r_draw.c

DOOM游戏的源码,研究DOS下游戏设计

// Emacs style mode select   -*- C++ -*- 
//-----------------------------------------------------------------------------
//
// $Id:$
//
// Copyright (C) 1993-1996 by id Software, Inc.
//
// This source is available for distribution and/or modification
// only under the terms of the DOOM Source Code License as
// published by id Software. All rights reserved.
//
// The source is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
// for more details.
//
// $Log:$
//
// DESCRIPTION:
//	The actual span/column drawing functions.
//	Here find the main potential for optimization,
//	 e.g. inline assembly, different algorithms.
//
//-----------------------------------------------------------------------------


static const char
rcsid[] = "$Id: r_draw.c,v 1.4 1997/02/03 16:47:55 b1 Exp $";


#include "doomdef.h"

#include "i_system.h"
#include "z_zone.h"
#include "w_wad.h"

#include "r_local.h"

// Needs access to LFB (guess what).
#include "v_video.h"

// State.
#include "doomstat.h"

void WriteDebug(char *);

// ?
#define MAXWIDTH			1120
#define MAXHEIGHT			832

// status bar height at bottom of screen
#define SBARHEIGHT		32

//
// All drawing to the view buffer is accomplished in this file.
// The other refresh files only know about ccordinates,
//  not the architecture of the frame buffer.
// Conveniently, the frame buffer is a linear one,
//  and we need only the base address,
//  and the total size == width*height*depth/8.,
//


byte *viewimage; 
int   viewwidth;
int	  scaledviewwidth;
int	  viewheight;
int	  viewwindowx;
int	  viewwindowy; 
byte *ylookup[MAXHEIGHT]; 
int   columnofs[MAXWIDTH]; 

// Color tables for different players,
//  translate a limited part to another
//  (color ramps used for  suit colors).
//
byte		translations[3][256];	
 
 


//
// R_DrawColumn
// Source is the top of the column to scale.
//
lighttable_t*		dc_colormap; 
int			dc_x; 
int			dc_yl; 
int			dc_yh; 
fixed_t			dc_iscale; 
fixed_t			dc_texturemid;

// first pixel in a column (possibly virtual) 
byte*			dc_source;		

// just for profiling 
int			dccount;

//
// A column is a vertical slice/span from a wall texture that,
//  given the DOOM style restrictions on the view orientation,
//  will always have constant z depth.
// Thus a special case loop for very fast rendering can
//  be used. It has also been used with Wolfenstein 3D.
// 
void R_DrawColumn (void) 
{ 
    int			count; 
    byte*		dest; 
    fixed_t		frac;
    fixed_t		fracstep;	 
 
    count = dc_yh - dc_yl; 

    // Zero length, column does not exceed a pixel.
    if (count < 0) 
	return; 
				 
#ifdef RANGECHECK 
    if ((unsigned)dc_x >= SCREENWIDTH
	|| dc_yl < 0
	|| dc_yh >= SCREENHEIGHT) 
	I_Error ("R_DrawColumn: %i to %i at %i", dc_yl, dc_yh, dc_x); 
#endif 

    // Framebuffer destination address.
    // Use ylookup LUT to avoid multiply with ScreenWidth.
    // Use columnofs LUT for subwindows? 
    dest = ylookup[dc_yl] + columnofs[dc_x];  

    // Determine scaling,
    //  which is the only mapping to be done.
    fracstep = dc_iscale; 
    frac = dc_texturemid + (dc_yl-centery)*fracstep; 

    // Inner loop that does the actual texture mapping,
    //  e.g. a DDA-lile scaling.
    // This is as fast as it gets.
    do 
    {
	// Re-map color indices from wall texture column
	//  using a lighting/special effects LUT.
	*dest = dc_colormap[dc_source[(frac>>FRACBITS)&127]];
	
	dest += SCREENWIDTH; 
	frac += fracstep;
	
