/*
Copyright (C) 1996-1997 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

*/
// d_polyset.c: routines for drawing sets of polygons sharing the same
// texture (used for Alias models)

#include "quakedef.h"
#include "r_local.h"
#include "d_local.h"

// !!! if this is changed, it must be changed in asm_draw.h too !!!
typedef struct {
    void *pdest;
    short *pz;
    int count;
    byte *ptex;
    int sfrac, tfrac, light, zi;
} spanpackage_t;

typedef struct {
    int isflattop;
    int numleftedges;
    int *pleftedgevert0;
    int *pleftedgevert1;
    int *pleftedgevert2;
    int numrightedges;
    int *prightedgevert0;
    int *prightedgevert1;
    int *prightedgevert2;
} edgetable;

int r_p0[6], r_p1[6], r_p2[6];

byte *d_pcolormap;

int d_xdenom;

static edgetable *pedgetable;
static edgetable edgetables[12] = {
    {0, 1, r_p0, r_p2, NULL, 2, r_p0, r_p1, r_p2},
    {0, 2, r_p1, r_p0, r_p2, 1, r_p1, r_p2, NULL},
    {1, 1, r_p0, r_p2, NULL, 1, r_p1, r_p2, NULL},
    {0, 1, r_p1, r_p0, NULL, 2, r_p1, r_p2, r_p0},
    {0, 2, r_p0, r_p2, r_p1, 1, r_p0, r_p1, NULL},
    {0, 1, r_p2, r_p1, NULL, 1, r_p2, r_p0, NULL},
    {0, 1, r_p2, r_p1, NULL, 2, r_p2, r_p0, r_p1},
    {0, 2, r_p2, r_p1, r_p0, 1, r_p2, r_p0, NULL},
    {0, 1, r_p1, r_p0, NULL, 1, r_p1, r_p2, NULL},
    {1, 1, r_p2, r_p1, NULL, 1, r_p0, r_p1, NULL},
    {1, 1, r_p1, r_p0, NULL, 1, r_p2, r_p0, NULL},
    {0, 1, r_p0, r_p2, NULL, 1, r_p0, r_p1, NULL},
};

int a_sstepxfrac, a_tstepxfrac, r_lstepx, a_ststepxwhole;
int r_sstepx, r_tstepx, r_lstepy, r_sstepy, r_tstepy;
int r_zistepx, r_zistepy;
int d_aspancount, d_countextrastep;

spanpackage_t *a_spans;
spanpackage_t *d_pedgespanpackage;
static int ystart;
byte *d_pdest, *d_ptex;
short *d_pz;
int d_sfrac, d_tfrac, d_light, d_zi;
int d_ptexextrastep, d_sfracextrastep;
int d_tfracextrastep, d_lightextrastep, d_pdestextrastep;
int d_lightbasestep, d_pdestbasestep, d_ptexbasestep;
int d_sfracbasestep, d_tfracbasestep;
int d_ziextrastep, d_zibasestep;
int d_pzextrastep, d_pzbasestep;

typedef struct {
    int quotient;
    int remainder;
} adivtab_t;

static adivtab_t adivtab[32 * 32] = {
#include "adivtab.h"
};

byte *skintable[MAX_LBM_HEIGHT];
static int skinwidth;
static byte *skinstart;

void D_PolysetDrawSpans8(spanpackage_t *pspanpackage);
void D_PolysetCalcGradients(int skinwidth);
void D_PolysetSetEdgeTable(void);
void D_RasterizeAliasPolySmooth(void);
void D_PolysetScanLeftEdge(int height);

#ifndef USE_X86_ASM
static void D_PolysetRecursiveTriangle(int *p1, int *p2, int *p3);
static void D_PolysetDrawSpans8_Translucent(spanpackage_t *pspanpackage);
static void D_PolysetRecursiveTriangle_Translucent(int *lp1, int *lp2, int *lp3);
#endif



/*
================
D_PolysetDraw
================
*/
void
D_PolysetDraw(void)
{
    int maxspans;
    spanpackage_t *spans;

    /*
     * Allocate one extra for spanpackage that marks end and then one
     * more because of cache line pretouching.
     *
     * TODO: put in span spilling to shrink list size
     */
    maxspans = r_refdef.vrectbottom + 2;
    spans = alloca(CACHE_PAD_ARRAY(maxspans, spanpackage_t) * sizeof(spanpackage_t));

    a_spans = CACHE_ALIGN_PTR(spans);
    if (r_affinetridesc.drawtype)
	D_DrawSubdiv();
    else
	D_DrawNonSubdiv();
}

