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poly3d.c

/*         ______   ___    ___ 
 *        /\  _  \ /\_ \  /\_ \ 
 *        \ \ \L\ \\//\ \ \//\ \      __     __   _ __   ___ 
 *         \ \  __ \ \ \ \  \ \ \   /'__`\ /'_ `\/\`'__\/ __`\
 *          \ \ \/\ \ \_\ \_ \_\ \_/\  __//\ \L\ \ \ \//\ \L\ \
 *           \ \_\ \_\/\____\/\____\ \____\ \____ \ \_\\ \____/
 *            \/_/\/_/\/____/\/____/\/____/\/___L\ \/_/ \/___/
 *                                           /\____/
 *                                           \_/__/
 *
 *      The 3d polygon rasteriser.
 *
 *      By Shawn Hargreaves.
 *
 *      Hicolor support added by Przemek Podsiadly. Complete support for
 *      all drawing modes in every color depth MMX optimisations and z-buffer
 *      added by Calin Andrian. Subpixel and subtexel accuracy, triangle
 *      functions and speed enhancements added by Bertrand Coconnier.
 *      Functions adapted to handle two coincident vertices by Ben Davis.
 *
 *      See readme.txt for copyright information.
 */


#include <limits.h>
#include <float.h>

#include "allegro.h"
#include "allegro/internal/aintern.h"

#ifdef ALLEGRO_ASMCAPA_HEADER
   #include ALLEGRO_ASMCAPA_HEADER
#endif

#ifdef ALLEGRO_USE_C
   #undef ALLEGRO_MMX
#endif


#ifdef ALLEGRO_MMX

/* for use by iscan.s */
uint32_t _mask_mmx_15[] = { 0x03E0001F, 0x007C };
uint32_t _mask_mmx_16[] = { 0x07E0001F, 0x00F8 };

#endif


void _poly_scanline_dummy(uintptr_t addr, int w, POLYGON_SEGMENT *info) { }

ZBUFFER *_zbuffer = NULL;

SCANLINE_FILLER _optim_alternative_drawer;


/* _fill_3d_edge_structure:
 *  Polygon helper function: initialises an edge structure for the 3d 
 *  rasterising code, using fixed point vertex structures. Returns 1 on
 *  success, or 0 if the edge is horizontal or clipped out of existence.
 */
int _fill_3d_edge_structure(POLYGON_EDGE *edge, AL_CONST V3D *v1, AL_CONST V3D *v2, int flags, BITMAP *bmp)
{
   int r1, r2, g1, g2, b1, b2;
   fixed h, step;

   /* swap vertices if they are the wrong way up */
   if (v2->y < v1->y) {
      AL_CONST V3D *vt;

      vt = v1;
      v1 = v2;
      v2 = vt;
   }

   /* set up screen rasterising parameters */
   edge->top = fixceil(v1->y);
   edge->bottom = fixceil(v2->y) - 1;

   if (edge->bottom < edge->top) return 0;

   h = v2->y - v1->y;
   step = (edge->top << 16) - v1->y;

   edge->dx = fixdiv(v2->x - v1->x, h);
   edge->x = v1->x + fixmul(step, edge->dx);

   edge->prev = NULL;
   edge->next = NULL;
   edge->w = 0;

   if (flags & INTERP_Z) {
      float h1 = 65536. / h;
      float step_f = fixtof(step);

      /* Z (depth) interpolation */
      float z1 = 65536. / v1->z;
      float z2 = 65536. / v2->z;

      edge->dat.dz = (z2 - z1) * h1;
      edge->dat.z = z1 + edge->dat.dz * step_f;

      if (flags & INTERP_FLOAT_UV) {
       /* floating point (perspective correct) texture interpolation */
       float fu1 = v1->u * z1;
       float fv1 = v1->v * z1;
       float fu2 = v2->u * z2;
       float fv2 = v2->v * z2;

       edge->dat.dfu = (fu2 - fu1) * h1;
       edge->dat.dfv = (fv2 - fv1) * h1;
       edge->dat.fu = fu1 + edge->dat.dfu * step_f;
       edge->dat.fv = fv1 + edge->dat.dfv * step_f;
      }
   }

   if (flags & INTERP_FLAT) {
      /* if clipping is enabled then clip edge */
      if (bmp->clip) {
         if (edge->top < bmp->ct) {
            edge->x += (bmp->ct - edge->top) * edge->dx;
          edge->top = bmp->ct;
         }

         if (edge->bottom >= bmp->cb)
          edge->bottom = bmp->cb - 1;
      }

      return (edge->bottom >= edge->top);
   }

   if (flags & INTERP_1COL) {
      /* single color shading interpolation */
      edge->dat.dc = fixdiv(itofix(v2->c - v1->c), h);
      edge->dat.c = itofix(v1->c) + fixmul(step, edge->dat.dc);
   }

   if (flags & INTERP_3COL) {
      /* RGB shading interpolation */
      if (flags & COLOR_TO_RGB) {
         AL_CONST int coldepth = bitmap_color_depth(bmp);
       r1 = getr_depth(coldepth, v1->c);
       r2 = getr_depth(coldepth, v2->c);
       g1 = getg_depth(coldepth, v1->c);
       g2 = getg_depth(coldepth, v2->c);
       b1 = getb_depth(coldepth, v1->c);
       b2 = getb_depth(coldepth, v2->c);
      } 
      else {
       r1 = (v1->c >> 16) & 0xFF;
       r2 = (v2->c >> 16) & 0xFF;
       g1 = (v1->c >> 8) & 0xFF;
       g2 = (v2->c >> 8) & 0xFF;
       b1 = v1->c & 0xFF;
       b2 = v2->c & 0xFF;
      }

      edge->dat.dr = fixdiv(itofix(r2 - r1), h);
      edge->dat.dg = fixdiv(itofix(g2 - g1), h);
      edge->dat.db = fixdiv(itofix(b2 - b1), h);
      edge->dat.r = itofix(r1) + fixmul(step, edge->dat.dr);
      edge->dat.g = itofix(g1) + fixmul(step, edge->dat.dg);
      edge->dat.b = itofix(b1) + fixmul(step, edge->dat.db);
   }

   if (flags & INTERP_FIX_UV) {
      /* fixed point (affine) texture interpolation */
      edge->dat.du = fixdiv(v2->u - v1->u, h);
      edge->dat.dv = fixdiv(v2->v - v1->v, h);
      edge->dat.u = v1->u + fixmul(step, edge->dat.du);
      edge->dat.v = v1->v + fixmul(step, edge->dat.dv);
   }

   /* if clipping is enabled then clip edge */
   if (bmp->clip) {
      if (edge->top < bmp->ct) {
         int gap = bmp->ct - edge->top;
         edge->top = bmp->ct;
         edge->x += gap * edge->dx;
         _clip_polygon_segment(&(edge->dat), itofix(gap), flags);
      }

      if (edge->bottom >= bmp->cb)
         edge->bottom = bmp->cb - 1;
   }

   return (edge->bottom >= edge->top);
}



/* _fill_3d_edge_structure_f:
 *  Polygon helper function: initialises an edge structure for the 3d 
 *  rasterising code, using floating point vertex structures. Returns 1 on
 *  success, or 0 if the edge is horizontal or clipped out of existence.
 */
int _fill_3d_edge_structure_f(POLYGON_EDGE *edge, AL_CONST V3D_f *v1, AL_CONST V3D_f *v2, int flags, BITMAP *bmp)
{
   int r1, r2, g1, g2, b1, b2;
   fixed h, step;
   float h1;

