// This source file contains the functions needed to process floors.
// (c) 1995 ACK Software (Lary Myers)
#include "ack3d.h"
#include "ackeng.h"
#include "ackext.h"

#define MAX_F_VIEWHALFHEIGHT   50

void DrawBackDrop(void);

extern  long FloorCosTable[];
extern    short   gWinStartX;
extern    short   gWinStartY;
extern    short   gWinEndX;
extern    short   gWinHalfHeight;
extern    UCHAR   *gScrnBufferCenter;
extern    long    WallDistTable[];

    long    zdTable[VIEW_WIDTH][50];
    long    mFactor;
    long    dFactor;

//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// Internal function called during the initialize process to setup the
// floor and light shading arrays.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void SetupFloors(ACKENG *ae)
{
    short   i,a;
    int     ht,scanline,ht1;
    int     Scale_Fac;
    long    scan1,scan2,f;
    long    x,y,dist;
    long    Lastx,Lasty;

for ( i=0; i<12;i++ ) scantables[i] = (char*)(ae->PalTable + (7*256));
for ( i=12;i<24;i++ ) scantables[i] = (char*)(ae->PalTable + (6*256));
for ( i=24;i<36;i++ ) scantables[i] = (char*)(ae->PalTable + (5*256));
for ( i=36;i<48;i++ ) scantables[i] = (char*)(ae->PalTable + (4*256));
for ( i=48;i<60;i++ ) scantables[i] = (char*)(ae->PalTable + (3*256));
for ( i=60;i<72;i++ ) scantables[i] = (char*)(ae->PalTable + (2*256));
for ( i=72;i<84;i++ ) scantables[i] = (char*)(ae->PalTable + (1*256));
for ( i=84;i<96;i++ ) scantables[i] = (char*)(ae->PalTable);

Scale_Fac = (89 - ViewHeight) * 5;

ht = 89 - ViewHeight;

ht *= Scale_Fac;

for (i = 0; i < VIEW_WIDTH; i++)
    {
    f = FloorCosTable[i];
    zdTable[i][0] = 0;
    for (scanline = 1; scanline < MAX_F_VIEWHALFHEIGHT; scanline++)
        {
        scan2 = ht / scanline;
        zdTable[i][scanline] = (f * scan2) >> 15;
        if (zdTable[i][scanline-1] < zdTable[i][scanline])
            zdTable[i][scanline-1] = zdTable[i][scanline];

        }
    }

// Some debugging values for internal use
mFactor = 10368;
dFactor = 160;

}

// Optimization attempts were made with drawing the rotating background
// as the ceiling was being drawn and drawing the entire background before
// drawing any ceiling tiles or walls. The former seemed to be faster
// in most cases, so the define below was used to toggle between the two
// methods.
#define DRAW_BACK       1

//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// Draws the floor and ceiling horizontally.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void AckDrawFloorHz(void)
{
    int     i,col,row,ht,Rcol,EndCol,BegCol;
    int     Scale_Fac,ScaleHt;
    UCHAR   *scr,*fscr,*bmp,*scrCeil,*cscr;
    UCHAR   *Rscr,*Rfscr,*RscrCeil,*Rcscr;
    UCHAR   *ba,*ba1,*Rba,*Rba1;
    short   va,va1;
    long    LastDist,scan2;
    long    cv,sv,dist,x,y,bx,by,mPos,bPos,wdist,bcol;
    long    Rbcol,Rwdist,xp,yp;
    long    *zd,*wPtr,*RwPtr,*xyPtr;
    long    fcv;
    UCHAR   ch;
    USHORT    bCode;

#if !(DRAW_BACK)
DrawBackDrop(); // Draw entire background
#endif

BegCol = gWinStartX;
EndCol = gWinEndX;

// Get the starting offset of the center row of the view
scr = gScrnBufferCenter + BegCol;
// Get the left side of the POV view
va = PlayerAngle - INT_ANGLE_32;
// Check for wrap-around
if (va < 0) va += INT_ANGLE_360;

// Adjust the viewing angle based on the starting view column
va += BegCol;
// and check for wrap-around
if (va >= INT_ANGLE_360)
    va -= INT_ANGLE_360;

// Get the starting column for the background, there are 640
// columns possible, so the remainder when we divide is where
// we want to begin displaying
bcol = va % 640;
// Temporarily hold onto the view height / 2
ht = gWinHalfHeight;
// Since our horizon should always have some form of wall or object,
// no matter how far away it is, we can optimize alittle here by not
// drawing the first few horizon rows (it does actually save time!).
// Start 5 video rows above the center row
scrCeil = scr - 1600;
// Start 6 video rows below the center row
scr += 1920;
// Initial right side of view
Rcol = 319;
wPtr = &WallDistTable[BegCol];      // Get pointers to avoid indexing
RwPtr = &WallDistTable[Rcol];

// The ScaleHt is used to determine the distance from the player for each
// row of the floor and ceiling. The value 89 was arrived at based on a
// reasonable height above the floor that the player is standing. By
// experimenting with this value, the effect of jumping up and down can
// be achieved, (as long as the walls and objects are made to jump by the
// same amount).
Scale_Fac = (89 - ViewHeight) * 5;
ScaleHt = 89 - ViewHeight;
ScaleHt *= Scale_Fac;