#ifndef USE_X86_ASM

/*
================
D_PolysetDrawFinalVerts
================
*/
void
D_PolysetDrawFinalVerts(finalvert_t *fv, int numverts)
{
    int i, z;
    short *zbuf;

    for (i = 0; i < numverts; i++, fv++) {
	// valid triangle coordinates for filling can include the bottom and
	// right clip edges, due to the fill rule; these shouldn't be drawn
	if ((fv->v[0] < r_refdef.vrectright) &&
	    (fv->v[1] < r_refdef.vrectbottom)) {
	    z = fv->v[5] >> 16;
	    zbuf = zspantable[fv->v[1]] + fv->v[0];
	    if (z >= *zbuf) {
		int pix;

		*zbuf = z;
		pix = skintable[fv->v[3] >> 16][fv->v[2] >> 16];
		pix = ((byte *)acolormap)[pix + (fv->v[4] & 0xFF00)];
		d_viewbuffer[d_scantable[fv->v[1]] + fv->v[0]] = pix;
	    }
	}
    }
}


/*
================
D_DrawSubdiv
================
*/
void
D_DrawSubdiv(void)
{
    mtriangle_t *ptri;
    finalvert_t *pfv, *index0, *index1, *index2;
    int i;
    int lnumtriangles;

    pfv = r_affinetridesc.pfinalverts;
    ptri = r_affinetridesc.ptriangles;
    lnumtriangles = r_affinetridesc.numtriangles;

    for (i = 0; i < lnumtriangles; i++) {
	index0 = pfv + ptri[i].vertindex[0];
	index1 = pfv + ptri[i].vertindex[1];
	index2 = pfv + ptri[i].vertindex[2];

	if (((index0->v[1] - index1->v[1]) *
	     (index0->v[0] - index2->v[0]) -
	     (index0->v[0] - index1->v[0]) *
	     (index0->v[1] - index2->v[1])) >= 0) {
	    continue;
	}

	d_pcolormap = &((byte *)acolormap)[index0->v[4] & 0xFF00];

	if (ptri[i].facesfront) {
            if (r_transtable) {
                D_PolysetRecursiveTriangle_Translucent(index0->v, index1->v, index2->v);
            } else {
                D_PolysetRecursiveTriangle(index0->v, index1->v, index2->v);
            }
	} else {
	    int s0, s1, s2;

	    s0 = index0->v[2];
	    s1 = index1->v[2];
	    s2 = index2->v[2];

	    if (index0->flags & ALIAS_ONSEAM)
		index0->v[2] += r_affinetridesc.seamfixupX16;
	    if (index1->flags & ALIAS_ONSEAM)
		index1->v[2] += r_affinetridesc.seamfixupX16;
	    if (index2->flags & ALIAS_ONSEAM)
		index2->v[2] += r_affinetridesc.seamfixupX16;

            if (r_transtable) {
                D_PolysetRecursiveTriangle_Translucent(index0->v, index1->v, index2->v);
            } else {
                D_PolysetRecursiveTriangle(index0->v, index1->v, index2->v);
            }
	    index0->v[2] = s0;
	    index1->v[2] = s1;
	    index2->v[2] = s2;
	}
    }
}


/*
================
D_DrawNonSubdiv
================
*/
void
D_DrawNonSubdiv(void)
{
    mtriangle_t *ptri;
    finalvert_t *pfv, *index0, *index1, *index2;
    int i;
    int lnumtriangles;

    pfv = r_affinetridesc.pfinalverts;
    ptri = r_affinetridesc.ptriangles;
    lnumtriangles = r_affinetridesc.numtriangles;

    for (i = 0; i < lnumtriangles; i++, ptri++) {
	index0 = pfv + ptri->vertindex[0];
	index1 = pfv + ptri->vertindex[1];
	index2 = pfv + ptri->vertindex[2];

	d_xdenom =
            (index0->v[1] - index1->v[1]) * (index0->v[0] - index2->v[0]) -
	    (index0->v[0] - index1->v[0]) * (index0->v[1] - index2->v[1]);

	if (d_xdenom >= 0) {
	    continue;
	}

	r_p0[0] = index0->v[0];	// u
	r_p0[1] = index0->v[1];	// v
	r_p0[2] = index0->v[2];	// s
	r_p0[3] = index0->v[3];	// t
	r_p0[4] = index0->v[4];	// light
	r_p0[5] = index0->v[5];	// iz