   /* swap vertices if they are the wrong way up */
   if (v2->y < v1->y) {
      AL_CONST V3D_f *vt;

      vt = v1;
      v1 = v2;
      v2 = vt;
   }

   /* set up screen rasterising parameters */
   edge->top = fixceil(ftofix(v1->y));
   edge->bottom = fixceil(ftofix(v2->y)) - 1;

   if (edge->bottom < edge->top) return 0;

   h1 = 1.0 / (v2->y - v1->y);
   h = ftofix(v2->y - v1->y);
   step = (edge->top << 16) - ftofix(v1->y);

   edge->dx = ftofix((v2->x - v1->x)  * h1);
   edge->x = ftofix(v1->x) + fixmul(step, edge->dx);

   edge->prev = NULL;
   edge->next = NULL;
   edge->w = 0;

   if (flags & INTERP_Z) {
      float step_f = fixtof(step);

      /* Z (depth) interpolation */
      float z1 = 1. / v1->z;
      float z2 = 1. / v2->z;

      edge->dat.dz = (z2 - z1) * h1;
      edge->dat.z = z1 + edge->dat.dz * step_f;

      if (flags & INTERP_FLOAT_UV) {
       /* floating point (perspective correct) texture interpolation */
       float fu1 = v1->u * z1 * 65536.;
       float fv1 = v1->v * z1 * 65536.;
       float fu2 = v2->u * z2 * 65536.;
       float fv2 = v2->v * z2 * 65536.;

       edge->dat.dfu = (fu2 - fu1) * h1;
       edge->dat.dfv = (fv2 - fv1) * h1;
       edge->dat.fu = fu1 + edge->dat.dfu * step_f;
       edge->dat.fv = fv1 + edge->dat.dfv * step_f;
      }
   }

   if (flags & INTERP_FLAT) {
      /* if clipping is enabled then clip edge */
      if (bmp->clip) {
         if (edge->top < bmp->ct) {
          edge->x += (bmp->ct - edge->top) * edge->dx;
          edge->top = bmp->ct;
         }

         if (edge->bottom >= bmp->cb)
          edge->bottom = bmp->cb - 1;
      }

      return (edge->bottom >= edge->top);
   }

   if (flags & INTERP_1COL) {
      /* single color shading interpolation */
      edge->dat.dc = fixdiv(itofix(v2->c - v1->c), h);
      edge->dat.c = itofix(v1->c) + fixmul(step, edge->dat.dc);
   }

   if (flags & INTERP_3COL) {
      /* RGB shading interpolation */
      if (flags & COLOR_TO_RGB) {
         AL_CONST int coldepth = bitmap_color_depth(bmp);
       r1 = getr_depth(coldepth, v1->c);
       r2 = getr_depth(coldepth, v2->c);
       g1 = getg_depth(coldepth, v1->c);
       g2 = getg_depth(coldepth, v2->c);
       b1 = getb_depth(coldepth, v1->c);
       b2 = getb_depth(coldepth, v2->c);
      } 
      else {
       r1 = (v1->c >> 16) & 0xFF;
       r2 = (v2->c >> 16) & 0xFF;
       g1 = (v1->c >> 8) & 0xFF;
       g2 = (v2->c >> 8) & 0xFF;
       b1 = v1->c & 0xFF;
       b2 = v2->c & 0xFF;
      }

      edge->dat.dr = fixdiv(itofix(r2 - r1), h);
      edge->dat.dg = fixdiv(itofix(g2 - g1), h);
      edge->dat.db = fixdiv(itofix(b2 - b1), h);
      edge->dat.r = itofix(r1) + fixmul(step, edge->dat.dr);
      edge->dat.g = itofix(g1) + fixmul(step, edge->dat.dg);
      edge->dat.b = itofix(b1) + fixmul(step, edge->dat.db);
   }

   if (flags & INTERP_FIX_UV) {
      /* fixed point (affine) texture interpolation */
      edge->dat.du = ftofix((v2->u - v1->u) * h1);
      edge->dat.dv = ftofix((v2->v - v1->v) * h1);
      edge->dat.u = ftofix(v1->u) + fixmul(step, edge->dat.du);
      edge->dat.v = ftofix(v1->v) + fixmul(step, edge->dat.dv);
   }

   /* if clipping is enabled then clip edge */
   if (bmp->clip) {
      if (edge->top < bmp->ct) {
         int gap = bmp->ct - edge->top;
         edge->top = bmp->ct;
         edge->x += gap * edge->dx;
         _clip_polygon_segment_f(&(edge->dat), gap, flags);
      }

      if (edge->bottom >= bmp->cb)
         edge->bottom = bmp->cb - 1;
   }

   return (edge->bottom >= edge->top);
}



/* _get_scanline_filler:
 *  Helper function for deciding which rasterisation function and 
 *  interpolation flags we should use for a specific polygon type.
 */
SCANLINE_FILLER _get_scanline_filler(int type, int *flags, POLYGON_SEGMENT *info, BITMAP *texture, BITMAP *bmp)
{
   typedef struct POLYTYPE_INFO 
   {
      SCANLINE_FILLER filler;
      SCANLINE_FILLER alternative;
   } POLYTYPE_INFO;

   static int polytype_interp_pal[] = 
   {
      INTERP_FLAT,
      INTERP_1COL,
      INTERP_3COL,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV | INTERP_1COL,
      INTERP_Z | INTERP_FLOAT_UV | INTERP_1COL | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV | INTERP_1COL,
      INTERP_Z | INTERP_FLOAT_UV | INTERP_1COL | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX
   };

   static int polytype_interp_tc[] = 
   {
      INTERP_FLAT,
      INTERP_3COL | COLOR_TO_RGB,
      INTERP_3COL,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV | INTERP_1COL,
      INTERP_Z | INTERP_FLOAT_UV | INTERP_1COL | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV | INTERP_1COL,
      INTERP_Z | INTERP_FLOAT_UV | INTERP_1COL | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX,
      INTERP_FIX_UV,
      INTERP_Z | INTERP_FLOAT_UV | OPT_FLOAT_UV_TO_FIX
   };

   #ifdef ALLEGRO_COLOR8
   static POLYTYPE_INFO polytype_info8[] =
   {
      {  _poly_scanline_dummy,            NULL },
      {  _poly_scanline_gcol8,            NULL },
      {  _poly_scanline_grgb8,            NULL },
      {  _poly_scanline_atex8,            NULL },
      {  _poly_scanline_ptex8,            _poly_scanline_atex8 },
      {  _poly_scanline_atex_mask8,       NULL },
      {  _poly_scanline_ptex_mask8,       _poly_scanline_atex_mask8 },
      {  _poly_scanline_atex_lit8,        NULL },
      {  _poly_scanline_ptex_lit8,        _poly_scanline_atex_lit8 },
      {  _poly_scanline_atex_mask_lit8,   NULL },
      {  _poly_scanline_ptex_mask_lit8,   _poly_scanline_atex_mask_lit8 },
      {  _poly_scanline_atex_trans8,      NULL },
      {  _poly_scanline_ptex_trans8,      _poly_scanline_atex_trans8 },
      {  _poly_scanline_atex_mask_trans8, NULL },
      {  _poly_scanline_ptex_mask_trans8, _poly_scanline_atex_mask_trans8 }
   };

