moved_edict[MAX_EDICTS];
	vec3_t      entorig, pushorig, mins, maxs, move;
	vec3_t      moved_from[MAX_EDICTS];

	if (!SVvector (pusher, velocity)[0] && !SVvector (pusher, velocity)[1]
		&& !SVvector (pusher, velocity)[2]) {
		SVfloat (pusher, ltime) += movetime;
		return;
	}

	for (i = 0; i < 3; i++) {
		move[i] = SVvector (pusher, velocity)[i] * movetime;
		mins[i] = SVvector (pusher, absmin)[i] + move[i];
		maxs[i] = SVvector (pusher, absmax)[i] + move[i];
	}

	VectorCopy (SVvector (pusher, origin), pushorig);

	// move the pusher to it's final position
	VectorAdd (SVvector (pusher, origin), move, SVvector (pusher, origin));
	SVfloat (pusher, ltime) += movetime;
	SV_LinkEdict (pusher, false);

	// see if any solid entities are inside the final position
	num_moved = 0;
	check = NEXT_EDICT (&sv_pr_state, sv.edicts);
	for (e = 1; e < sv.num_edicts;
		 e++, check = NEXT_EDICT (&sv_pr_state, check)) {
		if (check->free)
			continue;
		if (SVfloat (check, movetype) == MOVETYPE_PUSH
			|| SVfloat (check, movetype) == MOVETYPE_NONE
			|| SVfloat (check, movetype) == MOVETYPE_NOCLIP)
			continue;

		// if the entity is standing on the pusher, it will definately be moved
		if (!(((int) SVfloat (check, flags) & FL_ONGROUND)
			  && PROG_TO_EDICT (&sv_pr_state,
								SVentity (check, groundentity)) == pusher)) {
			if (SVvector (check, absmin)[0] >= maxs[0]
				|| SVvector (check, absmin)[1] >= maxs[1]
				|| SVvector (check, absmin)[2] >= maxs[2]
				|| SVvector (check, absmax)[0] <= mins[0]
				|| SVvector (check, absmax)[1] <= mins[1]
				|| SVvector (check, absmax)[2] <= mins[2])
				continue;

			// see if the ent's bbox is inside the pusher's final position
			if (!SV_TestEntityPosition (check))
				continue;
		}
		// remove the onground flag for non-players
		if (SVfloat (check, movetype) != MOVETYPE_WALK)
			SVfloat (check, flags) = (int) SVfloat (check, flags) &
				~FL_ONGROUND;

		VectorCopy (SVvector (check, origin), entorig);
		VectorCopy (SVvector (check, origin), moved_from[num_moved]);
		moved_edict[num_moved] = check;
		num_moved++;

		// try moving the contacted entity 
		SVfloat (pusher, solid) = SOLID_NOT;
		SV_PushEntity (check, move);
		SVfloat (pusher, solid) = SOLID_BSP;

		// if it is still inside the pusher, block
		block = SV_TestEntityPosition (check);
		if (block) {					// fail the move
			if (SVvector (check, mins)[0] == SVvector (check, maxs)[0])
				continue;
			if (SVfloat (check, solid) == SOLID_NOT || SVfloat (check, solid)
				== SOLID_TRIGGER) {	// corpse
				SVvector (check, mins)[0] = SVvector (check, mins)[1] = 0;
				VectorCopy (SVvector (check, mins), SVvector (check, maxs));
				continue;
			}

			VectorCopy (entorig, SVvector (check, origin));
			SV_LinkEdict (check, true);

			VectorCopy (pushorig, SVvector (pusher, origin));
			SV_LinkEdict (pusher, false);
			SVfloat (pusher, ltime) -= movetime;

			// if the pusher has a "blocked" function, call it
			// otherwise, just stay in place until the obstacle is gone
			if (SVfunc (pusher, blocked)) {
				*sv_globals.self =
					EDICT_TO_PROG (&sv_pr_state, pusher);
				*sv_globals.other =
					EDICT_TO_PROG (&sv_pr_state, check);
				PR_ExecuteProgram (&sv_pr_state, SVfunc (pusher, blocked));
			}
			// move back any entities we already moved
			for (i = 0; i < num_moved; i++) {
				VectorCopy (moved_from[i], SVvector (moved_edict[i], origin));
				SV_LinkEdict (moved_edict[i], false);
			}
			return;
		}
	}