    } while (count--); 
} 



// UNUSED.
// Loop unrolled.
#if 0
void R_DrawColumn (void) 
{ 
    int			count; 
    byte*		source;
    byte*		dest;
    byte*		colormap;
    
    unsigned		frac;
    unsigned		fracstep;
    unsigned		fracstep2;
    unsigned		fracstep3;
    unsigned		fracstep4;	 
 
    count = dc_yh - dc_yl + 1; 

    source = dc_source;
    colormap = dc_colormap;		 
    dest = ylookup[dc_yl] + columnofs[dc_x];  
	 
    fracstep = dc_iscale<<9; 
    frac = (dc_texturemid + (dc_yl-centery)*dc_iscale)<<9; 
 
    fracstep2 = fracstep+fracstep;
    fracstep3 = fracstep2+fracstep;
    fracstep4 = fracstep3+fracstep;
	
    while (count >= 8) 
    { 
	dest[0] = colormap[source[frac>>25]]; 
	dest[SCREENWIDTH] = colormap[source[(frac+fracstep)>>25]]; 
	dest[SCREENWIDTH*2] = colormap[source[(frac+fracstep2)>>25]]; 
	dest[SCREENWIDTH*3] = colormap[source[(frac+fracstep3)>>25]];
	
	frac += fracstep4; 

	dest[SCREENWIDTH*4] = colormap[source[frac>>25]]; 
	dest[SCREENWIDTH*5] = colormap[source[(frac+fracstep)>>25]]; 
	dest[SCREENWIDTH*6] = colormap[source[(frac+fracstep2)>>25]]; 
	dest[SCREENWIDTH*7] = colormap[source[(frac+fracstep3)>>25]]; 

	frac += fracstep4; 
	dest += SCREENWIDTH*8; 
	count -= 8;
    } 
	
    while (count > 0)
    { 
	*dest = colormap[source[frac>>25]]; 
	dest += SCREENWIDTH; 
	frac += fracstep; 
	count--;
    } 
}
#endif


void R_DrawColumnLow (void) 
{ 
    int			count; 
    byte*		dest; 
    byte*		dest2;
    fixed_t		frac;
    fixed_t		fracstep;	 
 
    count = dc_yh - dc_yl; 

    // Zero length.
    if (count < 0) 
	return; 
				 
#ifdef RANGECHECK 
    if ((unsigned)dc_x >= SCREENWIDTH
	|| dc_yl < 0
	|| dc_yh >= SCREENHEIGHT)
    {
	
	I_Error ("R_DrawColumn: %i to %i at %i", dc_yl, dc_yh, dc_x);
    }
    //	dccount++; 
#endif 
    // Blocky mode, need to multiply by 2.
    dc_x <<= 1;
    
    dest = ylookup[dc_yl] + columnofs[dc_x];
    dest2 = ylookup[dc_yl] + columnofs[dc_x+1];
    
    fracstep = dc_iscale; 
    frac = dc_texturemid + (dc_yl-centery)*fracstep;
    
    do 
    {
	// Hack. Does not work corretly.
	*dest2 = *dest = dc_colormap[dc_source[(frac>>FRACBITS)&127]];
	dest += SCREENWIDTH;
	dest2 += SCREENWIDTH;
	frac += fracstep; 

    } while (count--);
}


//
// Spectre/Invisibility.
//
#define FUZZTABLE		50 
#define FUZZOFF	1

int	fuzzoffset[FUZZTABLE] =
{
    FUZZOFF,-FUZZOFF,FUZZOFF,-FUZZOFF,FUZZOFF,FUZZOFF,-FUZZOFF,
    FUZZOFF,FUZZOFF,-FUZZOFF,FUZZOFF,FUZZOFF,FUZZOFF,-FUZZOFF,
    FUZZOFF,FUZZOFF,FUZZOFF,-FUZZOFF,-FUZZOFF,-FUZZOFF,-FUZZOFF,
    FUZZOFF,-FUZZOFF,-FUZZOFF,FUZZOFF,FUZZOFF,FUZZOFF,FUZZOFF,-FUZZOFF,
    FUZZOFF,-FUZZOFF,FUZZOFF,FUZZOFF,-FUZZOFF,-FUZZOFF,FUZZOFF,
    FUZZOFF,-FUZZOFF,-FUZZOFF,-FUZZOFF,-FUZZOFF,FUZZOFF,FUZZOFF,
    FUZZOFF,FUZZOFF,-FUZZOFF,FUZZOFF,FUZZOFF,-FUZZOFF,FUZZOFF 
}; 

int	fuzzpos = 0; 

void R_InitFuzzTable()
   {
    int i;

    for (i = 0; i < FUZZTABLE; i++)
       fuzzoffset[i] *= SCREENWIDTH;
   }

//
// Framebuffer postprocessing.
// Creates a fuzzy image by copying pixels
//  from adjacent ones to left and right.
// Used with an all black colormap, this
//  could create the SHADOW effect,
//  i.e. spectres and invisible players.
//
void R_DrawFuzzColumn (void) 
{ 
    int			count; 
    byte*		dest; 
    fixed_t		frac;
    fixed_t		fracstep;	 

