routing.cpp

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/*
All original material Copyright (C) 2002-2025 UFO: Alien Invasion.
 
Copyright (C) 1997-2001 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 the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
*/
 
#include "tracing.h"
#include "routing.h"
#include "common.h"
 
/*
===============================================================================
MAP TRACING DEBUGGING TABLES
===============================================================================
*/
 
bool debugTrace = false;
 
/*
==========================================================
  LOCAL CONSTANTS
==========================================================
*/
 
#define RT_NO_OPENING -1
 
/* Width of the box required to stand in a cell by an actor's feet.  */
#define halfMicrostepSize (PATHFINDING_MICROSTEP_SIZE / 2 - DIST_EPSILON)
/* This is a template for the extents of the box used by an actor's feet. */
static const AABB footBox(-halfMicrostepSize, -halfMicrostepSize, 0, halfMicrostepSize, halfMicrostepSize, 0);
 
/* Width of the box required to stand in a cell by an actor's torso.  */
#define half1x1Width (UNIT_SIZE * 1 / 2 - WALL_SIZE - DIST_EPSILON)
#define half2x2Width (UNIT_SIZE * 2 / 2 - WALL_SIZE - DIST_EPSILON)
/* These are templates for the extents of the box used by an actor's torso. */
static const AABB actor1x1Box(-half1x1Width, -half1x1Width, 0, half1x1Width, half1x1Width, 0);
static const AABB actor2x2Box(-half2x2Width, -half2x2Width, 0, half2x2Width, half2x2Width, 0);
 
/*
==========================================================
  LOCAL TYPES
==========================================================
*/
#if defined(COMPILE_MAP)
  #define RT_COMPLETEBOXTRACE_SIZE(mapTiles, b, list, lvl)      TR_SingleTileBoxTrace((mapTiles), Line(), (b), (lvl), MASK_NO_LIGHTCLIP, 0)
  #define RT_COMPLETEBOXTRACE_PASSAGE(mapTiles, line, b, list)  TR_SingleTileBoxTrace((mapTiles), (line), (b), TRACE_ALL_LEVELS, MASK_IMPASSABLE, MASK_PASSABLE)
 
#elif defined(COMPILE_UFO)
  #define RT_COMPLETEBOXTRACE_SIZE(mapTiles, b, list, lvl)      CM_EntCompleteBoxTrace((mapTiles), Line(), (b), (lvl), MASK_NO_LIGHTCLIP, 0, (list))
  #define RT_COMPLETEBOXTRACE_PASSAGE(mapTiles, line, b, list)  CM_EntCompleteBoxTrace((mapTiles), (line), (b), TRACE_ALL_LEVELS, MASK_IMPASSABLE, MASK_PASSABLE, (list))
 
#else
  #error Either COMPILE_MAP or COMPILE_UFO must be defined in order for tracing.c to work.
#endif

class RoutingData
{
public:
    mapTiles_t* mapTiles;
    Routing& routing;           
    actorSizeEnum_t actorSize;  
    const char** list;          
 
    RoutingData (mapTiles_t* mapTiles, Routing& r, actorSizeEnum_t actorSize, const char** list);
};
 
RoutingData::RoutingData (mapTiles_t* mapTiles, Routing& r, actorSizeEnum_t actorSize, const char** list) : routing(r)
{
    this->mapTiles = mapTiles;
    this->actorSize = actorSize;
    this->list = list;
}
 
static inline void RT_StepupSet (RoutingData* rtd, const int x, const int y, const int z, const int dir, const int val)
{
    rtd->routing.setStepup(rtd->actorSize, x, y, z, dir, val);
}
 
static inline void RT_ConnSetNoGo (RoutingData* rtd, const int x, const int y, const int z, const int dir)
{
    rtd->routing.setConn(rtd->actorSize, x, y, z, dir, 0);
    rtd->routing.setStepup(rtd->actorSize, x, y, z, dir, PATHFINDING_NO_STEPUP);
}

typedef struct place_s {
    pos3_t cell;    
    int floor;      
    int ceiling;    
    int floorZ;     
    bool usable;    
 
    inline bool isUsable (void) const
    {
        return usable;
    }
} place_t;
 
static inline void RT_PlaceInit (const Routing& routing, const actorSizeEnum_t actorSize, place_t* p, const int x, const int y, const int z)
{
    p->cell[0] = x;
    p->cell[1] = y;
    p->cell[2] = z;
    const int relCeiling = routing.getCeiling(actorSize, p->cell);
    p->floor = routing.getFloor(actorSize, x, y, z) + z * CELL_HEIGHT;
    p->ceiling = relCeiling + z * CELL_HEIGHT;
    p->floorZ = std::max(0, p->floor / CELL_HEIGHT) ;
    p->usable = (relCeiling && p->floor > -1 && p->ceiling - p->floor >= PATHFINDING_MIN_OPENING) ? true : false;
}
 
static inline bool RT_PlaceDoesIntersectEnough (const place_t* p, const place_t* other)
{
    return (std::min(p->ceiling, other->ceiling) - std::max(p->floor, other->floor) >= PATHFINDING_MIN_OPENING);
}

static inline int RT_PlaceIsShifted (const place_t* p, const place_t* other)
{
    if (!p->isUsable() || !other->isUsable())
        return 0;
    if (p->floor < other->floor && p->ceiling < other->ceiling)
        return 1;   /* stepping up */
    if (p->floor > other->floor && p->ceiling > other->ceiling)
        return 2;   /* stepping down */
    return 0;
}

typedef struct opening_s {
    int size;       
    int base;       
    int stepup;     
    int invstepup;  
} opening_t;
 
/*
==========================================================
  GRID ORIENTED MOVEMENT AND SCANNING
==========================================================
*/
 
#ifdef DEBUG
static void RT_DumpMap (const Routing& routing, actorSizeEnum_t actorSize, int lx, int ly, int lz, int hx, int hy, int hz)
{
    Com_Printf("\nRT_DumpMap (%i %i %i) (%i %i %i)\n", lx, ly, lz, hx, hy, hz);
    for (int z = hz; z >= lz; --z) {
        Com_Printf("\nLayer %i:\n   ", z);
        for (int x = lx; x <= hx; ++x) {
            Com_Printf("%9i", x);
        }
        Com_Printf("\n");
        for (int y = hy; y >= ly; --y) {
            Com_Printf("%3i ", y);
            for (int x = lx; x <= hx; ++x) {
                Com_Printf("%s%s%s%s "
                    , RT_CONN_NX(routing, actorSize, x, y, z) ? "w" : " "
                    , RT_CONN_PY(routing, actorSize, x, y, z) ? "n" : " "
                    , RT_CONN_NY(routing, actorSize, x, y, z) ? "s" : " "
                    , RT_CONN_PX(routing, actorSize, x, y, z) ? "e" : " "
                    );
            }
            Com_Printf("\n");
        }
    }
}

void RT_DumpWholeMap (mapTiles_t* mapTiles, const Routing& routing)
{
    AABB mapBox;
    RT_GetMapSize(mapTiles, mapBox);
 
    /* convert the coords */
    pos3_t start, end;
    VecToPos(mapBox.mins, start);
    VecToPos(mapBox.maxs, end);
    start[0]--;
    start[1]--;
 
