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C4_DRAW.C
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/* Catacomb Abyss Source Code
* Copyright (C) 1993-2014 Flat Rock Software
*
* 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
// C3_DRAW.C
#include "DEF.H"
#pragma hdrstop
//#define DRAWEACH // draw walls one at a time for debugging
unsigned highest;
unsigned mostwalls,numwalls;
/*
=============================================================================
LOCAL CONSTANTS
=============================================================================
*/
#define PI 3.141592657
#define ANGLEQUAD (ANGLES/4)
unsigned oldend;
#define FINEANGLES 3600
#define MINRATIO 16
const unsigned MAXSCALEHEIGHT = (VIEWWIDTH/2);
const unsigned MAXVISHEIGHT = (VIEWHEIGHT/2);
const unsigned BASESCALE = 32;
/*
=============================================================================
GLOBAL VARIABLES
=============================================================================
*/
//
// calculate location of screens in video memory so they have the
// maximum possible distance seperating them (for scaling overflow)
//
unsigned screenloc[3]= {PAGE1START,PAGE2START,PAGE3START};
unsigned freelatch = FREESTART;
boolean fizzlein;
long scaleshapecalll;
long scaletablecall;
/*
=============================================================================
LOCAL VARIABLES
=============================================================================
*/
long bytecount,endcount; // for profiling
int animframe;
int pixelangle[VIEWWIDTH];
int far finetangent[FINEANGLES+1];
int fineviewangle;
unsigned viewxpix,viewypix;
/*
============================================================================
3 - D DEFINITIONS
============================================================================
*/
fixed tileglobal = TILEGLOBAL;
fixed focallength = FOCALLENGTH;
fixed mindist = MINDIST;
int viewheight = VIEWHEIGHT;
fixed scale;
tilept tile,lasttile, // tile of wall being followed
focal, // focal point in tiles
left,mid,right; // rightmost tile in view
globpt edge,view;
int segstart[VIEWHEIGHT], // addline tracks line segment and draws
segend[VIEWHEIGHT],
segcolor[VIEWHEIGHT]; // only when the color changes
walltype walls[MAXWALLS],*leftwall,*rightwall;
//==========================================================================
//
// refresh stuff
//
int screenpage;
long lasttimecount;
//
// rendering stuff
//
int firstangle,lastangle;
fixed prestep;
fixed sintable[ANGLES+ANGLES/4],*costable = sintable+(ANGLES/4);
fixed viewx,viewy; // the focal point
int viewangle;
fixed viewsin,viewcos;
int zbuffer[VIEWXH+1]; // holds the height of the wall at that point
//==========================================================================
void DrawLine (int xl, int xh, int y,int color);
void DrawWall (walltype *wallptr);
void TraceRay (unsigned angle);
fixed FixedByFrac (fixed a, fixed b);
