// g_phys.c

#include "g_local.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.

*/


/*
============
SV_TestEntityPosition

============
*/
edict_t *SV_TestEntityPosition (edict_t *ent)
{
        trace_t trace;
        int             mask;

        if (ent->clipmask)
                mask = ent->clipmask;
        else
                mask = MASK_SOLID;
        trace = do_trace (ent->s.origin, ent->mins, ent->maxs, ent->s.origin, ent, mask);
        
        if (trace.startsolid)
                return g_edicts;
                
        return NULL;
}


/*
================
SV_CheckVelocity
================
*/
void SV_CheckVelocity (edict_t *ent)
{
        int             i;

//
// bound velocity
//
        for (i=0 ; i<3 ; i++)
        {
                if (ent->velocity[i] > sv_maxvelocity->value)
                        ent->velocity[i] = sv_maxvelocity->value;
                else if (ent->velocity[i] < -sv_maxvelocity->value)
                        ent->velocity[i] = -sv_maxvelocity->value;
        }
}

/*
=============
SV_RunThink

Runs thinking code for this frame if necessary
=============
*/
qboolean SV_RunThink (edict_t *ent)
{
        float   thinktime;

        thinktime = ent->nextthink;
        if (thinktime <= 0)
                return true;
        if (thinktime > level.time+0.001)
                return true;
        
        ent->nextthink = 0;
        if (!ent->think)
                gi.error ("NULL ent->think");
        ent->think (ent);

        return false;
}

/*
==================
SV_Impact

Two entities have touched, so run their touch functions
==================
*/
void SV_Impact (edict_t *e1, trace_t *trace)
{
        edict_t         *e2;
//      cplane_t        backplane;

        e2 = trace->ent;

        if (e1->touch && e1->solid != SOLID_NOT)
                e1->touch (e1, e2, &trace->plane, trace->surface);
        
        if (e2->touch && e2->solid != SOLID_NOT)
                e2->touch (e2, e1, NULL, NULL);
}


/*
==================
ClipVelocity

Slide off of the impacting object
returns the blocked flags (1 = floor, 2 = step / wall)
==================
*/
#define STOP_EPSILON    0.1

int ClipVelocity (vec3_t in, vec3_t normal, vec3_t out, float overbounce)
{
        float   backoff;
        float   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;
}


/*
============
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
============
*/
#define MAX_CLIP_PLANES 5
int SV_FlyMove (edict_t *ent, float time, int mask)
{
        edict_t         *hit;
        int                     bumpcount, numbumps;
        vec3_t          dir;
        float           d;
        int                     numplanes;
        vec3_t          planes[MAX_CLIP_PLANES];
        vec3_t          primal_velocity, original_velocity, new_velocity;
        int                     i, j;
        trace_t         trace;
        vec3_t          end;
        float           time_left;
        int                     blocked;
        
        numbumps = 4;
        
        blocked = 0;
        VectorCopy (ent->velocity, original_velocity);
        VectorCopy (ent->velocity, primal_velocity);
        numplanes = 0;
        
        time_left = time;

        ent->groundentity = NULL;
        for (bumpcount=0 ; bumpcount<numbumps ; bumpcount++)
        {
                for (i=0 ; i<3 ; i++)
                        end[i] = ent->s.origin[i] + time_left * ent->velocity[i];

                trace = do_trace (ent->s.origin, ent->mins, ent->maxs, end, ent, mask);

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

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

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

                hit = trace.ent;

                if (trace.plane.normal[2] > 0.7)
                {
                        blocked |= 1;           // floor
                        if ( hit->solid == SOLID_BSP)
                        {
                                ent->groundentity = hit;
                                ent->groundentity_linkcount = hit->linkcount;
                        }
                }
                if (!trace.plane.normal[2])
                {
                        blocked |= 2;           // step
                }

//
// run the impact function
//
                SV_Impact (ent, &trace);
                if (!ent->inuse)
                        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, 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++)
// The following VectorCompare was added in 3.20, adding it.  -FB
                                if ((j != i) && !VectorCompare (planes[i], planes[j]))
                                {
                                        if (DotProduct (new_velocity, planes[j]) < 0)
                                                break;  // not ok
                                }
                        if (j == numplanes)
                                break;
                }
                
                if (i != numplanes)
                {       // go along this plane
                        VectorCopy (new_velocity, ent->velocity);
                }
                else
                {       // go along the crease
                        if (numplanes != 2)
                        {
//                              gi.dprintf ("clip velocity, numplanes == %i\n",numplanes);
                                VectorCopy (vec3_origin, ent->velocity);
                                return 7;
                        }
                        CrossProduct (planes[0], planes[1], dir);
                        d = DotProduct (dir, ent->velocity);
                        VectorScale (dir, d, ent->velocity);
                }