    /* Dump the client map */
    RT_DumpMap(routing, ACTOR_SIZE_NORMAL, start[0], start[1], start[2], end[0], end[1], end[2]);
}
#endif

bool RT_CanActorStandHere (const Routing& routing, const int actorSize, const pos3_t pos)
{
    if (routing.getCeiling(actorSize, pos) - routing.getFloor(actorSize, pos) >= PLAYER_STANDING_HEIGHT / QUANT)
        return true;
    else
        return false;
}

void RT_GetMapSize (mapTiles_t* mapTiles, AABB& mapBox)
{
    const vec3_t normal = {UNIT_SIZE / 2, UNIT_SIZE / 2, UNIT_HEIGHT / 2};
    pos3_t start, end, test;
 
    /* Initialize start, end, and normal */
    VectorClear(start);
    VectorSet(end, PATHFINDING_WIDTH - 1, PATHFINDING_WIDTH - 1, PATHFINDING_HEIGHT - 1);
 
    for (int i = 0; i < 3; i++) {
        AABB box;
        /* Lower positive boundary */
        while (end[i] > start[i]) {
            /* Adjust ceiling */
            VectorCopy(start, test);
            test[i] = end[i];
            /* Prep boundary box */
            PosToVec(test, box.mins);
            VectorSubtract(box.mins, normal, box.mins);
            PosToVec(end, box.maxs);
            VectorAdd(box.maxs, normal, box.maxs);
            /* Test for stuff in a small box, if there is something then exit while */
            const trace_t trace = RT_COMPLETEBOXTRACE_SIZE(mapTiles, &box, nullptr, TRACE_VISIBLE_LEVELS);
            if (trace.fraction < 1.0)
                break;
            /* There is nothing, lower the boundary. */
            end[i]--;
        }
 
        /* Raise negative boundary */
        while (end[i] > start[i]) {
            /* Adjust ceiling */
            VectorCopy(end, test);
            test[i] = start[i];
 
            /* Prep boundary box */
            PosToVec(start, box.mins);
            VectorSubtract(box.mins, normal, box.mins);
            PosToVec(test, box.maxs);
            VectorAdd(box.maxs, normal, box.maxs);
            box.maxs[i] -= DIST_EPSILON;            /* stay away from the upper bound just a little bit, so we don't catch a touching brush */
 
            /* Test for stuff in the box, if there is something then exit while */
            const trace_t trace = RT_COMPLETEBOXTRACE_SIZE(mapTiles, &box, nullptr, TRACE_VISIBLE_LEVELS);
            if (trace.fraction < 1.0)
                break;
            /* There is nothing, raise the boundary. */
            start[i]++;
        }
    }
 
    /* Com_Printf("Extents: (%i, %i, %i) to (%i, %i, %i)\n", start[0], start[1], start[2], end[0], end[1], end[2]); */
 
    /* convert to vectors */
    PosToVec(start, mapBox.mins);
    PosToVec(end, mapBox.maxs);
 
    /* Stretch to the exterior edges of our extents */
    VectorSubtract(mapBox.mins, normal, mapBox.mins);
    VectorAdd(mapBox.maxs, normal, mapBox.maxs);
}
 
 
/*
===============================================================================
NEW MAP TRACING FUNCTIONS
===============================================================================
*/

bool RT_AllCellsBelowAreFilled (const Routing& routing, const int actorSize, const pos3_t pos)
{
    /* the -1 level is considered solid ground */
    if (pos[2] == 0)
        return true;
 
    for (int i = 0; i < pos[2]; i++) {
        if (routing.getCeiling(actorSize, pos[0], pos[1], i) != 0)
            return false;
    }
    return true;
}

int RT_CheckCell (mapTiles_t* mapTiles, Routing& routing, const int actorSize, const int x, const int y, const int z, const char** list)
{
    /* Width of the box required to stand in a cell by an actor's torso.  */
    const float halfActorWidth = UNIT_SIZE * actorSize / 2 - WALL_SIZE - DIST_EPSILON;
    /* This is a template for the extents of the box used by an actor's legs. */
    const AABB legBox(-halfMicrostepSize, -halfMicrostepSize, 0,
                        halfMicrostepSize,  halfMicrostepSize, QuantToModel(PATHFINDING_LEGROOMHEIGHT) - DIST_EPSILON * 2);
    /* This is a template for the extents of the box used by an actor's torso. */
    const AABB torsoBox(-halfActorWidth, -halfActorWidth, QuantToModel(PATHFINDING_LEGROOMHEIGHT),
                          halfActorWidth,  halfActorWidth, QuantToModel(PATHFINDING_MIN_OPENING) - DIST_EPSILON * 2);
    /* This is a template for the ceiling trace after an actor's torso space has been found. */
    const AABB ceilBox(-halfActorWidth, -halfActorWidth, 0,
                         halfActorWidth,  halfActorWidth, 0);
 
    vec3_t start, end; /* Start and end of the downward traces. */
    vec3_t tstart, tend; /* Start and end of the upward traces. */
    AABB box; /* Holds the exact bounds to be traced for legs and torso. */
    pos3_t pos;
    float bottom, top; /* Floor and ceiling model distances from the cell base. (in mapunits) */
 
    assert(actorSize > ACTOR_SIZE_INVALID && actorSize <= ACTOR_MAX_SIZE);
    /* x and y cannot exceed PATHFINDING_WIDTH - actorSize */
    assert((x >= 0) && (x <= PATHFINDING_WIDTH - actorSize));
    assert((y >= 0) && (y <= PATHFINDING_WIDTH - actorSize));
    assert(z < PATHFINDING_HEIGHT);
 
    /* calculate tracing coordinates */
    VectorSet(pos, x, y, z);
    SizedPosToVec(pos, actorSize, end); /* end is now at the center of the cells the actor occupies. */
 
    /* prepare fall down check */
    VectorCopy(end, start);
    /*
     * Adjust these points so that start to end is from the top of the cell to the bottom of the model.
     */
#ifdef DEBUG
    float initial = start[2] + UNIT_HEIGHT / 2; /* This is the top-most starting point in this cell. */
#endif
    start[2] += UNIT_HEIGHT / 2 - QUANT; /* This one QUANT unit below initial. */
    end[2] = -UNIT_HEIGHT * 2; /* To the bottom of the model! (Plus some for good measure) */
 
    /*
     * Trace for a floor.  Steps:
     * 1. Start at the top of the designated cell and scan toward the model's base.
     * 2. If we do not find a brush, then this cell is bottomless and not enterable.
     * 3. We have found an upward facing brush.  Scan up PATHFINDING_LEGROOMHEIGHT height.
     * 4. If we find anything, then this space is too small of an opening.  Restart just below our current floor.
     * 5. Trace up towards the model ceiling with a box as large as the actor.  The first obstruction encountered
     *      marks the ceiling.  If there are no obstructions, the model ceiling is the ceiling.
     * 6. If the opening between the floor and the ceiling is not at least PATHFINDING_MIN_OPENING tall, then
     *      restart below the current floor.
     */
    for (;;) { /* Loop forever, we will exit if we hit the model bottom or find a valid floor. */
 