fixed FixedAdd (void);
fixed TransformX (fixed gx, fixed gy);
int FollowTrace (fixed tracex, fixed tracey, long deltax, long deltay, int max);
int BackTrace (int finish);
void ForwardTrace (void);
int TurnClockwise (void);
int TurnCounterClockwise (void);
void FollowWall (void);
void NewScene (void);
void BuildTables (void);
//==========================================================================
#if 0
/*
==================
=
= DrawLine
=
= Must be in write mode 2 with all planes enabled
= The bit mask is left set to the end value, so clear it after all lines are
= drawn
=
= draws a black dot at the left edge of the line
=
==================
*/
unsigned static char dotmask[8] = {0x80,0x40,0x20,0x10,8,4,2,1};
unsigned static char leftmask[8] = {0xff,0x7f,0x3f,0x1f,0xf,7,3,1};
unsigned static char rightmask[8] = {0x80,0xc0,0xe0,0xf0,0xf8,0xfc,0xfe,0xff};
void DrawLine (int xl, int xh, int y,int color)
{
unsigned dest,xlp,xlb,xhb,maskleft,maskright,maskdot,mid;
xlb=xl/8;
xhb=xh/8;
if (xh<xl)
Quit("DrawLine: xh<xl");
if (y<VIEWY)
Quit("DrawLine: y<VIEWY");
if (y>VIEWYH)
Quit("DrawLine: y>VIEWYH");
xlp = xl&7;
maskleft = leftmask[xlp];
maskright = rightmask[xh&7];
mid = xhb-xlb-1;
dest = bufferofs+ylookup[y]+xlb;
//
// set the GC index register to point to the bit mask register
//
asm mov al,GC_BITMASK
asm mov dx,GC_INDEX
asm out dx,al
if (xlb==xhb)
{
//
// entire line is in one byte
//
maskleft&=maskright;
asm mov es,[screenseg]
asm mov di,[dest]
asm mov dx,GC_INDEX+1
asm mov al,[BYTE PTR maskleft]
asm out dx,al // mask off pixels
asm mov al,[BYTE PTR color]
asm xchg al,[es:di] // load latches and write pixels
return;
}
asm mov es,[screenseg]
asm mov di,[dest]
asm mov dx,GC_INDEX+1
asm mov bh,[BYTE PTR color]
//
// draw left side
//
asm mov al,[BYTE PTR maskleft]
asm out dx,al // mask off pixels
asm mov al,bh
asm xchg al,[es:di] // load latches and write pixels
asm inc di
//
// draw middle
//
asm mov al,255
asm out dx,al // no masking
asm mov al,bh
asm mov cx,[mid]
asm rep stosb
//
// draw right side
//
asm mov al,[BYTE PTR maskright]
asm out dx,al // mask off pixels
asm xchg bh,[es:di] // load latches and write pixels
}
//==========================================================================
void DrawLineDot (int xl, int xh, int y,int color)
{
unsigned dest,xlp,xlb,xhb,maskleft,maskright,maskdot,mid;
xlb=xl/8;
xhb=xh/8;
if (xh<xl)
Quit("DrawLine: xh<xl");
if (y<VIEWY)
Quit("DrawLine: y<VIEWY");
if (y>VIEWYH)
Quit("DrawLine: y>VIEWYH");
xlp = xl&7;
maskdot = dotmask[xlp];
maskleft = leftmask[xlp];
maskright = rightmask[xh&7];
mid = xhb-xlb-1;
dest = bufferofs+ylookup[y]+xlb;
//
// set the GC index register to point to the bit mask register
//
asm mov al,GC_BITMASK
asm mov dx,GC_INDEX
asm out dx,al
if (xlb==xhb)
{
//
// entire line is in one byte
//
maskleft&=maskright;
asm mov es,[screenseg]
asm mov di,[dest]
asm mov dx,GC_INDEX+1