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

        return blocked;
}


/*
============
SV_AddGravity

============
*/
void SV_AddGravity (edict_t *ent)
{
        ent->velocity[2] -= ent->gravity * sv_gravity->value * 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  start;
        vec3_t  end;
        int             mask;

        VectorCopy (ent->s.origin, start);
        VectorAdd (start, push, end);

retry:
        if (ent->clipmask)
                mask = ent->clipmask;
        else
                mask = MASK_SOLID;

        trace = do_trace (start, ent->mins, ent->maxs, end, ent, mask);
        
        VectorCopy (trace.endpos, ent->s.origin);
        gi.linkentity (ent);

        if (trace.fraction != 1.0)
        {
                SV_Impact (ent, &trace);

                // if the pushed entity went away and the pusher is still there
                if (!trace.ent->inuse && ent->inuse)
                {
                        // move the pusher back and try again
                        VectorCopy (start, ent->s.origin);
                        gi.linkentity (ent);
                        goto retry;
                }
        }

        if (ent->inuse)
                G_TouchTriggers (ent);

        return trace;
}                                       


typedef struct
{
        edict_t *ent;
        vec3_t  origin;
        vec3_t  angles;
        float   deltayaw;
} pushed_t;
pushed_t        pushed[MAX_EDICTS], *pushed_p;

edict_t *obstacle;

/*
============
SV_Push

Objects need to be moved back on a failed push,
otherwise riders would continue to slide.
============
*/
qboolean SV_Push (edict_t *pusher, vec3_t move, vec3_t amove)
{
        int                     i, e;
        edict_t         *check, *block;
        vec3_t          mins, maxs;
        pushed_t        *p;
        vec3_t          org, org2, move2, forward, right, up;

        // clamp the move to 1/8 units, so the position will
        // be accurate for client side prediction
        for (i=0 ; i<3 ; i++)
        {
                float   temp;
                temp = move[i]*8.0;
                if (temp > 0.0)
                        temp += 0.5;
                else
                        temp -= 0.5;
                move[i] = 0.125 * (int)temp;
        }

        // find the bounding box
        for (i=0 ; i<3 ; i++)
        {
                mins[i] = pusher->absmin[i] + move[i];
                maxs[i] = pusher->absmax[i] + move[i];
        }

// we need this for pushing things later
        VectorSubtract (vec3_origin, amove, org);
        AngleVectors (org, forward, right, up);

// save the pusher's original position
        pushed_p->ent = pusher;
        VectorCopy (pusher->s.origin, pushed_p->origin);
        VectorCopy (pusher->s.angles, pushed_p->angles);
        if (pusher->client)
                pushed_p->deltayaw = pusher->client->ps.pmove.delta_angles[YAW];
        pushed_p++;

// move the pusher to it's final position
        VectorAdd (pusher->s.origin, move, pusher->s.origin);
        VectorAdd (pusher->s.angles, amove, pusher->s.angles);
        gi.linkentity (pusher);

// see if any solid entities are inside the final position
        check = g_edicts+1;
        for (e = 1; e < globals.num_edicts; e++, check++)
        {
                if (!check->inuse)
                        continue;
                if (check->movetype == MOVETYPE_PUSH
                || check->movetype == MOVETYPE_STOP
                || check->movetype == MOVETYPE_NONE
                || check->movetype == MOVETYPE_NOCLIP)
                        continue;

                if (!check->area.prev)
                        continue;               // not linked in anywhere

        // if the entity is standing on the pusher, it will definitely be moved
                if (check->groundentity != pusher)
                {
                        // see if the ent needs to be tested
                        if ( check->absmin[0] >= maxs[0]
                        || check->absmin[1] >= maxs[1]
                        || check->absmin[2] >= maxs[2]
                        || check->absmax[0] <= mins[0]
                        || check->absmax[1] <= mins[1]
                        || check->absmax[2] <= mins[2] )
                                continue;

                        // see if the ent's bbox is inside the pusher's final position
                        if (!SV_TestEntityPosition (check))
                                continue;
                }

                if ((pusher->movetype == MOVETYPE_PUSH) || (check->groundentity == pusher))
                {
                        // move this entity
                        pushed_p->ent = check;
                        VectorCopy (check->s.origin, pushed_p->origin);
                        VectorCopy (check->s.angles, pushed_p->angles);
                        pushed_p++;