	r_p1[0] = index1->v[0];
	r_p1[1] = index1->v[1];
	r_p1[2] = index1->v[2];
	r_p1[3] = index1->v[3];
	r_p1[4] = index1->v[4];
	r_p1[5] = index1->v[5];

	r_p2[0] = index2->v[0];
	r_p2[1] = index2->v[1];
	r_p2[2] = index2->v[2];
	r_p2[3] = index2->v[3];
	r_p2[4] = index2->v[4];
	r_p2[5] = index2->v[5];

	if (!ptri->facesfront) {
	    if (index0->flags & ALIAS_ONSEAM)
		r_p0[2] += r_affinetridesc.seamfixupX16;
	    if (index1->flags & ALIAS_ONSEAM)
		r_p1[2] += r_affinetridesc.seamfixupX16;
	    if (index2->flags & ALIAS_ONSEAM)
		r_p2[2] += r_affinetridesc.seamfixupX16;
	}

	D_PolysetSetEdgeTable();
	D_RasterizeAliasPolySmooth();
    }
}


/*
================
D_PolysetRecursiveTriangle
================
*/
static void
D_PolysetRecursiveTriangle(int *lp1, int *lp2, int *lp3)
{
    int *temp;
    int d;
    int new[6];
    int z;
    short *zbuf;

    d = lp2[0] - lp1[0];
    if (d < -1 || d > 1)
	goto split;
    d = lp2[1] - lp1[1];
    if (d < -1 || d > 1)
	goto split;

    d = lp3[0] - lp2[0];
    if (d < -1 || d > 1)
	goto split2;
    d = lp3[1] - lp2[1];
    if (d < -1 || d > 1)
	goto split2;

    d = lp1[0] - lp3[0];
    if (d < -1 || d > 1)
	goto split3;
    d = lp1[1] - lp3[1];
    if (d < -1 || d > 1) {
      split3:
	temp = lp1;
	lp1 = lp3;
	lp3 = lp2;
	lp2 = temp;

	goto split;
    }

    return;			// entire tri is filled

  split2:
    temp = lp1;
    lp1 = lp2;
    lp2 = lp3;
    lp3 = temp;

  split:
// split this edge
    new[0] = (lp1[0] + lp2[0]) >> 1;
    new[1] = (lp1[1] + lp2[1]) >> 1;
    new[2] = (lp1[2] + lp2[2]) >> 1;
    new[3] = (lp1[3] + lp2[3]) >> 1;
    new[5] = (lp1[5] + lp2[5]) >> 1;

// draw the point if splitting a leading edge
    if (lp2[1] > lp1[1])
	goto nodraw;
    if ((lp2[1] == lp1[1]) && (lp2[0] < lp1[0]))
	goto nodraw;


    z = new[5] >> 16;
    zbuf = zspantable[new[1]] + new[0];
    if (z >= *zbuf) {
	int pix;

	*zbuf = z;
	pix = d_pcolormap[skintable[new[3] >> 16][new[2] >> 16]];
	d_viewbuffer[d_scantable[new[1]] + new[0]] = pix;
    }

  nodraw:
// recursively continue
    D_PolysetRecursiveTriangle(lp3, lp1, new);
    D_PolysetRecursiveTriangle(lp3, new, lp2);
}

#endif /* USE_X86_ASM */


/*
================
D_PolysetUpdateTables
================
*/
void
D_PolysetUpdateTables(void)
{
    int i;
    byte *s;

    if (r_affinetridesc.skinwidth != skinwidth || r_affinetridesc.pskin != skinstart) {
	skinwidth = r_affinetridesc.skinwidth;
	skinstart = r_affinetridesc.pskin;
	s = skinstart;
	for (i = 0; i < MAX_LBM_HEIGHT; i++, s += skinwidth)
	    skintable[i] = s;
    }
}


#ifndef USE_X86_ASM

/*
===================
D_PolysetScanLeftEdge
====================
*/
void
D_PolysetScanLeftEdge(int height)
{
    do {
	d_pedgespanpackage->pdest = d_pdest;
	d_pedgespanpackage->pz = d_pz;
	d_pedgespanpackage->count = d_aspancount;
	d_pedgespanpackage->ptex = d_ptex;

	d_pedgespanpackage->sfrac = d_sfrac;
	d_pedgespanpackage->tfrac = d_tfrac;