asm mov al,[BYTE PTR maskleft]
asm out dx,al // mask off pixels
asm mov al,[BYTE PTR color]
asm xchg al,[es:di] // load latches and write pixels
//
// write the black dot at the start
//
asm mov al,[BYTE PTR maskdot]
asm out dx,al // mask off pixels
asm xor al,al
asm xchg al,[es:di] // load latches and write pixels
return;
}
asm mov es,[screenseg]
asm mov di,[dest]
asm mov dx,GC_INDEX+1
asm mov bh,[BYTE PTR color]
//
// draw left side
//
asm mov al,[BYTE PTR maskleft]
asm out dx,al // mask off pixels
asm mov al,bh
asm xchg al,[es:di] // load latches and write pixels
//
// write the black dot at the start
//
asm mov al,[BYTE PTR maskdot]
asm out dx,al // mask off pixels
asm xor al,al
asm xchg al,[es:di] // load latches and write pixels
asm inc di
//
// draw middle
//
asm mov al,255
asm out dx,al // no masking
asm mov al,bh
asm mov cx,[mid]
asm rep stosb
//
// draw right side
//
asm mov al,[BYTE PTR maskright]
asm out dx,al // mask off pixels
asm xchg bh,[es:di] // load latches and write pixels
}
#endif
//==========================================================================
long wallscalesource;
#ifdef DRAWEACH
/*
====================
=
= ScaleOneWall
=
====================
*/
void near ScaleOneWall (int xl, int xh)
{
int x,pixwidth,height;
*(((unsigned *)&wallscalesource)+1) = wallseg[xl];
for (x=xl;x<=xh;x+=pixwidth)
{
height = wallheight[x];
pixwidth = wallwidth[x];
(unsigned)wallscalesource = wallofs[x];
*(((unsigned *)&scaletablecall)+1) = (unsigned)scaledirectory[height];
(unsigned)scaletablecall = scaledirectory[height]->codeofs[0];
//
// scale a byte wide strip of wall
//
asm mov bx,[x]
asm mov di,bx
asm shr di,1
asm shr di,1
asm shr di,1 // X in bytes
asm add di,[bufferofs]
asm and bx,7
asm shl bx,1
asm shl bx,1
asm shl bx,1
asm add bx,[pixwidth] // bx = pixel*8+pixwidth-1
asm dec bx
asm mov al,BYTE PTR [bitmasks1+bx]
asm mov dx,GC_INDEX+1
asm out dx,al // set bit mask register
asm mov es,[screenseg]
asm lds si,[wallscalesource]
asm call [DWORD PTR ss:scaletablecall] // scale the line of pixels
asm mov al,BYTE PTR [ss:bitmasks2+bx]
asm or al,al
asm jz nosecond
//
// draw a second byte for vertical strips that cross two bytes
//
asm inc di
asm out dx,al // set bit mask register
asm call [DWORD PTR ss:scaletablecall] // scale the line of pixels
nosecond:
asm mov ax,ss
asm mov ds,ax
}
}
#endif
// EAST / WEST WALLS
//
int walllight1[NUMFLOORS] = {0,
W_WARP1EWPIC,
W_NEMPICEWPIC,W_PENTAEWPIC,W_ALTER_LFPIC,W_ALTER_RTPIC,
W_SUB1EWPIC,W_SUB2EWPIC,W_SUB3EWPIC,
W_TORCH1PIC,W_TORCH2PIC,
W_LSUB_STONEPIC,
W_BLOODY_LSUB_STONEPIC,
W_BREATH_LWALL1PIC,W_BREATH_LWALL2PIC,
EXPWALL1PIC,EXPWALL2PIC,EXPWALL3PIC,
W_WOOD_DOORWAYPIC,W_WOOD_DOORWAY_GLOWPIC,
W_WATER1EWPIC,W_DRAIN1EWPIC,
W_WATER2EWPIC,W_DRAIN2EWPIC,
W_WOODEN_DOORPIC,W_WOOD_DOOREWPIC,W_METAL_DOORPIC,W_GLOW_DOORPIC,
W_FINALEXITPIC,
W_WATER_EXP1PIC,W_WATER_EXP2PIC,W_WATER_EXP3PIC,
