r_segs.c

doom游戏

R_StoreWallRange
( int	start,
  int	stop )
{
    fixed_t		hyp;
    fixed_t		sineval;
    angle_t		distangle, offsetangle;
    fixed_t		vtop;
    int			lightnum;

    // don't overflow and crash
    if (ds_p == &drawsegs[MAXDRAWSEGS])
	return;		
		
#ifdef RANGECHECK
    if (start >=viewwidth || start > stop)
	I_Error ("Bad R_RenderWallRange: %i to %i", start , stop);
#endif
    
    sidedef = curline->sidedef;
    linedef = curline->linedef;

    // mark the segment as visible for auto map
    linedef->flags |= ML_MAPPED;
    
    // calculate rw_distance for scale calculation
    rw_normalangle = curline->angle + ANG90;
    offsetangle = abs(rw_normalangle-rw_angle1);
    
    if (offsetangle > ANG90)
	offsetangle = ANG90;

    distangle = ANG90 - offsetangle;
    hyp = R_PointToDist (curline->v1->x, curline->v1->y);
    sineval = finesine[distangle>>ANGLETOFINESHIFT];
    rw_distance = FixedMul (hyp, sineval);
		
	
    ds_p->x1 = rw_x = start;
    ds_p->x2 = stop;
    ds_p->curline = curline;
    rw_stopx = stop+1;
    
    // calculate scale at both ends and step
    ds_p->scale1 = rw_scale = 
	R_ScaleFromGlobalAngle (viewangle + xtoviewangle[start]);
    
    if (stop > start )
    {
	ds_p->scale2 = R_ScaleFromGlobalAngle (viewangle + xtoviewangle[stop]);
	ds_p->scalestep = rw_scalestep = 
	    (ds_p->scale2 - rw_scale) / (stop-start);
    }
    else
    {
	// UNUSED: try to fix the stretched line bug
#if 0
	if (rw_distance < FRACUNIT/2)
	{
	    fixed_t		trx,try;
	    fixed_t		gxt,gyt;

	    trx = curline->v1->x - viewx;
	    try = curline->v1->y - viewy;
			
	    gxt = FixedMul(trx,viewcos); 
	    gyt = -FixedMul(try,viewsin); 
	    ds_p->scale1 = FixedDiv(projection, gxt-gyt)<<detailshift;
	}
#endif
	ds_p->scale2 = ds_p->scale1;
    }
    
    // calculate texture boundaries
    //  and decide if floor / ceiling marks are needed
    worldtop = frontsector->ceilingheight - viewz;
    worldbottom = frontsector->floorheight - viewz;
	
    midtexture = toptexture = bottomtexture = maskedtexture = 0;
    ds_p->maskedtexturecol = NULL;
	
    if (!backsector)
    {
	// single sided line
	midtexture = texturetranslation[sidedef->midtexture];
	// a single sided line is terminal, so it must mark ends
	markfloor = markceiling = true;
	if (linedef->flags & ML_DONTPEGBOTTOM)
	{
	    vtop = frontsector->floorheight +
		textureheight[sidedef->midtexture];
	    // bottom of texture at bottom
	    rw_midtexturemid = vtop - viewz;	
	}
	else
	{
	    // top of texture at top
	    rw_midtexturemid = worldtop;
	}
	rw_midtexturemid += sidedef->rowoffset;

	ds_p->silhouette = SIL_BOTH;
	ds_p->sprtopclip = screenheightarray;
	ds_p->sprbottomclip = negonearray;
	ds_p->bsilheight = MAXINT;
	ds_p->tsilheight = MININT;
    }
    else
    {
	// two sided line
	ds_p->sprtopclip = ds_p->sprbottomclip = NULL;
	ds_p->silhouette = 0;
	
	if (frontsector->floorheight > backsector->floorheight)
	{
	    ds_p->silhouette = SIL_BOTTOM;
	    ds_p->bsilheight = frontsector->floorheight;
	}
	else if (backsector->floorheight > viewz)
	{
	    ds_p->silhouette = SIL_BOTTOM;
	    ds_p->bsilheight = MAXINT;
	    // ds_p->sprbottomclip = negonearray;
	}
	
	if (frontsector->ceilingheight < backsector->ceilingheight)
	{
	    ds_p->silhouette |= SIL_TOP;
	    ds_p->tsilheight = frontsector->ceilingheight;
	}
	else if (backsector->ceilingheight < viewz)
	{
	    ds_p->silhouette |= SIL_TOP;
	    ds_p->tsilheight = MININT;
	    // ds_p->sprtopclip = screenheightarray;
	}
		
	if (backsector->ceilingheight <= frontsector->floorheight)
	{
	    ds_p->sprbottomclip = negonearray;
	    ds_p->bsilheight = MAXINT;
	    ds_p->silhouette |= SIL_BOTTOM;
	}
	
	if (backsector->floorheight >= frontsector->ceilingheight)
	{
	    ds_p->sprtopclip = screenheightarray;
	    ds_p->tsilheight = MININT;
	    ds_p->silhouette |= SIL_TOP;
	}
	
	worldhigh = backsector->ceilingheight - viewz;
	worldlow = backsector->floorheight - viewz;
		