    // Adjust borders. Low... 
    if (!dc_yl) 
	dc_yl = 1;

    // .. and high.
    if (dc_yh == viewheight-1) 
	dc_yh = viewheight - 2; 
		 
    count = dc_yh - dc_yl; 

    // Zero length.
    if (count < 0) 
	return; 

    
#ifdef RANGECHECK 
    if ((unsigned)dc_x >= SCREENWIDTH
	|| dc_yl < 0 || dc_yh >= SCREENHEIGHT)
    {
	I_Error ("R_DrawFuzzColumn: %i to %i at %i",
		 dc_yl, dc_yh, dc_x);
    }
#endif


    // Keep till detailshift bug in blocky mode fixed,
    //  or blocky mode removed.
    /* WATCOM code 
    if (detailshift)
    {
	if (dc_x & 1)
	{
	    outpw (GC_INDEX,GC_READMAP+(2<<8) ); 
	    outp (SC_INDEX+1,12); 
	}
	else
	{
	    outpw (GC_INDEX,GC_READMAP); 
	    outp (SC_INDEX+1,3); 
	}
	dest = destview + dc_yl*80 + (dc_x>>1); 
    }
    else
    {
	outpw (GC_INDEX,GC_READMAP+((dc_x&3)<<8) ); 
	outp (SC_INDEX+1,1<<(dc_x&3)); 
	dest = destview + dc_yl*80 + (dc_x>>2); 
    }*/

    
    // Does not work with blocky mode.
    dest = ylookup[dc_yl] + columnofs[dc_x];

    // Looks familiar.
    fracstep = dc_iscale; 
    frac = dc_texturemid + (dc_yl-centery)*fracstep; 

    // Looks like an attempt at dithering,
    //  using the colormap #6 (of 0-31, a bit
    //  brighter than average).
    do 
    {
	// Lookup framebuffer, and retrieve
	//  a pixel that is either one column
	//  left or right of the current one.
	// Add index from colormap to index.
	*dest = colormaps[6*256+dest[fuzzoffset[fuzzpos]]]; 

	// Clamp table lookup index.
	if (++fuzzpos == FUZZTABLE) 
	    fuzzpos = 0;
	
	dest += SCREENWIDTH;

	frac += fracstep; 
    } while (count--); 
} 
 
  
 

//
// R_DrawTranslatedColumn
// Used to draw player sprites
//  with the green colorramp mapped to others.
// Could be used with different translation
//  tables, e.g. the lighter colored version
//  of the BaronOfHell, the HellKnight, uses
//  identical sprites, kinda brightened up.
//
byte*	dc_translation;
byte*	translationtables;

void R_DrawTranslatedColumn (void) 
{ 
    int			count; 
    byte*		dest; 
    fixed_t		frac;
    fixed_t		fracstep;	 
 
    count = dc_yh - dc_yl; 
    if (count < 0) 
	return; 
				 
#ifdef RANGECHECK 
    if ((unsigned)dc_x >= SCREENWIDTH
	|| dc_yl < 0
	|| dc_yh >= SCREENHEIGHT)
    {
	I_Error ( "R_DrawColumn: %i to %i at %i",
		  dc_yl, dc_yh, dc_x);
    }
    
#endif 


    // WATCOM VGA specific.
    /* Keep for fixing.
    if (detailshift)
    {
	if (dc_x & 1)
	    outp (SC_INDEX+1,12); 
	else
	    outp (SC_INDEX+1,3);
	
	dest = destview + dc_yl*80 + (dc_x>>1); 
    }
    else
    {
	outp (SC_INDEX+1,1<<(dc_x&3)); 

	dest = destview + dc_yl*80 + (dc_x>>2); 
    }*/

    
    // FIXME. As above.
    dest = ylookup[dc_yl] + columnofs[dc_x]; 

    // Looks familiar.
    fracstep = dc_iscale; 
    frac = dc_texturemid + (dc_yl-centery)*fracstep; 

    // Here we do an additional index re-mapping.
    do 
    {
	// Translation tables are used
	//  to map certain colorramps to other ones,
	//  used with PLAY sprites.
	// Thus the "green" ramp of the player 0 sprite
	//  is mapped to gray, red, black/indigo.