W_PRE_CHEATSPIC,W_CHEAT_WARPPIC,W_CHEAT_FREEZEPIC,W_SURFACE_PLAQPIC,
W_WATER_GATEEW1PIC,
WALL8LPIC,WALL9LPIC,WALL10DPIC,WALL11LPIC,WALL12LPIC,WALL13LPIC,WALL14LPIC,WALL15LPIC,
WALL16LPIC,WALL17LPIC,W_WINDOWEWPIC,WALL19LPIC,WALL20LPIC,WALL21LPIC,
WALL22LPIC,WALL23LPIC,WALL24LPIC,WALL25LPIC,WALL26LPIC,WALL27LPIC,
WALL28LPIC,WALL29LPIC,WALL30LPIC,WALL31LPIC,
W_BREATH_LWALL4PIC,W_BREATH_LWALL3PIC,
MAGE_STATUEPIC,ZOMBIE_STATUEPIC,EYE_STATUEPIC,NEM_STATUEPIC,
SKELETON_STATUEPIC,SPOOK_STATUEPIC,ORCH_STATUEPIC,
};
// NORTH / SOUTH WALLS
//
int walldark1[NUMFLOORS] = {0,
W_WARP1NSPIC,
W_NEMPICEWPIC,W_PENTANSPIC,1,1,
W_SUB1NSPIC,W_SUB2NSPIC,W_SUB3NSPIC,
W_TORCH1PIC,W_TORCH2PIC,
W_DSUB_STONEPIC,
W_BLOODY_DSUB_STONEPIC,
W_BREATH_DWALL1PIC,W_BREATH_DWALL2PIC,
EXPWALL1PIC,EXPWALL2PIC,EXPWALL3PIC,
W_WOOD_DOORWAYPIC,W_WOOD_DOORWAY_GLOWPIC,
W_WATER1NSPIC,W_DRAIN1NSPIC,
W_WATER2NSPIC,W_DRAIN2NSPIC,
W_WOODEN_DOORPIC,W_WOOD_DOORNSPIC,W_METAL_DOORPIC,W_GLOW_DOORPIC,
W_FINALEXITPIC,
W_WATER_EXP1PIC,W_WATER_EXP2PIC,W_WATER_EXP3PIC,
W_CHEAT_GODPIC,W_CHEAT_ITEMSPIC,W_POST_CHEATPIC,W_SURFACE_PLAQPIC,
W_WATER_GATENS1PIC,
WALL8DPIC,WALL9DPIC,WALL10LPIC,WALL11DPIC,WALL12DPIC,WALL13DPIC,WALL14DPIC,WALL15DPIC,
WALL16DPIC,WALL17DPIC,W_WINDOWNSPIC,WALL19DPIC,WALL20DPIC,WALL21DPIC,
WALL22DPIC,WALL23DPIC,WALL24DPIC,WALL25DPIC,WALL26DPIC,WALL27DPIC,
WALL28DPIC,WALL29DPIC,WALL30DPIC,WALL31DPIC,
W_BREATH_DWALL4PIC,W_BREATH_DWALL3PIC,
MAGE_STATUEPIC,ZOMBIE_STATUEPIC,EYE_STATUEPIC,NEM_STATUEPIC,
SKELETON_STATUEPIC,SPOOK_STATUEPIC,ORCH_STATUEPIC,
};
// EAST / WEST WALLS
//
int walllight2[NUMFLOORS] = {0,
W_WARP2EWPIC,
W_NEMPICEWPIC,W_PENTAEWPIC,W_ALTER_LFPIC,W_ALTER_RTPIC,
W_SUB1EWPIC,W_SUB2EWPIC,W_SUB3EWPIC,
W_TORCH2PIC,W_TORCH1PIC,
W_LSUB_STONEPIC,
W_BLOODY_LSUB_STONEPIC,
W_BREATH_LWALL2PIC,W_BREATH_LWALL1PIC,
EXPWALL2PIC,EXPWALL1PIC,EXPWALL3PIC,
W_WOOD_DOORWAYPIC,W_WOOD_DOORWAY_GLOWPIC,
W_WATER2EWPIC,W_DRAIN2EWPIC,
W_WATER1EWPIC,W_DRAIN1EWPIC,
W_WOODEN_DOORPIC,W_WOOD_DOOREWPIC,W_METAL_DOORPIC,W_GLOW_DOORPIC,
W_FINALEXITPIC,
W_WATER_EXP2PIC,W_WATER_EXP1PIC,W_WATER_EXP1PIC,
W_PRE_CHEATSPIC,W_CHEAT_WARPPIC,W_CHEAT_FREEZEPIC,W_SURFACE_PLAQPIC,
W_WATER_GATEEW2PIC,
WALL8LPIC,WALL9LPIC,WALL10DPIC,WALL11LPIC,WALL12LPIC,WALL13LPIC,WALL14LPIC,WALL15LPIC,
WALL16LPIC,WALL17LPIC,W_WINDOWEWPIC,WALL19LPIC,WALL20LPIC,WALL21LPIC,
WALL22LPIC,WALL23LPIC,WALL24LPIC,WALL25LPIC,WALL26LPIC,WALL27LPIC,
WALL28LPIC,WALL29LPIC,WALL30LPIC,WALL31LPIC,
W_BREATH_LWALL3PIC,W_BREATH_LWALL4PIC,
MAGE_STATUEPIC,ZOMBIE_STATUEPIC,EYE_STATUEPIC,NEM_STATUEPIC,
SKELETON_STATUEPIC,SPOOK_STATUEPIC,ORCH_STATUEPIC,
};
// NORTH / SOUTH WALLS
//
int walldark2[NUMFLOORS] = {0,
W_WARP2NSPIC,
W_NEMPICEWPIC,W_PENTANSPIC,1,1,
W_SUB1NSPIC,W_SUB2NSPIC,W_SUB3NSPIC,
W_TORCH2PIC,W_TORCH1PIC,
W_DSUB_STONEPIC,
W_BLOODY_DSUB_STONEPIC,
W_BREATH_DWALL2PIC,W_BREATH_DWALL1PIC,
EXPWALL2PIC,EXPWALL1PIC,EXPWALL3PIC,
W_WOOD_DOORWAYPIC,W_WOOD_DOORWAY_GLOWPIC,