   #ifdef ALLEGRO_MMX
   static POLYTYPE_INFO polytype_info8x[] =
   {
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  _poly_scanline_grgb8x,   NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL },
      {  NULL,                    NULL }
   };

   static POLYTYPE_INFO polytype_info8d[] =
   {
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL },
      {  NULL,                           NULL }
   };
   #endif
   #endif

   #ifdef ALLEGRO_COLOR16
   static POLYTYPE_INFO polytype_info15[] =
   {
      {  _poly_scanline_dummy,             NULL },
      {  _poly_scanline_grgb15,            NULL },
      {  _poly_scanline_grgb15,            NULL },
      {  _poly_scanline_atex16,            NULL },
      {  _poly_scanline_ptex16,            _poly_scanline_atex16 },
      {  _poly_scanline_atex_mask15,       NULL },
      {  _poly_scanline_ptex_mask15,       _poly_scanline_atex_mask15 },
      {  _poly_scanline_atex_lit15,        NULL },
      {  _poly_scanline_ptex_lit15,        _poly_scanline_atex_lit15 },
      {  _poly_scanline_atex_mask_lit15,   NULL },
      {  _poly_scanline_ptex_mask_lit15,   _poly_scanline_atex_mask_lit15 },
      {  _poly_scanline_atex_trans15,      NULL },
      {  _poly_scanline_ptex_trans15,      _poly_scanline_atex_trans15 },
      {  _poly_scanline_atex_mask_trans15, NULL },
      {  _poly_scanline_ptex_mask_trans15, _poly_scanline_atex_mask_trans15 }
   };

   #ifdef ALLEGRO_MMX
   static POLYTYPE_INFO polytype_info15x[] =
   {
      {  NULL,                            NULL },
      {  _poly_scanline_grgb15x,          NULL },
      {  _poly_scanline_grgb15x,          NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_atex_lit15x,      NULL },
      {  _poly_scanline_ptex_lit15x,      _poly_scanline_atex_lit15x },
      {  _poly_scanline_atex_mask_lit15x, NULL },
      {  _poly_scanline_ptex_mask_lit15x, _poly_scanline_atex_mask_lit15x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };

   static POLYTYPE_INFO polytype_info15d[] =
   {
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_lit15d,      _poly_scanline_atex_lit15x },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_mask_lit15d, _poly_scanline_atex_mask_lit15x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };
   #endif

   static POLYTYPE_INFO polytype_info16[] =
   {
      {  _poly_scanline_dummy,             NULL },
      {  _poly_scanline_grgb16,            NULL },
      {  _poly_scanline_grgb16,            NULL },
      {  _poly_scanline_atex16,            NULL },
      {  _poly_scanline_ptex16,            _poly_scanline_atex16 },
      {  _poly_scanline_atex_mask16,       NULL },
      {  _poly_scanline_ptex_mask16,       _poly_scanline_atex_mask16 },
      {  _poly_scanline_atex_lit16,        NULL },
      {  _poly_scanline_ptex_lit16,        _poly_scanline_atex_lit16 },
      {  _poly_scanline_atex_mask_lit16,   NULL },
      {  _poly_scanline_ptex_mask_lit16,   _poly_scanline_atex_mask_lit16 },
      {  _poly_scanline_atex_trans16,      NULL },
      {  _poly_scanline_ptex_trans16,      _poly_scanline_atex_trans16 },
      {  _poly_scanline_atex_mask_trans16, NULL },
      {  _poly_scanline_ptex_mask_trans16, _poly_scanline_atex_mask_trans16 }
   };

   #ifdef ALLEGRO_MMX
   static POLYTYPE_INFO polytype_info16x[] =
   {
      {  NULL,                            NULL },
      {  _poly_scanline_grgb16x,          NULL },
      {  _poly_scanline_grgb16x,          NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_atex_lit16x,      NULL },
      {  _poly_scanline_ptex_lit16x,      _poly_scanline_atex_lit16x },
      {  _poly_scanline_atex_mask_lit16x, NULL },
      {  _poly_scanline_ptex_mask_lit16x, _poly_scanline_atex_mask_lit16x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };

   static POLYTYPE_INFO polytype_info16d[] =
   {
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_lit16d,      _poly_scanline_atex_lit16x },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_mask_lit16d, _poly_scanline_atex_mask_lit16x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };
   #endif
   #endif

   #ifdef ALLEGRO_COLOR24
   static POLYTYPE_INFO polytype_info24[] =
   {
      {  _poly_scanline_dummy,             NULL },
      {  _poly_scanline_grgb24,            NULL },
      {  _poly_scanline_grgb24,            NULL },
      {  _poly_scanline_atex24,            NULL },
      {  _poly_scanline_ptex24,            _poly_scanline_atex24 },
      {  _poly_scanline_atex_mask24,       NULL },
      {  _poly_scanline_ptex_mask24,       _poly_scanline_atex_mask24 },
      {  _poly_scanline_atex_lit24,        NULL },
      {  _poly_scanline_ptex_lit24,        _poly_scanline_atex_lit24 },
      {  _poly_scanline_atex_mask_lit24,   NULL },
      {  _poly_scanline_ptex_mask_lit24,   _poly_scanline_atex_mask_lit24 },
      {  _poly_scanline_atex_trans24,      NULL },
      {  _poly_scanline_ptex_trans24,      _poly_scanline_atex_trans24 },
      {  _poly_scanline_atex_mask_trans24, NULL },
      {  _poly_scanline_ptex_mask_trans24, _poly_scanline_atex_mask_trans24 }
   };

   #ifdef ALLEGRO_MMX
   static POLYTYPE_INFO polytype_info24x[] =
   {
      {  NULL,                            NULL },
      {  _poly_scanline_grgb24x,          NULL },
      {  _poly_scanline_grgb24x,          NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_atex_lit24x,      NULL },
      {  _poly_scanline_ptex_lit24x,      _poly_scanline_atex_lit24x },
      {  _poly_scanline_atex_mask_lit24x, NULL },
      {  _poly_scanline_ptex_mask_lit24x, _poly_scanline_atex_mask_lit24x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };

   static POLYTYPE_INFO polytype_info24d[] =
   {
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_lit24d,      _poly_scanline_atex_lit24x },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_mask_lit24d, _poly_scanline_atex_mask_lit24x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };
   #endif
   #endif

