Quake-2

r_poly.c (29528B)

---

 /*
 Copyright (C) 1997-2001 Id Software, Inc.
 
 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
 */
 #include <assert.h>
 #include "r_local.h"
 
 #define AFFINE_SPANLET_SIZE      16
 #define AFFINE_SPANLET_SIZE_BITS 4
 
 typedef struct
 {
 	byte     *pbase, *pdest;
 	short	 *pz;
 	fixed16_t s, t;
 	fixed16_t sstep, tstep;
 	int       izi, izistep, izistep_times_2;
 	int       spancount;
 	unsigned  u, v;
 } spanletvars_t;
 
 spanletvars_t s_spanletvars;
 
 static int r_polyblendcolor;
 
 static espan_t	*s_polygon_spans;
 
 polydesc_t	r_polydesc;
 
 msurface_t *r_alpha_surfaces;
 
 extern int *r_turb_turb;
 
 static int		clip_current;
 vec5_t	r_clip_verts[2][MAXWORKINGVERTS+2];
 
 static int		s_minindex, s_maxindex;
 
 static void R_DrawPoly( qboolean iswater );
 
 /*
 ** R_DrawSpanletOpaque
 */
 void R_DrawSpanletOpaque( void )
 {
 	unsigned btemp;
 
 	do
 	{
 		unsigned ts, tt;
 
 		ts = s_spanletvars.s >> 16;
 		tt = s_spanletvars.t >> 16;
 
 		btemp = *(s_spanletvars.pbase + (ts) + (tt) * cachewidth);
 		if (btemp != 255)
 		{
 			if (*s_spanletvars.pz <= (s_spanletvars.izi >> 16))
 			{
 				*s_spanletvars.pz    = s_spanletvars.izi >> 16;
 				*s_spanletvars.pdest = btemp;
 			}
 		}
 
 		s_spanletvars.izi += s_spanletvars.izistep;
 		s_spanletvars.pdest++;
 		s_spanletvars.pz++;
 		s_spanletvars.s += s_spanletvars.sstep;
 		s_spanletvars.t += s_spanletvars.tstep;
 	} while (--s_spanletvars.spancount > 0);
 }
 
 /*
 ** R_DrawSpanletTurbulentStipple33
 */
 void R_DrawSpanletTurbulentStipple33( void )
 {
 	unsigned btemp;
 	int	     sturb, tturb;
 	byte    *pdest = s_spanletvars.pdest;
 	short   *pz    = s_spanletvars.pz;
 	int      izi   = s_spanletvars.izi;
 	
 	if ( s_spanletvars.v & 1 )
 	{
 		s_spanletvars.pdest += s_spanletvars.spancount;
 		s_spanletvars.pz    += s_spanletvars.spancount;
 
 		if ( s_spanletvars.spancount == AFFINE_SPANLET_SIZE )
 			s_spanletvars.izi += s_spanletvars.izistep << AFFINE_SPANLET_SIZE_BITS;
 		else
 			s_spanletvars.izi += s_spanletvars.izistep * s_spanletvars.izistep;
 		
 		if ( s_spanletvars.u & 1 )
 		{
 			izi += s_spanletvars.izistep;
 			s_spanletvars.s   += s_spanletvars.sstep;
 			s_spanletvars.t   += s_spanletvars.tstep;
 
 			pdest++;
 			pz++;
 			s_spanletvars.spancount--;
 		}
 
 		s_spanletvars.sstep   *= 2;
 		s_spanletvars.tstep   *= 2;
 
 		while ( s_spanletvars.spancount > 0 )
 		{
 			sturb = ((s_spanletvars.s + r_turb_turb[(s_spanletvars.t>>16)&(CYCLE-1)])>>16)&63;
 			tturb = ((s_spanletvars.t + r_turb_turb[(s_spanletvars.s>>16)&(CYCLE-1)])>>16)&63;
 			
 			btemp = *( s_spanletvars.pbase + ( sturb ) + ( tturb << 6 ) );
 			
 			if ( *pz <= ( izi >> 16 ) )
 				*pdest = btemp;
 			
 			izi               += s_spanletvars.izistep_times_2;
 			s_spanletvars.s   += s_spanletvars.sstep;
 			s_spanletvars.t   += s_spanletvars.tstep;
 			
 			pdest += 2;
 			pz    += 2;
 			
 			s_spanletvars.spancount -= 2;
 		}
 	}
 }
 
 /*
 ** R_DrawSpanletTurbulentStipple66
 */
 void R_DrawSpanletTurbulentStipple66( void )
 {
 	unsigned btemp;
 	int	     sturb, tturb;
 	byte    *pdest = s_spanletvars.pdest;
 	short   *pz    = s_spanletvars.pz;
 	int      izi   = s_spanletvars.izi;
 	
 	if ( !( s_spanletvars.v & 1 ) )
 	{
 		s_spanletvars.pdest += s_spanletvars.spancount;
 		s_spanletvars.pz    += s_spanletvars.spancount;
 
 		if ( s_spanletvars.spancount == AFFINE_SPANLET_SIZE )
 			s_spanletvars.izi += s_spanletvars.izistep << AFFINE_SPANLET_SIZE_BITS;
 		else
 			s_spanletvars.izi += s_spanletvars.izistep * s_spanletvars.izistep;
 		
 		if ( s_spanletvars.u & 1 )
 		{
 			izi += s_spanletvars.izistep;
 			s_spanletvars.s   += s_spanletvars.sstep;
 			s_spanletvars.t   += s_spanletvars.tstep;
 
