r_segs.c

使用Doom引擎开发的著名游戏《毁灭巫师》的源代码。

	if (ds_p == &drawsegs[MAXDRAWSEGS])
		return;         // don't overflow and crash

#ifdef RANGECHECK
	if (start >=viewwidth || start > stop)
		I_Error ("Bad R_RenderWallRange: %i to %i", start , stop);
#endif
#ifdef __NeXT__
	RD_DrawLine (curline);
#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
	{
	//
	// 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);
		}
#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];
			rw_midtexturemid = vtop - viewz;        // bottom of texture at bottom
		}
		else
			rw_midtexturemid = worldtop;            // top of texture at top
		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
		|| backsector->special != frontsector->special)
			markfloor = true;
		else
			markfloor = false;                              // same plane on both sides

		if (worldhigh != worldtop
		|| backsector->ceilingpic != frontsector->ceilingpic
		|| backsector->lightlevel != frontsector->lightlevel)
			markceiling = true;
		else
			markceiling = false;                    // same plane on both sides

		if (backsector->ceilingheight <= frontsector->floorheight
		|| backsector->floorheight >= frontsector->ceilingheight)
			markceiling = markfloor = true;         // closed door

		if (worldhigh < worldtop)
		{       // top texture
			toptexture = texturetranslation[sidedef->toptexture];
			if (linedef->flags & ML_DONTPEGTOP)
				rw_toptexturemid = worldtop;            // top of texture at top
			else
			{
				vtop = backsector->ceilingheight +
					textureheight[sidedef->toptexture];
				rw_toptexturemid = vtop - viewz;        // bottom of texture
			}
		}
		if (worldlow > worldbottom)
		{       // bottom texture
			bottomtexture = texturetranslation[sidedef->bottomtexture];
			if (linedef->flags & ML_DONTPEGBOTTOM )
			{               // bottom of texture at bottom
				rw_bottomtexturemid = worldtop;// top of texture at top
			}
			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];
			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 definately invisible and doesn't need to be marked
//
	if (frontsector->floorheight >= viewz)
		markfloor = false;                              // above view plane
	if (frontsector->ceilingheight <= viewz
	&& frontsector->ceilingpic != skyflatnum)
		markceiling = false;                    // below view plane

//
// 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++;
}