   #ifdef ALLEGRO_COLOR32
   static POLYTYPE_INFO polytype_info32[] =
   {
      {  _poly_scanline_dummy,             NULL },
      {  _poly_scanline_grgb32,            NULL },
      {  _poly_scanline_grgb32,            NULL },
      {  _poly_scanline_atex32,            NULL },
      {  _poly_scanline_ptex32,            _poly_scanline_atex32 },
      {  _poly_scanline_atex_mask32,       NULL },
      {  _poly_scanline_ptex_mask32,       _poly_scanline_atex_mask32 },
      {  _poly_scanline_atex_lit32,        NULL },
      {  _poly_scanline_ptex_lit32,        _poly_scanline_atex_lit32 },
      {  _poly_scanline_atex_mask_lit32,   NULL },
      {  _poly_scanline_ptex_mask_lit32,   _poly_scanline_atex_mask_lit32 },
      {  _poly_scanline_atex_trans32,      NULL },
      {  _poly_scanline_ptex_trans32,      _poly_scanline_atex_trans32 },
      {  _poly_scanline_atex_mask_trans32, NULL },
      {  _poly_scanline_ptex_mask_trans32, _poly_scanline_atex_mask_trans32 }
   };

   #ifdef ALLEGRO_MMX
   static POLYTYPE_INFO polytype_info32x[] =
   {
      {  NULL,                            NULL },
      {  _poly_scanline_grgb32x,          NULL },
      {  _poly_scanline_grgb32x,          NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_atex_lit32x,      NULL },
      {  _poly_scanline_ptex_lit32x,      _poly_scanline_atex_lit32x },
      {  _poly_scanline_atex_mask_lit32x, NULL },
      {  _poly_scanline_ptex_mask_lit32x, _poly_scanline_atex_mask_lit32x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };

   static POLYTYPE_INFO polytype_info32d[] =
   {
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_lit32d,      _poly_scanline_atex_lit32x },
      {  NULL,                            NULL },
      {  _poly_scanline_ptex_mask_lit32d, _poly_scanline_atex_mask_lit32x },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL },
      {  NULL,                            NULL }
   };
   #endif
   #endif

   #ifdef ALLEGRO_COLOR8
   static POLYTYPE_INFO polytype_info8z[] =
   {
      {  _poly_zbuf_flat8,            NULL },
      {  _poly_zbuf_gcol8,            NULL },
      {  _poly_zbuf_grgb8,            NULL },
      {  _poly_zbuf_atex8,            NULL },
      {  _poly_zbuf_ptex8,            _poly_zbuf_atex8 },
      {  _poly_zbuf_atex_mask8,       NULL },
      {  _poly_zbuf_ptex_mask8,       _poly_zbuf_atex_mask8 },
      {  _poly_zbuf_atex_lit8,        NULL },
      {  _poly_zbuf_ptex_lit8,        _poly_zbuf_atex_lit8 },
      {  _poly_zbuf_atex_mask_lit8,   NULL },
      {  _poly_zbuf_ptex_mask_lit8,   _poly_zbuf_atex_mask_lit8 },
      {  _poly_zbuf_atex_trans8,      NULL },
      {  _poly_zbuf_ptex_trans8,      _poly_zbuf_atex_trans8 },
      {  _poly_zbuf_atex_mask_trans8, NULL },
      {  _poly_zbuf_ptex_mask_trans8, _poly_zbuf_atex_mask_trans8 }
   };
   #endif

   #ifdef ALLEGRO_COLOR16
   static POLYTYPE_INFO polytype_info15z[] =
   {
      {  _poly_zbuf_flat16,            NULL },
      {  _poly_zbuf_grgb15,            NULL },
      {  _poly_zbuf_grgb15,            NULL },
      {  _poly_zbuf_atex16,            NULL },
      {  _poly_zbuf_ptex16,            _poly_zbuf_atex16 },
      {  _poly_zbuf_atex_mask15,       NULL },
      {  _poly_zbuf_ptex_mask15,       _poly_zbuf_atex_mask15 },
      {  _poly_zbuf_atex_lit15,        NULL },
      {  _poly_zbuf_ptex_lit15,        _poly_zbuf_atex_lit15 },
      {  _poly_zbuf_atex_mask_lit15,   NULL },
      {  _poly_zbuf_ptex_mask_lit15,   _poly_zbuf_atex_mask_lit15 },
      {  _poly_zbuf_atex_trans15,      NULL },
      {  _poly_zbuf_ptex_trans15,      _poly_zbuf_atex_trans15 },
      {  _poly_zbuf_atex_mask_trans15, NULL },
      {  _poly_zbuf_ptex_mask_trans15, _poly_zbuf_atex_mask_trans15 }
   };

   static POLYTYPE_INFO polytype_info16z[] =
   {
      {  _poly_zbuf_flat16,            NULL },
      {  _poly_zbuf_grgb16,            NULL },
      {  _poly_zbuf_grgb16,            NULL },
      {  _poly_zbuf_atex16,            NULL },
      {  _poly_zbuf_ptex16,            _poly_zbuf_atex16 },
      {  _poly_zbuf_atex_mask16,       NULL },
      {  _poly_zbuf_ptex_mask16,       _poly_zbuf_atex_mask16 },
      {  _poly_zbuf_atex_lit16,        NULL },
      {  _poly_zbuf_ptex_lit16,        _poly_zbuf_atex_lit16 },
      {  _poly_zbuf_atex_mask_lit16,   NULL },
      {  _poly_zbuf_ptex_mask_lit16,   _poly_zbuf_atex_mask_lit16 },
      {  _poly_zbuf_atex_trans16,      NULL },
      {  _poly_zbuf_ptex_trans16,      _poly_zbuf_atex_trans16 },
      {  _poly_zbuf_atex_mask_trans16, NULL },
      {  _poly_zbuf_ptex_mask_trans16, _poly_zbuf_atex_mask_trans16 }
   };
   #endif

   #ifdef ALLEGRO_COLOR24
   static POLYTYPE_INFO polytype_info24z[] =
   {
      {  _poly_zbuf_flat24,            NULL },
      {  _poly_zbuf_grgb24,            NULL },
      {  _poly_zbuf_grgb24,            NULL },
      {  _poly_zbuf_atex24,            NULL },
      {  _poly_zbuf_ptex24,            _poly_zbuf_atex24 },
      {  _poly_zbuf_atex_mask24,       NULL },
      {  _poly_zbuf_ptex_mask24,       _poly_zbuf_atex_mask24 },
      {  _poly_zbuf_atex_lit24,        NULL },
      {  _poly_zbuf_ptex_lit24,        _poly_zbuf_atex_lit24 },
      {  _poly_zbuf_atex_mask_lit24,   NULL },
      {  _poly_zbuf_ptex_mask_lit24,   _poly_zbuf_atex_mask_lit24 },
      {  _poly_zbuf_atex_trans24,      NULL },
      {  _poly_zbuf_ptex_trans24,      _poly_zbuf_atex_trans24 },
      {  _poly_zbuf_atex_mask_trans24, NULL },
      {  _poly_zbuf_ptex_mask_trans24, _poly_zbuf_atex_mask_trans24 }
   };
   #endif