W_WATER2NSPIC,W_DRAIN2NSPIC,
W_WATER1NSPIC,W_DRAIN1NSPIC,
W_WOODEN_DOORPIC,W_WOOD_DOORNSPIC,W_METAL_DOORPIC,W_GLOW_DOORPIC,
W_FINALEXITPIC,
W_WATER_EXP2PIC,W_WATER_EXP1PIC,W_WATER_EXP1PIC,
W_CHEAT_GODPIC,W_CHEAT_ITEMSPIC,W_POST_CHEATPIC,W_SURFACE_PLAQPIC,
W_WATER_GATENS2PIC,
WALL8DPIC,WALL9DPIC,WALL10LPIC,WALL11DPIC,WALL12DPIC,WALL13DPIC,WALL14DPIC,WALL15DPIC,
WALL16DPIC,WALL17DPIC,W_WINDOWNSPIC,WALL19DPIC,WALL20DPIC,WALL21DPIC,
WALL22DPIC,WALL23DPIC,WALL24DPIC,WALL25DPIC,WALL26DPIC,WALL27DPIC,
WALL28DPIC,WALL29DPIC,WALL30DPIC,WALL31DPIC,
W_BREATH_DWALL3PIC,W_BREATH_DWALL4PIC,
MAGE_STATUEPIC,ZOMBIE_STATUEPIC,EYE_STATUEPIC,NEM_STATUEPIC,
SKELETON_STATUEPIC,SPOOK_STATUEPIC,ORCH_STATUEPIC,
};
/*
=====================
=
= DrawVWall
=
= Draws a wall by vertical segments, for texture mapping!
=
= wallptr->side is true for east/west walls (constant x)
=
= fracheight and fracstep are 16.16 bit fractions
=
=====================
*/
void DrawVWall (walltype *wallptr)
{
int x,i;
unsigned source;
unsigned width,sourceint;
unsigned wallpic,wallpicseg;
unsigned skip;
long fracheight,fracstep,longheightchange;
unsigned height;
int heightchange;
unsigned slope,distance;
int traceangle,angle;
int mapadd;
unsigned lastpix,lastsource,lastwidth;
short mike;
if (wallptr->rightclip < wallptr->leftclip)
Quit ("DrawVWall: Right < Left");
//
// setup for height calculation
//
wallptr->height1 >>= 1;
wallptr->height2 >>= 1;
wallptr->planecoord>>=10; // remove non significant bits
width = wallptr->x2 - wallptr->x1;
if (width)
{
heightchange = wallptr->height2 - wallptr->height1;
asm mov ax,[heightchange]
asm mov WORD PTR [longheightchange+2],ax
asm mov WORD PTR [longheightchange],0 // avoid long shift by 16
fracstep = longheightchange/width;
}
fracheight = ((long)wallptr->height1<<16)+0x8000;
skip = wallptr->leftclip - wallptr->x1;
if (skip)
fracheight += fracstep*skip;
//
// setup for texture mapping
//
// mapadd is 64*64 (to keep source positive) + the origin wall intercept
// distance has 6 unit bits, and 6 frac bits
// traceangle is the center view angle in FINEANGLES, moved to be in
// the +-90 degree range (to thew right of origin)
//
traceangle = fineviewangle;
//
// find wall picture to map from
//
if (wallptr->side)
{ // east or west wall
if (wallptr->color == 1)
mike = 1;
if (animframe)
wallpic = walllight2[wallptr->color];
else
wallpic = walllight1[wallptr->color];
if (wallptr->planecoord < viewxpix)
{
distance = viewxpix-wallptr->planecoord;
traceangle -= FINEANGLES/2;
mapadd = (64-viewypix&63); // the pixel spot of the origin
}
else
{
distance = wallptr->planecoord-viewxpix;
// traceangle is correct
mapadd = viewypix&63; // the pixel spot of the origin
}
}
else
{ // north or south wall
if (wallptr->color == 1)
mike = 1;
if (animframe)
wallpic = walldark2[wallptr->color];
else
wallpic = walldark1[wallptr->color];
if (wallptr->planecoord < viewypix)
{