                        // try moving the contacted entity 
                        VectorAdd (check->s.origin, move, check->s.origin);
                        if (check->client)
                        {       // FIXME: doesn't rotate monsters?
                                check->client->ps.pmove.delta_angles[YAW] += amove[YAW];
                        }

                        // figure movement due to the pusher's amove
                        VectorSubtract (check->s.origin, pusher->s.origin, org);
                        org2[0] = DotProduct (org, forward);
                        org2[1] = -DotProduct (org, right);
                        org2[2] = DotProduct (org, up);
                        VectorSubtract (org2, org, move2);
                        VectorAdd (check->s.origin, move2, check->s.origin);

                        // may have pushed them off an edge
                        if (check->groundentity != pusher)
                                check->groundentity = NULL;

                        block = SV_TestEntityPosition (check);
                        if (!block)
                        {       // pushed ok
                                gi.linkentity (check);
                                // impact?
                                continue;
                        }

                        // if it is ok to leave in the old position, do it
                        // this is only relevent for riding entities, not pushed
                        // FIXME: this doesn't acount for rotation
                        VectorSubtract (check->s.origin, move, check->s.origin);
                        block = SV_TestEntityPosition (check);
                        if (!block)
                        {
                                pushed_p--;
                                continue;
                        }
                }
                
                // save off the obstacle so we can call the block function
                obstacle = check;

                // move back any entities we already moved
                // go backwards, so if the same entity was pushed
                // twice, it goes back to the original position
                for (p=pushed_p-1 ; p>=pushed ; p--)
                {
                        VectorCopy (p->origin, p->ent->s.origin);
                        VectorCopy (p->angles, p->ent->s.angles);
                        if (p->ent->client)
                        {
                                p->ent->client->ps.pmove.delta_angles[YAW] = p->deltayaw;
                        }
                        gi.linkentity (p->ent);
                }
                return false;
        }

//FIXME: is there a better way to handle this?
        // see if anything we moved has touched a trigger
        for (p=pushed_p-1 ; p>=pushed ; p--)
                G_TouchTriggers (p->ent);

        return true;
}

/*
================
SV_Physics_Pusher

Bmodel objects don't interact with each other, but
push all box objects
================
*/
void SV_Physics_Pusher (edict_t *ent)
{
        vec3_t          move, amove;
        edict_t         *part, *mv;

        // if not a team captain, so movement will be handled elsewhere
        if ( ent->flags & FL_TEAMSLAVE)
                return;

        // make sure all team slaves can move before commiting
        // any moves or calling any think functions
        // if the move is blocked, all moved objects will be backed out
//retry:
        pushed_p = pushed;
        for (part = ent ; part ; part=part->teamchain)
        {
                if (part->velocity[0] || part->velocity[1] || part->velocity[2] ||
                        part->avelocity[0] || part->avelocity[1] || part->avelocity[2]
                        )
                {       // object is moving
                        VectorScale (part->velocity, FRAMETIME, move);
                        VectorScale (part->avelocity, FRAMETIME, amove);

                        if (!SV_Push (part, move, amove))
                                break;  // move was blocked
                }
        }
        if (pushed_p > &pushed[MAX_EDICTS])
                gi.error (ERR_FATAL, "pushed_p > &pushed[MAX_EDICTS], memory corrupted");

        if (part)
        {
                // the move failed, bump all nextthink times and back out moves
                for (mv = ent ; mv ; mv=mv->teamchain)
                {
                        if (mv->nextthink > 0)
                                mv->nextthink += FRAMETIME;
                }

                // if the pusher has a "blocked" function, call it
                // otherwise, just stay in place until the obstacle is gone
                if (part->blocked)
                        part->blocked (part, obstacle);
#if 0
                // if the pushed entity went away and the pusher is still there
                if (!obstacle->inuse && part->inuse)
                        goto retry;
#endif
        }
        else
        {
                // the move succeeded, so call all think functions
                for (part = ent ; part ; part=part->teamchain)
                {
                        SV_RunThink (part);
                }
        }
}

//==================================================================

/*
=============
SV_Physics_None

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

/*
=============
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 (ent->s.angles, FRAMETIME, ent->avelocity, ent->s.angles);
        VectorMA (ent->s.origin, FRAMETIME, ent->velocity, ent->s.origin);

        gi.linkentity (ent);
}

/*
==============================================================================