   #ifdef ALLEGRO_COLOR32
   static POLYTYPE_INFO polytype_info32z[] =
   {
      {  _poly_zbuf_flat32,            NULL },
      {  _poly_zbuf_grgb32,            NULL },
      {  _poly_zbuf_grgb32,            NULL },
      {  _poly_zbuf_atex32,            NULL },
      {  _poly_zbuf_ptex32,            _poly_zbuf_atex32 },
      {  _poly_zbuf_atex_mask32,       NULL },
      {  _poly_zbuf_ptex_mask32,       _poly_zbuf_atex_mask32 },
      {  _poly_zbuf_atex_lit32,        NULL },
      {  _poly_zbuf_ptex_lit32,        _poly_zbuf_atex_lit32 },
      {  _poly_zbuf_atex_mask_lit32,   NULL },
      {  _poly_zbuf_ptex_mask_lit32,   _poly_zbuf_atex_mask_lit32 },
      {  _poly_zbuf_atex_trans32,      NULL },
      {  _poly_zbuf_ptex_trans32,      _poly_zbuf_atex_trans32 },
      {  _poly_zbuf_atex_mask_trans32, NULL },
      {  _poly_zbuf_ptex_mask_trans32, _poly_zbuf_atex_mask_trans32 }
   };
   #endif

   int zbuf = type & POLYTYPE_ZBUF;

   int *interpinfo;
   POLYTYPE_INFO *typeinfo, *typeinfo_zbuf;

   #ifdef ALLEGRO_MMX
   POLYTYPE_INFO *typeinfo_mmx, *typeinfo_3d;
   #endif

   switch (bitmap_color_depth(bmp)) {

      #ifdef ALLEGRO_COLOR8

       case 8:
          interpinfo = polytype_interp_pal;
          typeinfo = polytype_info8;
       #ifdef ALLEGRO_MMX
          typeinfo_mmx = polytype_info8x;
          typeinfo_3d = polytype_info8d;
       #endif
          typeinfo_zbuf = polytype_info8z;
          break;

      #endif

      #ifdef ALLEGRO_COLOR16

       case 15:
          interpinfo = polytype_interp_tc;
          typeinfo = polytype_info15;
       #ifdef ALLEGRO_MMX
          typeinfo_mmx = polytype_info15x;
          typeinfo_3d = polytype_info15d;
       #endif
          typeinfo_zbuf = polytype_info15z;
          break;

       case 16:
          interpinfo = polytype_interp_tc;
          typeinfo = polytype_info16;
       #ifdef ALLEGRO_MMX
          typeinfo_mmx = polytype_info16x;
          typeinfo_3d = polytype_info16d;
       #endif
          typeinfo_zbuf = polytype_info16z;
          break;

      #endif

      #ifdef ALLEGRO_COLOR24

       case 24:
          interpinfo = polytype_interp_tc;
          typeinfo = polytype_info24;
       #ifdef ALLEGRO_MMX
          typeinfo_mmx = polytype_info24x;
          typeinfo_3d = polytype_info24d;
       #endif
          typeinfo_zbuf = polytype_info24z;
          break;

      #endif

      #ifdef ALLEGRO_COLOR32

       case 32:
          interpinfo = polytype_interp_tc;
          typeinfo = polytype_info32;
       #ifdef ALLEGRO_MMX
          typeinfo_mmx = polytype_info32x;
          typeinfo_3d = polytype_info32d;
       #endif
          typeinfo_zbuf = polytype_info32z;
          break;

      #endif

      default:
       return NULL;
   }

   type = MID(0, type & ~POLYTYPE_ZBUF, POLYTYPE_MAX-1);
   *flags = interpinfo[type];

   if (texture) {
      info->texture = texture->line[0];
      info->umask = texture->w - 1;
      info->vmask = texture->h - 1;
      info->vshift = 0;
      while ((1 << info->vshift) < texture->w)
       info->vshift++;
   }
   else {
      info->texture = NULL;
      info->umask = info->vmask = info->vshift = 0;
   }

   info->seg = bmp->seg;
   bmp_select(bmp);

   if (zbuf) {
      *flags |= INTERP_Z + INTERP_ZBUF;
      _optim_alternative_drawer = typeinfo_zbuf[type].alternative;
      return typeinfo_zbuf[type].filler;
   }

   #ifdef ALLEGRO_MMX
   if ((cpu_capabilities & CPU_MMX) && (typeinfo_mmx[type].filler)) {
      if ((cpu_capabilities & CPU_3DNOW) && (typeinfo_3d[type].filler)) {
       _optim_alternative_drawer = typeinfo_3d[type].alternative;
       return typeinfo_3d[type].filler;
      }
      _optim_alternative_drawer = typeinfo_mmx[type].alternative;
      return typeinfo_mmx[type].filler;
   }
   #endif

   _optim_alternative_drawer = typeinfo[type].alternative;

   return typeinfo[type].filler;
}



/* _clip_polygon_segment_f:
 *  Updates interpolation state values when skipping several places, eg.
 *  clipping the first part of a scanline.
 */
void _clip_polygon_segment_f(POLYGON_SEGMENT *info, int gap, int flags)
{
   if (flags & INTERP_1COL)
      info->c += info->dc * gap;

   if (flags & INTERP_3COL) {
      info->r += info->dr * gap;
      info->g += info->dg * gap;
      info->b += info->db * gap;
   }

   if (flags & INTERP_FIX_UV) {
      info->u += info->du * gap;
      info->v += info->dv * gap;
   }

   if (flags & INTERP_Z) {
      info->z += info->dz * gap;

      if (flags & INTERP_FLOAT_UV) {
       info->fu += info->dfu * gap;
       info->fv += info->dfv * gap;
      }
   }
}



/* draw_polygon_segment: 
 *  Polygon helper function to fill a scanline. Calculates deltas for 
 *  whichever values need interpolating, clips the segment, and then calls
 *  the lowlevel scanline filler.
 */
static void draw_polygon_segment(BITMAP *bmp, int ytop, int ybottom, POLYGON_EDGE *e1, POLYGON_EDGE *e2, SCANLINE_FILLER drawer, int flags, int color, POLYGON_SEGMENT *info)
{
   int x, y, w, gap;
   fixed step, width;
   POLYGON_SEGMENT *s1, *s2;
   AL_CONST SCANLINE_FILLER save_drawer = drawer;

   /* ensure that e1 is the left edge and e2 is the right edge */
   if ((e2->x < e1->x) || ((e1->x == e2->x) && (e2->dx < e1->dx))) {
      POLYGON_EDGE *et = e1;
      e1 = e2;
      e2 = et;
   }

   s1 = &(e1->dat);
   s2 = &(e2->dat);

   if (flags & INTERP_FLAT)
      info->c = color;