}

void
SV_Physics_Pusher (edict_t *ent)
{
	float       movetime, oldltime, thinktime;

	oldltime = SVfloat (ent, ltime);

	thinktime = SVfloat (ent, nextthink);
	if (thinktime < SVfloat (ent, ltime) + host_frametime) {
		movetime = thinktime - SVfloat (ent, ltime);
		if (movetime < 0)
			movetime = 0;
	} else
		movetime = host_frametime;

	if (movetime) {
		SV_PushMove (ent, movetime);	// advances SVfloat (ent, ltime) if not
										// blocked
	}

	if (thinktime > oldltime && thinktime <= SVfloat (ent, ltime)) {
		SVfloat (ent, nextthink) = 0;
		*sv_globals.time = sv.time;
		*sv_globals.self = EDICT_TO_PROG (&sv_pr_state, ent);
		*sv_globals.other = EDICT_TO_PROG (&sv_pr_state, sv.edicts);
		PR_ExecuteProgram (&sv_pr_state, SVfunc (ent, think));
		if (ent->free)
			return;
	}

}

// CLIENT MOVEMENT ============================================================

/*
  SV_CheckStuck

  This is a big hack to try and fix the rare case of getting stuck in the world
  clipping hull.
*/
void
SV_CheckStuck (edict_t *ent)
{
	int         i, j, z;
	vec3_t      org;

	if (!SV_TestEntityPosition (ent)) {
		VectorCopy (SVvector (ent, origin), SVvector (ent, oldorigin));
		return;
	}

	VectorCopy (SVvector (ent, origin), org);
	VectorCopy (SVvector (ent, oldorigin), SVvector (ent, origin));
	if (!SV_TestEntityPosition (ent)) {
		Con_DPrintf ("Unstuck.\n");
		SV_LinkEdict (ent, true);
		return;
	}

	for (z = 0; z < 18; z++)
		for (i = -1; i <= 1; i++)
			for (j = -1; j <= 1; j++) {
				SVvector (ent, origin)[0] = org[0] + i;
				SVvector (ent, origin)[1] = org[1] + j;
				SVvector (ent, origin)[2] = org[2] + z;
				if (!SV_TestEntityPosition (ent)) {
					Con_DPrintf ("Unstuck.\n");
					SV_LinkEdict (ent, true);
					return;
				}
			}

	VectorCopy (org, SVvector (ent, origin));
	Con_DPrintf ("player is stuck.\n");
}

qboolean
SV_CheckWater (edict_t *ent)
{
	int         cont;
	vec3_t      point;

	point[0] = SVvector (ent, origin)[0];
	point[1] = SVvector (ent, origin)[1];
	point[2] = SVvector (ent, origin)[2] + SVvector (ent, mins)[2] + 1;

	SVfloat (ent, waterlevel) = 0;
	SVfloat (ent, watertype) = CONTENTS_EMPTY;
	cont = SV_PointContents (point);
	if (cont <= CONTENTS_WATER) {
		SVfloat (ent, watertype) = cont;
		SVfloat (ent, waterlevel) = 1;
		point[2] = SVvector (ent, origin)[2] + (SVvector (ent, mins)[2] +
												SVvector (ent, maxs)[2]) * 0.5;
		cont = SV_PointContents (point);
		if (cont <= CONTENTS_WATER) {
			SVfloat (ent, waterlevel) = 2;
			point[2] = SVvector (ent, origin)[2] + SVvector (ent, view_ofs)[2];
			cont = SV_PointContents (point);
			if (cont <= CONTENTS_WATER)
				SVfloat (ent, waterlevel) = 3;
		}
	}

	return SVfloat (ent, waterlevel) > 1;
}

void
SV_WallFriction (edict_t *ent, trace_t *trace)
{
	float       d, i;
	vec3_t      forward, right, up, into, side;

	AngleVectors (SVvector (ent, v_angle), forward, right, up);
	d = DotProduct (trace->plane.normal, forward);

	d += 0.5;
	if (d >= 0)
		return;

	// cut the tangential velocity
	i = DotProduct (trace->plane.normal, SVvector (ent, velocity));
	VectorScale (trace->plane.normal, i, into);
	VectorSubtract (SVvector (ent, velocity), into, side);

	SVvector (ent, velocity)[0] = side[0] * (1 + d);
	SVvector (ent, velocity)[1] = side[1] * (1 + d);
}

/*
  SV_TryUnstick

  Player has come to a dead stop, possibly due to the problem with limited
  float precision at some angle joins in the BSP hull.

  Try fixing by pushing one pixel in each direction.