 			pdest++;
 			pz++;
 			s_spanletvars.spancount--;
 		}
 
 		s_spanletvars.sstep   *= 2;
 		s_spanletvars.tstep   *= 2;
 
 		while ( s_spanletvars.spancount > 0 )
 		{
 			sturb = ((s_spanletvars.s + r_turb_turb[(s_spanletvars.t>>16)&(CYCLE-1)])>>16)&63;
 			tturb = ((s_spanletvars.t + r_turb_turb[(s_spanletvars.s>>16)&(CYCLE-1)])>>16)&63;
 			
 			btemp = *( s_spanletvars.pbase + ( sturb ) + ( tturb << 6 ) );
 			
 			if ( *pz <= ( izi >> 16 ) )
 				*pdest = btemp;
 			
 			izi               += s_spanletvars.izistep_times_2;
 			s_spanletvars.s   += s_spanletvars.sstep;
 			s_spanletvars.t   += s_spanletvars.tstep;
 			
 			pdest += 2;
 			pz    += 2;
 			
 			s_spanletvars.spancount -= 2;
 		}
 	}
 	else
 	{
 		s_spanletvars.pdest += s_spanletvars.spancount;
 		s_spanletvars.pz    += s_spanletvars.spancount;
 
 		if ( s_spanletvars.spancount == AFFINE_SPANLET_SIZE )
 			s_spanletvars.izi += s_spanletvars.izistep << AFFINE_SPANLET_SIZE_BITS;
 		else
 			s_spanletvars.izi += s_spanletvars.izistep * s_spanletvars.izistep;
 		
 		while ( s_spanletvars.spancount > 0 )
 		{
 			sturb = ((s_spanletvars.s + r_turb_turb[(s_spanletvars.t>>16)&(CYCLE-1)])>>16)&63;
 			tturb = ((s_spanletvars.t + r_turb_turb[(s_spanletvars.s>>16)&(CYCLE-1)])>>16)&63;
 			
 			btemp = *( s_spanletvars.pbase + ( sturb ) + ( tturb << 6 ) );
 			
 			if ( *pz <= ( izi >> 16 ) )
 				*pdest = btemp;
 			
 			izi               += s_spanletvars.izistep;
 			s_spanletvars.s   += s_spanletvars.sstep;
 			s_spanletvars.t   += s_spanletvars.tstep;
 			
 			pdest++;
 			pz++;
 			
 			s_spanletvars.spancount--;
 		}
 	}
 }
 
 /*
 ** R_DrawSpanletTurbulentBlended
 */
 void R_DrawSpanletTurbulentBlended66( void )
 {
 	unsigned btemp;
 	int	     sturb, tturb;
 
 	do
 	{
 		sturb = ((s_spanletvars.s + r_turb_turb[(s_spanletvars.t>>16)&(CYCLE-1)])>>16)&63;
 		tturb = ((s_spanletvars.t + r_turb_turb[(s_spanletvars.s>>16)&(CYCLE-1)])>>16)&63;
 
 		btemp = *( s_spanletvars.pbase + ( sturb ) + ( tturb << 6 ) );
 
 		if ( *s_spanletvars.pz <= ( s_spanletvars.izi >> 16 ) )
 			*s_spanletvars.pdest = vid.alphamap[btemp*256+*s_spanletvars.pdest];
 
 		s_spanletvars.izi += s_spanletvars.izistep;
 		s_spanletvars.pdest++;
 		s_spanletvars.pz++;
 		s_spanletvars.s += s_spanletvars.sstep;
 		s_spanletvars.t += s_spanletvars.tstep;
 
 	} while ( --s_spanletvars.spancount > 0 );
 }
 
 void R_DrawSpanletTurbulentBlended33( void )
 {
 	unsigned btemp;
 	int	     sturb, tturb;
 
 	do
 	{
 		sturb = ((s_spanletvars.s + r_turb_turb[(s_spanletvars.t>>16)&(CYCLE-1)])>>16)&63;
 		tturb = ((s_spanletvars.t + r_turb_turb[(s_spanletvars.s>>16)&(CYCLE-1)])>>16)&63;
 
 		btemp = *( s_spanletvars.pbase + ( sturb ) + ( tturb << 6 ) );
 
 		if ( *s_spanletvars.pz <= ( s_spanletvars.izi >> 16 ) )
 			*s_spanletvars.pdest = vid.alphamap[btemp+*s_spanletvars.pdest*256];
 
 		s_spanletvars.izi += s_spanletvars.izistep;
 		s_spanletvars.pdest++;
 		s_spanletvars.pz++;
 		s_spanletvars.s += s_spanletvars.sstep;
 		s_spanletvars.t += s_spanletvars.tstep;
 
 	} while ( --s_spanletvars.spancount > 0 );
 }
 
 /*
 ** R_DrawSpanlet33
 */
 void R_DrawSpanlet33( void )
 {
 	unsigned btemp;
 
 	do
 	{
 		unsigned ts, tt;
 
 		ts = s_spanletvars.s >> 16;
 		tt = s_spanletvars.t >> 16;
 
 		btemp = *(s_spanletvars.pbase + (ts) + (tt) * cachewidth);
 
 		if ( btemp != 255 )
 		{
 			if (*s_spanletvars.pz <= (s_spanletvars.izi >> 16))
 			{
 				*s_spanletvars.pdest = vid.alphamap[btemp+*s_spanletvars.pdest*256];
 			}
 		}
 
 		s_spanletvars.izi += s_spanletvars.izistep;
 		s_spanletvars.pdest++;
 		s_spanletvars.pz++;
 		s_spanletvars.s += s_spanletvars.sstep;
 		s_spanletvars.t += s_spanletvars.tstep;
 	} while (--s_spanletvars.spancount > 0);
 }
 
 void R_DrawSpanletConstant33( void )
 {
 	do
 	{
 		if (*s_spanletvars.pz <= (s_spanletvars.izi >> 16))
 		{
 			*s_spanletvars.pdest = vid.alphamap[r_polyblendcolor+*s_spanletvars.pdest*256];
 		}
 
 		s_spanletvars.izi += s_spanletvars.izistep;
 		s_spanletvars.pdest++;
 		s_spanletvars.pz++;
 	} while (--s_spanletvars.spancount > 0);
 }
 