// Here we loop through each column of the viewing window
for (col = BegCol; col < EndCol; col += 2)
    {
// Pick up the cosine and sine values for the current angle
    cv = CosTable[va];
    sv = SinTable[va];
// Point to the left side of the current floor and ceiling columns
    fscr = scr;
    cscr = scrCeil;
// Advance the columns for the next pass
    scr += 2;
    scrCeil += 2;
// Pick up the current distance to the wall that was found for the
// current column
    wdist = *wPtr;
// Advance the wall distance pointer for the next pass
    wPtr += 2;

#if DRAW_BACK
// Pick up the pointer to the background image for the current column
    ba = BackArray[bcol++];
// Check for wrap-around in our 640 column image
    if (bcol > 639) bcol = 0;
// Pick up the next column as well since the floor and ceiling are
// always done in low resolution
    ba1 = BackArray[bcol++];
    if (bcol > 639) bcol = 0;
    ba += ht;
    ba1 += ht;
#endif

// Initialize a last distance variable
    LastDist = -1;
// Our floor cosine is used to counteract a fisheye effect
    fcv = FloorCosTable[col];

    for (row = 6; row <= ht; row++)
        {

        scan2 = ScaleHt / row;
// Get the distance for the current column and row position
        dist = (fcv * scan2) >> 15;

// If we're still closer than any wall
        if (dist < wdist)
            {
// Do some extra calculations if it's a new distance from last time
// (Sometimes our distance works out to be the same so we can avoid
// the next few lines)
            if (dist != LastDist)
                {
                x = xPglobal + ((cv * dist) >> 16);
                y = yPglobal + ((sv * dist) >> 16);
                LastDist = dist;
                }
            mPos = (y & 0xFC0) + (x >> 6);      // Calc the Map Posn
            if (mPos < 0L || mPos > 4095L)
                continue;
            bPos = (y & 63) + ((x & 63)<<6);    // Calc the Bitmap Pixel

// Get the bitmap number for our floor
            bCode = FloorMap[mPos];
// And use it to pull the actual bitmap from our array of wall bitmaps
            bmp = WallbMaps[bCode];
// Make sure it's really a bitmap and then get the actual pixel to display
            if (bmp != NULL)
                ch = bmp[bPos];

// Place the pixel in this column as well as the next. Since we have a
// scattering effect we can display in low resolution without too much
// loss in detail. This really speeds up the drawing of the floor and
// ceiling.
            *fscr = ch;                         // Put it into two locations
            fscr[1] = ch;                       // for low resolution

// Only draw a ceiling pixel if there is a ceiling tile placed in the map
// This gives the effect of seeing the background through holes in the ceiling
            if ((bCode = CeilMap[mPos]) != 0)
                {
                bmp = WallbMaps[bCode];
                if (bmp != NULL)
                    ch = bmp[bPos];
                *cscr = ch;
                cscr[1] = ch;
                }
#if DRAW_BACK
// If no ceiling is drawn, then we need to draw the background image
            else
                {
                *cscr = *ba;
                cscr[1] = *ba1;
                }
#endif
            }

        fscr += 320;        // Advance our screen position for the floor
        cscr -= 320;        // and the ceiling

#if DRAW_BACK
// Advance the pointers to the background image for the next pass
        ba--;
        ba1--;
#endif
        }

// Advance our current viewing angle by 2 since we are in low resolution
    va += 2;
// and check for wrap-around
    if (va >= INT_ANGLE_360) va -= INT_ANGLE_360;
    }

}

//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// Draws the floor and ceiling horizontally.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void AckDrawCeilingOnlyNS(void)
{
    int     i,col,row,ht,Rcol,EndCol,BegCol;
    int     Scale_Fac,ScaleHt;
    UCHAR   *scr,*fscr,*bmp,*scrCeil,*cscr;
    UCHAR   *Rscr,*Rfscr,*RscrCeil,*Rcscr;
    UCHAR   *ba,*ba1,*Rba,*Rba1;
    short   va,va1;
    long    LastDist,scan2;
    long    cv,sv,dist,x,y,bx,by,mPos,bPos,wdist,bcol;
    long    Rbcol,Rwdist,xp,yp;
    long    *zd,*wPtr,*RwPtr,*xyPtr;
    long    fcv;
    UCHAR   ch;
    USHORT    bCode;

#if !(DRAW_BACK)
DrawBackDrop(); // Draw entire background
#endif

BegCol = gWinStartX;
EndCol = gWinEndX;

// Get the starting offset of the center row of the view
scr = gScrnBufferCenter + BegCol;
// Get the left side of the POV view
va = PlayerAngle - INT_ANGLE_32;
// Check for wrap-around
if (va < 0) va += INT_ANGLE_360;

// Adjust the viewing angle based on the starting view column
va += BegCol;
// and check for wrap-around
if (va >= INT_ANGLE_360)
    va -= INT_ANGLE_360;

