#ifdef	USE_ZBUFFER
#define	inc()        { u += du; v += dv; w += dw; }
#define	fill(pel, z) { *zBuffer++ = (unsigned short int)(z); }

unsigned short int *draw_affine8flat(int n, unsigned short int *zBuffer, int w, int dw)
{
  while (n--) {
    fill(texture.indexed[multMuls[iv] + iu], w);
    inc();
  }
  return zBuffer;
}
#endif

/* given a span (x0,y)..(x1,y), draw a perspective-correct span for it */
/*
 * the zbuffer is interesting for dynamic model-draw etc.
 * the buffers values (1/z) are all under 0, we can try to
 * store them as 16bit-wide-fraction
 *
 * while(n--) {
 *   *zbuf++ = (unsigned short int)(w); / we need only the lower part /
 *   w += dw;
 * }
 *
 */
void draw_spans8flat(int y, int sx, int ex)
{
  unsigned char *pBuffer = (unsigned char *)localDim.frameBuffer + multRows[y] + sx;
  int len = ex - sx, rlen;

#ifdef	USE_ZBUFFER
  unsigned short int *zBuffer = localDim.zBuffer + multRows[y] + sx;
  float w0, w1;
  int w, dw;							/* 1/zbuffer */
  int slen, end;
  float prew = tmap[6] + y * tmap[8];
  float prev = tmap[3] + y * tmap[5];
  float preu = tmap[0] + y * tmap[2];

  /* compute (u,v) at left end */
  w0 = 1 / (prew + sx * tmap[7]);				/* 1/zbuffer */

  for (slen = len >> SUBDIV_SHIFT; slen > 0; slen--) {
    w = FLOAT_TO_FIX(w0);					/* 1/zbuffer */

    end = sx + SUBDIV;
    w1 = 1 / (prew + end * tmap[7]);

    dw = (FLOAT_TO_FIX(v1) - w) >> SUBDIV_SHIFT;		/* 1/zbuffer */

    zBuffer = draw_affine8flat(SUBDIV, zBuffer, w, dw);
    sx = end;

    w0 = w1;							/* 1/zbuffer */
  }

  w = FLOAT_TO_FIX(w0);						/* 1/zbuffer */
  if ((rlen = (len & SUBDIV_MASK) - 1)) {			/* a) do not calc if only draw 1 pixel */
    end = sx + rlen;
    w1 = 1 / (prew + end * tmap[7]);

    dw = FLOAT_TO_FIX((w1 - w0) / rlen);			/* 1/zbuffer */
  }
  /* a) but draw that pixel surely */
  draw_affine8flat(rlen + 1, zBuffer, w, dw);			/* for the last pixel the du and dv are thrown away */
#endif
  for (rlen = len - 1 - 1; rlen >= 0; rlen--)
    *pBuffer++ = textureColor;
}