  This is a hack, but in the interest of good gameplay...
*/
int
SV_TryUnstick (edict_t *ent, vec3_t oldvel)
{
	int         i, clip;
	vec3_t      dir, oldorg;
	trace_t     steptrace;

	VectorCopy (SVvector (ent, origin), oldorg);
	VectorCopy (vec3_origin, dir);

	for (i = 0; i < 8; i++) {
		// try pushing a little in an axial direction
		switch (i) {
		case 0:
			dir[0] = 2;
			dir[1] = 0;
			break;
		case 1:
			dir[0] = 0;
			dir[1] = 2;
			break;
		case 2:
			dir[0] = -2;
			dir[1] = 0;
			break;
		case 3:
			dir[0] = 0;
			dir[1] = -2;
			break;
		case 4:
			dir[0] = 2;
			dir[1] = 2;
			break;
		case 5:
			dir[0] = -2;
			dir[1] = 2;
			break;
		case 6:
			dir[0] = 2;
			dir[1] = -2;
			break;
		case 7:
			dir[0] = -2;
			dir[1] = -2;
			break;
		}

		SV_PushEntity (ent, dir);

		// retry the original move
		SVvector (ent, velocity)[0] = oldvel[0];
		SVvector (ent, velocity)[1] = oldvel[1];
		SVvector (ent, velocity)[2] = 0;
		clip = SV_FlyMove (ent, 0.1, &steptrace);

		if (fabs (oldorg[1] - SVvector (ent, origin)[1]) > 4
			|| fabs (oldorg[0] - SVvector (ent, origin)[0]) > 4) {
//			Con_DPrintf ("unstuck!\n");
			return clip;
		}
		// go back to the original pos and try again
		VectorCopy (oldorg, SVvector (ent, origin));
	}

	VectorCopy (vec3_origin, SVvector (ent, velocity));
	return 7;							// still not moving
}

#define	STEPSIZE	18

/*
  SV_WalkMove

  Only used by players
*/
void
SV_WalkMove (edict_t *ent)
{
	int         clip, oldonground;
	vec3_t      upmove, downmove, nosteporg, nostepvel, oldorg, oldvel;
	trace_t     steptrace, downtrace;

	// do a regular slide move unless it looks like you ran into a step
	oldonground = (int) SVfloat (ent, flags) & FL_ONGROUND;
	SVfloat (ent, flags) = (int) SVfloat (ent, flags) & ~FL_ONGROUND;

	VectorCopy (SVvector (ent, origin), oldorg);
	VectorCopy (SVvector (ent, velocity), oldvel);

	clip = SV_FlyMove (ent, host_frametime, &steptrace);

	if (!(clip & 2))
		return;							// move didn't block on a step

	if (!oldonground && SVfloat (ent, waterlevel) == 0)
		return;							// don't stair up while jumping

	if (SVfloat (ent, movetype) != MOVETYPE_WALK)
		return;							// gibbed by a trigger

	if (sv_nostep->int_val)
		return;

	if ((int) SVfloat (sv_player, flags) & FL_WATERJUMP)
		return;

	VectorCopy (SVvector (ent, origin), nosteporg);
	VectorCopy (SVvector (ent, velocity), nostepvel);

	// try moving up and forward to go up a step
	VectorCopy (oldorg, SVvector (ent, origin));	// back to start pos
	VectorCopy (vec3_origin, upmove);
	VectorCopy (vec3_origin, downmove);
	upmove[2] = STEPSIZE;
	downmove[2] = -STEPSIZE + oldvel[2] * host_frametime;

	// move up
	SV_PushEntity (ent, upmove);		// FIXME: don't link?

	// move forward
	SVvector (ent, velocity)[0] = oldvel[0];
	SVvector (ent, velocity)[1] = oldvel[1];
	SVvector (ent, velocity)[2] = 0;
	clip = SV_FlyMove (ent, host_frametime, &steptrace);

	// check for stuckness, possibly due to the limited precision of floats
	// in the clipping hulls
	if (clip) {
		if (fabs (oldorg[1] - SVvector (ent, origin)[1]) < 0.03125
			&& fabs (oldorg[0] - SVvector (ent, origin)[0]) < 0.03125) {
			// stepping up didn't make any progress
			clip = SV_TryUnstick (ent, oldvel);
		}
	}
	// extra friction based on view angle
	if (clip & 2)
		SV_WallFriction (ent, &steptrace);

	// move down
	downtrace = SV_PushEntity (ent, downmove);	// FIXME: don't link?

	if (downtrace.plane.normal[2] > 0.7) {
		if (SVfloat (ent, solid) == SOLID_BSP) {
			SVfloat (ent, flags) = (int) SVfloat (ent, flags) | FL_ONGROUND;
			SVfloat (ent, groundentity) = EDICT_TO_PROG (&sv_pr_state,
														 downtrace.ent);
		}
	} else {
		// if the push down didn't end up on good ground, use the move without
		// the step up.  This happens near wall / slope combinations, and can
		// cause the player to hop up higher on a slope too steep to climb  
		VectorCopy (nosteporg, SVvector (ent, origin));
		VectorCopy (nostepvel, SVvector (ent, velocity));
	}
}