// Get the starting column for the background, there are 640
// columns possible, so the remainder when we divide is where
// we want to begin displaying
bcol = va % 640;
// Temporarily hold onto the view height / 2
ht = gWinHalfHeight;
// Since our horizon should always have some form of wall or object,
// no matter how far away it is, we can optimize alittle here by not
// drawing the first few horizon rows (it does actually save time!).
// Start 5 video rows above the center row
scrCeil = scr - 1600;
// Initial right side of view
Rcol = 319;
wPtr = &WallDistTable[BegCol];      // Get pointers to avoid indexing
RwPtr = &WallDistTable[Rcol];

// The ScaleHt is used to determine the distance from the player for each
// row of the floor and ceiling. The value 89 was arrived at based on a
// reasonable height above the floor that the player is standing. By
// experimenting with this value, the effect of jumping up and down can
// be achieved, (as long as the walls and objects are made to jump by the
// same amount).
Scale_Fac = (89 - ViewHeight) * 5;
ScaleHt = 89 - ViewHeight;
ScaleHt *= Scale_Fac;

// Here we loop through each column of the viewing window
for (col = BegCol; col < EndCol; col += 2)
    {
// Pick up the cosine and sine values for the current angle
    cv = CosTable[va];
    sv = SinTable[va];
// Point to the left side of the current ceiling columns
    cscr = scrCeil;
// Advance the columns for the next pass
    scrCeil += 2;
// Pick up the current distance to the wall that was found for the
// current column
    wdist = *wPtr;
// Advance the wall distance pointer for the next pass
    wPtr += 2;

#if DRAW_BACK
// Pick up the pointer to the background image for the current column
    ba = BackArray[bcol++];
// Check for wrap-around in our 640 column image
    if (bcol > 639) bcol = 0;
// Pick up the next column as well since the floor and ceiling are
// always done in low resolution
    ba1 = BackArray[bcol++];
    if (bcol > 639) bcol = 0;
    ba += ht;
    ba1 += ht;
#endif

// Initialize a last distance variable
    LastDist = -1;
// Our floor cosine is used to counteract a fisheye effect
    fcv = FloorCosTable[col];

    for (row = 6; row <= ht; row++)
        {

        scan2 = ScaleHt / row;
// Get the distance for the current column and row position
        dist = (fcv * scan2) >> 15;

// If we're still closer than any wall
        if (dist < wdist)
            {
// Do some extra calculations if it's a new distance from last time
// (Sometimes our distance works out to be the same so we can avoid
// the next few lines)
            if (dist != LastDist)
                {
                x = xPglobal + ((cv * dist) >> 16);
                y = yPglobal + ((sv * dist) >> 16);
                LastDist = dist;
                }
            mPos = (y & 0xFC0) + (x >> 6);      // Calc the Map Posn
            if (mPos < 0L || mPos > 4095L)
                continue;
            bPos = (y & 63) + ((x & 63)<<6);    // Calc the Bitmap Pixel

// Only draw a ceiling pixel if there is a ceiling tile placed in the map
// This gives the effect of seeing the background through holes in the ceiling
            if ((bCode = CeilMap[mPos]) != 0)
                {
                bmp = WallbMaps[bCode];
                if (bmp != NULL)
                    ch = bmp[bPos];
                *cscr = ch;
                cscr[1] = ch;
                }
#if DRAW_BACK
// If no ceiling is drawn, then we need to draw the background image
            else
                {
                *cscr = *ba;
                cscr[1] = *ba1;
                }
#endif
            }

        cscr -= 320;        // and the ceiling

#if DRAW_BACK
// Advance the pointers to the background image for the next pass
        ba--;
        ba1--;
#endif
        }

// Advance our current viewing angle by 2 since we are in low resolution
    va += 2;
// and check for wrap-around
    if (va >= INT_ANGLE_360) va -= INT_ANGLE_360;
    }

}

//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// Draws the floor and ceiling horizontally.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void AckDrawFloorOnlyNS(void)
{
    int     i,col,row,ht,Rcol,EndCol,BegCol;
    int     Scale_Fac,ScaleHt;
    UCHAR   *scr,*fscr,*bmp,*scrCeil,*cscr;
    UCHAR   *Rscr,*Rfscr,*RscrCeil,*Rcscr;
    UCHAR   *ba,*ba1,*Rba,*Rba1;
    short   va,va1;
    long    LastDist,scan2;
    long    cv,sv,dist,x,y,bx,by,mPos,bPos,wdist,bcol;
    long    Rbcol,Rwdist,xp,yp;
    long    *zd,*wPtr,*RwPtr,*xyPtr;
    long    fcv;
    UCHAR   ch;
    USHORT    bCode;

#if !(DRAW_BACK)
DrawBackDrop(); // Draw entire background
#endif

BegCol = gWinStartX;
EndCol = gWinEndX;

// Get the starting offset of the center row of the view
scr = gScrnBufferCenter + BegCol;
// Get the left side of the POV view
va = PlayerAngle - INT_ANGLE_32;
// Check for wrap-around
if (va < 0) va += INT_ANGLE_360;

// Adjust the viewing angle based on the starting view column
va += BegCol;
// and check for wrap-around
if (va >= INT_ANGLE_360)
    va -= INT_ANGLE_360;