	// FIXME: need to clamp l, s, t, at both ends?
	d_pedgespanpackage->light = d_light;
	d_pedgespanpackage->zi = d_zi;

	d_pedgespanpackage++;

	errorterm += erroradjustup;
	if (errorterm >= 0) {
	    d_pdest += d_pdestextrastep;
	    d_pz += d_pzextrastep;
	    d_aspancount += d_countextrastep;
	    d_ptex += d_ptexextrastep;
	    d_sfrac += d_sfracextrastep;
	    d_ptex += d_sfrac >> 16;

	    d_sfrac &= 0xFFFF;
	    d_tfrac += d_tfracextrastep;
	    if (d_tfrac & 0x10000) {
		d_ptex += r_affinetridesc.skinwidth;
		d_tfrac &= 0xFFFF;
	    }
	    d_light += d_lightextrastep;
	    d_zi += d_ziextrastep;
	    errorterm -= erroradjustdown;
	} else {
	    d_pdest += d_pdestbasestep;
	    d_pz += d_pzbasestep;
	    d_aspancount += ubasestep;
	    d_ptex += d_ptexbasestep;
	    d_sfrac += d_sfracbasestep;
	    d_ptex += d_sfrac >> 16;
	    d_sfrac &= 0xFFFF;
	    d_tfrac += d_tfracbasestep;
	    if (d_tfrac & 0x10000) {
		d_ptex += r_affinetridesc.skinwidth;
		d_tfrac &= 0xFFFF;
	    }
	    d_light += d_lightbasestep;
	    d_zi += d_zibasestep;
	}
    } while (--height);
}

#endif /* USE_X86_ASM */


/*
===================
D_PolysetSetUpForLineScan
====================
*/
static void
D_PolysetSetUpForLineScan(fixed8_t startvertu, fixed8_t startvertv, fixed8_t endvertu, fixed8_t endvertv)
{
    double dm, dn;
    int tm, tn;
    adivtab_t *ptemp;

// TODO: implement x86 version

    errorterm = -1;

    tm = endvertu - startvertu;
    tn = endvertv - startvertv;

    if (((tm <= 16) && (tm >= -15)) && ((tn <= 16) && (tn >= -15))) {
	ptemp = &adivtab[((tm + 15) << 5) + (tn + 15)];
	ubasestep = ptemp->quotient;
	erroradjustup = ptemp->remainder;
	erroradjustdown = tn;
    } else {
	dm = (double)tm;
	dn = (double)tn;

	FloorDivMod(dm, dn, &ubasestep, &erroradjustup);

	erroradjustdown = dn;
    }
}


#ifndef USE_X86_ASM

/*
================
D_PolysetCalcGradients
================
*/
void
D_PolysetCalcGradients(int skinwidth)
{
    float xstepdenominv, ystepdenominv, t0, t1;
    float p01_minus_p21, p11_minus_p21, p00_minus_p20, p10_minus_p20;

    p00_minus_p20 = r_p0[0] - r_p2[0];
    p01_minus_p21 = r_p0[1] - r_p2[1];
    p10_minus_p20 = r_p1[0] - r_p2[0];
    p11_minus_p21 = r_p1[1] - r_p2[1];

    xstepdenominv = 1.0 / (float)d_xdenom;

    ystepdenominv = -xstepdenominv;

// ceil () for light so positive steps are exaggerated, negative steps
// diminished,  pushing us away from underflow toward overflow. Underflow is
// very visible, overflow is very unlikely, because of ambient lighting
    t0 = r_p0[4] - r_p2[4];
    t1 = r_p1[4] - r_p2[4];
    r_lstepx = (int)
	ceilf((t1 * p01_minus_p21 - t0 * p11_minus_p21) * xstepdenominv);
    r_lstepy = (int)
	ceilf((t1 * p00_minus_p20 - t0 * p10_minus_p20) * ystepdenominv);

    t0 = r_p0[2] - r_p2[2];
    t1 = r_p1[2] - r_p2[2];
    r_sstepx = (int)((t1 * p01_minus_p21 - t0 * p11_minus_p21) *
		     xstepdenominv);
    r_sstepy = (int)((t1 * p00_minus_p20 - t0 * p10_minus_p20) *
		     ystepdenominv);

    t0 = r_p0[3] - r_p2[3];
    t1 = r_p1[3] - r_p2[3];
    r_tstepx = (int)((t1 * p01_minus_p21 - t0 * p11_minus_p21) *
		     xstepdenominv);
    r_tstepy = (int)((t1 * p00_minus_p20 - t0 * p10_minus_p20) *
		     ystepdenominv);