 /*
 ** R_DrawSpanlet66
 */
 void R_DrawSpanlet66( void )
 {
 	unsigned btemp;
 
 	do
 	{
 		unsigned ts, tt;
 
 		ts = s_spanletvars.s >> 16;
 		tt = s_spanletvars.t >> 16;
 
 		btemp = *(s_spanletvars.pbase + (ts) + (tt) * cachewidth);
 
 		if ( btemp != 255 )
 		{
 			if (*s_spanletvars.pz <= (s_spanletvars.izi >> 16))
 			{
 				*s_spanletvars.pdest = vid.alphamap[btemp*256+*s_spanletvars.pdest];
 			}
 		}
 
 		s_spanletvars.izi += s_spanletvars.izistep;
 		s_spanletvars.pdest++;
 		s_spanletvars.pz++;
 		s_spanletvars.s += s_spanletvars.sstep;
 		s_spanletvars.t += s_spanletvars.tstep;
 	} while (--s_spanletvars.spancount > 0);
 }
 
 /*
 ** R_DrawSpanlet33Stipple
 */
 void R_DrawSpanlet33Stipple( void )
 {
 	unsigned btemp;
 	byte    *pdest = s_spanletvars.pdest;
 	short   *pz    = s_spanletvars.pz;
 	int      izi   = s_spanletvars.izi;
 	
 	if ( r_polydesc.stipple_parity ^ ( s_spanletvars.v & 1 ) )
 	{
 		s_spanletvars.pdest += s_spanletvars.spancount;
 		s_spanletvars.pz    += s_spanletvars.spancount;
 
 		if ( s_spanletvars.spancount == AFFINE_SPANLET_SIZE )
 			s_spanletvars.izi += s_spanletvars.izistep << AFFINE_SPANLET_SIZE_BITS;
 		else
 			s_spanletvars.izi += s_spanletvars.izistep * s_spanletvars.izistep;
 		
 		if ( r_polydesc.stipple_parity ^ ( s_spanletvars.u & 1 ) )
 		{
 			izi += s_spanletvars.izistep;
 			s_spanletvars.s   += s_spanletvars.sstep;
 			s_spanletvars.t   += s_spanletvars.tstep;
 
 			pdest++;
 			pz++;
 			s_spanletvars.spancount--;
 		}
 
 		s_spanletvars.sstep *= 2;
 		s_spanletvars.tstep *= 2;
 
 		while ( s_spanletvars.spancount > 0 )
 		{
 			unsigned s = s_spanletvars.s >> 16;
 			unsigned t = s_spanletvars.t >> 16;
 
 			btemp = *( s_spanletvars.pbase + ( s ) + ( t * cachewidth ) );
 			
 			if ( btemp != 255 )
 			{
 				if ( *pz <= ( izi >> 16 ) )
 					*pdest = btemp;
 			}
 			
 			izi               += s_spanletvars.izistep_times_2;
 			s_spanletvars.s   += s_spanletvars.sstep;
 			s_spanletvars.t   += s_spanletvars.tstep;
 			
 			pdest += 2;
 			pz    += 2;
 			
 			s_spanletvars.spancount -= 2;
 		}
 	}
 }
 
 /*
 ** R_DrawSpanlet66Stipple
 */
 void R_DrawSpanlet66Stipple( void )
 {
 	unsigned btemp;
 	byte    *pdest = s_spanletvars.pdest;
 	short   *pz    = s_spanletvars.pz;
 	int      izi   = s_spanletvars.izi;
 
 	s_spanletvars.pdest += s_spanletvars.spancount;
 	s_spanletvars.pz    += s_spanletvars.spancount;
 
 	if ( s_spanletvars.spancount == AFFINE_SPANLET_SIZE )
 		s_spanletvars.izi += s_spanletvars.izistep << AFFINE_SPANLET_SIZE_BITS;
 	else
 		s_spanletvars.izi += s_spanletvars.izistep * s_spanletvars.izistep;
 
 	if ( r_polydesc.stipple_parity ^ ( s_spanletvars.v & 1 ) )
 	{
 		if ( r_polydesc.stipple_parity ^ ( s_spanletvars.u & 1 ) )
 		{
 			izi += s_spanletvars.izistep;
 			s_spanletvars.s += s_spanletvars.sstep;
 			s_spanletvars.t += s_spanletvars.tstep;
 
 			pdest++;
 			pz++;
 			s_spanletvars.spancount--;
 		}
 
 		s_spanletvars.sstep *= 2;
 		s_spanletvars.tstep *= 2;
 
 		while ( s_spanletvars.spancount > 0 )
 		{
 			unsigned s = s_spanletvars.s >> 16;
 			unsigned t = s_spanletvars.t >> 16;
 			
 			btemp = *( s_spanletvars.pbase + ( s ) + ( t * cachewidth ) );
 