// Get the starting column for the background, there are 640
// columns possible, so the remainder when we divide is where
// we want to begin displaying
bcol = va % 640;
// Temporarily hold onto the view height / 2
ht = gWinHalfHeight;
// Since our horizon should always have some form of wall or object,
// no matter how far away it is, we can optimize alittle here by not
// drawing the first few horizon rows (it does actually save time!).
// Start 6 video rows below the center row
scr += 1920;
// Initial right side of view
Rcol = 319;
wPtr = &WallDistTable[BegCol];      // Get pointers to avoid indexing
RwPtr = &WallDistTable[Rcol];

// The ScaleHt is used to determine the distance from the player for each
// row of the floor and ceiling. The value 89 was arrived at based on a
// reasonable height above the floor that the player is standing. By
// experimenting with this value, the effect of jumping up and down can
// be achieved, (as long as the walls and objects are made to jump by the
// same amount).
Scale_Fac = (89 - ViewHeight) * 5;
ScaleHt = 89 - ViewHeight;
ScaleHt *= Scale_Fac;

// Here we loop through each column of the viewing window
for (col = BegCol; col < EndCol; col += 2)
    {
// Pick up the cosine and sine values for the current angle
    cv = CosTable[va];
    sv = SinTable[va];
// Point to the left side of the current floor and ceiling columns
    fscr = scr;
// Advance the columns for the next pass
    scr += 2;
// Pick up the current distance to the wall that was found for the
// current column
    wdist = *wPtr;
// Advance the wall distance pointer for the next pass
    wPtr += 2;

#if DRAW_BACK
// Pick up the pointer to the background image for the current column
    ba = BackArray[bcol++];
// Check for wrap-around in our 640 column image
    if (bcol > 639) bcol = 0;
// Pick up the next column as well since the floor and ceiling are
// always done in low resolution
    ba1 = BackArray[bcol++];
    if (bcol > 639) bcol = 0;
    ba += ht;
    ba1 += ht;
#endif

// Initialize a last distance variable
    LastDist = -1;
// Our floor cosine is used to counteract a fisheye effect
    fcv = FloorCosTable[col];

    for (row = 6; row <= ht; row++)
        {

        scan2 = ScaleHt / row;
// Get the distance for the current column and row position
        dist = (fcv * scan2) >> 15;

// If we're still closer than any wall
        if (dist < wdist)
            {
// Do some extra calculations if it's a new distance from last time
// (Sometimes our distance works out to be the same so we can avoid
// the next few lines)
            if (dist != LastDist)
                {
                x = xPglobal + ((cv * dist) >> 16);
                y = yPglobal + ((sv * dist) >> 16);
                LastDist = dist;
                }
            mPos = (y & 0xFC0) + (x >> 6);      // Calc the Map Posn
            if (mPos < 0L || mPos > 4095L)
                continue;
            bPos = (y & 63) + ((x & 63)<<6);    // Calc the Bitmap Pixel

// Get the bitmap number for our floor
            bCode = FloorMap[mPos];
// And use it to pull the actual bitmap from our array of wall bitmaps
            bmp = WallbMaps[bCode];
// Make sure it's really a bitmap and then get the actual pixel to display
            if (bmp != NULL)
                ch = bmp[bPos];

// Place the pixel in this column as well as the next. Since we have a
// scattering effect we can display in low resolution without too much
// loss in detail. This really speeds up the drawing of the floor and
// ceiling.
            *fscr = ch;                         // Put it into two locations
            fscr[1] = ch;                       // for low resolution
            }

        fscr += 320;        // Advance our screen position for the floor

#if DRAW_BACK
// Advance the pointers to the background image for the next pass
        ba--;
        ba1--;
#endif
        }

// Advance our current viewing angle by 2 since we are in low resolution
    va += 2;
// and check for wrap-around
    if (va >= INT_ANGLE_360) va -= INT_ANGLE_360;
    }

}


//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// The function performs the same process as AckDrawFloorHz except here
// we include light shading with distance.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void AckDrawFloor(void)
{
    int     i,col,row,ht,Rcol,EndCol,BegCol;
    int     Scale_Fac,ScaleHt;
    UCHAR   *scr,*fscr,*bmp,*scrCeil,*cscr;
    UCHAR   *Rscr,*Rfscr,*RscrCeil,*Rcscr;
    UCHAR   *ba,*ba1,*Rba,*Rba1;
    char    *stPtr;
    short   va,va1,LineNum;
    long    LastDist,scan2;
    long    cv,sv,dist,x,y,bx,by,mPos,bPos,wdist,bcol;
    long    Rbcol,Rwdist,xp,yp;
    long    *zd,*wPtr,*RwPtr,*xyPtr;
    long    fcv;
    UCHAR   ch;
    USHORT    bCode;

#if !(DRAW_BACK)
DrawBackDrop(); // Draw entire background
#endif

BegCol = gWinStartX;
EndCol = gWinEndX;

// Get the starting offset of the center row of the view
scr = gScrnBufferCenter + BegCol;
// Get the left side of the POV view
va = PlayerAngle - INT_ANGLE_32;
// Check for wrap-around
if (va < 0) va += INT_ANGLE_360;