    t0 = r_p0[5] - r_p2[5];
    t1 = r_p1[5] - r_p2[5];
    r_zistepx = (int)((t1 * p01_minus_p21 - t0 * p11_minus_p21) *
		      xstepdenominv);
    r_zistepy = (int)((t1 * p00_minus_p20 - t0 * p10_minus_p20) *
		      ystepdenominv);

    a_sstepxfrac = r_sstepx & 0xFFFF;
    a_tstepxfrac = r_tstepx & 0xFFFF;

    a_ststepxwhole = skinwidth * (r_tstepx >> 16) + (r_sstepx >> 16);
}


/*
================
D_PolysetDrawSpans8
================
*/
void
D_PolysetDrawSpans8(spanpackage_t *pspanpackage)
{
    int lcount;
    byte *lpdest;
    byte *lptex;
    int lsfrac, ltfrac;
    int llight;
    int lzi;
    short *lpz;

    do {
	lcount = d_aspancount - pspanpackage->count;

	errorterm += erroradjustup;
	if (errorterm >= 0) {
	    d_aspancount += d_countextrastep;
	    errorterm -= erroradjustdown;
	} else {
	    d_aspancount += ubasestep;
	}

	if (lcount) {
	    lpdest = pspanpackage->pdest;
	    lptex = pspanpackage->ptex;
	    lpz = pspanpackage->pz;
	    lsfrac = pspanpackage->sfrac;
	    ltfrac = pspanpackage->tfrac;
	    llight = pspanpackage->light;
	    lzi = pspanpackage->zi;

	    do {
		if ((lzi >> 16) >= *lpz) {
		    *lpdest = ((byte *)acolormap)[*lptex + (llight & 0xFF00)];
		    *lpz = lzi >> 16;
		}
		lpdest++;
		lzi += r_zistepx;
		lpz++;
		llight += r_lstepx;
		lptex += a_ststepxwhole;
		lsfrac += a_sstepxfrac;
		lptex += lsfrac >> 16;
		lsfrac &= 0xFFFF;
		ltfrac += a_tstepxfrac;
		if (ltfrac & 0x10000) {
		    lptex += r_affinetridesc.skinwidth;
		    ltfrac &= 0xFFFF;
		}
	    } while (--lcount);
	}

	pspanpackage++;
    } while (pspanpackage->count != -999999);
}
#endif /* USE_X86_ASM */


/*
================
D_RasterizeAliasPolySmooth
================
*/
void
D_RasterizeAliasPolySmooth(void)
{
    int initialleftheight, initialrightheight;
    int *plefttop, *prighttop, *pleftbottom, *prightbottom;
    int working_lstepx, originalcount;

    plefttop = pedgetable->pleftedgevert0;
    prighttop = pedgetable->prightedgevert0;

    pleftbottom = pedgetable->pleftedgevert1;
    prightbottom = pedgetable->prightedgevert1;

    initialleftheight = pleftbottom[1] - plefttop[1];
    initialrightheight = prightbottom[1] - prighttop[1];

//
// set the s, t, and light gradients, which are consistent across the triangle
// because being a triangle, things are affine
//
    D_PolysetCalcGradients(r_affinetridesc.skinwidth);

//
// rasterize the polygon
//

//
// scan out the top (and possibly only) part of the left edge
//
    D_PolysetSetUpForLineScan(plefttop[0], plefttop[1], pleftbottom[0], pleftbottom[1]);

    d_pedgespanpackage = a_spans;

    ystart = plefttop[1];
    d_aspancount = plefttop[0] - prighttop[0];
    d_ptex = (byte *)r_affinetridesc.pskin + (plefttop[2] >> 16) + (plefttop[3] >> 16) * r_affinetridesc.skinwidth;

#ifdef USE_X86_ASM
    d_sfrac = (plefttop[2] & 0xFFFF) << 16;
    d_tfrac = (plefttop[3] & 0xFFFF) << 16;
    d_pzbasestep = (d_zwidth + ubasestep) << 1;
    d_pzextrastep = d_pzbasestep + 2;
#else
    d_sfrac = plefttop[2] & 0xFFFF;
    d_tfrac = plefttop[3] & 0xFFFF;
    d_pzbasestep = d_zwidth + ubasestep;
    d_pzextrastep = d_pzbasestep + 1;
#endif

    d_light = plefttop[4];
    d_zi = plefttop[5];

    d_pdestbasestep = screenwidth + ubasestep;
    d_pdestextrastep = d_pdestbasestep + 1;
    d_pdest = (byte *)d_viewbuffer + ystart * screenwidth + plefttop[0];

    d_pz = d_pzbuffer + ystart * d_zwidth + plefttop[0];

