r_poly.c

Quake 2 Source code for students by Theerthan You can also download from idsoftwares.com

*/
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
*/
// PGM - iswater was qboolean. changed to allow passing more flags
void R_PolygonDrawSpans(espan_t *pspan, int iswater )
{
	int			count;
	fixed16_t	snext, tnext;
	float		sdivz, tdivz, zi, z, du, dv, spancountminus1;
	float		sdivzspanletstepu, tdivzspanletstepu, zispanletstepu;

	s_spanletvars.pbase = cacheblock;

//PGM
	if ( iswater & SURF_WARP)
		r_turb_turb = sintable + ((int)(r_newrefdef.time*SPEED)&(CYCLE-1));
	else if (iswater & SURF_FLOWING)
		r_turb_turb = blanktable;
//PGM

	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;