        /* Check if a previous iteration has brought us too close to the bottom of the model. */
        if (start[2] <= QuantToModel(PATHFINDING_MIN_OPENING)) {
            /* There is no useable brush underneath this starting point. */
            routing.setFilled(actorSize, x, y, 0, z);   /* mark all cells to the model base as filled. */
            return 0;                                   /* return (a z-value of)0 to indicate we just scanned the model bottom. */
        }
 
        trace_t tr = RT_COMPLETEBOXTRACE_PASSAGE(mapTiles, Line(start, end), &footBox, list);
        if (tr.fraction >= 1.0) {                       /* If there is no brush underneath this starting point, */
            routing.setFilled(actorSize, x, y, 0, z);   /* mark all cells to the model base as filled. */
            return 0;                                   /* return (a z-value of)0 to indicate we just scanned the model bottom. */
        }
 
        /* We have hit a brush that faces up and can be stood on. A potential floor. Look for a ceiling. */
        bottom = tr.endpos[2];  /* record the floor position. */
 
#ifdef DEBUG
        assert(initial > bottom);
#endif
 
        /* Record the hit position in tstart for later use. */
        VectorCopy(tr.endpos, tstart);
 
        /* Prep the start and end of the "leg room" test. */
        box.set(legBox);
        box.shift(tstart);  /* Now box has the lower and upper required foot space extent */
 
        tr = RT_COMPLETEBOXTRACE_PASSAGE(mapTiles, Line(), &box, list);
        if (tr.fraction < 1.0) {
            /*
             * There is a premature obstruction.  We can't use this as a floor.
             * Check under start.  We need to have at least the minimum amount of clearance from our ceiling,
             * So start at that point.
             */
            start[2] = bottom - QuantToModel(PATHFINDING_MIN_OPENING);
            /* Restart  with the new start[] value */
            continue;
        }
 
        /* Prep the start and end of the "torso room" test. */
        box.set(torsoBox);
        box.shift(tstart);  /* Now box has the lower and upper required torso space extent */
 
        tr = RT_COMPLETEBOXTRACE_PASSAGE(mapTiles, Line(), &box, list);
        if (tr.fraction < 1.0) {
            /*
             * There is a premature obstruction.  We can't use this as a floor.
             * Check under start.  We need to have at least the minimum amount of clearance from our ceiling,
             * So start at that point.
             */
            start[2] = bottom - QuantToModel(PATHFINDING_MIN_OPENING);
            /* Restart */
            continue;
        }
 
        /*
         * If we are here, then the immediate floor is unobstructed MIN_OPENING units high.
         * This is a valid floor.  Find the actual ceiling.
         */
 
        tstart[2] = box.maxs[2]; /* The box trace for height starts at the top of the last trace. */
        VectorCopy(tstart, tend);
        tend[2] = PATHFINDING_HEIGHT * UNIT_HEIGHT; /* tend now reaches the model ceiling. */
 
        tr = RT_COMPLETEBOXTRACE_PASSAGE(mapTiles, Line(tstart, tend), &ceilBox, list);
 
        /* We found the ceiling. */
        top = tr.endpos[2];
 
        /*
         * There is one last possibility:
         * If our found ceiling is above the cell we started the scan in, then we may have scanned up through another
         * floor (one sided brush).  If this is the case, we set the ceiling to QUANT below the floor of the above
         * ceiling if it is lower than our found ceiling.
         */
        if (tr.endpos[2] > (z + 1) * UNIT_HEIGHT) {
            const float topf = (z + 1) * UNIT_HEIGHT + QuantToModel(routing.getFloor(actorSize, x, y, z + 1) - 1);
            top = std::min(tr.endpos[2], topf);
        }
 
        /* We found the ceiling. */
        top = tr.endpos[2];
 
        /* exit the infinite while loop */
        break;
    }
 
    UFO_assert(bottom <= top, "\nassert(bottom <= top): x=%i y=%i bottom=%f top=%f\n", x, y, bottom, top);
 
    /* top and bottom are absolute model heights.  Find the actual cell z coordinates for these heights.
     * ...but before rounding, give back the DIST_EPSILON that was added by the trace.
     * Actually, we have to give back two DIST_EPSILON to prevent rounding issues */
    bottom -= 2 * DIST_EPSILON;
    top += 2 * DIST_EPSILON;
    const int bottomQ = ModelFloorToQuant(bottom); /* Convert to QUANT units to ensure the floor is rounded up to the correct value. */
    const int topQ = ModelCeilingToQuant(top); /* Convert to QUANT units to ensure the floor is rounded down to the correct value. */
    const int fz = floorf(bottomQ / CELL_HEIGHT); /* Ensure we round down to get the bottom-most affected cell */
    const int cz = std::min(z, (int)(floorf((topQ - 1) / CELL_HEIGHT))); /* Use the lower of z or the calculated ceiling */
 
    assert(fz <= cz);
 
    /* Last, update the floors and ceilings of cells from (x, y, fz) to (x, y, cz) */
    for (int i = fz; i <= cz; i++) {
        /* Round up floor to keep feet out of model. */
        routing.setFloor(actorSize, x, y, i, bottomQ - i * CELL_HEIGHT);
        /* Round down ceiling to heep head out of model.  Also offset by floor and max at 255. */
        routing.setCeiling(actorSize, x, y, i, topQ - i * CELL_HEIGHT);
    }
 
    /* Also, update the floors of any filled cells immediately above the ceiling up to our original cell. */
    routing.setFilled(actorSize, x, y, cz + 1, z);
 
    /* Return the lowest z coordinate that we updated floors for. */
    return fz;
}
 

static int RT_FillPassageData (RoutingData* rtd, const int dir, const int  x, const int y, const int z, const int openingSize, const int openingBase, const int stepup)
{
    const int openingTop = openingBase + openingSize;
 
    /* Final interpretation:
     * We now have the floor and the ceiling of the passage traveled between the two cells.
     * This span may cover many cells vertically.  We can use this to our advantage:
     * +Like in the floor tracing, we can assign the direction value for multiple cells and
     *  skip some scans.
     * +The value of each current cell will list the max allowed height of an actor in the passageway,
     *  which also can be used to see if an actor can fly upward.
     * +The allowed height will be based off the floor in the cell or the bottom of the cell; we do not
     *  want super tall characters to fly through ceilings.
     * +To see if an actor can fly down, we check the cells on level down to see if the diagonal movement
     *  can be made and that both have ceilings above the current level.
     */

    const int fz = z;
    int cz = ceil((float)openingTop / CELL_HEIGHT) - 1;
    cz = std::min(PATHFINDING_HEIGHT - 1, cz);
 
    /* last chance- if cz < z, then bail (and there is an error with the ceiling data somewhere */
    if (cz < z) {
        /* We can't go this way. */
        RT_ConnSetNoGo(rtd, x, y, z, dir);  /* Passage found but below current cell */
        return z;
    }
 
    /* Passage found */
 
    assert(fz <= z && z <= cz);
 