TOSS / BOUNCE

==============================================================================
*/


/* 
 ============= 
 SV_Physics_Bounce 
 bounce movement. When onground, do nothing. 
 This is a copy of SV_Physics_Toss() modified to provide more realistic 
 bounce physics
 ============= 
*/ 


void SV_Physics_Bounce (edict_t *ent);


void SV_Physics_Bounce (edict_t *ent) 
{ 
        trace_t trace; 
        vec3_t move, planeVel, normalVel, temp; 
        edict_t *slave; 
        qboolean wasinwater; 
        qboolean isinwater; 
        vec3_t old_origin; 
        float movetime; 

// regular thinking 
        SV_RunThink (ent); 
        if (!ent->inuse) 
                return; 

// if not a team captain, so movement will be handled elsewhere 
        if ( ent->flags & FL_TEAMSLAVE) 
                return; 

        if (ent->velocity[2] > 0) 
                ent->groundentity = NULL; 
// check for the groundentity going away 
        if (ent->groundentity) 
                if (!ent->groundentity->inuse) 
                        ent->groundentity = NULL; 
// if onground, return without moving 
        if (ent->groundentity) 
                return; 
        VectorCopy (ent->s.origin, old_origin); 
        SV_CheckVelocity (ent); 

        // move angles 
        VectorMA (ent->s.angles, FRAMETIME, ent->avelocity, ent->s.angles); 

        // add gravity 
        ent->velocity[2] -= ent->gravity * sv_gravity->value * FRAMETIME; 
        movetime = FRAMETIME; 
        while (movetime > 0) 
        { 
        // move origin 
                VectorScale (ent->velocity, movetime, move); 
        // do the move (checking to see if we hit anything) 
                trace = SV_PushEntity (ent, move); 
        // SV_PushEntity might have called touch() functions so its possible we disappeared 
                if (!ent->inuse) 
                        return; 
                // we hit something so calculate rebound velocity etc. 
                if (trace.fraction < 1) 
                { 
                // find component of velocity in direction of normal 
                        VectorScale (trace.plane.normal, DotProduct (trace.plane.normal, ent->velocity), normalVel); 
                // find component of velocity parallel to plane of impact 
                        VectorSubtract (ent->velocity, normalVel, planeVel); 
       // apply friction (lose 25% of velocity parallel to impact plane) 
                        VectorScale (planeVel, 0.75, planeVel); 
                // calculate final velocity (rebound with 60% of impact velocity) 
                // negative since rebound causes direction reversal 
                        VectorMA (planeVel, -0.6, normalVel, ent->velocity); 
                // stop if on ground 
                // only consider stopping if impact plane is less than 45 degrees with respect to horizontal 
                // arccos(0.7) ~ 45 degrees 
                        if (trace.plane.normal[2] > 0.7) 
                        { 
                                VectorCopy (ent->velocity, temp); 
                        // zero out z component (vertical) since we want to consider horizontal and vertical motion
//                              separately 
                                temp[2] = 0; 
                                if ((VectorLength (temp) < 20) && (ent->velocity[2] < ent->gravity * sv_gravity->value * FRAMETIME * 1.5)) 
                                { 
                                        ent->groundentity = trace.ent; 
                                        ent->groundentity_linkcount = trace.ent->linkcount; 
                                        VectorCopy (vec3_origin, ent->velocity); 
                                        VectorCopy (vec3_origin, ent->avelocity); 
                                        break; // stopped, so no further simulation is necessary 
                                } 
                        } 
                } 
        // remaining amount of FRAMETIME left to simulate 
                movetime *= (1.0 - trace.fraction); 
        } 

    // check for water transition 
        wasinwater = (ent->watertype & MASK_WATER); 
        ent->watertype = gi.pointcontents (ent->s.origin); 
        isinwater = ent->watertype & MASK_WATER; 

        if (isinwater) 
                ent->waterlevel = 1; 
        else 
                ent->waterlevel = 0; 

        if (!wasinwater && isinwater) 
                gi.positioned_sound (old_origin, g_edicts, CHAN_AUTO, gi.soundindex("misc/h2ohit1.wav"), 1, 1, 0); 
        else 
        if (wasinwater && !isinwater) 
                gi.positioned_sound (ent->s.origin, g_edicts, CHAN_AUTO, gi.soundindex("misc/h2ohit1.wav"), 1, 1, 0); 