   /* for each scanline in the polygon... */
   for (y=ytop; y<=ybottom; y++) {
      x = fixceil(e1->x);
      w = fixceil(e2->x) - x;
      drawer = save_drawer;

      if (drawer == _poly_scanline_dummy) {
         if (w > 0)
          bmp->vtable->hfill(bmp, x, y, x+w-1, color);
      }
      else {
         step = (x << 16) - e1->x;
         width = e2->x - e1->x;
/*
 *  Nasty trick :
 *  In order to avoid divisions by zero, width is set to -1. This way s1 and s2
 *  are still being updated but the scanline is not drawn since w == 0.
 */
       if (width == 0)
          width = -1 << 16;
/*
 *  End of nasty trick.
 */
       if (flags & INTERP_1COL) {
          info->dc = fixdiv(s2->c - s1->c, width);
          info->c = s1->c + fixmul(step, info->dc);
          s1->c += s1->dc;
          s2->c += s2->dc;
       }

       if (flags & INTERP_3COL) {
          info->dr = fixdiv(s2->r - s1->r, width);
          info->dg = fixdiv(s2->g - s1->g, width);
          info->db = fixdiv(s2->b - s1->b, width);
          info->r = s1->r + fixmul(step, info->dr);
          info->g = s1->g + fixmul(step, info->dg);
          info->b = s1->b + fixmul(step, info->db);

          s1->r += s1->dr;
          s2->r += s2->dr;
          s1->g += s1->dg;
          s2->g += s2->dg;
          s1->b += s1->db;
          s2->b += s2->db;
       }

       if (flags & INTERP_FIX_UV) {
          info->du = fixdiv(s2->u - s1->u, width);
          info->dv = fixdiv(s2->v - s1->v, width);
          info->u = s1->u + fixmul(step, info->du);
          info->v = s1->v + fixmul(step, info->dv);

          s1->u += s1->du;
          s2->u += s2->du;
          s1->v += s1->dv;
          s2->v += s2->dv;
       }

       if (flags & INTERP_Z) {
          float step_f = fixtof(step);
          float w1 = 65536. / width;

          info->dz = (s2->z - s1->z) * w1;
          info->z = s1->z + info->dz * step_f;
          s1->z += s1->dz;
          s2->z += s2->dz;

          if (flags & INTERP_FLOAT_UV) {
             info->dfu = (s2->fu - s1->fu) * w1;
             info->dfv = (s2->fv - s1->fv) * w1;
             info->fu = s1->fu + info->dfu * step_f;
             info->fv = s1->fv + info->dfv * step_f;

             s1->fu += s1->dfu;
             s2->fu += s2->dfu;
             s1->fv += s1->dfv;
             s2->fv += s2->dfv;
          }
       }

       /* if clipping is enabled then clip the segment */
       if (bmp->clip) {
          if (x < bmp->cl) {
             gap = bmp->cl - x;
             x = bmp->cl;
             w -= gap;
             _clip_polygon_segment_f(info, gap, flags);
          }

          if (x+w > bmp->cr)
             w = bmp->cr - x;
       }

       if (w > 0) {
          int dx = x * BYTES_PER_PIXEL(bitmap_color_depth(bmp));
          
          if ((flags & OPT_FLOAT_UV_TO_FIX) && (info->dz == 0)) {
             float z1 = 1. / info->z;
             info->u = info->fu * z1;
             info->v = info->fv * z1;
             info->du = info->dfu * z1;
             info->dv = info->dfv * z1;
             drawer = _optim_alternative_drawer;
          }

            if (flags & INTERP_ZBUF) 
               info->zbuf_addr = bmp_write_line(_zbuffer, y) + x * sizeof(float);

          info->read_addr = bmp_read_line(bmp, y) + dx;
          drawer(bmp_write_line(bmp, y) + dx, w, info);
       }
      }

      e1->x += e1->dx;
      e2->x += e2->dx;
   }
}



/* do_polygon3d:
 *  Helper function for rendering 3d polygon, used by both the fixed point
 *  and floating point drawing functions.
 */
static void do_polygon3d(BITMAP *bmp, int top, int bottom, POLYGON_EDGE *left_edge, SCANLINE_FILLER drawer, int flags, int color, POLYGON_SEGMENT *info)
{
   int ytop, ybottom;
   #ifdef ALLEGRO_DOS
      int old87 = 0;
   #endif
   POLYGON_EDGE *right_edge;
   ASSERT(bmp);

   /* set fpu to single-precision, truncate mode */
   #ifdef ALLEGRO_DOS
      if (flags & (INTERP_Z | INTERP_FLOAT_UV))
         old87 = _control87(PC_24 | RC_CHOP, MCW_PC | MCW_RC);
   #endif

   acquire_bitmap(bmp);

   if ((left_edge->prev != left_edge->next) && (left_edge->prev->top == top))
      left_edge = left_edge->prev;

   right_edge = left_edge->next;

   ytop = top;
   for (;;) {
      if (right_edge->bottom <= left_edge->bottom)
       ybottom = right_edge->bottom;
      else
       ybottom = left_edge->bottom;

      /* fill the scanline */
      draw_polygon_segment(bmp, ytop, ybottom, left_edge, right_edge, drawer, flags, color, info);

      if (ybottom >= bottom) break;

      /* update edges */
      if (ybottom >= left_edge->bottom)
       left_edge = left_edge->prev;
      if (ybottom >= right_edge->bottom)
       right_edge = right_edge->next;

      ytop = ybottom + 1;
   }

   bmp_unwrite_line(bmp);
   release_bitmap(bmp);

   /* reset fpu mode */
   #ifdef ALLEGRO_DOS
      if (flags & (INTERP_Z | INTERP_FLOAT_UV))
         _control87(old87, MCW_PC | MCW_RC);
   #endif
}



/* polygon3d:
 *  Draws a 3d polygon in the specified mode. The vertices parameter should
 *  be followed by that many pointers to V3D structures, which describe each
 *  vertex of the polygon.
 */
void _soft_polygon3d(BITMAP *bmp, int type, BITMAP *texture, int vc, V3D *vtx[])
{
   int c;
   int flags;
   int top = INT_MAX;
   int bottom = INT_MIN;
   V3D *v1, *v2;
   POLYGON_EDGE *edge, *edge0, *start_edge;
   POLYGON_EDGE *list_edges = NULL;
   POLYGON_SEGMENT info;
   SCANLINE_FILLER drawer;
   ASSERT(bmp);

   if (vc < 3)
      return;

   /* set up the drawing mode */
   drawer = _get_scanline_filler(type, &flags, &info, texture, bmp);
   if (!drawer)
      return;

   /* allocate some space for the active edge table */
   _grow_scratch_mem(sizeof(POLYGON_EDGE) * vc);
   start_edge = edge0 = edge = (POLYGON_EDGE *)_scratch_mem;

   /* fill the double-linked list of edges (order unimportant) */
   v2 = vtx[vc-1];

   for (c=0; c<vc; c++) {
      v1 = v2;
      v2 = vtx[c];

      if (_fill_3d_edge_structure(edge, v1, v2, flags, bmp)) {
       if (edge->top < top) {
            top = edge->top;
          start_edge = edge;
         }

       if (edge->bottom > bottom)
            bottom = edge->bottom;

         if (list_edges) {
            list_edges->next = edge;
          edge->prev = list_edges;
         }

       list_edges = edge;
       edge++;
      }
   }

   if (list_edges) {
      /* close the double-linked list */
      edge0->prev = --edge;
      edge->next = edge0;

      /* render the polygon */
      do_polygon3d(bmp, top, bottom, start_edge, drawer, flags, vtx[0]->c, &info);
   }
}



/* polygon3d_f:
 *  Floating point version of polygon3d().
 */
void _soft_polygon3d_f(BITMAP *bmp, int type, BITMAP *texture, int vc, V3D_f *vtx[])
{
   int c;
   int flags;
   int top = INT_MAX;
   int bottom = INT_MIN;
   V3D_f *v1, *v2;
   POLYGON_EDGE *edge, *edge0, *start_edge;
   POLYGON_EDGE *list_edges = NULL;
   POLYGON_SEGMENT info;
   SCANLINE_FILLER drawer;
   ASSERT(bmp);

   if (vc < 3)
      return;