    /* Last, update the connections of cells from (x, y, fz) to (x, y, cz) for direction dir */
    for (int i = fz; i <= cz; i++) {
        /* Offset from the floor or the bottom of the current cell, whichever is higher. */
        const int oh = openingTop - std::max(openingBase, i * CELL_HEIGHT);
        /* Only if > 0 */
        assert (oh >= 0);
        rtd->routing.setConn(rtd->actorSize, x, y, i, dir, oh);
        /* The stepup is 0 for all cells that are not at the floor. */
        RT_StepupSet(rtd, x, y, i, dir, 0);
    }
 
    RT_StepupSet(rtd, x, y, z, dir, stepup);
 
    /*
     * Return the highest z coordinate scanned- cz if fz==cz, z==cz, or the floor in cz is negative.
     * Otherwise cz - 1 to recheck cz in case there is a floor in cz with its own ceiling.
     */
    if (fz == cz || z == cz || rtd->routing.getFloor(rtd->actorSize, x, y, cz) < 0)
        return cz;
    return cz - 1;
}

static trace_t RT_ObstructedTrace (const RoutingData* rtd, const Line& traceLine, int hi, int lo)
{
    AABB box; 
    const float halfActorWidth = UNIT_SIZE * rtd->actorSize / 2 - WALL_SIZE - DIST_EPSILON;
 
    /* Configure the box trace extents. The box is relative to the original floor. */
    VectorSet(box.maxs, halfActorWidth, halfActorWidth, QuantToModel(hi) - DIST_EPSILON);
    VectorSet(box.mins, -halfActorWidth, -halfActorWidth, QuantToModel(lo)  + DIST_EPSILON);
 
    /* perform the trace, then return true if the trace was obstructed. */
    return RT_COMPLETEBOXTRACE_PASSAGE(rtd->mapTiles, traceLine, &box, rtd->list);
}
 

static int RT_FindOpeningFloorFrac (const RoutingData* rtd, const vec3_t start, const vec3_t end, const float frac, const int startingHeight)
{
    vec3_t mstart, mend;       
    const AABB* box = (rtd->actorSize == ACTOR_SIZE_NORMAL ? &actor1x1Box : &actor2x2Box);
 
    /* Position mstart and mend at the fraction point */
    VectorInterpolation(start, end, frac, mstart);
    VectorCopy(mstart, mend);
    mstart[2] = QuantToModel(startingHeight) + (QUANT / 2); /* Set at the starting height, plus a little more to keep us off a potential surface. */
    mend[2] = -QUANT;  /* Set below the model. */
 
    const trace_t tr = RT_COMPLETEBOXTRACE_PASSAGE(rtd->mapTiles, Line(mstart, mend), box, rtd->list);
 
    /* OK, now we have the floor height value in tr.endpos[2].
     * Divide by QUANT and round up.
     */
    return ModelFloorToQuant(tr.endpos[2] - DIST_EPSILON);
}
 

static int RT_FindOpeningCeilingFrac (const RoutingData* rtd, const vec3_t start, const vec3_t end, const float frac, const int startingHeight)
{
    vec3_t mstart, mend;    
    const AABB* box = (rtd->actorSize == ACTOR_SIZE_NORMAL ? &actor1x1Box : &actor2x2Box);  
 
    /* Position mstart and mend at the midpoint */
    VectorInterpolation(start, end, frac, mstart);
    VectorCopy(mstart, mend);
    mstart[2] = QuantToModel(startingHeight) - (QUANT / 2); /* Set at the starting height, minus a little more to keep us off a potential surface. */
    mend[2] = UNIT_HEIGHT * PATHFINDING_HEIGHT + QUANT;  /* Set above the model. */
 
    const trace_t tr = RT_COMPLETEBOXTRACE_PASSAGE(rtd->mapTiles, Line(mstart, mend), box, rtd->list);
 
    /* OK, now we have the floor height value in tr.endpos[2].
     * Divide by QUANT and round down. */
    return ModelCeilingToQuant(tr.endpos[2] + DIST_EPSILON);
}
 

static int RT_FindOpeningFloor (const RoutingData* rtd, const vec3_t start, const vec3_t end, const int startingHeight, const int floorLimit)
{
    /* Look for additional space below init_bottom, down to lowest_bottom. */
    int midfloor;
 
    if (start[0] == end[0] || start[1] == end[1]) {
        /* For orthogonal dirs, find the height at the midpoint. */
        midfloor = RT_FindOpeningFloorFrac(rtd, start, end, 0.5, startingHeight);
    } else {
        /* If this is diagonal, trace the 1/3 and 2/3 points instead. */
        /* 1/3 point */
        midfloor = RT_FindOpeningFloorFrac(rtd, start, end, 0.33, startingHeight);
 
        /* 2/3 point */
        const int midfloor2 = RT_FindOpeningFloorFrac(rtd, start, end, 0.66, startingHeight);
        midfloor = std::max(midfloor, midfloor2);
    }
 
    /* return the highest floor. */
    return std::max(floorLimit, midfloor);
}
 

static int RT_FindOpeningCeiling (const RoutingData* rtd, const vec3_t start, const vec3_t end, const int startingHeight, const int ceilLimit)
{
    int midceil;
 
    if (start[0] == end[0] || start[1] == end[1]) {
        /* For orthogonal dirs, find the height at the midpoint. */
        midceil = RT_FindOpeningCeilingFrac(rtd, start, end, 0.5, startingHeight);
    } else {
        /* If this is diagonal, trace the 1/3 and 2/3 points instead. */
        /* 1/3 point */
        midceil = RT_FindOpeningCeilingFrac(rtd, start, end, 0.33, startingHeight);
 
        /* 2/3 point */
        const int midceil2 = RT_FindOpeningCeilingFrac(rtd, start, end, 0.66, startingHeight);
        midceil = std::min(midceil, midceil2);
    }
 
    /* return the lowest ceiling. */
    return std::min(ceilLimit, midceil);
}
 
 
static int RT_CalcNewZ (const RoutingData* rtd, const int ax, const int ay, const int top, const int hi)
{
    int temp_z = floorf((hi - 1) / CELL_HEIGHT);
    temp_z = std::min(temp_z, PATHFINDING_HEIGHT - 1);
    int adj_lo = rtd->routing.getFloor(rtd->actorSize, ax, ay, temp_z) + temp_z * CELL_HEIGHT;
    if (adj_lo > hi) {
        temp_z--;
        adj_lo = rtd->routing.getFloor(rtd->actorSize, ax, ay, temp_z) + temp_z * CELL_HEIGHT;
    }
    if (adj_lo >= 0 && top - adj_lo >= PATHFINDING_MIN_OPENING - PATHFINDING_MIN_STEPUP) {
        return floorf(adj_lo / CELL_HEIGHT);    /* Found floor in destination cell */
    }
 
    return RT_NO_OPENING;   /* Skipping found floor in destination cell- not enough opening */
}
 