distance = viewypix-wallptr->planecoord;
traceangle -= FINEANGLES/4;
mapadd = viewxpix&63; // the pixel spot of the origin
}
else
{
distance = wallptr->planecoord-viewypix;
traceangle -= FINEANGLES*3/4;
mapadd = (64-viewxpix&63); // the pixel spot of the origin
}
}
mapadd = 64*64-mapadd; // make sure it stays positive
wallpicseg = (unsigned)walldirectory[wallpic-FIRSTWALLPIC];
if (traceangle > FINEANGLES/2)
traceangle -= FINEANGLES;
//
// calculate everything
//
// IMPORTANT! This loop is executed around 5000 times / second!
//
lastpix = lastsource = (unsigned)-1;
for (x = wallptr->leftclip ; x <= wallptr->rightclip ; x++)
{
//
// height
//
asm mov ax,WORD PTR [fracheight]
asm mov dx,WORD PTR [fracheight+2]
asm mov cx,dx
asm add ax,WORD PTR [fracstep]
asm adc dx,WORD PTR [fracstep+2]
asm mov WORD PTR [fracheight],ax
asm mov WORD PTR [fracheight+2],dx
asm mov bx,[x]
asm shl bx,1
asm cmp cx,MAXSCALEHEIGHT
asm jbe storeheight
asm mov cx,MAXSCALEHEIGHT
storeheight:
asm mov WORD PTR [wallheight+bx],cx
asm mov WORD PTR [zbuffer+bx],cx
// height = fracheight>>16;
// fracheight += fracstep;
// if (height > MAXSCALEHEIGHT)
// height = MAXSCALEHEIGHT;
// wallheight[x] = zbuffer[x] = height;
//
// texture map
//
angle = pixelangle[x]+traceangle;
if (angle<0)
angle+=FINEANGLES;
slope = finetangent[angle];
//
// distance is an unsigned 6.6 bit number (12 pixel bits)
// slope is a signed 5.10 bit number
// result is a signed 11.16 bit number
//
#if 0
source = distance*slope;
source >>=20;
source += mapadd;
source &= 63; // mask off the unused units
source = 63-source;
source <<= 6; // multiply by 64 for offset into pic
#endif
asm mov ax,[distance]
asm imul [slope] // ax is the source pixel
asm mov al,ah
asm shr al,1
asm shr al,1 // low 6 bits is now pixel number
asm add ax,[mapadd]
asm and ax,63
asm mov dx,63
asm sub dx,ax // otherwise it is backwards
asm shl dx,1
asm shl dx,1
asm shl dx,1
asm shl dx,1
asm shl dx,1
asm shl dx,1 // *64 to index into shape
asm mov [source],dx
if (source != lastsource)
{
if (lastpix != (unsigned)-1)
{
wallofs[lastpix] = lastsource;
wallseg[lastpix] = wallpicseg;
wallwidth[lastpix] = lastwidth;
}
lastpix = x;
lastsource = source;
lastwidth = 1;
}
else
lastwidth++; // optimized draw, same map as last one
}
wallofs[lastpix] = lastsource;
wallseg[lastpix] = wallpicseg;
wallwidth[lastpix] = lastwidth;
}
//==========================================================================
/*
=================
=
= TraceRay
=
= Used to find the left and rightmost tile in the view area to be traced from
= Follows a ray of the given angle from viewx,viewy in the global map until
= it hits a solid tile
= sets:
= tile.x,tile.y : tile coordinates of contacted tile
= tilecolor : solid tile's color
=
==================
*/
int tilecolor;
void TraceRay (unsigned angle)
{
long tracex,tracey,tracexstep,traceystep,searchx,searchy;
fixed fixtemp;
int otx,oty,searchsteps;