    /* TODO: can reuse partial expressions here */

    /*
     * for negative steps in x along left edge, bias toward overflow rather
     * than underflow (sort of turning the floor () we did in the gradient
     * calcs into ceil (), but plus a little bit)
     */
    if (ubasestep < 0)
	working_lstepx = r_lstepx - 1;
    else
	working_lstepx = r_lstepx;

    d_countextrastep = ubasestep + 1;
    d_ptexbasestep = ((r_sstepy + r_sstepx * ubasestep) >> 16) + ((r_tstepy + r_tstepx * ubasestep) >> 16) * r_affinetridesc.skinwidth;
#ifdef USE_X86_ASM
    d_sfracbasestep = (r_sstepy + r_sstepx * ubasestep) << 16;
    d_tfracbasestep = (r_tstepy + r_tstepx * ubasestep) << 16;
#else
    d_sfracbasestep = (r_sstepy + r_sstepx * ubasestep) & 0xFFFF;
    d_tfracbasestep = (r_tstepy + r_tstepx * ubasestep) & 0xFFFF;
#endif
    d_lightbasestep = r_lstepy + working_lstepx * ubasestep;
    d_zibasestep = r_zistepy + r_zistepx * ubasestep;

    d_ptexextrastep = ((r_sstepy + r_sstepx * d_countextrastep) >> 16) + ((r_tstepy + r_tstepx * d_countextrastep) >> 16) * r_affinetridesc.skinwidth;
#ifdef USE_X86_ASM
    d_sfracextrastep = (r_sstepy + r_sstepx * d_countextrastep) << 16;
    d_tfracextrastep = (r_tstepy + r_tstepx * d_countextrastep) << 16;
#else
    d_sfracextrastep = (r_sstepy + r_sstepx * d_countextrastep) & 0xFFFF;
    d_tfracextrastep = (r_tstepy + r_tstepx * d_countextrastep) & 0xFFFF;
#endif
    d_lightextrastep = d_lightbasestep + working_lstepx;
    d_ziextrastep = d_zibasestep + r_zistepx;

    D_PolysetScanLeftEdge(initialleftheight);

//
// scan out the bottom part of the left edge, if it exists
//
    if (pedgetable->numleftedges == 2) {
	int height;

	plefttop = pleftbottom;
	pleftbottom = pedgetable->pleftedgevert2;

	D_PolysetSetUpForLineScan(plefttop[0], plefttop[1], pleftbottom[0], pleftbottom[1]);

	height = pleftbottom[1] - plefttop[1];

// TODO: make this a function; modularize this function in general

	ystart = plefttop[1];
	d_aspancount = plefttop[0] - prighttop[0];
	d_ptex = (byte *)r_affinetridesc.pskin + (plefttop[2] >> 16) + (plefttop[3] >> 16) * r_affinetridesc.skinwidth;
	d_sfrac = 0;
	d_tfrac = 0;
	d_light = plefttop[4];
	d_zi = plefttop[5];

	d_pdestbasestep = screenwidth + ubasestep;
	d_pdestextrastep = d_pdestbasestep + 1;
	d_pdest = (byte *)d_viewbuffer + ystart * screenwidth + plefttop[0];
#ifdef USE_X86_ASM
	d_pzbasestep = (d_zwidth + ubasestep) << 1;
	d_pzextrastep = d_pzbasestep + 2;
#else
	d_pzbasestep = d_zwidth + ubasestep;
	d_pzextrastep = d_pzbasestep + 1;
#endif
	d_pz = d_pzbuffer + ystart * d_zwidth + plefttop[0];

	if (ubasestep < 0)
	    working_lstepx = r_lstepx - 1;
	else
	    working_lstepx = r_lstepx;

	d_countextrastep = ubasestep + 1;
	d_ptexbasestep = ((r_sstepy + r_sstepx * ubasestep) >> 16) + ((r_tstepy + r_tstepx * ubasestep) >> 16) * r_affinetridesc.skinwidth;
#ifdef USE_X86_ASM
	d_sfracbasestep = (r_sstepy + r_sstepx * ubasestep) << 16;
	d_tfracbasestep = (r_tstepy + r_tstepx * ubasestep) << 16;
#else
	d_sfracbasestep = (r_sstepy + r_sstepx * ubasestep) & 0xFFFF;
	d_tfracbasestep = (r_tstepy + r_tstepx * ubasestep) & 0xFFFF;
#endif
	d_lightbasestep = r_lstepy + working_lstepx * ubasestep;
	d_zibasestep = r_zistepy + r_zistepx * ubasestep;