static int RT_TraceOpening (const RoutingData* rtd, const vec3_t start, const vec3_t end, const int ax, const int ay, const int bottom, const int top, int lo, int hi, int* foundLow, int* foundHigh)
{
    const trace_t tr = RT_ObstructedTrace(rtd, Line(start, end), hi, lo);
    if (tr.fraction >= 1.0) {
        lo = RT_FindOpeningFloor(rtd, start, end, lo, bottom);
        hi = RT_FindOpeningCeiling(rtd, start, end, hi, top);
        if (hi - lo >= PATHFINDING_MIN_OPENING) {
            if (lo == -1) {
                /* Bailing- no floor in destination cell. */
                *foundLow = *foundHigh = 0;
                return RT_NO_OPENING;
            }
            /* This opening works, use it! */
            *foundLow = lo;
            *foundHigh = hi;
            /* Find the floor for the highest adjacent cell in this passage. */
            const int tempZ = RT_CalcNewZ(rtd, ax, ay, top, hi);
            if (tempZ != RT_NO_OPENING)
                return tempZ;
        }
    }
    *foundLow = *foundHigh = hi;
    return RT_NO_OPENING;
}
 

static int RT_FindOpening (RoutingData* rtd, const place_t* from, const int ax, const int ay, const int bottom, const int top, int* foundLow, int* foundHigh)
{
    if (bottom == -1) {
        /* Bailing- no floor in current cell. */
        *foundLow = *foundHigh = 0;
        return RT_NO_OPENING;
    }
 
    vec3_t start, end;
    pos3_t pos;
 
    /* Initialize the starting vector */
    SizedPosToVec(from->cell, rtd->actorSize, start);
 
    /* Initialize the ending vector */
    VectorSet(pos, ax, ay, from->cell[2]);
    SizedPosToVec(pos, rtd->actorSize, end);
 
    /* Initialize the z component of both vectors */
    start[2] = end[2] = 0;
 
    /* ----- sky trace ------ */
    /* shortcut: if both ceilings are the sky, we can check for walls
     * AND determine the bottom of the passage in just one trace */
    if (from->ceiling >= PATHFINDING_HEIGHT * CELL_HEIGHT
     && from->cell[2] * CELL_HEIGHT + rtd->routing.getCeiling(rtd->actorSize, ax, ay, from->cell[2]) >= PATHFINDING_HEIGHT * CELL_HEIGHT) {
        vec3_t sky, earth;
        const AABB* box = (rtd->actorSize == ACTOR_SIZE_NORMAL ? &actor1x1Box : &actor2x2Box);
        int tempBottom;
 
        VectorInterpolation(start, end, 0.5, sky);  /* center it halfway between the cells */
        VectorCopy(sky, earth);
        sky[2] = UNIT_HEIGHT * PATHFINDING_HEIGHT;  /* Set to top of model. */
        earth[2] = QuantToModel(bottom);
 
        const trace_t tr = RT_COMPLETEBOXTRACE_PASSAGE(rtd->mapTiles, Line(sky, earth), box, rtd->list);
        tempBottom = ModelFloorToQuant(tr.endpos[2]);
        if (tempBottom <= bottom + PATHFINDING_MIN_STEPUP) {
            const int hi = bottom + PATHFINDING_MIN_OPENING;
            /* Found opening with sky trace. */
            *foundLow = tempBottom;
            *foundHigh = CELL_HEIGHT * PATHFINDING_HEIGHT;
            return RT_CalcNewZ(rtd, ax, ay, top, hi);
        }
    }
    /* Warning: never try to make this an 'else if', or 'arched entry' situations will fail !! */
 
    /* ----- guaranteed opening trace ------ */
    /* Now calculate the "guaranteed" opening, if any. If the opening from
     * the floor to the ceiling is not too tall, there must be a section that
     * will always be vacant if there is a usable passage of any size and at
     * any height. */
    int tempZ;
    if (top - bottom < PATHFINDING_MIN_OPENING * 2) {
        const int lo = top - PATHFINDING_MIN_OPENING;
        const int hi = bottom + PATHFINDING_MIN_OPENING;
 
        tempZ = RT_TraceOpening(rtd, start, end, ax, ay, bottom, top, lo, hi, foundLow, foundHigh);
    } else {
        /* ----- brute force trace ------ */
        /* There is no "guaranteed" opening, brute force search. */
        int lo = bottom;
        tempZ = 0;
        while (lo <= top - PATHFINDING_MIN_OPENING) {
            /* Check for a 1 QUANT opening. */
            tempZ = RT_TraceOpening(rtd, start, end, ax, ay, bottom, top, lo, lo + 1, foundLow, foundHigh);
            if (tempZ != RT_NO_OPENING)
                break;
            /* Credit to Duke: We skip the minimum opening, as if there is a
             * viable opening, even one slice above, that opening would be open. */
            lo += PATHFINDING_MIN_OPENING;
        }
    }
    return tempZ;
}
 

static int RT_MicroTrace (RoutingData* rtd, const place_t* from, const int ax, const int ay, const int az, const int stairwaySituation, opening_t* opening)
{
    /* OK, now we have a viable shot across.  Run microstep tests now. */
    /* Now calculate the stepup at the floor using microsteps. */
    const int top = opening->base + opening->size;
    signed char bases[UNIT_SIZE / PATHFINDING_MICROSTEP_SIZE + 1];
    /* Shortcut the value of UNIT_SIZE / PATHFINDING_MICROSTEP_SIZE. */
    const int steps = UNIT_SIZE / PATHFINDING_MICROSTEP_SIZE;
    vec3_t start, end;
    pos3_t pos;
 
    /* First prepare the two known end values. */
    bases[0] = from->floor;
    const int floorVal = rtd->routing.getFloor(rtd->actorSize, ax, ay, az);
    bases[steps] = std::max(0, floorVal) + az * CELL_HEIGHT;
 
    /* Initialize the starting vector */
    SizedPosToVec(from->cell, rtd->actorSize, start);
 
    /* Initialize the ending vector */
    VectorSet(pos, ax, ay, az);
    SizedPosToVec(pos, rtd->actorSize, end);
 
    /* Now prep the z values for start and end. */
    start[2] = QuantToModel(opening->base) + 1; 
    end[2] = -QUANT;
 
    /* Memorize the start and end x,y points */
    const float sx = start[0];
    const float sy = start[1];
    const float ex = end[0];
    const float ey = end[1];
 
    int newBottom = std::max(bases[0], bases[steps]);
    /* Now calculate the rest of the microheights. */
    for (int i = 1; i < steps; i++) {
        start[0] = end[0] = sx + (ex - sx) * (i / (float)steps);
        start[1] = end[1] = sy + (ey - sy) * (i / (float)steps);
 
        /* perform the trace, then return true if the trace was obstructed. */
        const trace_t tr = RT_COMPLETEBOXTRACE_PASSAGE(rtd->mapTiles, Line(start, end), &footBox, rtd->list);
        if (tr.fraction >= 1.0f) {
            bases[i] = -1;
        } else {
            bases[i] = ModelFloorToQuant(tr.endpos[2] - DIST_EPSILON);
            /* Walking through glass fix:
             * It is possible to have an obstruction that can be skirted around diagonally
             * because the microtraces are so tiny.  But, we have a full size trace in opening->base
             * that apporoximates where legroom ends.  If the found floor of the middle microtrace is
             * too low, then set it to the worst case scenario floor based on base->opening.
             */
            if (i == floor(steps / 2.0) && bases[i] < opening->base - PATHFINDING_MIN_STEPUP) {
                if (debugTrace)
                    Com_Printf("Adjusting middle trace- the known base is too high. \n");
                bases[i] = opening->base - PATHFINDING_MIN_STEPUP;
            }
        }
 
        if (debugTrace)
            Com_Printf("Microstep %i from (%f, %f, %f) to (%f, %f, %f) = %i [%f]\n",
                i, start[0], start[1], start[2], end[0], end[1], end[2], bases[i], tr.endpos[2]);\
 
        newBottom = std::max(newBottom, (int)bases[i]);
    }
 
    if (debugTrace)
        Com_Printf("z:%i az:%i bottom:%i new_bottom:%i top:%i bases[0]:%i bases[%i]:%i\n", from->cell[2], az, opening->base, newBottom, top, bases[0], steps, bases[steps]);
 