tracexstep = costable[angle];
traceystep = sintable[angle];
//
// advance point so it is even with the view plane before we start checking
//
fixtemp = FixedByFrac(prestep,tracexstep);
tracex = viewx+fixtemp;
fixtemp = FixedByFrac(prestep,traceystep);
tracey = viewy-fixtemp;
tile.x = tracex>>TILESHIFT; // starting point in tiles
tile.y = tracey>>TILESHIFT;
if (tracexstep<0) // use 2's complement, not signed magnitude
tracexstep = -(tracexstep&0x7fffffff);
if (traceystep<0) // use 2's complement, not signed magnitude
traceystep = -(traceystep&0x7fffffff);
//
// we assume viewx,viewy is not inside a solid tile, so go ahead one step
//
do // until a solid tile is hit
{
otx = tile.x;
oty = tile.y;
spotvis[otx][oty] = true;
tracex += tracexstep;
tracey -= traceystep;
tile.x = tracex>>TILESHIFT;
tile.y = tracey>>TILESHIFT;
if (tile.x!=otx && tile.y!=oty && (tilemap[otx][tile.y] || tilemap[tile.x][oty]) )
{
//
// trace crossed two solid tiles, so do a binary search along the line
// to find a spot where only one tile edge is crossed
//
searchsteps = 0;
searchx = tracexstep;
searchy = traceystep;
do
{
searchx/=2;
searchy/=2;
if (tile.x!=otx && tile.y!=oty)
{
// still too far
tracex -= searchx;
tracey += searchy;
}
else
{
// not far enough, no tiles crossed
tracex += searchx;
tracey -= searchy;
}
//
// if it is REAL close, go for the most clockwise intersection
//
if (++searchsteps == 16)
{
tracex = (long)otx<<TILESHIFT;
tracey = (long)oty<<TILESHIFT;
if (tracexstep>0)
{
if (traceystep<0)
{
tracex += TILEGLOBAL-1;
tracey += TILEGLOBAL;
}
else
{
tracex += TILEGLOBAL;
}
}
else
{
if (traceystep<0)
{
tracex --;
tracey += TILEGLOBAL-1;
}
else
{
tracey --;
}
}
}
tile.x = tracex>>TILESHIFT;
tile.y = tracey>>TILESHIFT;
} while (( tile.x!=otx && tile.y!=oty) || (tile.x==otx && tile.y==oty) );
}
} while (!(tilecolor = tilemap[tile.x][tile.y]) );
}
//==========================================================================
/*
========================
=
= FixedByFrac
=
= multiply a 16/16 bit, 2's complement fixed point number by a 16 bit
= fraction, passed as a signed magnitude 32 bit number
=
========================
*/
#pragma warn -rvl // I stick the return value in with ASMs
fixed FixedByFrac (fixed a, fixed b)
{
fixed value;
//
// setup
//
asm mov si,[WORD PTR b+2] // sign of result = sign of fraction
asm mov ax,[WORD PTR a]
asm mov cx,[WORD PTR a+2]
asm or cx,cx
asm jns aok: // negative?
asm not ax
asm not cx
asm add ax,1
asm adc cx,0
asm xor si,0x8000 // toggle sign of result
aok:
//
// multiply cx:ax by bx
//
asm mov bx,[WORD PTR b]
asm mul bx // fraction*fraction
asm mov di,dx // di is low word of result
asm mov ax,cx //
asm mul bx // units*fraction
asm add ax,di
asm adc dx,0
//
// put result dx:ax in 2's complement
//
asm test si,0x8000 // is the result negative?
asm jz ansok:
asm not ax
asm not dx
asm add ax,1
asm adc dx,0
ansok:;
}
#pragma warn +rvl