	d_ptexextrastep = ((r_sstepy + r_sstepx * d_countextrastep) >> 16) + ((r_tstepy + r_tstepx * d_countextrastep) >> 16) * r_affinetridesc.skinwidth;
#ifdef USE_X86_ASM
	d_sfracextrastep = ((r_sstepy + r_sstepx * d_countextrastep) & 0xFFFF) << 16;
	d_tfracextrastep = ((r_tstepy + r_tstepx * d_countextrastep) & 0xFFFF) << 16;
#else
	d_sfracextrastep = (r_sstepy + r_sstepx * d_countextrastep) & 0xFFFF;
	d_tfracextrastep = (r_tstepy + r_tstepx * d_countextrastep) & 0xFFFF;
#endif
	d_lightextrastep = d_lightbasestep + working_lstepx;
	d_ziextrastep = d_zibasestep + r_zistepx;

	D_PolysetScanLeftEdge(height);
    }
// scan out the top (and possibly only) part of the right edge, updating the
// count field
    d_pedgespanpackage = a_spans;

    D_PolysetSetUpForLineScan(prighttop[0], prighttop[1], prightbottom[0], prightbottom[1]);
    d_aspancount = 0;
    d_countextrastep = ubasestep + 1;
    originalcount = a_spans[initialrightheight].count;
    a_spans[initialrightheight].count = -999999; // mark end of the spanpackages

    if (r_transtable) {
        D_PolysetDrawSpans8_Translucent(a_spans);
    } else {
        D_PolysetDrawSpans8(a_spans);
    }

// scan out the bottom part of the right edge, if it exists
    if (pedgetable->numrightedges == 2) {
	int height;
	spanpackage_t *pstart;

	pstart = a_spans + initialrightheight;
	pstart->count = originalcount;

	d_aspancount = prightbottom[0] - prighttop[0];

	prighttop = prightbottom;
	prightbottom = pedgetable->prightedgevert2;

	height = prightbottom[1] - prighttop[1];

	D_PolysetSetUpForLineScan(prighttop[0], prighttop[1],
				  prightbottom[0], prightbottom[1]);

	d_countextrastep = ubasestep + 1;
	a_spans[initialrightheight + height].count = -999999; // mark end of the spanpackages

        if (r_transtable) {
            D_PolysetDrawSpans8_Translucent(pstart);
        } else {
            D_PolysetDrawSpans8(pstart);
        }
    }
}


/*
================
D_PolysetSetEdgeTable
================
*/
void
D_PolysetSetEdgeTable(void)
{
    int edgetableindex;

    edgetableindex = 0;		// assume the vertices are already in
    //  top to bottom order

//
// determine which edges are right & left, and the order in which
// to rasterize them
//
    if (r_p0[1] >= r_p1[1]) {
	if (r_p0[1] == r_p1[1]) {
	    if (r_p0[1] < r_p2[1])
		pedgetable = &edgetables[2];
	    else
		pedgetable = &edgetables[5];

	    return;
	} else {
	    edgetableindex = 1;
	}
    }

    if (r_p0[1] == r_p2[1]) {
	if (edgetableindex)
	    pedgetable = &edgetables[8];
	else
	    pedgetable = &edgetables[9];

	return;
    } else if (r_p1[1] == r_p2[1]) {
	if (edgetableindex)
	    pedgetable = &edgetables[10];
	else
	    pedgetable = &edgetables[11];

	return;
    }

    if (r_p0[1] > r_p2[1])
	edgetableindex += 2;

    if (r_p1[1] > r_p2[1])
	edgetableindex += 4;

    pedgetable = &edgetables[edgetableindex];
}


// ======================================================================
// Translucency
// ======================================================================

#ifndef USE_X86_ASM

/*
================
D_PolysetDrawSpans8_Translucent
================
*/
static void
D_PolysetDrawSpans8_Translucent(spanpackage_t *pspanpackage)
{
    int lcount;
    byte *lpdest;
    byte *lptex;
    int lsfrac, ltfrac;
    int llight;
    int lzi;
    short *lpz;

    do {
	lcount = d_aspancount - pspanpackage->count;

	errorterm += erroradjustup;
	if (errorterm >= 0) {
	    d_aspancount += d_countextrastep;
	    errorterm -= erroradjustdown;
	} else {
	    d_aspancount += ubasestep;
	}