 			if ( btemp != 255 )
 			{
 				if ( *pz <= ( izi >> 16 ) )
 					*pdest = btemp;
 			}
 			
 			izi             += s_spanletvars.izistep_times_2;
 			s_spanletvars.s += s_spanletvars.sstep;
 			s_spanletvars.t += s_spanletvars.tstep;
 			
 			pdest += 2;
 			pz    += 2;
 			
 			s_spanletvars.spancount -= 2;
 		}
 	}
 	else
 	{
 		while ( s_spanletvars.spancount > 0 )
 		{
 			unsigned s = s_spanletvars.s >> 16;
 			unsigned t = s_spanletvars.t >> 16;
 			
 			btemp = *( s_spanletvars.pbase + ( s ) + ( t * cachewidth ) );
 			
 			if ( btemp != 255 )
 			{
 				if ( *pz <= ( izi >> 16 ) )
 					*pdest = btemp;
 			}
 			
 			izi             += s_spanletvars.izistep;
 			s_spanletvars.s += s_spanletvars.sstep;
 			s_spanletvars.t += s_spanletvars.tstep;
 			
 			pdest++;
 			pz++;
 			
 			s_spanletvars.spancount--;
 		}
 	}
 }
 
 /*
 ** R_ClipPolyFace
 **
 ** Clips the winding at clip_verts[clip_current] and changes clip_current
 ** Throws out the back side
 */
 int R_ClipPolyFace (int nump, clipplane_t *pclipplane)
 {
 	int		i, outcount;
 	float	dists[MAXWORKINGVERTS+3];
 	float	frac, clipdist, *pclipnormal;
 	float	*in, *instep, *outstep, *vert2;
 
 	clipdist = pclipplane->dist;
 	pclipnormal = pclipplane->normal;
 	
 // calc dists
 	if (clip_current)
 	{
 		in = r_clip_verts[1][0];
 		outstep = r_clip_verts[0][0];
 		clip_current = 0;
 	}
 	else
 	{
 		in = r_clip_verts[0][0];
 		outstep = r_clip_verts[1][0];
 		clip_current = 1;
 	}
 	
 	instep = in;
 	for (i=0 ; i<nump ; i++, instep += sizeof (vec5_t) / sizeof (float))
 	{
 		dists[i] = DotProduct (instep, pclipnormal) - clipdist;
 	}
 	
 // handle wraparound case
 	dists[nump] = dists[0];
 	memcpy (instep, in, sizeof (vec5_t));
 
 
 // clip the winding
 	instep = in;
 	outcount = 0;
 
 	for (i=0 ; i<nump ; i++, instep += sizeof (vec5_t) / sizeof (float))
 	{
 		if (dists[i] >= 0)
 		{
 			memcpy (outstep, instep, sizeof (vec5_t));
 			outstep += sizeof (vec5_t) / sizeof (float);
 			outcount++;
 		}
 
 		if (dists[i] == 0 || dists[i+1] == 0)
 			continue;
 
 		if ( (dists[i] > 0) == (dists[i+1] > 0) )
 			continue;
 			
 	// split it into a new vertex
 		frac = dists[i] / (dists[i] - dists[i+1]);
 			
 		vert2 = instep + sizeof (vec5_t) / sizeof (float);
 		
 		outstep[0] = instep[0] + frac*(vert2[0] - instep[0]);
 		outstep[1] = instep[1] + frac*(vert2[1] - instep[1]);
 		outstep[2] = instep[2] + frac*(vert2[2] - instep[2]);
 		outstep[3] = instep[3] + frac*(vert2[3] - instep[3]);
 		outstep[4] = instep[4] + frac*(vert2[4] - instep[4]);
 
 		outstep += sizeof (vec5_t) / sizeof (float);
 		outcount++;
 	}	
 	
 	return outcount;
 }
 
 /*
 ** R_PolygonDrawSpans
 */
 void R_PolygonDrawSpans(espan_t *pspan, qboolean iswater )
 {
 	int			count;
 	fixed16_t	snext, tnext;
 	float		sdivz, tdivz, zi, z, du, dv, spancountminus1;
 	float		sdivzspanletstepu, tdivzspanletstepu, zispanletstepu;
 
 	s_spanletvars.pbase = cacheblock;
 
 	if ( iswater )
 		r_turb_turb = sintable + ((int)(r_newrefdef.time*SPEED)&(CYCLE-1));
 
 	sdivzspanletstepu = d_sdivzstepu * AFFINE_SPANLET_SIZE;
 	tdivzspanletstepu = d_tdivzstepu * AFFINE_SPANLET_SIZE;
 	zispanletstepu = d_zistepu * AFFINE_SPANLET_SIZE;
 
 // we count on FP exceptions being turned off to avoid range problems
 	s_spanletvars.izistep = (int)(d_zistepu * 0x8000 * 0x10000);
 	s_spanletvars.izistep_times_2 = s_spanletvars.izistep * 2;
 
 	s_spanletvars.pz = 0;
 
 	do
 	{
 		s_spanletvars.pdest   = (byte *)d_viewbuffer + ( d_scantable[pspan->v] /*r_screenwidth * pspan->v*/) + pspan->u;
 		s_spanletvars.pz      = d_pzbuffer + (d_zwidth * pspan->v) + pspan->u;
 		s_spanletvars.u       = pspan->u;
 		s_spanletvars.v       = pspan->v;
 
 		count = pspan->count;
 
 		if (count <= 0)
 			goto NextSpan;
 