// Adjust the viewing angle based on the starting view column
va += BegCol;
// and check for wrap-around
if (va >= INT_ANGLE_360)
    va -= INT_ANGLE_360;

// Get the starting column for the background, there are 640
// columns possible, so the remainder when we divide is where
// we want to begin displaying
bcol = va % 640;
// Temporarily hold onto the view height / 2
ht = gWinHalfHeight;
// Since our horizon should always have some form of wall or object,
// no matter how far away it is, we can optimize alittle here by not
// drawing the first few horizon rows (it does actually save time!).
// Start 5 video rows above the center row
scrCeil = scr - 1600;
// Start 6 video rows below the center row
scr += 1920;
// Initial right side of view
Rcol = 319;
wPtr = &WallDistTable[BegCol];      // Get pointers to avoid indexing
RwPtr = &WallDistTable[Rcol];

// The ScaleHt is used to determine the distance from the player for each
// row of the floor and ceiling. The value 89 was arrived at based on a
// reasonable height above the floor that the player is standing. By
// experimenting with this value, the effect of jumping up and down can
// be achieved, (as long as the walls and objects are made to jump by the
// same amount).
Scale_Fac = (89 - ViewHeight) * 5;
ScaleHt = 89 - ViewHeight;
ScaleHt *= Scale_Fac;

// Here we loop through each column of the viewing window
for (col = BegCol; col < EndCol; col += 2)
    {
// Pick up the cosine and sine values for the current angle
    cv = CosTable[va];
    sv = SinTable[va];
// Point to the left side of the current floor and ceiling columns
    fscr = scr;
    cscr = scrCeil;
// Advance the columns for the next pass
    scr += 2;
    scrCeil += 2;
// Pick up the current distance to the wall that was found for the
// current column
    wdist = *wPtr;
// Advance the wall distance pointer for the next pass
    wPtr += 2;

#if DRAW_BACK
// Pick up the pointer to the background image for the current column
    ba = BackArray[bcol++];
// Check for wrap-around in our 640 column image
    if (bcol > 639) bcol = 0;
// Pick up the next column as well since the floor and ceiling are
// always done in low resolution
    ba1 = BackArray[bcol++];
    if (bcol > 639) bcol = 0;
    ba += ht;
    ba1 += ht;
#endif

// Initialize a last distance variable
    LastDist = -1;
// Our floor cosine is used to counteract a fisheye effect
    fcv = FloorCosTable[col];
    LineNum = 0;

    for (row = 6; row <= ht; row++)
        {
        stPtr = scantables[LineNum++];

        scan2 = ScaleHt / row;
// Get the distance for the current column and row position
        dist = (fcv * scan2) >> 15;

// If we're still closer than any wall
        if (dist < wdist)
            {
// Do some extra calculations if it's a new distance from last time
// (Sometimes our distance works out to be the same so we can avoid
// the next few lines)
            if (dist != LastDist)
                {
                x = xPglobal + ((cv * dist) >> 16);
                y = yPglobal + ((sv * dist) >> 16);
                LastDist = dist;
                }
            mPos = (y & 0xFC0) + (x >> 6);      // Calc the Map Posn
            if (mPos < 0L || mPos > 4095L)
                continue;
            bPos = (y & 63) + ((x & 63)<<6);    // Calc the Bitmap Pixel

// Get the bitmap number for our floor
            bCode = FloorMap[mPos];
// And use it to pull the actual bitmap from our array of wall bitmaps
            bmp = WallbMaps[bCode];
// Make sure it's really a bitmap and then get the actual pixel to display
            if (bmp != NULL)
                ch = bmp[bPos];

            ch = stPtr[ch]; // Get shaded value for pixel

// Place the pixel in this column as well as the next. Since we have a
// scattering effect we can display in low resolution without too much
// loss in detail. This really speeds up the drawing of the floor and
// ceiling.
            *fscr = ch;                         // Put it into two locations
            fscr[1] = ch;                       // for low resolution

// Only draw a ceiling pixel if there is a ceiling tile placed in the map
// This gives the effect of seeing the background through holes in the ceiling
            if ((bCode = CeilMap[mPos]) != 0)
                {
                bmp = WallbMaps[bCode];
                if (bmp != NULL)
                    ch = bmp[bPos];
                ch = stPtr[ch];     // Get shaded value for pixel
                *cscr = ch;
                cscr[1] = ch;
                }
#if DRAW_BACK
// If no ceiling is drawn, then we need to draw the background image
            else
                {
                *cscr = *ba;
                cscr[1] = *ba1;
                }
#endif
            }

        fscr += 320;        // Advance our screen position for the floor
        cscr -= 320;        // and the ceiling

#if DRAW_BACK
// Advance the pointers to the background image for the next pass
        ba--;
        ba1--;
#endif
        }

// Advance our current viewing angle by 2 since we are in low resolution
    va += 2;
// and check for wrap-around
    if (va >= INT_ANGLE_360) va -= INT_ANGLE_360;
    }

