r_segs.c

doom游戏

// 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:
//	All the clipping: columns, horizontal spans, sky columns.
//
//-----------------------------------------------------------------------------


static const char
rcsid[] = "$Id: r_segs.c,v 1.3 1997/01/29 20:10:19 b1 Exp $";





#include <stdlib.h>

#include "i_system.h"

#include "doomdef.h"
#include "doomstat.h"

#include "r_local.h"
#include "r_sky.h"


// OPTIMIZE: closed two sided lines as single sided

// True if any of the segs textures might be visible.
boolean		segtextured;	

// False if the back side is the same plane.
boolean		markfloor;	
boolean		markceiling;

boolean		maskedtexture;
int		toptexture;
int		bottomtexture;
int		midtexture;


angle_t		rw_normalangle;
// angle to line origin
int		rw_angle1;	

//
// regular wall
//
int		rw_x;
int		rw_stopx;
angle_t		rw_centerangle;
fixed_t		rw_offset;
fixed_t		rw_distance;
fixed_t		rw_scale;
fixed_t		rw_scalestep;
fixed_t		rw_midtexturemid;
fixed_t		rw_toptexturemid;
fixed_t		rw_bottomtexturemid;

int		worldtop;
int		worldbottom;
int		worldhigh;
int		worldlow;

fixed_t		pixhigh;
fixed_t		pixlow;
fixed_t		pixhighstep;
fixed_t		pixlowstep;

fixed_t		topfrac;
fixed_t		topstep;

fixed_t		bottomfrac;
fixed_t		bottomstep;


lighttable_t**	walllights;

short*		maskedtexturecol;



//
// R_RenderMaskedSegRange
//
void
R_RenderMaskedSegRange
( drawseg_t*	ds,
  int		x1,
  int		x2 )
{
    unsigned	index;
    column_t*	col;
    int		lightnum;
    int		texnum;
    
    // Calculate light table.
    // Use different light tables
    //   for horizontal / vertical / diagonal. Diagonal?
    // OPTIMIZE: get rid of LIGHTSEGSHIFT globally
    curline = ds->curline;
    frontsector = curline->frontsector;
    backsector = curline->backsector;
    texnum = texturetranslation[curline->sidedef->midtexture];
	
    lightnum = (frontsector->lightlevel >> LIGHTSEGSHIFT)+extralight;

    if (curline->v1->y == curline->v2->y)
	lightnum--;
    else if (curline->v1->x == curline->v2->x)
	lightnum++;

    if (lightnum < 0)		
	walllights = scalelight[0];
    else if (lightnum >= LIGHTLEVELS)
	walllights = scalelight[LIGHTLEVELS-1];
    else
	walllights = scalelight[lightnum];

    maskedtexturecol = ds->maskedtexturecol;

    rw_scalestep = ds->scalestep;		
    spryscale = ds->scale1 + (x1 - ds->x1)*rw_scalestep;
    mfloorclip = ds->sprbottomclip;
    mceilingclip = ds->sprtopclip;
    
    // find positioning
    if (curline->linedef->flags & ML_DONTPEGBOTTOM)
    {
	dc_texturemid = frontsector->floorheight > backsector->floorheight
	    ? frontsector->floorheight : backsector->floorheight;
	dc_texturemid = dc_texturemid + textureheight[texnum] - viewz;
    }
    else
    {
	dc_texturemid =frontsector->ceilingheight<backsector->ceilingheight
	    ? frontsector->ceilingheight : backsector->ceilingheight;
	dc_texturemid = dc_texturemid - viewz;
    }
    dc_texturemid += curline->sidedef->rowoffset;
			
    if (fixedcolormap)
	dc_colormap = fixedcolormap;
    
    // draw the columns
    for (dc_x = x1 ; dc_x <= x2 ; dc_x++)
    {
	// calculate lighting
	if (maskedtexturecol[dc_x] != MAXSHORT)
	{
	    if (!fixedcolormap)
	    {
		index = spryscale>>LIGHTSCALESHIFT;

		if (index >=  MAXLIGHTSCALE )
		    index = MAXLIGHTSCALE-1;

		dc_colormap = walllights[index];
	    }
			
	    sprtopscreen = centeryfrac - FixedMul(dc_texturemid, spryscale);
	    dc_iscale = 0xffffffffu / (unsigned)spryscale;
	    
	    // draw the texture
	    col = (column_t *)( 
		(byte *)R_GetColumn(texnum,maskedtexturecol[dc_x]) -3);
			
	    R_DrawMaskedColumn (col);
	    maskedtexturecol[dc_x] = MAXSHORT;
	}
	spryscale += rw_scalestep;
    }
	