    /* Now find the maximum stepup moving from (x, y) to (ax, ay). */
    /* Initialize stepup. */
    int current_h = bases[0];
    int highest_h = -1;
    int highest_i = 1;
    opening->stepup = 0; 
    int skipped = 0;
    for (int i = 1; i <= steps; i++) {
        if (debugTrace)
            Com_Printf("Tracing forward i:%i h:%i\n", i, current_h);
        /* If there is a rise, use it. */
        if (bases[i] >= current_h || ++skipped > PATHFINDING_MICROSTEP_SKIP) {
            if (skipped == PATHFINDING_MICROSTEP_SKIP) {
                i = highest_i;
                if (debugTrace)
                    Com_Printf(" Skipped too many steps, reverting to i:%i\n", i);
            }
            opening->stepup = std::max(opening->stepup, bases[i] - current_h);
            current_h = bases[i];
            highest_h = -2;
            highest_i = i + 1;
            skipped = 0;
            if (debugTrace)
                Com_Printf(" Advancing b:%i stepup:%i\n", bases[i], opening->stepup);
        } else {
            /* We are skipping this step in case the actor can step over this lower step. */
            /* Record the step in case it is the highest of the low steps. */
            if (bases[i] > highest_h) {
                highest_h = bases[i];
                highest_i = i;
            }
            if (debugTrace)
                Com_Printf(" Skipped because we are falling, skip:%i.\n", skipped);
            /* If this is the last iteration, make sure we go back and get our last stepup tests. */
            if (i == steps) {
                skipped = PATHFINDING_MICROSTEP_SKIP;
                i = highest_i - 1;
                if (debugTrace)
                    Com_Printf(" Tripping skip counter to perform last tests.\n");
            }
        }
    }

    /* Now find the maximum stepup moving from (x, y) to (ax, ay). */
    /* Initialize stepup. */
    current_h = bases[steps];
    highest_h = -1;
    highest_i = steps - 1;  
    opening->invstepup = 0; 
    skipped = 0;
    for (int i = steps - 1; i >= 0; i--) {
        if (debugTrace)
            Com_Printf("Tracing backward i:%i h:%i\n", i, current_h);
        /* If there is a rise, use it. */
        if (bases[i] >= current_h || ++skipped > PATHFINDING_MICROSTEP_SKIP) {
            if (skipped == PATHFINDING_MICROSTEP_SKIP) {
                i = highest_i;
                if (debugTrace)
                    Com_Printf(" Skipped too many steps, reverting to i:%i\n", i);
            }
            opening->invstepup = std::max(opening->invstepup, bases[i] - current_h);
            current_h = bases[i];
            highest_h = -2;
            highest_i = i - 1;
            skipped = 0;
            if (debugTrace)
                Com_Printf(" Advancing b:%i stepup:%i\n", bases[i], opening->invstepup);
        } else {
            /* We are skipping this step in case the actor can step over this lower step. */
            /* Record the step in case it is the highest of the low steps. */
            if (bases[i] > highest_h) {
                highest_h = bases[i];
                highest_i = i;
            }
            if (debugTrace)
                Com_Printf(" Skipped because we are falling, skip:%i.\n", skipped);
            /* If this is the last iteration, make sure we go back and get our last stepup tests. */
            if (i == 0) {
                skipped = PATHFINDING_MICROSTEP_SKIP;
                i = highest_i + 1;
                if (debugTrace)
                    Com_Printf(" Tripping skip counter to perform last tests.\n");
            }
        }
    }
 
    if (stairwaySituation) {
        const int middle = bases[4];        /* terrible hack by Duke. This relies on PATHFINDING_MICROSTEP_SIZE being set to 4 !! */
 
        if (stairwaySituation == 1) {       /* stepping up */
            if (bases[1] <= middle &&       /* if nothing in the 1st part of the passage is higher than what's at the border */
                bases[2] <= middle &&
                bases[3] <= middle ) {
                if (debugTrace)
                    Com_Printf("Addition granted by ugly stair hack-stepping up.\n");
                return opening->base - middle;
            }
        } else if (stairwaySituation == 2) {/* stepping down */
            if (bases[5] <= middle &&       /* same for the 2nd part of the passage */
                bases[6] <= middle &&
                bases[7] <= middle ) {
                if (debugTrace)
                    Com_Printf("Addition granted by ugly stair hack-stepping down.\n");
                return opening->base - middle;
            }
        }
    }
 
    /* Return the confirmed passage opening. */
    return opening->base - newBottom;
}
 

static int RT_TraceOnePassage (RoutingData* rtd, const place_t* from, const place_t* to, opening_t* opening)
{
    int hi; 
    const int z = from->cell[2];
    const int lower = std::max(from->floor, to->floor);
    const int upper = std::min(from->ceiling, to->ceiling);
    const int ax = to->cell[0];
    const int ay = to->cell[1];
 
    RT_FindOpening(rtd, from, ax, ay, lower, upper, &opening->base, &hi);
    /* calc opening found so far and set stepup */
    opening->size = hi - opening->base;
    const int az = to->floorZ; 
 
    /* We subtract MIN_STEPUP because that is foot space-
     * the opening there only needs to be the microtrace
     * wide and not the usual dimensions.
     */
    if (az != RT_NO_OPENING && opening->size >= PATHFINDING_MIN_OPENING - PATHFINDING_MIN_STEPUP) {
        const int srcFloor = from->floor;
        const int dstFloor = rtd->routing.getFloor(rtd->actorSize, ax, ay, az) + az * CELL_HEIGHT;
        /* if we already have enough headroom, try to skip microtracing */
        if (opening->size < ACTOR_MAX_HEIGHT
            || abs(srcFloor - opening->base) > PATHFINDING_MIN_STEPUP
            || abs(dstFloor - opening->base) > PATHFINDING_MIN_STEPUP) {
            const int stairway = RT_PlaceIsShifted(from, to);
            /* This returns the total opening height, as the
             * microtrace may reveal more passage height from the foot space. */
            const int bonusSize = RT_MicroTrace(rtd, from, ax, ay, az, stairway, opening);
            opening->base -= bonusSize;
            opening->size = hi - opening->base; /* re-calculate */
        } else {
            /* Skipping microtracing, just set the stepup values. */
            opening->stepup = std::max(0, opening->base - srcFloor);
            opening->invstepup = std::max(0, opening->base - dstFloor);
        }
 