 	// calculate the initial s/z, t/z, 1/z, s, and t and clamp
 		du = (float)pspan->u;
 		dv = (float)pspan->v;
 
 		sdivz = d_sdivzorigin + dv*d_sdivzstepv + du*d_sdivzstepu;
 		tdivz = d_tdivzorigin + dv*d_tdivzstepv + du*d_tdivzstepu;
 
 		zi = d_ziorigin + dv*d_zistepv + du*d_zistepu;
 		z = (float)0x10000 / zi;	// prescale to 16.16 fixed-point
 	// we count on FP exceptions being turned off to avoid range problems
 		s_spanletvars.izi = (int)(zi * 0x8000 * 0x10000);
 
 		s_spanletvars.s = (int)(sdivz * z) + sadjust;
 		s_spanletvars.t = (int)(tdivz * z) + tadjust;
 
 		if ( !iswater )
 		{
 			if (s_spanletvars.s > bbextents)
 				s_spanletvars.s = bbextents;
 			else if (s_spanletvars.s < 0)
 				s_spanletvars.s = 0;
 
 			if (s_spanletvars.t > bbextentt)
 				s_spanletvars.t = bbextentt;
 			else if (s_spanletvars.t < 0)
 				s_spanletvars.t = 0;
 		}
 
 		do
 		{
 		// calculate s and t at the far end of the span
 			if (count >= AFFINE_SPANLET_SIZE )
 				s_spanletvars.spancount = AFFINE_SPANLET_SIZE;
 			else
 				s_spanletvars.spancount = count;
 
 			count -= s_spanletvars.spancount;
 
 			if (count)
 			{
 			// calculate s/z, t/z, zi->fixed s and t at far end of span,
 			// calculate s and t steps across span by shifting
 				sdivz += sdivzspanletstepu;
 				tdivz += tdivzspanletstepu;
 				zi += zispanletstepu;
 				z = (float)0x10000 / zi;	// prescale to 16.16 fixed-point
 
 				snext = (int)(sdivz * z) + sadjust;
 				tnext = (int)(tdivz * z) + tadjust;
 
 				if ( !iswater )
 				{
 					if (snext > bbextents)
 						snext = bbextents;
 					else if (snext < AFFINE_SPANLET_SIZE)
 						snext = AFFINE_SPANLET_SIZE;	// prevent round-off error on <0 steps from
 									//  from causing overstepping & running off the
 									//  edge of the texture
 
 					if (tnext > bbextentt)
 						tnext = bbextentt;
 					else if (tnext < AFFINE_SPANLET_SIZE)
 						tnext = AFFINE_SPANLET_SIZE;	// guard against round-off error on <0 steps
 				}
 
 				s_spanletvars.sstep = (snext - s_spanletvars.s) >> AFFINE_SPANLET_SIZE_BITS;
 				s_spanletvars.tstep = (tnext - s_spanletvars.t) >> AFFINE_SPANLET_SIZE_BITS;
 			}
 			else
 			{
 			// calculate s/z, t/z, zi->fixed s and t at last pixel in span (so
 			// can't step off polygon), clamp, calculate s and t steps across
 			// span by division, biasing steps low so we don't run off the
 			// texture
 				spancountminus1 = (float)(s_spanletvars.spancount - 1);
 				sdivz += d_sdivzstepu * spancountminus1;
 				tdivz += d_tdivzstepu * spancountminus1;
 				zi += d_zistepu * spancountminus1;
 				z = (float)0x10000 / zi;	// prescale to 16.16 fixed-point
 				snext = (int)(sdivz * z) + sadjust;
 				tnext = (int)(tdivz * z) + tadjust;
 
 				if ( !iswater )
 				{
 					if (snext > bbextents)
 						snext = bbextents;
 					else if (snext < AFFINE_SPANLET_SIZE)
 						snext = AFFINE_SPANLET_SIZE;	// prevent round-off error on <0 steps from
 									//  from causing overstepping & running off the
 									//  edge of the texture
 
 					if (tnext > bbextentt)
 						tnext = bbextentt;
 					else if (tnext < AFFINE_SPANLET_SIZE)
 						tnext = AFFINE_SPANLET_SIZE;	// guard against round-off error on <0 steps
 				}
 
 				if (s_spanletvars.spancount > 1)
 				{
 					s_spanletvars.sstep = (snext - s_spanletvars.s) / (s_spanletvars.spancount - 1);
 					s_spanletvars.tstep = (tnext - s_spanletvars.t) / (s_spanletvars.spancount - 1);
 				}
 			}
 
 			if ( iswater )
 			{
 				s_spanletvars.s = s_spanletvars.s & ((CYCLE<<16)-1);
 				s_spanletvars.t = s_spanletvars.t & ((CYCLE<<16)-1);
 			}
 
 			r_polydesc.drawspanlet();
 
 			s_spanletvars.s = snext;
 			s_spanletvars.t = tnext;
 
 		} while (count > 0);
 
 NextSpan:
 		pspan++;
 