        // move teamslaves 
        for (slave = ent->teamchain; slave; slave = slave->teamchain) 
        { 
                VectorCopy (ent->s.origin, slave->s.origin); 
                gi.linkentity (slave); 
        } 
} 






/*
=============
SV_Physics_Toss

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

// regular thinking
        SV_RunThink (ent);

        // if not a team captain, so movement will be handled elsewhere
        if ( ent->flags & FL_TEAMSLAVE)
                return;

        if (ent->velocity[2] > 0)
                ent->groundentity = NULL;

// check for the groundentity going away
        if (ent->groundentity)
                if (!ent->groundentity->inuse)
                        ent->groundentity = NULL;

// if onground, return without moving
        if ( ent->groundentity )
                return;

        VectorCopy (ent->s.origin, old_origin);

        SV_CheckVelocity (ent);

// add gravity
        if (ent->movetype != MOVETYPE_FLY
        && ent->movetype != MOVETYPE_FLYMISSILE)
                SV_AddGravity (ent);

// move angles
        VectorMA (ent->s.angles, FRAMETIME, ent->avelocity, ent->s.angles);

// move origin
        VectorScale (ent->velocity, FRAMETIME, move);
        trace = SV_PushEntity (ent, move);
        if (!ent->inuse)
                return;

                // zucc added from action to cause blood splatters
                if (trace.fraction < 1 && ent->movetype == MOVETYPE_BLOOD)
                {
                        if (!ent->splatted)
                        {
                                AddSplat (ent->owner, ent->s.origin, trace.plane.normal);
                                ent->splatted = true;
                        }
                        
                        return;
                }


        
                if (trace.fraction < 1)
        {
                if (ent->movetype == MOVETYPE_BOUNCE)    
                        backoff = 1.4;  // 1.5 is normal  -Zucc/FB
                else
                        backoff = 1;

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

        // stop if on ground
                if (trace.plane.normal[2] > 0.7)
                {       
                        // zucc moved velocity check down from 60
                        if (ent->velocity[2] < 10 || ent->movetype != MOVETYPE_BOUNCE )
                        {
                                ent->groundentity = trace.ent;
                                ent->groundentity_linkcount = trace.ent->linkcount;
                                VectorCopy (vec3_origin, ent->velocity);
                                VectorCopy (vec3_origin, ent->avelocity);
                        }
                }

//              if (ent->touch)
//                      ent->touch (ent, trace.ent, &trace.plane, trace.surface);
        }
        
// check for water transition
        wasinwater = (ent->watertype & MASK_WATER);
        ent->watertype = gi.pointcontents (ent->s.origin);
        isinwater = ent->watertype & MASK_WATER;

        if (isinwater)
                ent->waterlevel = 1;
        else
                ent->waterlevel = 0;

        if (!wasinwater && isinwater)
                gi.positioned_sound (old_origin, g_edicts, CHAN_AUTO, gi.soundindex("misc/h2ohit1.wav"), 1, 1, 0);
        else if (wasinwater && !isinwater)
                gi.positioned_sound (ent->s.origin, g_edicts, CHAN_AUTO, gi.soundindex("misc/h2ohit1.wav"), 1, 1, 0);

// move teamslaves
        for (slave = ent->teamchain; slave; slave = slave->teamchain)
        {
                VectorCopy (ent->s.origin, slave->s.origin);
                gi.linkentity (slave);
        }
}

/*
===============================================================================

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.
FIXME: is this true?
=============
*/

//FIXME: hacked in for E3 demo
#define sv_stopspeed            100
#define sv_friction                     6
#define sv_waterfriction        1

void SV_AddRotationalFriction (edict_t *ent)
{
        int             n;
        float   adjustment;

        VectorMA (ent->s.angles, FRAMETIME, ent->avelocity, ent->s.angles);
        adjustment = FRAMETIME * sv_stopspeed * sv_friction;
        for (n = 0; n < 3; n++)
        {
                if (ent->avelocity[n] > 0)
                {
                        ent->avelocity[n] -= adjustment;
                        if (ent->avelocity[n] < 0)
                                ent->avelocity[n] = 0;
                }
                else
                {
                        ent->avelocity[n] += adjustment;
                        if (ent->avelocity[n] > 0)
                                ent->avelocity[n] = 0;
                }
        }
}

void SV_Physics_Step (edict_t *ent)
{
        qboolean        wasonground;
        qboolean        hitsound = false;
        float           *vel;
        float           speed, newspeed, control;
        float           friction;
        edict_t         *groundentity;
        int                     mask;