}

//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// Draw ceiling texture bitmaps only. Floor is assumed to be a solid color.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void AckDrawCeilingOnly(void)
{
    int     i,col,row,ht,Rcol,EndCol,BegCol;
    int     Scale_Fac,ScaleHt;
    UCHAR   *scr,*fscr,*bmp,*scrCeil,*cscr;
    UCHAR   *Rscr,*Rfscr,*RscrCeil,*Rcscr;
    UCHAR   *ba,*ba1,*Rba,*Rba1;
    short   va,va1,LineNum;
    char    *stPtr;
    long    LastDist,scan2;
    long    cv,sv,dist,x,y,bx,by,mPos,bPos,wdist,bcol;
    long    Rbcol,Rwdist,xp,yp;
    long    *zd,*wPtr,*RwPtr,*xyPtr;
    long    fcv;
    UCHAR   ch;
    USHORT    bCode;

#if !(DRAW_BACK)
DrawBackDrop(); // Draw entire background
#endif

BegCol = gWinStartX;
EndCol = gWinEndX;

// Get the starting offset of the center row of the view
scr = gScrnBufferCenter + BegCol;
// Get the left side of the POV view
va = PlayerAngle - INT_ANGLE_32;
// Check for wrap-around
if (va < 0) va += INT_ANGLE_360;

// Adjust the viewing angle based on the starting view column
va += BegCol;
// and check for wrap-around
if (va >= INT_ANGLE_360)
    va -= INT_ANGLE_360;

// Get the starting column for the background, there are 640
// columns possible, so the remainder when we divide is where
// we want to begin displaying
bcol = va % 640;
// Temporarily hold onto the view height / 2
ht = gWinHalfHeight;
// Since our horizon should always have some form of wall or object,
// no matter how far away it is, we can optimize alittle here by not
// drawing the first few horizon rows (it does actually save time!).
// Start 5 video rows above the center row
scrCeil = scr - 1600;
// Initial right side of view
Rcol = 319;
wPtr = &WallDistTable[BegCol];      // Get pointers to avoid indexing
RwPtr = &WallDistTable[Rcol];

// The ScaleHt is used to determine the distance from the player for each
// row of the floor and ceiling. The value 89 was arrived at based on a
// reasonable height above the floor that the player is standing. By
// experimenting with this value, the effect of jumping up and down can
// be achieved, (as long as the walls and objects are made to jump by the
// same amount).
Scale_Fac = (89 - ViewHeight) * 5;
ScaleHt = 89 - ViewHeight;
ScaleHt *= Scale_Fac;

// Here we loop through each column of the viewing window
for (col = BegCol; col < EndCol; col += 2)
    {
// Pick up the cosine and sine values for the current angle
    cv = CosTable[va];
    sv = SinTable[va];
// Point to the left side of the current ceiling columns
    cscr = scrCeil;
// Advance the columns for the next pass
    scrCeil += 2;
// Pick up the current distance to the wall that was found for the
// current column
    wdist = *wPtr;
// Advance the wall distance pointer for the next pass
    wPtr += 2;

#if DRAW_BACK
// Pick up the pointer to the background image for the current column
    ba = BackArray[bcol++];
// Check for wrap-around in our 640 column image
    if (bcol > 639) bcol = 0;
// Pick up the next column as well since the floor and ceiling are
// always done in low resolution
    ba1 = BackArray[bcol++];
    if (bcol > 639) bcol = 0;
    ba += ht;
    ba1 += ht;
#endif

// Initialize a last distance variable
    LastDist = -1;
// Our floor cosine is used to counteract a fisheye effect
    fcv = FloorCosTable[col];
    LineNum = 0;

    for (row = 6; row <= ht; row++)
        {
        stPtr = scantables[LineNum++];
        scan2 = ScaleHt / row;
// Get the distance for the current column and row position
        dist = (fcv * scan2) >> 15;

// If we're still closer than any wall
        if (dist < wdist)
            {
// Do some extra calculations if it's a new distance from last time
// (Sometimes our distance works out to be the same so we can avoid
// the next few lines)
            if (dist != LastDist)
                {
                x = xPglobal + ((cv * dist) >> 16);
                y = yPglobal + ((sv * dist) >> 16);
                LastDist = dist;
                }
            mPos = (y & 0xFC0) + (x >> 6);      // Calc the Map Posn
            if (mPos < 0L || mPos > 4095L)
                continue;
            bPos = (y & 63) + ((x & 63)<<6);    // Calc the Bitmap Pixel

// Only draw a ceiling pixel if there is a ceiling tile placed in the map
// This gives the effect of seeing the background through holes in the ceiling
            if ((bCode = CeilMap[mPos]) != 0)
                {
                bmp = WallbMaps[bCode];
                if (bmp != NULL)
                    ch = bmp[bPos];

                ch = stPtr[ch]; // Get shaded pixel
                *cscr = ch;
                cscr[1] = ch;
                }
#if DRAW_BACK
// If no ceiling is drawn, then we need to draw the background image
            else
                {
                *cscr = *ba;
                cscr[1] = *ba1;
                }
#endif
            }

        cscr -= 320;        // and the ceiling

#if DRAW_BACK
// Advance the pointers to the background image for the next pass
        ba--;
        ba1--;
#endif
        }

// Advance our current viewing angle by 2 since we are in low resolution
    va += 2;
// and check for wrap-around
    if (va >= INT_ANGLE_360) va -= INT_ANGLE_360;
    }