/*
  SV_Physics_Client

  Player character actions
*/
void
SV_Physics_Client (edict_t *ent, int num)
{
	if (!svs.clients[num - 1].active)
		return;							// unconnected slot

	// call standard client pre-think
	*sv_globals.time = sv.time;
	*sv_globals.self = EDICT_TO_PROG (&sv_pr_state, ent);
	PR_ExecuteProgram (&sv_pr_state,
					   sv_funcs.PlayerPreThink);

	// do a move
	SV_CheckVelocity (ent);

	// decide which move function to call
	switch ((int) SVfloat (ent, movetype)) {
	case MOVETYPE_NONE:
		if (!SV_RunThink (ent))
			return;
		break;

	case MOVETYPE_WALK:
		if (!SV_RunThink (ent))
			return;
		if (!SV_CheckWater (ent) && !((int) SVfloat (ent, flags) &
									  FL_WATERJUMP))
			SV_AddGravity (ent);
		SV_CheckStuck (ent);
		SV_WalkMove (ent);
		break;

	case MOVETYPE_TOSS:
	case MOVETYPE_BOUNCE:
		SV_Physics_Toss (ent);
		break;

	case MOVETYPE_FLY:
		if (!SV_RunThink (ent))
			return;
		SV_FlyMove (ent, host_frametime, NULL);
		break;

	case MOVETYPE_NOCLIP:
		if (!SV_RunThink (ent))
			return;
		VectorMA (SVvector (ent, origin), host_frametime, SVvector (ent, velocity),
				  SVvector (ent, origin));
		break;

	default:
		Sys_Error ("SV_Physics_client: bad movetype %i",
				   (int) SVfloat (ent, movetype));
	}

	// call standard player post-think
	SV_LinkEdict (ent, true);

	*sv_globals.time = sv.time;
	*sv_globals.self = EDICT_TO_PROG (&sv_pr_state, ent);
	PR_ExecuteProgram (&sv_pr_state,
					   sv_funcs.PlayerPostThink);
}

/*
	SV_Physics_None

	Non moving objects can only think
*/
void
SV_Physics_None (edict_t *ent)
{
	// regular thinking
	SV_RunThink (ent);
	SV_LinkEdict (ent, false);
}

/*
	SV_Physics_Noclip

	A moving object that doesn't obey physics
*/
void
SV_Physics_Noclip (edict_t *ent)
{
	// regular thinking
	if (!SV_RunThink (ent))
		return;

	VectorMA (SVvector (ent, angles), host_frametime,
			  SVvector (ent, avelocity), SVvector (ent, angles));
	VectorMA (SVvector (ent, origin), host_frametime, SVvector (ent, velocity),
			  SVvector (ent, origin));

	SV_LinkEdict (ent, false);
}

/* TOSS / BOUNCE */

void
SV_CheckWaterTransition (edict_t *ent)
{
	int         cont;

	cont = SV_PointContents (SVvector (ent, origin));

	if (!SVfloat (ent, watertype)) {			// just spawned here
		SVfloat (ent, watertype) = cont;
		SVfloat (ent, waterlevel) = 1;
		return;
	}

	if (cont <= CONTENTS_WATER) {
		if (SVfloat (ent, watertype) == CONTENTS_EMPTY) {
			// just crossed into water
			SV_StartSound (ent, 0, "misc/h2ohit1.wav", 255, 1);
		}
		SVfloat (ent, watertype) = cont;
		SVfloat (ent, waterlevel) = 1;
	} else {
		if (SVfloat (ent, watertype) != CONTENTS_EMPTY) {
			// just crossed into water
			SV_StartSound (ent, 0, "misc/h2ohit1.wav", 255, 1);
		}
		SVfloat (ent, watertype) = CONTENTS_EMPTY;
		SVfloat (ent, waterlevel) = cont;
	}
}

/*
	SV_Physics_Toss

	Toss, bounce, and fly movement.  When onground, do nothing.
*/
void
SV_Physics_Toss (edict_t *ent)
{
	float       backoff;
	trace_t     trace;
	vec3_t      move;

	// regular thinking
	if (!SV_RunThink (ent))
		return;

	// if onground, return without moving
	if (((int) SVfloat (ent, flags) & FL_ONGROUND))
		return;

	SV_CheckVelocity (ent);