        // airborn monsters should always check for ground
        if (!ent->groundentity)
                M_CheckGround (ent);

        groundentity = ent->groundentity;

        SV_CheckVelocity (ent);

        if (groundentity)
                wasonground = true;
        else
                wasonground = false;
                
        if (ent->avelocity[0] || ent->avelocity[1] || ent->avelocity[2])
                SV_AddRotationalFriction (ent);

        // add gravity except:
        //   flying monsters
        //   swimming monsters who are in the water
        if (! wasonground)
                if (!(ent->flags & FL_FLY))
                        if (!((ent->flags & FL_SWIM) && (ent->waterlevel > 2)))
                        {
                                if (ent->velocity[2] < sv_gravity->value*-0.1)
                                        hitsound = true;
                                if (ent->waterlevel == 0)
                                        SV_AddGravity (ent);
                        }

        // friction for flying monsters that have been given vertical velocity
        if ((ent->flags & FL_FLY) && (ent->velocity[2] != 0))
        {
                speed = fabs(ent->velocity[2]);
                control = speed < sv_stopspeed ? sv_stopspeed : speed;
                friction = sv_friction/3;
                newspeed = speed - (FRAMETIME * control * friction);
                if (newspeed < 0)
                        newspeed = 0;
                newspeed /= speed;
                ent->velocity[2] *= newspeed;
        }

        // friction for flying monsters that have been given vertical velocity
        if ((ent->flags & FL_SWIM) && (ent->velocity[2] != 0))
        {
                speed = fabs(ent->velocity[2]);
                control = speed < sv_stopspeed ? sv_stopspeed : speed;
                newspeed = speed - (FRAMETIME * control * sv_waterfriction * ent->waterlevel);
                if (newspeed < 0)
                        newspeed = 0;
                newspeed /= speed;
                ent->velocity[2] *= newspeed;
        }

        if (ent->velocity[2] || ent->velocity[1] || ent->velocity[0])
        {
                // apply friction
                // let dead monsters who aren't completely onground slide
                if ((wasonground) || (ent->flags & (FL_SWIM|FL_FLY)))
                        if (!(ent->health <= 0.0 && !M_CheckBottom(ent)))
                        {
                                vel = ent->velocity;
                                speed = sqrt(vel[0]*vel[0] +vel[1]*vel[1]);
                                if (speed)
                                {
                                        friction = sv_friction;

                                        control = speed < sv_stopspeed ? sv_stopspeed : speed;
                                        newspeed = speed - FRAMETIME*control*friction;

                                        if (newspeed < 0)
                                                newspeed = 0;
                                        newspeed /= speed;

                                        vel[0] *= newspeed;
                                        vel[1] *= newspeed;
                                }
                        }

                if (ent->svflags & SVF_MONSTER)
                        mask = MASK_MONSTERSOLID;
                else
                        mask = MASK_SOLID;
                SV_FlyMove (ent, FRAMETIME, mask);

                gi.linkentity (ent);
                G_TouchTriggers (ent);

// Following check was added in 3.20.  Adding here.  -FB
                if (!ent->inuse)
                        return;

                if (ent->groundentity)
                        if (!wasonground)
                                if (hitsound)
                                        gi.sound (ent, 0, gi.soundindex("world/land.wav"), 1, 1, 0);
        }

// regular thinking
        SV_RunThink (ent);
}

//============================================================================
/*
================
G_RunEntity

================
*/
void G_RunEntity (edict_t *ent)
{
        if (ent->prethink)
                ent->prethink (ent);

        switch ( (int)ent->movetype)
        {
        case MOVETYPE_PUSH:
        case MOVETYPE_STOP:
                SV_Physics_Pusher (ent);
                break;
        case MOVETYPE_NONE:
                SV_Physics_None (ent);
                break;
        case MOVETYPE_NOCLIP:
                SV_Physics_Noclip (ent);
                break;
        case MOVETYPE_STEP:
                SV_Physics_Step (ent);
                break;
        
        case MOVETYPE_BOUNCE:
                        SV_Physics_Bounce (ent); // provided by siris
                        break;
        case MOVETYPE_TOSS:
        case MOVETYPE_FLY:
                // zucc added for blood splatting
                case MOVETYPE_BLOOD:
        // zucc
                case MOVETYPE_FLYMISSILE:
                SV_Physics_Toss (ent);
                break;
        default:
                gi.error ("SV_Physics: bad movetype %i", (int)ent->movetype);                   
        }
}