	// hack to allow height changes in outdoor areas
	if (frontsector->ceilingpic == skyflatnum 
	    && backsector->ceilingpic == skyflatnum)
	{
	    worldtop = worldhigh;
	}
	
			
	if (worldlow != worldbottom 
	    || backsector->floorpic != frontsector->floorpic
	    || backsector->lightlevel != frontsector->lightlevel)
	{
	    markfloor = true;
	}
	else
	{
	    // same plane on both sides
	    markfloor = false;
	}
	
			
	if (worldhigh != worldtop 
	    || backsector->ceilingpic != frontsector->ceilingpic
	    || backsector->lightlevel != frontsector->lightlevel)
	{
	    markceiling = true;
	}
	else
	{
	    // same plane on both sides
	    markceiling = false;
	}
	
	if (backsector->ceilingheight <= frontsector->floorheight
	    || backsector->floorheight >= frontsector->ceilingheight)
	{
	    // closed door
	    markceiling = markfloor = true;
	}
	

	if (worldhigh < worldtop)
	{
	    // top texture
	    toptexture = texturetranslation[sidedef->toptexture];
	    if (linedef->flags & ML_DONTPEGTOP)
	    {
		// top of texture at top
		rw_toptexturemid = worldtop;
	    }
	    else
	    {
		vtop =
		    backsector->ceilingheight
		    + textureheight[sidedef->toptexture];
		
		// bottom of texture
		rw_toptexturemid = vtop - viewz;	
	    }
	}
	if (worldlow > worldbottom)
	{
	    // bottom texture
	    bottomtexture = texturetranslation[sidedef->bottomtexture];

	    if (linedef->flags & ML_DONTPEGBOTTOM )
	    {
		// bottom of texture at bottom
		// top of texture at top
		rw_bottomtexturemid = worldtop;
	    }
	    else	// top of texture at top
		rw_bottomtexturemid = worldlow;
	}
	rw_toptexturemid += sidedef->rowoffset;
	rw_bottomtexturemid += sidedef->rowoffset;
	
	// allocate space for masked texture tables
	if (sidedef->midtexture)
	{
	    // masked midtexture
	    maskedtexture = true;
	    ds_p->maskedtexturecol = maskedtexturecol = lastopening - rw_x;
	    lastopening += rw_stopx - rw_x;
	}
    }
    
    // calculate rw_offset (only needed for textured lines)
    segtextured = midtexture | toptexture | bottomtexture | maskedtexture;

    if (segtextured)
    {
	offsetangle = rw_normalangle-rw_angle1;
	
	if (offsetangle > ANG180)
	    offsetangle = -offsetangle;

	if (offsetangle > ANG90)
	    offsetangle = ANG90;

	sineval = finesine[offsetangle >>ANGLETOFINESHIFT];
	rw_offset = FixedMul (hyp, sineval);

	if (rw_normalangle-rw_angle1 < ANG180)
	    rw_offset = -rw_offset;

	rw_offset += sidedef->textureoffset + curline->offset;
	rw_centerangle = ANG90 + viewangle - rw_normalangle;
	
	// calculate light table
	//  use different light tables
	//  for horizontal / vertical / diagonal
	// OPTIMIZE: get rid of LIGHTSEGSHIFT globally
	if (!fixedcolormap)
	{
	    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];
	}
    }
    
    // if a floor / ceiling plane is on the wrong side
    //  of the view plane, it is definitely invisible
    //  and doesn't need to be marked.
    
  
    if (frontsector->floorheight >= viewz)
    {
	// above view plane
	markfloor = false;
    }
    
    if (frontsector->ceilingheight <= viewz 
	&& frontsector->ceilingpic != skyflatnum)
    {
	// below view plane
	markceiling = false;
    }

    
    // calculate incremental stepping values for texture edges
    worldtop >>= 4;
    worldbottom >>= 4;
	
    topstep = -FixedMul (rw_scalestep, worldtop);
    topfrac = (centeryfrac>>4) - FixedMul (worldtop, rw_scale);

    bottomstep = -FixedMul (rw_scalestep,worldbottom);
    bottomfrac = (centeryfrac>>4) - FixedMul (worldbottom, rw_scale);
	
    if (backsector)
    {	
	worldhigh >>= 4;
	worldlow >>= 4;

	if (worldhigh < worldtop)
	{
	    pixhigh = (centeryfrac>>4) - FixedMul (worldhigh, rw_scale);
	    pixhighstep = -FixedMul (rw_scalestep,worldhigh);
	}
	
	if (worldlow > worldbottom)
	{
	    pixlow = (centeryfrac>>4) - FixedMul (worldlow, rw_scale);
	    pixlowstep = -FixedMul (rw_scalestep,worldlow);
	}
    }
    
    // render it
    if (markceiling)
	ceilingplane = R_CheckPlane (ceilingplane, rw_x, rw_stopx-1);
    
    if (markfloor)
	floorplane = R_CheckPlane (floorplane, rw_x, rw_stopx-1);

    R_RenderSegLoop ();

    
    // save sprite clipping info
    if ( ((ds_p->silhouette & SIL_TOP) || maskedtexture)
	 && !ds_p->sprtopclip)
    {
	_memcpy (lastopening, ceilingclip+start, 2*(rw_stopx-start));
	ds_p->sprtopclip = lastopening - start;
	lastopening += rw_stopx - start;
    }
    
    if ( ((ds_p->silhouette & SIL_BOTTOM) || maskedtexture)
	 && !ds_p->sprbottomclip)
    {
	_memcpy (lastopening, floorclip+start, 2*(rw_stopx-start));
	ds_p->sprbottomclip = lastopening - start;
	lastopening += rw_stopx - start;	
    }

    if (maskedtexture && !(ds_p->silhouette&SIL_TOP))
    {
	ds_p->silhouette |= SIL_TOP;
	ds_p->tsilheight = MININT;
    }
    if (maskedtexture && !(ds_p->silhouette&SIL_BOTTOM))
    {
	ds_p->silhouette |= SIL_BOTTOM;
	ds_p->bsilheight = MAXINT;
    }
    ds_p++;
}