	if (lcount) {
	    lpdest = pspanpackage->pdest;
	    lptex = pspanpackage->ptex;
	    lpz = pspanpackage->pz;
	    lsfrac = pspanpackage->sfrac;
	    ltfrac = pspanpackage->tfrac;
	    llight = pspanpackage->light;
	    lzi = pspanpackage->zi;

	    do {
		if ((lzi >> 16) >= *lpz) {
                    int pixel = ((byte *)acolormap)[*lptex + (llight & 0xFF00)];
		    *lpdest = r_transtable[(((int)*lpdest) << 8) + pixel];
		}
		lpdest++;
		lzi += r_zistepx;
		lpz++;
		llight += r_lstepx;
		lptex += a_ststepxwhole;
		lsfrac += a_sstepxfrac;
		lptex += lsfrac >> 16;
		lsfrac &= 0xFFFF;
		ltfrac += a_tstepxfrac;
		if (ltfrac & 0x10000) {
		    lptex += r_affinetridesc.skinwidth;
		    ltfrac &= 0xFFFF;
		}
	    } while (--lcount);
	}

	pspanpackage++;
    } while (pspanpackage->count != -999999);
}

/*
================
D_PolysetDrawFinalVerts_Translucent
================
*/
void
D_PolysetDrawFinalVerts_Translucent(finalvert_t *fv, int numverts)
{
    int i, z;
    short *zbuf;
    byte *pdest;

    for (i = 0; i < numverts; i++, fv++) {
	// valid triangle coordinates for filling can include the bottom and
	// right clip edges, due to the fill rule; these shouldn't be drawn
	if ((fv->v[0] < r_refdef.vrectright) && (fv->v[1] < r_refdef.vrectbottom)) {
	    z = fv->v[5] >> 16;
	    zbuf = zspantable[fv->v[1]] + fv->v[0];
	    if (z >= *zbuf) {
		int pixel = skintable[fv->v[3] >> 16][fv->v[2] >> 16];
		pixel = ((byte *)acolormap)[pixel + (fv->v[4] & 0xFF00)];
                pdest = &d_viewbuffer[d_scantable[fv->v[1]] + fv->v[0]];
                *pdest = r_transtable[(((int)*pdest) << 8) + pixel];
	    }
	}
    }
}

/*
================
D_PolysetRecursiveTriangle_Translucent
================
*/
static void
D_PolysetRecursiveTriangle_Translucent(int *lp1, int *lp2, int *lp3)
{
    int *temp;
    int d;
    int new[6];
    int z;
    short *zbuf;

    d = lp2[0] - lp1[0];
    if (d < -1 || d > 1)
	goto split;
    d = lp2[1] - lp1[1];
    if (d < -1 || d > 1)
	goto split;

    d = lp3[0] - lp2[0];
    if (d < -1 || d > 1)
	goto split2;
    d = lp3[1] - lp2[1];
    if (d < -1 || d > 1)
	goto split2;

    d = lp1[0] - lp3[0];
    if (d < -1 || d > 1)
	goto split3;
    d = lp1[1] - lp3[1];
    if (d < -1 || d > 1) {
      split3:
	temp = lp1;
	lp1 = lp3;
	lp3 = lp2;
	lp2 = temp;

	goto split;
    }

    return;			// entire tri is filled

  split2:
    temp = lp1;
    lp1 = lp2;
    lp2 = lp3;
    lp3 = temp;

  split:
// split this edge
    new[0] = (lp1[0] + lp2[0]) >> 1;
    new[1] = (lp1[1] + lp2[1]) >> 1;
    new[2] = (lp1[2] + lp2[2]) >> 1;
    new[3] = (lp1[3] + lp2[3]) >> 1;
    new[5] = (lp1[5] + lp2[5]) >> 1;

// draw the point if splitting a leading edge
    if (lp2[1] > lp1[1])
	goto nodraw;
    if ((lp2[1] == lp1[1]) && (lp2[0] < lp1[0]))
	goto nodraw;


    z = new[5] >> 16;
    zbuf = zspantable[new[1]] + new[0];
    if (z >= *zbuf) {
	int pixel = d_pcolormap[skintable[new[3] >> 16][new[2] >> 16]];
        byte *pdest = &d_viewbuffer[d_scantable[new[1]] + new[0]];
        *pdest = r_transtable[(((int)*pdest) << 8) + pixel];
    }

  nodraw:
// recursively continue
    D_PolysetRecursiveTriangle_Translucent(lp3, lp1, new);
    D_PolysetRecursiveTriangle_Translucent(lp3, new, lp2);
}

#endif
