quake2-action/p_trail.c

#include "g_local.h"


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

PLAYER TRAIL

==============================================================================

This is a circular list containing the a list of points of where
the player has been recently.  It is used by monsters for pursuit.

.origin         the spot
.owner          forward link
.aiment         backward link
*/


#define TRAIL_LENGTH    8

edict_t         *trail[TRAIL_LENGTH];
int                     trail_head;
qboolean        trail_active = false;

#define NEXT(n)         (((n) + 1) & (TRAIL_LENGTH - 1))
#define PREV(n)         (((n) - 1) & (TRAIL_LENGTH - 1))


void PlayerTrail_Init (void)
{
        int             n;

        if (deathmatch->value /* FIXME || coop */)
                return;

        for (n = 0; n < TRAIL_LENGTH; n++)
        {
                trail[n] = G_Spawn();
                trail[n]->classname = "player_trail";
        }

        trail_head = 0;
        trail_active = true;
}


void PlayerTrail_Add (vec3_t spot)
{
        vec3_t  temp;

        if (!trail_active)
                return;

        VectorCopy (spot, trail[trail_head]->s.origin);

        trail[trail_head]->timestamp = level.time;

        VectorSubtract (spot, trail[PREV(trail_head)]->s.origin, temp);
        trail[trail_head]->s.angles[1] = vectoyaw (temp);

        trail_head = NEXT(trail_head);
}


void PlayerTrail_New (vec3_t spot)
{
        if (!trail_active)
                return;

        PlayerTrail_Init ();
        PlayerTrail_Add (spot);
}


edict_t *PlayerTrail_PickFirst (edict_t *self)
{
        int             marker;
        int             n;

        if (!trail_active)
                return NULL;

        for (marker = trail_head, n = TRAIL_LENGTH; n; n--)
        {
                if(trail[marker]->timestamp <= self->monsterinfo.trail_time)
                        marker = NEXT(marker);
                else
                        break;
        }

        if (visible(self, trail[marker]))
        {
                return trail[marker];
        }

        if (visible(self, trail[PREV(marker)]))
        {
                return trail[PREV(marker)];
        }

        return trail[marker];
}

edict_t *PlayerTrail_PickNext (edict_t *self)
{
        int             marker;
        int             n;

        if (!trail_active)
                return NULL;

        for (marker = trail_head, n = TRAIL_LENGTH; n; n--)
        {
                if(trail[marker]->timestamp <= self->monsterinfo.trail_time)
                        marker = NEXT(marker);
                else
                        break;
        }

        return trail[marker];
}

edict_t *PlayerTrail_LastSpot (void)
{
        return trail[PREV(trail_head)];
}