 	} while (pspan->count != DS_SPAN_LIST_END);
 }
 
 /*
 **
 ** R_PolygonScanLeftEdge
 **
 ** Goes through the polygon and scans the left edge, filling in 
 ** screen coordinate data for the spans
 */
 void R_PolygonScanLeftEdge (void)
 {
 	int			i, v, itop, ibottom, lmaxindex;
 	emitpoint_t	*pvert, *pnext;
 	espan_t		*pspan;
 	float		du, dv, vtop, vbottom, slope;
 	fixed16_t	u, u_step;
 
 	pspan = s_polygon_spans;
 	i = s_minindex;
 	if (i == 0)
 		i = r_polydesc.nump;
 
 	lmaxindex = s_maxindex;
 	if (lmaxindex == 0)
 		lmaxindex = r_polydesc.nump;
 
 	vtop = ceil (r_polydesc.pverts[i].v);
 
 	do
 	{
 		pvert = &r_polydesc.pverts[i];
 		pnext = pvert - 1;
 
 		vbottom = ceil (pnext->v);
 
 		if (vtop < vbottom)
 		{
 			du = pnext->u - pvert->u;
 			dv = pnext->v - pvert->v;
 
 			slope = du / dv;
 			u_step = (int)(slope * 0x10000);
 		// adjust u to ceil the integer portion
 			u = (int)((pvert->u + (slope * (vtop - pvert->v))) * 0x10000) +
 					(0x10000 - 1);
 			itop = (int)vtop;
 			ibottom = (int)vbottom;
 
 			for (v=itop ; v<ibottom ; v++)
 			{
 				pspan->u = u >> 16;
 				pspan->v = v;
 				u += u_step;
 				pspan++;
 			}
 		}
 
 		vtop = vbottom;
 
 		i--;
 		if (i == 0)
 			i = r_polydesc.nump;
 
 	} while (i != lmaxindex);
 }
 
 /*
 ** R_PolygonScanRightEdge
 **
 ** Goes through the polygon and scans the right edge, filling in
 ** count values.
 */
 void R_PolygonScanRightEdge (void)
 {
 	int			i, v, itop, ibottom;
 	emitpoint_t	*pvert, *pnext;
 	espan_t		*pspan;
 	float		du, dv, vtop, vbottom, slope, uvert, unext, vvert, vnext;
 	fixed16_t	u, u_step;
 
 	pspan = s_polygon_spans;
 	i = s_minindex;
 
 	vvert = r_polydesc.pverts[i].v;
 	if (vvert < r_refdef.fvrecty_adj)
 		vvert = r_refdef.fvrecty_adj;
 	if (vvert > r_refdef.fvrectbottom_adj)
 		vvert = r_refdef.fvrectbottom_adj;
 
 	vtop = ceil (vvert);
 
 	do
 	{
 		pvert = &r_polydesc.pverts[i];
 		pnext = pvert + 1;
 
 		vnext = pnext->v;
 		if (vnext < r_refdef.fvrecty_adj)
 			vnext = r_refdef.fvrecty_adj;
 		if (vnext > r_refdef.fvrectbottom_adj)
 			vnext = r_refdef.fvrectbottom_adj;
 
 		vbottom = ceil (vnext);
 
 		if (vtop < vbottom)
 		{
 			uvert = pvert->u;
 			if (uvert < r_refdef.fvrectx_adj)
 				uvert = r_refdef.fvrectx_adj;
 			if (uvert > r_refdef.fvrectright_adj)
 				uvert = r_refdef.fvrectright_adj;
 
 			unext = pnext->u;
 			if (unext < r_refdef.fvrectx_adj)
 				unext = r_refdef.fvrectx_adj;
 			if (unext > r_refdef.fvrectright_adj)
 				unext = r_refdef.fvrectright_adj;
 
 			du = unext - uvert;
 			dv = vnext - vvert;
 			slope = du / dv;
 			u_step = (int)(slope * 0x10000);
 		// adjust u to ceil the integer portion
 			u = (int)((uvert + (slope * (vtop - vvert))) * 0x10000) +
 					(0x10000 - 1);
 			itop = (int)vtop;
 			ibottom = (int)vbottom;
 
 			for (v=itop ; v<ibottom ; v++)
 			{
 				pspan->count = (u >> 16) - pspan->u;
 				u += u_step;
 				pspan++;
 			}
 		}
 
 		vtop = vbottom;
 		vvert = vnext;
 
 		i++;
 		if (i == r_polydesc.nump)
 			i = 0;
 
 	} while (i != s_maxindex);
 
 	pspan->count = DS_SPAN_LIST_END;	// mark the end of the span list 
 }
 
 /*
 ** R_ClipAndDrawPoly
 */
 void R_ClipAndDrawPoly( float alpha, qboolean isturbulent, qboolean textured )
 {
 	emitpoint_t	outverts[MAXWORKINGVERTS+3], *pout;
 	float		*pv;
 	int			i, nump;
 	float		scale;
 	vec3_t		transformed, local;
 
 	if ( !textured )
 	{
 		r_polydesc.drawspanlet = R_DrawSpanletConstant33;
 	}
 	else
 	{
 
 		/*
 		** choose the correct spanlet routine based on alpha
 		*/
 		if ( alpha == 1 )
 		{
 			// isturbulent is ignored because we know that turbulent surfaces
 			// can't be opaque
 			r_polydesc.drawspanlet = R_DrawSpanletOpaque;
 		}
 		else
 		{
 			if ( sw_stipplealpha->value )
 			{
 				if ( isturbulent )
 				{
 					if ( alpha > 0.33 )
 						r_polydesc.drawspanlet = R_DrawSpanletTurbulentStipple66;
 					else 
 						r_polydesc.drawspanlet = R_DrawSpanletTurbulentStipple33;
 				}
 				else
 				{
 					if ( alpha > 0.33 )
 						r_polydesc.drawspanlet = R_DrawSpanlet66Stipple;
 					else 
 						r_polydesc.drawspanlet = R_DrawSpanlet33Stipple;
 				}
 			}
 			else
 			{
 				if ( isturbulent )
 				{
 					if ( alpha > 0.33 )
 						r_polydesc.drawspanlet = R_DrawSpanletTurbulentBlended66;
 					else
 						r_polydesc.drawspanlet = R_DrawSpanletTurbulentBlended33;
 				}
 				else
 				{
 					if ( alpha > 0.33 )
 						r_polydesc.drawspanlet = R_DrawSpanlet66;
 					else 
 						r_polydesc.drawspanlet = R_DrawSpanlet33;
 				}
 			}
 		}
 	}
 