	// add gravity
	if (SVfloat (ent, movetype) != MOVETYPE_FLY
		&& SVfloat (ent, movetype) != MOVETYPE_FLYMISSILE)
		SV_AddGravity (ent);

	// move angles
	VectorMA (SVvector (ent, angles), host_frametime,
			  SVvector (ent, avelocity), SVvector (ent, angles));

	// move origin
	VectorScale (SVvector (ent, velocity), host_frametime, move);
	trace = SV_PushEntity (ent, move);
	if (trace.fraction == 1)
		return;
	if (ent->free)
		return;

	if (SVfloat (ent, movetype) == MOVETYPE_BOUNCE)
		backoff = 1.5;
	else
		backoff = 1;

	ClipVelocity (SVvector (ent, velocity), trace.plane.normal,
				  SVvector (ent, velocity), backoff);

	// stop if on ground
	if (trace.plane.normal[2] > 0.7) {
		if (SVvector (ent, velocity)[2] < 60 || SVfloat (ent, movetype) !=
			MOVETYPE_BOUNCE) {
			SVfloat (ent, flags) = (int) SVfloat (ent, flags) | FL_ONGROUND;
			SVentity (ent, groundentity) = EDICT_TO_PROG (&sv_pr_state,
														  trace.ent);
			VectorCopy (vec3_origin, SVvector (ent, velocity));
			VectorCopy (vec3_origin, SVvector (ent, avelocity));
		}
	}
	// check for in water
	SV_CheckWaterTransition (ent);
}

/* STEPPING MOVEMENT */

/*
	SV_Physics_Step

	Monsters freefall when they don't have a ground entity, otherwise
	all movement is done with discrete steps.

	This is also used for objects that have become still on the ground, but
	will fall if the floor is pulled out from under them.
*/
void
SV_Physics_Step (edict_t *ent)
{
	qboolean    hitsound;

	// freefall if not on ground
	if (!((int) SVfloat (ent, flags) & (FL_ONGROUND | FL_FLY | FL_SWIM))) {
		if (SVvector (ent, velocity)[2] < sv_gravity->value * -0.1)
			hitsound = true;
		else
			hitsound = false;

		SV_AddGravity (ent);
		SV_CheckVelocity (ent);
		SV_FlyMove (ent, host_frametime, NULL);
		SV_LinkEdict (ent, true);

		if ((int) SVfloat (ent, flags) & FL_ONGROUND)	// just hit ground
		{
			if (hitsound)
				SV_StartSound (ent, 0, "demon/dland2.wav", 255, 1);
		}
	}
	// regular thinking
	SV_RunThink (ent);

	SV_CheckWaterTransition (ent);
}

void
SV_Physics (void)
{
	int         i;
	edict_t    *ent;

	// let the progs know that a new frame has started
	*sv_globals.self =
		EDICT_TO_PROG (&sv_pr_state, sv.edicts);
	*sv_globals.other =
		EDICT_TO_PROG (&sv_pr_state, sv.edicts);
	*sv_globals.time = sv.time;
	PR_ExecuteProgram (&sv_pr_state, sv_funcs.StartFrame);

//	SV_CheckAllEnts ();

	// treat each object in turn
	ent = sv.edicts;
	for (i = 0; i < sv.num_edicts; i++, ent = NEXT_EDICT (&sv_pr_state, ent)) {
		if (ent->free)
			continue;

		if (*sv_globals.force_retouch) {
			SV_LinkEdict (ent, true);	// force retouch even for stationary
		}

		if (i > 0 && i <= svs.maxclients)
			SV_Physics_Client (ent, i);
		else if (SVfloat (ent, movetype) == MOVETYPE_PUSH)
			SV_Physics_Pusher (ent);
		else if (SVfloat (ent, movetype) == MOVETYPE_NONE)
			SV_Physics_None (ent);
		else if (SVfloat (ent, movetype) == MOVETYPE_NOCLIP)
			SV_Physics_Noclip (ent);
		else if (SVfloat (ent, movetype) == MOVETYPE_STEP)
			SV_Physics_Step (ent);
		else if (SVfloat (ent, movetype) == MOVETYPE_TOSS
				 || SVfloat (ent, movetype) == MOVETYPE_BOUNCE
				 || SVfloat (ent, movetype) == MOVETYPE_FLY
				 || SVfloat (ent, movetype) == MOVETYPE_FLYMISSILE)
				SV_Physics_Toss (ent);
		else
			Sys_Error ("SV_Physics: bad movetype %i",
					   (int) SVfloat (ent, movetype));
	}

	if (*sv_globals.force_retouch)
		(*sv_globals.force_retouch)--;

	sv.time += host_frametime;
}