   /* set up the drawing mode */
   drawer = _get_scanline_filler(type, &flags, &info, texture, bmp);
   if (!drawer)
      return;

   /* allocate some space for the active edge table */
   _grow_scratch_mem(sizeof(POLYGON_EDGE) * vc);
   start_edge = edge0 = edge = (POLYGON_EDGE *)_scratch_mem;

   /* fill the double-linked list of edges in clockwise order */
   v2 = vtx[vc-1];

   for (c=0; c<vc; c++) {
      v1 = v2;
      v2 = vtx[c];

      if (_fill_3d_edge_structure_f(edge, v1, v2, flags, bmp)) {
         if (edge->top < top) {
            top = edge->top;
          start_edge = edge;
         }

       if (edge->bottom > bottom)
            bottom = edge->bottom;

         if (list_edges) {
            list_edges->next = edge;
          edge->prev = list_edges;
         }

       list_edges = edge;
       edge++;
      }
   }

   if (list_edges) {
      /* close the double-linked list */
      edge0->prev = --edge;
      edge->next = edge0;

      /* render the polygon */
      do_polygon3d(bmp, top, bottom, start_edge, drawer, flags, vtx[0]->c, &info);
   }
}



/* draw_triangle_part:
 *  Triangle helper function to fill a triangle part. Computes interpolation,
 *  clips the segment, and then calls the lowlevel scanline filler.
 */
static void draw_triangle_part(BITMAP *bmp, int ytop, int ybottom, POLYGON_EDGE *left_edge, POLYGON_EDGE *right_edge, SCANLINE_FILLER drawer, int flags, int color, POLYGON_SEGMENT *info)
{
   int x, y, w;
   int gap;
   AL_CONST int test_optim = (flags & OPT_FLOAT_UV_TO_FIX) && (info->dz == 0);
   fixed step;
   POLYGON_SEGMENT *s1;

   /* ensure that left_edge and right_edge are the right way round */
   if ((right_edge->x < left_edge->x) ||
     ((left_edge->x == right_edge->x) && (right_edge->dx < left_edge->dx))) {
      POLYGON_EDGE *other_edge = left_edge;
      left_edge = right_edge;
      right_edge = other_edge;
   }

   s1 = &(left_edge->dat);

   if (flags & INTERP_FLAT)
      info->c = color;

   for (y=ytop; y<=ybottom; y++) {
      x = fixceil(left_edge->x);
      w = fixceil(right_edge->x) - x;
      step = (x << 16) - left_edge->x;

      if (drawer == _poly_scanline_dummy) {
         if (w > 0)
          bmp->vtable->hfill(bmp, x, y, x+w-1, color);
      }
      else {
       if (flags & INTERP_1COL) {
          info->c = s1->c + fixmul(step, info->dc);
            s1->c += s1->dc;
         }

       if (flags & INTERP_3COL) {
          info->r = s1->r + fixmul(step, info->dr);
          info->g = s1->g + fixmul(step, info->dg);
          info->b = s1->b + fixmul(step, info->db);

          s1->r += s1->dr;
          s1->g += s1->dg;
          s1->b += s1->db;
       }

       if (flags & INTERP_FIX_UV) {
          info->u = s1->u + fixmul(step, info->du);
          info->v = s1->v + fixmul(step, info->dv);

          s1->u += s1->du;
          s1->v += s1->dv;
       }

       if (flags & INTERP_Z) {
          float step_f = fixtof(step);

          info->z = s1->z + info->dz * step_f;
          s1->z += s1->dz;

          if (flags & INTERP_FLOAT_UV) {
             info->fu = s1->fu + info->dfu * step_f;
             info->fv = s1->fv + info->dfv * step_f;

             s1->fu += s1->dfu;
             s1->fv += s1->dfv;
          }
       }

       /* if clipping is enabled then clip the segment */
       if (bmp->clip) {
          if (x < bmp->cl) {
             gap = bmp->cl - x;
             x = bmp->cl;
             w -= gap;
             _clip_polygon_segment_f(info, gap, flags);
          }

          if (x+w > bmp->cr)
             w = bmp->cr - x;
       }

       if (w > 0) {
          int dx = x * BYTES_PER_PIXEL(bitmap_color_depth(bmp));
          
          if (test_optim) {
             float z1 = 1. / info->z;
             info->u = info->fu * z1;
             info->v = info->fv * z1;
             info->du = info->dfu * z1;
             info->dv = info->dfv * z1;
             drawer = _optim_alternative_drawer;
          }

            if (flags & INTERP_ZBUF) 
               info->zbuf_addr = bmp_write_line(_zbuffer, y) + x * sizeof(float);

          info->read_addr = bmp_read_line(bmp, y) + dx;
          drawer(bmp_write_line(bmp, y) + dx, w, info);
       }
      }

      left_edge->x += left_edge->dx;
      right_edge->x += right_edge->dx;
   }
}



/* _triangle_deltas:
 *  Triangle3d helper function to calculate the deltas. (For triangles,
 *  deltas are constant over the whole triangle).
 */
static void _triangle_deltas(BITMAP *bmp, fixed w, POLYGON_SEGMENT *s1, POLYGON_SEGMENT *info, AL_CONST V3D *v, int flags)
{
   if (flags & INTERP_1COL)
      info->dc = fixdiv(s1->c - itofix(v->c), w);

   if (flags & INTERP_3COL) {
      int r, g, b;

      if (flags & COLOR_TO_RGB) {
             AL_CONST int coldepth = bitmap_color_depth(bmp);
       r = getr_depth(coldepth, v->c);
       g = getg_depth(coldepth, v->c);
       b = getb_depth(coldepth, v->c);
      }
      else {
       r = (v->c >> 16) & 0xFF;
       g = (v->c >> 8) & 0xFF;
       b = v->c & 0xFF;
      }

      info->dr = fixdiv(s1->r - itofix(r), w);
      info->dg = fixdiv(s1->g - itofix(g), w);
      info->db = fixdiv(s1->b - itofix(b), w);
   }

   if (flags & INTERP_FIX_UV) {
      info->du = fixdiv(s1->u - v->u, w);
      info->dv = fixdiv(s1->v - v->v, w);
   }

   if (flags & INTERP_Z) {
      float w1 = 65536. / w;

      /* Z (depth) interpolation */
      float z1 = 65536. / v->z;

      info->dz = (s1->z - z1) * w1;

      if (flags & INTERP_FLOAT_UV) {
       /* floating point (perspective correct) texture interpolation */
       float fu1 = v->u * z1;
       float fv1 = v->v * z1;

       info->dfu = (s1->fu - fu1) * w1;
       info->dfv = (s1->fv - fv1) * w1;
      }
   }
}