 	// clip to the frustum in worldspace
 	nump = r_polydesc.nump;
 	clip_current = 0;
 
 	for (i=0 ; i<4 ; i++)
 	{
 		nump = R_ClipPolyFace (nump, &view_clipplanes[i]);
 		if (nump < 3)
 			return;
 		if (nump > MAXWORKINGVERTS)
 			ri.Sys_Error(ERR_DROP, "R_ClipAndDrawPoly: too many points: %d", nump );
 	}
 
 // transform vertices into viewspace and project
 	pv = &r_clip_verts[clip_current][0][0];
 
 	for (i=0 ; i<nump ; i++)
 	{
 		VectorSubtract (pv, r_origin, local);
 		TransformVector (local, transformed);
 
 		if (transformed[2] < NEAR_CLIP)
 			transformed[2] = NEAR_CLIP;
 
 		pout = &outverts[i];
 		pout->zi = 1.0 / transformed[2];
 
 		pout->s = pv[3];
 		pout->t = pv[4];
 		
 		scale = xscale * pout->zi;
 		pout->u = (xcenter + scale * transformed[0]);
 
 		scale = yscale * pout->zi;
 		pout->v = (ycenter - scale * transformed[1]);
 
 		pv += sizeof (vec5_t) / sizeof (pv);
 	}
 
 // draw it
 	r_polydesc.nump = nump;
 	r_polydesc.pverts = outverts;
 
 	R_DrawPoly( isturbulent );
 }
 
 /*
 ** R_BuildPolygonFromSurface
 */
 void R_BuildPolygonFromSurface(msurface_t *fa)
 {
 	int			i, lindex, lnumverts;
 	medge_t		*pedges, *r_pedge;
 	int			vertpage;
 	float		*vec;
 	vec5_t     *pverts;
 	float       tmins[2] = { 0, 0 };
 
 	r_polydesc.nump = 0;
 
 	// reconstruct the polygon
 	pedges = currentmodel->edges;
 	lnumverts = fa->numedges;
 	vertpage = 0;
 
 	pverts = r_clip_verts[0];
 
 	for (i=0 ; i<lnumverts ; i++)
 	{
 		lindex = currentmodel->surfedges[fa->firstedge + i];
 
 		if (lindex > 0)
 		{
 			r_pedge = &pedges[lindex];
 			vec = currentmodel->vertexes[r_pedge->v[0]].position;
 		}
 		else
 		{
 			r_pedge = &pedges[-lindex];
 			vec = currentmodel->vertexes[r_pedge->v[1]].position;
 		}
 
 		VectorCopy (vec, pverts[i] );
 	}
 
 	VectorCopy( fa->texinfo->vecs[0], r_polydesc.vright );
 	VectorCopy( fa->texinfo->vecs[1], r_polydesc.vup );
 	VectorCopy( fa->plane->normal, r_polydesc.vpn );
 	VectorCopy( r_origin, r_polydesc.viewer_position );
 
 	if ( fa->flags & SURF_PLANEBACK )
 	{
 		VectorSubtract( vec3_origin, r_polydesc.vpn, r_polydesc.vpn );
 	}
 
 	if ( fa->texinfo->flags & SURF_WARP )
 	{
 		r_polydesc.pixels       = fa->texinfo->image->pixels[0];
 		r_polydesc.pixel_width  = fa->texinfo->image->width;
 		r_polydesc.pixel_height = fa->texinfo->image->height;
 	}
 	else
 	{
 		surfcache_t *scache;
 
 		scache = D_CacheSurface( fa, 0 );
 
 		r_polydesc.pixels       = scache->data;
 		r_polydesc.pixel_width  = scache->width;
 		r_polydesc.pixel_height = scache->height;
 
 		tmins[0] = fa->texturemins[0];
 		tmins[1] = fa->texturemins[1];
 	}
 
 	r_polydesc.dist = DotProduct( r_polydesc.vpn, pverts[0] );
 
 	r_polydesc.s_offset = fa->texinfo->vecs[0][3] - tmins[0];
 	r_polydesc.t_offset = fa->texinfo->vecs[1][3] - tmins[1];
 
 	// scrolling texture addition
 	if (fa->texinfo->flags & SURF_FLOWING)
 	{
 		r_polydesc.s_offset += -128 * ( (r_newrefdef.time*0.25) - (int)(r_newrefdef.time*0.25) );
 	}
 
 	r_polydesc.nump = lnumverts;
 }
 
 /*
 ** R_PolygonCalculateGradients
 */
 void R_PolygonCalculateGradients (void)
 {
 	vec3_t		p_normal, p_saxis, p_taxis;
 	float		distinv;
 