        /* Now place an upper bound on stepup */
        if (opening->stepup > PATHFINDING_MAX_STEPUP) {
            opening->stepup = PATHFINDING_NO_STEPUP;
        } else {
            /* Add rise/fall bit as needed. */
            if (az < z && opening->invstepup <= PATHFINDING_MAX_STEPUP)
            /* BIG_STEPDOWN indicates 'walking down', don't set it if we're 'falling' */
                opening->stepup |= PATHFINDING_BIG_STEPDOWN;
            else if (az > z)
                opening->stepup |= PATHFINDING_BIG_STEPUP;
        }
 
        /* Now place an upper bound on stepup */
        if (opening->invstepup > PATHFINDING_MAX_STEPUP) {
            opening->invstepup = PATHFINDING_NO_STEPUP;
        } else {
            /* Add rise/fall bit as needed. */
            if (az > z)
                opening->invstepup |= PATHFINDING_BIG_STEPDOWN;
            else if (az < z)
                opening->invstepup |= PATHFINDING_BIG_STEPUP;
        }
 
        if (opening->size >= PATHFINDING_MIN_OPENING) {
            return opening->size;
        }
    }
 
    opening->stepup = PATHFINDING_NO_STEPUP;
    opening->invstepup = PATHFINDING_NO_STEPUP;
    return 0;
}

static void RT_TracePassage (RoutingData* rtd, const int x, const int y, const int z, const int ax, const int ay, opening_t* opening)
{
    place_t from, to, above;
    const place_t* placeToCheck = nullptr;
 
    RT_PlaceInit(rtd->routing, rtd->actorSize, &from, x, y, z);
    RT_PlaceInit(rtd->routing, rtd->actorSize, &to, ax, ay, z);
 
    const int aboveCeil = (z < PATHFINDING_HEIGHT - 1) ? rtd->routing.getCeiling(rtd->actorSize, ax, ay, z + 1) + (z + 1) * CELL_HEIGHT : to.ceiling;
    const int lowCeil = std::min(from.ceiling, (rtd->routing.getCeiling(rtd->actorSize, ax, ay, z) == 0 || to.ceiling - from.floor < PATHFINDING_MIN_OPENING) ? aboveCeil : to.ceiling);
 
    /*
     * First check the ceiling for the cell beneath the adjacent floor to see
     * if there is a potential opening.  The difference between the
     * ceiling and the floor is at least PATHFINDING_MIN_OPENING tall, then
     * scan it to see if we can use it.  If we can, then one of two things
     * will happen:
     *  - The actual adjacent cell has no floor of its own, and we will walk
     *      or fall into the cell below the adjacent cell anyway.
     *  - There is a floor in the adjacent cell, but we will not be able to
     *      walk into it anyway because there cannot be any steps if there is
     *      a passage.  An actor can walk down into the cell ONLY IF it's
     *      negative stepup meets or exceeds the change in floor height.
     *      No actors will be allowed to fall because they cannot temporarily
     *      occupy the space beneath the floor in the adjacent cell to fall
     *      (all actors in the cell must be ON TOP of the floor in the cell).
     * If there is no passage, then the obstruction may be used as steps to
     * climb up to the adjacent floor.
     */
    if (to.isUsable() && RT_PlaceDoesIntersectEnough(&from, &to)) {
        placeToCheck = &to;
    } else if (z < PATHFINDING_HEIGHT - 1) {
        RT_PlaceInit(rtd->routing, rtd->actorSize, &above, ax, ay, z + 1);
        if (above.isUsable() && RT_PlaceDoesIntersectEnough(&from, &above)) {
            placeToCheck = &above;
        }
    }
    if (!placeToCheck) {
        /* If we got here, then there is no opening from floor to ceiling. */
        opening->stepup = PATHFINDING_NO_STEPUP;
        opening->invstepup = PATHFINDING_NO_STEPUP;
        opening->base = lowCeil;
        opening->size = 0;
        return;
    }
 
    /*
     * Now that we got here, we know that either the opening between the
     * ceiling below the adjacent cell and the current floor is too small or
     * obstructed.  Try to move onto the adjacent floor.
     */
    RT_TraceOnePassage(rtd, &from, placeToCheck, opening);
    if (opening->size < PATHFINDING_MIN_OPENING) {
        /* If we got here, then there is no useable opening from floor to ceiling. */
        opening->stepup = PATHFINDING_NO_STEPUP;
        opening->invstepup = PATHFINDING_NO_STEPUP;
        opening->base = lowCeil;
        opening->size = 0;
    }
}
 

static int RT_UpdateConnection (RoutingData* rtd, const int x, const int y, const int ax, const int ay, const int z, const int dir)
{
    const int ceiling = rtd->routing.getCeiling(rtd->actorSize, x, y, z);
    const int adjCeiling = rtd->routing.getCeiling(rtd->actorSize, ax, ay, z);
    const int upperAdjCeiling = (z < PATHFINDING_HEIGHT - 1) ? rtd->routing.getCeiling(rtd->actorSize, ax, ay, z + 1) : adjCeiling;
 
    if ((adjCeiling == 0 && upperAdjCeiling == 0) || ceiling == 0) {
        /* We can't go this way. */
        RT_ConnSetNoGo(rtd, x, y, z, dir);
        return z;
    }

    const int absCeiling = ceiling + z * CELL_HEIGHT;
//  const int absAdjCeiling = adjCeiling + z * CELL_HEIGHT;     /* temporarily unused */
    const int absExtAdjCeiling = (z < PATHFINDING_HEIGHT - 1) ? adjCeiling + (z + 1) * CELL_HEIGHT : absCeiling;
    const int absFloor = rtd->routing.getFloor(rtd->actorSize, x, y, z) + z * CELL_HEIGHT;
    const int absAdjFloor = rtd->routing.getFloor(rtd->actorSize, ax, ay, z) + z * CELL_HEIGHT;
 
    if (absCeiling < absAdjFloor || absExtAdjCeiling < absFloor) {
        /* We can't go this way. */
        RT_ConnSetNoGo(rtd, x, y, z, dir);
        return z;
    }

    opening_t opening;  
    RT_TracePassage(rtd, x, y, z, ax, ay, &opening);

    const int newZ = RT_FillPassageData(rtd, dir, x, y, z, opening.size, opening.base, opening.stepup);
 
    return newZ;
}
 

void RT_UpdateConnectionColumn (mapTiles_t* mapTiles, Routing& routing, const int actorSize, const int x, const int y, const int dir, const char** list, const int minZ, const int maxZ)
{
    int z = minZ;   
    /* the essential data passed down the calltree */
    RoutingData rtd(mapTiles, routing, actorSize, list);
 
    /* get the neighbor cell's coordinates */
    const int ax = x + dvecs[dir][0];
    const int ay = y + dvecs[dir][1];
 
    assert(actorSize > ACTOR_SIZE_INVALID && actorSize <= ACTOR_MAX_SIZE);
    assert((x >= 0) && (x <= PATHFINDING_WIDTH - actorSize));
    assert((y >= 0) && (y <= PATHFINDING_WIDTH - actorSize));
 
#ifdef DEBUG
    /* just a place to place a breakpoint */
    if (x == 126 && y == 129 && dir == 2) {
        z = 7;
    }
#endif
 