}


//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// Draw floor textured bitmaps only. Ceiling is a solid color.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void AckDrawFloorOnly(void)
{
    int     i,col,row,ht,Rcol,EndCol,BegCol;
    int     Scale_Fac,ScaleHt;
    UCHAR   *scr,*fscr,*bmp,*scrCeil,*cscr;
    UCHAR   *Rscr,*Rfscr,*RscrCeil,*Rcscr;
    UCHAR   *ba,*ba1,*Rba,*Rba1;
    short   va,va1,LineNum;
    char    *stPtr;
    long    LastDist,scan2;
    long    cv,sv,dist,x,y,bx,by,mPos,bPos,wdist,bcol;
    long    Rbcol,Rwdist,xp,yp;
    long    *zd,*wPtr,*RwPtr,*xyPtr;
    long    fcv;
    UCHAR   ch;
    USHORT    bCode;

#if !(DRAW_BACK)
DrawBackDrop(); // Draw entire background
#endif

BegCol = gWinStartX;
EndCol = gWinEndX;

// Get the starting offset of the center row of the view
scr = gScrnBufferCenter + BegCol;
// Get the left side of the POV view
va = PlayerAngle - INT_ANGLE_32;
// Check for wrap-around
if (va < 0) va += INT_ANGLE_360;

// Adjust the viewing angle based on the starting view column
va += BegCol;
// and check for wrap-around
if (va >= INT_ANGLE_360)
    va -= INT_ANGLE_360;

// Get the starting column for the background, there are 640
// columns possible, so the remainder when we divide is where
// we want to begin displaying
bcol = va % 640;
// Temporarily hold onto the view height / 2
ht = gWinHalfHeight;
// Since our horizon should always have some form of wall or object,
// no matter how far away it is, we can optimize alittle here by not
// drawing the first few horizon rows (it does actually save time!).
// Start 6 video rows below the center row
scr += 1920;
// Initial right side of view
Rcol = 319;
wPtr = &WallDistTable[BegCol];      // Get pointers to avoid indexing
RwPtr = &WallDistTable[Rcol];

// The ScaleHt is used to determine the distance from the player for each
// row of the floor and ceiling. The value 89 was arrived at based on a
// reasonable height above the floor that the player is standing. By
// experimenting with this value, the effect of jumping up and down can
// be achieved, (as long as the walls and objects are made to jump by the
// same amount).
Scale_Fac = (89 - ViewHeight) * 5;
ScaleHt = 89 - ViewHeight;
ScaleHt *= Scale_Fac;

// Here we loop through each column of the viewing window
for (col = BegCol; col < EndCol; col += 2)
    {
// Pick up the cosine and sine values for the current angle
    cv = CosTable[va];
    sv = SinTable[va];
// Point to the left side of the current floor and ceiling columns
    fscr = scr;
// Advance the columns for the next pass
    scr += 2;
// Pick up the current distance to the wall that was found for the
// current column
    wdist = *wPtr;
// Advance the wall distance pointer for the next pass
    wPtr += 2;

#if DRAW_BACK
// Pick up the pointer to the background image for the current column
    ba = BackArray[bcol++];
// Check for wrap-around in our 640 column image
    if (bcol > 639) bcol = 0;
// Pick up the next column as well since the floor and ceiling are
// always done in low resolution
    ba1 = BackArray[bcol++];
    if (bcol > 639) bcol = 0;
    ba += ht;
    ba1 += ht;
#endif

// Initialize a last distance variable
    LastDist = -1;
// Our floor cosine is used to counteract a fisheye effect
    fcv = FloorCosTable[col];
    LineNum = 0;

    for (row = 6; row <= ht; row++)
        {
        stPtr = scantables[LineNum++];
        scan2 = ScaleHt / row;
// Get the distance for the current column and row position
        dist = (fcv * scan2) >> 15;

// If we're still closer than any wall
        if (dist < wdist)
            {
// Do some extra calculations if it's a new distance from last time
// (Sometimes our distance works out to be the same so we can avoid
// the next few lines)
            if (dist != LastDist)
                {
                x = xPglobal + ((cv * dist) >> 16);
                y = yPglobal + ((sv * dist) >> 16);
                LastDist = dist;
                }
            mPos = (y & 0xFC0) + (x >> 6);      // Calc the Map Posn
            if (mPos < 0L || mPos > 4095L)
                continue;
            bPos = (y & 63) + ((x & 63)<<6);    // Calc the Bitmap Pixel

// Get the bitmap number for our floor
            bCode = FloorMap[mPos];
// And use it to pull the actual bitmap from our array of wall bitmaps
            bmp = WallbMaps[bCode];
// Make sure it's really a bitmap and then get the actual pixel to display
            if (bmp != NULL)
                ch = bmp[bPos];

            ch = stPtr[ch]; // Get shaded pixel

// Place the pixel in this column as well as the next. Since we have a
// scattering effect we can display in low resolution without too much
// loss in detail. This really speeds up the drawing of the floor and
// ceiling.
            *fscr = ch;                         // Put it into two locations
            fscr[1] = ch;                       // for low resolution
            }

        fscr += 320;        // Advance our screen position for the floor

#if DRAW_BACK
// Advance the pointers to the background image for the next pass
        ba--;
        ba1--;
#endif
        }