 	TransformVector (r_polydesc.vpn, p_normal);
 	TransformVector (r_polydesc.vright, p_saxis);
 	TransformVector (r_polydesc.vup, p_taxis);
 
 	distinv = 1.0 / (-(DotProduct (r_polydesc.viewer_position, r_polydesc.vpn)) + r_polydesc.dist );
 
 	d_sdivzstepu  =  p_saxis[0] * xscaleinv;
 	d_sdivzstepv  = -p_saxis[1] * yscaleinv;
 	d_sdivzorigin =  p_saxis[2] - xcenter * d_sdivzstepu - ycenter * d_sdivzstepv;
 
 	d_tdivzstepu  =  p_taxis[0] * xscaleinv;
 	d_tdivzstepv  = -p_taxis[1] * yscaleinv;
 	d_tdivzorigin =  p_taxis[2] - xcenter * d_tdivzstepu - ycenter * d_tdivzstepv;
 
 	d_zistepu =   p_normal[0] * xscaleinv * distinv;
 	d_zistepv =  -p_normal[1] * yscaleinv * distinv;
 	d_ziorigin =  p_normal[2] * distinv - xcenter * d_zistepu - ycenter * d_zistepv;
 
 	sadjust = (fixed16_t) ( ( DotProduct( r_polydesc.viewer_position, r_polydesc.vright) + r_polydesc.s_offset ) * 0x10000 );
 	tadjust = (fixed16_t) ( ( DotProduct( r_polydesc.viewer_position, r_polydesc.vup   ) + r_polydesc.t_offset ) * 0x10000 );
 
 // -1 (-epsilon) so we never wander off the edge of the texture
 	bbextents = (r_polydesc.pixel_width << 16) - 1;
 	bbextentt = (r_polydesc.pixel_height << 16) - 1;
 }
 
 /*
 ** R_DrawPoly
 **
 ** Polygon drawing function.  Uses the polygon described in r_polydesc
 ** to calculate edges and gradients, then renders the resultant spans.
 **
 ** This should NOT be called externally since it doesn't do clipping!
 */
 static void R_DrawPoly( qboolean iswater )
 {
 	int			i, nump;
 	float		ymin, ymax;
 	emitpoint_t	*pverts;
 	espan_t	spans[MAXHEIGHT+1];
 
 	s_polygon_spans = spans;
 
 // find the top and bottom vertices, and make sure there's at least one scan to
 // draw
 	ymin = 999999.9;
 	ymax = -999999.9;
 	pverts = r_polydesc.pverts;
 
 	for (i=0 ; i<r_polydesc.nump ; i++)
 	{
 		if (pverts->v < ymin)
 		{
 			ymin = pverts->v;
 			s_minindex = i;
 		}
 
 		if (pverts->v > ymax)
 		{
 			ymax = pverts->v;
 			s_maxindex = i;
 		}
 
 		pverts++;
 	}
 
 	ymin = ceil (ymin);
 	ymax = ceil (ymax);
 
 	if (ymin >= ymax)
 		return;		// doesn't cross any scans at all
 
 	cachewidth = r_polydesc.pixel_width;
 	cacheblock = r_polydesc.pixels;
 
 // copy the first vertex to the last vertex, so we don't have to deal with
 // wrapping
 	nump = r_polydesc.nump;
 	pverts = r_polydesc.pverts;
 	pverts[nump] = pverts[0];
 
 	R_PolygonCalculateGradients ();
 	R_PolygonScanLeftEdge ();
 	R_PolygonScanRightEdge ();
 
 	R_PolygonDrawSpans( s_polygon_spans, iswater );
 }
 
 /*
 ** R_DrawAlphaSurfaces
 */
 void R_DrawAlphaSurfaces( void )
 {
 	msurface_t *s = r_alpha_surfaces;
 
 	currentmodel = r_worldmodel;
 
 	modelorg[0] = -r_origin[0];
 	modelorg[1] = -r_origin[1];
 	modelorg[2] = -r_origin[2];
 
 	while ( s )
 	{
 		R_BuildPolygonFromSurface( s );
 
 		if (s->texinfo->flags & SURF_TRANS66)
 			R_ClipAndDrawPoly( 0.60f, ( s->texinfo->flags & SURF_WARP) != 0, true );
 		else
 			R_ClipAndDrawPoly( 0.30f, ( s->texinfo->flags & SURF_WARP) != 0, true );
 
 		s = s->nextalphasurface;
 	}
 	
 	r_alpha_surfaces = NULL;
 }
 
 /*
 ** R_IMFlatShadedQuad
 */
 void R_IMFlatShadedQuad( vec3_t a, vec3_t b, vec3_t c, vec3_t d, int color, float alpha )
 {
 	vec3_t s0, s1;
 
 	r_polydesc.nump = 4;
 	VectorCopy( r_origin, r_polydesc.viewer_position );
 
 	VectorCopy( a, r_clip_verts[0][0] );
 	VectorCopy( b, r_clip_verts[0][1] );
 	VectorCopy( c, r_clip_verts[0][2] );
 	VectorCopy( d, r_clip_verts[0][3] );
 
 	r_clip_verts[0][0][3] = 0;
 	r_clip_verts[0][1][3] = 0;
 	r_clip_verts[0][2][3] = 0;
 	r_clip_verts[0][3][3] = 0;
 
 	r_clip_verts[0][0][4] = 0;
 	r_clip_verts[0][1][4] = 0;
 	r_clip_verts[0][2][4] = 0;
 	r_clip_verts[0][3][4] = 0;
 
 	VectorSubtract( d, c, s0 );
 	VectorSubtract( c, b, s1 );
 	CrossProduct( s0, s1, r_polydesc.vpn );
 	VectorNormalize( r_polydesc.vpn );
 
 	r_polydesc.dist = DotProduct( r_polydesc.vpn, r_clip_verts[0][0] );
 
 	r_polyblendcolor = color;
 
 	R_ClipAndDrawPoly( alpha, false, false );
 }