}




//
// R_RenderSegLoop
// Draws zero, one, or two textures (and possibly a masked
//  texture) for walls.
// Can draw or mark the starting pixel of floor and ceiling
//  textures.
// CALLED: CORE LOOPING ROUTINE.
//
#define HEIGHTBITS		12
#define HEIGHTUNIT		(1<<HEIGHTBITS)

void R_RenderSegLoop (void)
{
    angle_t		angle;
    unsigned		index;
    int			yl;
    int			yh;
    int			mid;
    fixed_t		texturecolumn;
    int			top;
    int			bottom;

    //texturecolumn = 0;				// shut up compiler warning
	
    for ( ; rw_x < rw_stopx ; rw_x++)
    {
	// mark floor / ceiling areas
	yl = (topfrac+HEIGHTUNIT-1)>>HEIGHTBITS;

	// no space above wall?
	if (yl < ceilingclip[rw_x]+1)
	    yl = ceilingclip[rw_x]+1;
	
	if (markceiling)
	{
	    top = ceilingclip[rw_x]+1;
	    bottom = yl-1;

	    if (bottom >= floorclip[rw_x])
		bottom = floorclip[rw_x]-1;

	    if (top <= bottom)
	    {
		ceilingplane->top[rw_x] = top;
		ceilingplane->bottom[rw_x] = bottom;
	    }
	}
		
	yh = bottomfrac>>HEIGHTBITS;

	if (yh >= floorclip[rw_x])
	    yh = floorclip[rw_x]-1;

	if (markfloor)
	{
	    top = yh+1;
	    bottom = floorclip[rw_x]-1;
	    if (top <= ceilingclip[rw_x])
		top = ceilingclip[rw_x]+1;
	    if (top <= bottom)
	    {
		floorplane->top[rw_x] = top;
		floorplane->bottom[rw_x] = bottom;
	    }
	}
	
	// texturecolumn and lighting are independent of wall tiers
	if (segtextured)
	{
	    // calculate texture offset
	    angle = (rw_centerangle + xtoviewangle[rw_x])>>ANGLETOFINESHIFT;
	    texturecolumn = rw_offset-FixedMul(finetangent[angle],rw_distance);
	    texturecolumn >>= FRACBITS;
	    // calculate lighting
	    index = rw_scale>>LIGHTSCALESHIFT;

	    if (index >=  MAXLIGHTSCALE )
		index = MAXLIGHTSCALE-1;

	    dc_colormap = walllights[index];
	    dc_x = rw_x;
	    dc_iscale = 0xffffffffu / (unsigned)rw_scale;
	}
	
	// draw the wall tiers
	if (midtexture)
	{
	    // single sided line
	    dc_yl = yl;
	    dc_yh = yh;
	    dc_texturemid = rw_midtexturemid;
	    dc_source = R_GetColumn(midtexture,texturecolumn);
	    colfunc ();
	    ceilingclip[rw_x] = viewheight;
	    floorclip[rw_x] = -1;
	}
	else
	{
	    // two sided line
	    if (toptexture)
	    {
		// top wall
		mid = pixhigh>>HEIGHTBITS;
		pixhigh += pixhighstep;

		if (mid >= floorclip[rw_x])
		    mid = floorclip[rw_x]-1;

		if (mid >= yl)
		{
		    dc_yl = yl;
		    dc_yh = mid;
		    dc_texturemid = rw_toptexturemid;
		    dc_source = R_GetColumn(toptexture,texturecolumn);
		    colfunc ();
		    ceilingclip[rw_x] = mid;
		}
		else
		    ceilingclip[rw_x] = yl-1;
	    }
	    else
	    {
		// no top wall
		if (markceiling)
		    ceilingclip[rw_x] = yl-1;
	    }
			
	    if (bottomtexture)
	    {
		// bottom wall
		mid = (pixlow+HEIGHTUNIT-1)>>HEIGHTBITS;
		pixlow += pixlowstep;

		// no space above wall?
		if (mid <= ceilingclip[rw_x])
		    mid = ceilingclip[rw_x]+1;
		
		if (mid <= yh)
		{
		    dc_yl = mid;
		    dc_yh = yh;
		    dc_texturemid = rw_bottomtexturemid;
		    dc_source = R_GetColumn(bottomtexture,
					    texturecolumn);
		    colfunc ();
		    floorclip[rw_x] = mid;
		}
		else
		    floorclip[rw_x] = yh+1;
	    }
	    else
	    {
		// no bottom wall
		if (markfloor)
		    floorclip[rw_x] = yh+1;
	    }
			
	    if (maskedtexture)
	    {
		// save texturecol
		//  for backdrawing of masked mid texture
		maskedtexturecol[rw_x] = texturecolumn;
	    }
	}
		
	rw_scale += rw_scalestep;
	topfrac += topstep;
	bottomfrac += bottomstep;
    }
}




//
// R_StoreWallRange
// A wall segment will be drawn
//  between start and stop pixels (inclusive).
//
void