// Advance our current viewing angle by 2 since we are in low resolution
    va += 2;
// and check for wrap-around
    if (va >= INT_ANGLE_360) va -= INT_ANGLE_360;
    }

}




//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
// This function performs the same process as AckDrawFloorHz except
// we don't need to check for a bitmap index for every pixel since only
// one bitmap will be used for the floor and one bitmap for the ceiling.
// Draws a floor that contains only one type of bitmap. This is a much
// faster process and may be useful in some applications.
//ħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħħ
void AckDrawOneFloor(void)
{
    int     i,col,row,ht,Rcol,EndCol,BegCol;
    int     Scale_Fac,ScaleHt;
    UCHAR   *scr,*fscr,*bmp,*cbmp,*scrCeil,*cscr;
    UCHAR   *Rscr,*Rfscr,*RscrCeil,*Rcscr;
    UCHAR   *ba,*ba1,*Rba,*Rba1;
    short   va,va1;
    long    LastDist,scan2;
    long    cv,sv,dist,x,y,bx,by,mPos,bPos,wdist,bcol;
    long    Rbcol,Rwdist,xp,yp;
    long    *zd,*wPtr,*RwPtr,*xyPtr;
    long    fcv;
    UCHAR   ch;
    USHORT    bCode;


BegCol = gWinStartX;
EndCol = gWinEndX;

// Get the starting offset of the center row of the view
scr = gScrnBufferCenter + BegCol;
// Get the left side of the POV view
va = PlayerAngle - INT_ANGLE_32;
// Check for wrap-around
if (va < 0) va += INT_ANGLE_360;

// Adjust the viewing angle based on the starting view column
va += BegCol;
// and check for wrap-around
if (va >= INT_ANGLE_360)
    va -= INT_ANGLE_360;

// Temporarily hold onto the view height / 2
ht = gWinHalfHeight;
// Since our horizon should always have some form of wall or object,
// no matter how far away it is, we can optimize alittle here by not
// drawing the first few horizon rows (it does actually save time!).
// Start 5 video rows above the center row
scrCeil = scr - 1600;
// Start 6 video rows below the center row
scr += 1920;
// Initial right side of view
Rcol = 319;
wPtr = &WallDistTable[BegCol];      // Get pointers to avoid indexing
RwPtr = &WallDistTable[Rcol];

// The ScaleHt is used to determine the distance from the player for each
// row of the floor and ceiling. The value 89 was arrived at based on a
// reasonable height above the floor that the player is standing. By
// experimenting with this value, the effect of jumping up and down can
// be achieved, (as long as the walls and objects are made to jump by the
// same amount).
Scale_Fac = (89 - ViewHeight) * 5;
ScaleHt = 89 - ViewHeight;
ScaleHt *= Scale_Fac;

bmp = aeGlobal->bMaps[aeGlobal->FloorBitmap];
cbmp = aeGlobal->bMaps[aeGlobal->CeilBitmap];

// Here we loop through each column of the viewing window
for (col = BegCol; col < EndCol; col += 2)
    {
// Pick up the cosine and sine values for the current angle
    cv = CosTable[va];
    sv = SinTable[va];
// Point to the left side of the current floor and ceiling columns
    fscr = scr;
    cscr = scrCeil;
// Advance the columns for the next pass
    scr += 2;
    scrCeil += 2;
// Pick up the current distance to the wall that was found for the
// current column
    wdist = *wPtr;
// Advance the wall distance pointer for the next pass
    wPtr += 2;

// Initialize a last distance variable
    LastDist = -1;
// Our floor cosine is used to counteract a fisheye effect
    fcv = FloorCosTable[col];

    for (row = 6; row <= ht; row++)
        {
        scan2 = ScaleHt / row;
// Get the distance for the current column and row position
        dist = (fcv * scan2) >> 15;

// If we're still closer than any wall
        if (dist < wdist)
            {
// Do some extra calculations if it's a new distance from last time
// (Sometimes our distance works out to be the same so we can avoid
// the next few lines)
            if (dist != LastDist)
                {
                x = xPglobal + ((cv * dist) >> 16);
                y = yPglobal + ((sv * dist) >> 16);
                LastDist = dist;
                }

            bPos = (y & 63) + ((x & 63)<<6);    // Calc the Bitmap Pixel
            ch = bmp[bPos];

// Place the pixel in this column as well as the next. Since we have a
// scattering effect we can display in low resolution without too much
// loss in detail. This really speeds up the drawing of the floor and
// ceiling.
            *fscr = ch;                         // Put it into two locations
            fscr[1] = ch;                       // for low resolution

            ch = cbmp[bPos];
            *cscr = ch;
            cscr[1] = ch;
            }

        fscr += 320;        // Advance our screen position for the floor
        cscr -= 320;        // and the ceiling
        }

// Advance our current viewing angle by 2 since we are in low resolution
    va += 2;
// and check for wrap-around
    if (va >= INT_ANGLE_360) va -= INT_ANGLE_360;
    }

}

// **** End of Source ****