    /* if our destination cell is out of bounds, bail. */
    if (ax < 0 || ax > PATHFINDING_WIDTH - actorSize || ay < 0 || ay > PATHFINDING_WIDTH - actorSize) {
        /* We can't go this way. */
        RT_ConnSetNoGo(&rtd, x, y, z, dir);
        return;
    }
 
    /* Main loop */
    for (z = minZ; z < maxZ; z++) {
        /* The last z value processed by the tracing function.  */
        const int new_z = RT_UpdateConnection(&rtd, x, y, ax, ay, z, dir);
        assert(new_z >= z);
        z = new_z;
    }
}
 
void RT_WriteCSVFiles (const Routing& routing, const char* baseFilename, const GridBox& box)
{
    char filename[MAX_OSPATH], ext[MAX_OSPATH];
 
    /* An elevation files- dumps the floor and ceiling levels relative to each cell. */
    for (int i = 1; i <= ACTOR_MAX_SIZE; i++) {
        strncpy(filename, baseFilename, sizeof(filename) - 1);
        sprintf(ext, ".%i.elevation.csv", i);
        Com_DefaultExtension(filename, sizeof(filename), ext);
        ScopedFile f;
        FS_OpenFile(filename, &f, FILE_WRITE);
        if (!f)
            Sys_Error("Could not open file %s.", filename);
        FS_Printf(&f, ",");
        for (int x = box.getMinX(); x <= box.getMaxX() - i + 1; x++)
            FS_Printf(&f, "x:%i,", x);
        FS_Printf(&f, "\n");
        for (int z = box.getMaxZ(); z >= box.getMinZ(); z--) {
            for (int y = box.getMaxY(); y >= box.getMinY() - i + 1; y--) {
                FS_Printf(&f, "z:%i  y:%i,", z ,y);
                for (int x = box.getMinX(); x <= box.getMaxX() - i + 1; x++) {
                    /* compare results */
                    FS_Printf(&f, "h:%i c:%i,", routing.getFloor(i, x, y, z), routing.getCeiling(i, x, y, z));
                }
                FS_Printf(&f, "\n");
            }
            FS_Printf(&f, "\n");
        }
    }
 
    /* Output the walls/passage files. */
    for (int i = 1; i <= ACTOR_MAX_SIZE; i++) {
        strncpy(filename, baseFilename, sizeof(filename) - 1);
        sprintf(ext, ".%i.walls.csv", i);
        Com_DefaultExtension(filename, sizeof(filename), ext);
        ScopedFile f;
        FS_OpenFile(filename, &f, FILE_WRITE);
        if (!f)
            Sys_Error("Could not open file %s.", filename);
        FS_Printf(&f, ",");
        for (int x = box.getMinX(); x <= box.getMaxX() - i + 1; x++)
            FS_Printf(&f, "x:%i,", x);
        FS_Printf(&f, "\n");
        for (int z = box.getMaxZ(); z >= box.getMinZ(); z--) {
            for (int y = box.getMaxY(); y >= box.getMinY() - i + 1; y--) {
                FS_Printf(&f, "z:%i  y:%i,", z, y);
                for (int x = box.getMinX(); x <= box.getMaxX() - i + 1; x++) {
                    /* compare results */
                    FS_Printf(&f, "\"");
 
                    /* NW corner */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_NX_PY(routing, i, x, y, z), RT_STEPUP_NX_PY(routing, i, x, y, z));
 
                    /* N side */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_PY(routing, i, x, y, z), RT_STEPUP_PY(routing, i, x, y, z));
 
                    /* NE corner */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_PX_PY(routing, i, x, y, z), RT_STEPUP_PX_PY(routing, i, x, y, z));
 
                    FS_Printf(&f, "\n");
 
                    /* W side */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_NX(routing, i, x, y, z), RT_STEPUP_NX(routing, i, x, y, z));
 
                    /* Center - display floor height */
                    FS_Printf(&f, "_%+2i_ ", routing.getFloor(i, x, y, z));
 
                    /* E side */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_PX(routing, i, x, y, z), RT_STEPUP_PX(routing, i, x, y, z));
 
                    FS_Printf(&f, "\n");
 
                    /* SW corner */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_NX_NY(routing, i, x, y, z), RT_STEPUP_NX_NY(routing, i, x, y, z));
 
                    /* S side */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_NY(routing, i, x, y, z), RT_STEPUP_NY(routing, i, x, y, z));
 
                    /* SE corner */
                    FS_Printf(&f, "%3i-%3i ", RT_CONN_PX_NY(routing, i, x, y, z), RT_STEPUP_PX_NY(routing, i, x, y, z));
 
                    FS_Printf(&f, "\",");
                }
                FS_Printf(&f, "\n");
            }
            FS_Printf(&f, "\n");
        }
    }
}
 
#ifdef DEBUG
int RT_DebugSpecial (mapTiles_t* mapTiles, Routing& routing, const int actorSize, const int x, const int y, const int dir, const char** list)
{
    RoutingData rtd(mapTiles, routing, actorSize, list);    /* the essential data passed down the calltree */
 
    /* get the neighbor cell's coordinates */
    const int ax = x + dvecs[dir][0];
    const int ay = y + dvecs[dir][1];

    const int new_z = RT_UpdateConnection(&rtd, x, y, ax, ay, 0, dir);
    return new_z;
}

void RT_DebugPathDisplay (Routing& routing, actorSizeEnum_t actorSize, int x, int y, int z)
{
    Com_Printf("data at cursor XYZ(%i, %i, %i) Floor(%i) Ceiling(%i)\n", x, y, z,
        routing.getFloor(actorSize, x, y, z),
        routing.getCeiling(actorSize, x, y, z) );
    Com_Printf("connections ortho: (PX=%i, NX=%i, PY=%i, NY=%i))\n",
        RT_CONN_PX(routing, actorSize, x, y, z),        /* dir = 0 */
        RT_CONN_NX(routing, actorSize, x, y, z),        /* 1 */
        RT_CONN_PY(routing, actorSize, x, y, z),        /* 2 */
        RT_CONN_NY(routing, actorSize, x, y, z) );      /* 3 */
    Com_Printf("connections diago: (PX_PY=%i, NX_NY=%i, NX_PY=%i, PX_NY=%i))\n",
        RT_CONN_PX_PY(routing, actorSize, x, y, z),     /* dir = 4 */
        RT_CONN_NX_NY(routing, actorSize, x, y, z),     /* 5 */
        RT_CONN_NX_PY(routing, actorSize, x, y, z),     /* 6 */
        RT_CONN_PX_NY(routing, actorSize, x, y, z) );   /* 7 */
    Com_Printf("stepup ortho: (PX=%i, NX=%i, PY=%i, NY=%i))\n",
        RT_STEPUP_PX(routing, actorSize, x, y, z),      /* dir = 0 */
        RT_STEPUP_NX(routing, actorSize, x, y, z),      /* 1 */
        RT_STEPUP_PY(routing, actorSize, x, y, z),      /* 2 */
        RT_STEPUP_NY(routing, actorSize, x, y, z) );    /* 3 */
}
 
#endif