/* _triangle_deltas_f:
 *  Floating point version of _triangle_deltas().
 */
static void _triangle_deltas_f(BITMAP *bmp, fixed w, POLYGON_SEGMENT *s1, POLYGON_SEGMENT *info, AL_CONST V3D_f *v, int flags)
{
   if (flags & INTERP_1COL)
      info->dc = fixdiv(s1->c - itofix(v->c), w);

   if (flags & INTERP_3COL) {
      int r, g, b;

      if (flags & COLOR_TO_RGB) {
             AL_CONST int coldepth = bitmap_color_depth(bmp);
       r = getr_depth(coldepth, v->c);
       g = getg_depth(coldepth, v->c);
       b = getb_depth(coldepth, v->c);
      }
      else {
       r = (v->c >> 16) & 0xFF;
       g = (v->c >> 8) & 0xFF;
       b = v->c & 0xFF;
      }

      info->dr = fixdiv(s1->r - itofix(r), w);
      info->dg = fixdiv(s1->g - itofix(g), w);
      info->db = fixdiv(s1->b - itofix(b), w);
   }

   if (flags & INTERP_FIX_UV) {
      info->du = fixdiv(s1->u - ftofix(v->u), w);
      info->dv = fixdiv(s1->v - ftofix(v->v), w);
   }

   if (flags & INTERP_Z) {
      float w1 = 65536. / w;

      /* Z (depth) interpolation */
      float z1 = 1. / v->z;

      info->dz = (s1->z - z1) * w1;

      if (flags & INTERP_FLOAT_UV) {
       /* floating point (perspective correct) texture interpolation */
       float fu1 = v->u * z1 * 65536.;
       float fv1 = v->v * z1 * 65536.;

       info->dfu = (s1->fu - fu1) * w1;
       info->dfv = (s1->fv - fv1) * w1;
      }
   }
}



/* _clip_polygon_segment:
 *  Fixed point version of _clip_polygon_segment_f().
 */
void _clip_polygon_segment(POLYGON_SEGMENT *info, fixed gap, int flags)
{
   if (flags & INTERP_1COL)
      info->c += fixmul(info->dc, gap);

   if (flags & INTERP_3COL) {
      info->r += fixmul(info->dr, gap);
      info->g += fixmul(info->dg, gap);
      info->b += fixmul(info->db, gap);
   }

   if (flags & INTERP_FIX_UV) {
      info->u += fixmul(info->du, gap);
      info->v += fixmul(info->dv, gap);
   }

   if (flags & INTERP_Z) {
      float gap_f = fixtof(gap);

      info->z += info->dz * gap_f;

      if (flags & INTERP_FLOAT_UV) {
       info->fu += info->dfu * gap_f;
       info->fv += info->dfv * gap_f;
      }
   }
}



/* triangle3d:
 *  Draws a 3d triangle.
 */
void _soft_triangle3d(BITMAP *bmp, int type, BITMAP *texture, V3D *v1, V3D *v2, V3D *v3)
{
   int flags;

   #ifdef ALLEGRO_DOS
      int old87 = 0;
   #endif

   int color = v1->c;
   V3D *vt1, *vt2, *vt3;
   POLYGON_EDGE edge1, edge2;
   POLYGON_SEGMENT info;
   SCANLINE_FILLER drawer;
   ASSERT(bmp);

   /* set up the drawing mode */
   drawer = _get_scanline_filler(type, &flags, &info, texture, bmp);
   if (!drawer)
      return;

   /* sort the vertices so that vt1->y <= vt2->y <= vt3->y */
   if (v1->y > v2->y) {
      vt1 = v2;
      vt2 = v1;
   }
   else {
      vt1 = v1;
      vt2 = v2;
   }

   if (vt1->y > v3->y) {
      vt3 = vt1;
      vt1 = v3;
   }
   else
      vt3 = v3;

   if (vt2->y > vt3->y) {
      V3D* vtemp = vt2;
      vt2 = vt3;
      vt3 = vtemp;
   }

   /* set fpu to single-precision, truncate mode */
   #ifdef ALLEGRO_DOS
      if (flags & (INTERP_Z | INTERP_FLOAT_UV))
       old87 = _control87(PC_24 | RC_CHOP, MCW_PC | MCW_RC);
   #endif

   /* do 3D triangle*/
   if (_fill_3d_edge_structure(&edge1, vt1, vt3, flags, bmp)) {

      acquire_bitmap(bmp);

      /* calculate deltas */
      if (drawer != _poly_scanline_dummy) {
       fixed w, h;
       POLYGON_SEGMENT s1 = edge1.dat;

       h = vt2->y - (edge1.top << 16);
       _clip_polygon_segment(&s1, h, flags);

       w = edge1.x + fixmul(h, edge1.dx) - vt2->x;
       if (w) _triangle_deltas(bmp, w, &s1, &info, vt2, flags);
      }

      /* draws part between y1 and y2 */
      if (_fill_3d_edge_structure(&edge2, vt1, vt2, flags, bmp))
       draw_triangle_part(bmp, edge2.top, edge2.bottom, &edge1, &edge2, drawer, flags, color, &info);

      /* draws part between y2 and y3 */
      if (_fill_3d_edge_structure(&edge2, vt2, vt3, flags, bmp))
       draw_triangle_part(bmp, edge2.top, edge2.bottom, &edge1, &edge2, drawer, flags, color, &info);

      bmp_unwrite_line(bmp);
      release_bitmap(bmp);
   }

   /* reset fpu mode */
   #ifdef ALLEGRO_DOS
      if (flags & (INTERP_Z | INTERP_FLOAT_UV))
       _control87(old87, MCW_PC | MCW_RC);
   #endif
}



/* triangle3d_f:
 *  Draws a 3d triangle.
 */
void _soft_triangle3d_f(BITMAP *bmp, int type, BITMAP *texture, V3D_f *v1, V3D_f *v2, V3D_f *v3)
{
   int flags;

   #ifdef ALLEGRO_DOS
      int old87 = 0;
   #endif

   int color = v1->c;
   V3D_f *vt1, *vt2, *vt3;
   POLYGON_EDGE edge1, edge2;
   POLYGON_SEGMENT info;
   SCANLINE_FILLER drawer;
   ASSERT(bmp);

   /* set up the drawing mode */
   drawer = _get_scanline_filler(type, &flags, &info, texture, bmp);
   if (!drawer)
      return;

   /* sort the vertices so that vt1->y <= vt2->y <= vt3->y */
   if (v1->y > v2->y) {
      vt1 = v2;
      vt2 = v1;
   }
   else {
      vt1 = v1;
      vt2 = v2;
   }

   if (vt1->y > v3->y) {
      vt3 = vt1;
      vt1 = v3;
   }
   else
      vt3 = v3;

   if (vt2->y > vt3->y) {
      V3D_f* vtemp = vt2;
      vt2 = vt3;
      vt3 = vtemp;
   }

   /* set fpu to single-precision, truncate mode */
   #ifdef ALLEGRO_DOS
      if (flags & (INTERP_Z | INTERP_FLOAT_UV))
         old87 = _control87(PC_24 | RC_CHOP, MCW_PC | MCW_RC);
   #endif

   /* do 3D triangle*/
   if (_fill_3d_edge_structure_f(&edge1, vt1, vt3, flags, bmp)) {

      acquire_bitmap(bmp);

      /* calculate deltas */
      if (drawer != _poly_scanline_dummy) {
       fixed w, h;
       POLYGON_SEGMENT s1 = edge1.dat;

       h = ftofix(vt2->y) - (edge1.top << 16);
       _clip_polygon_segment(&s1, h, flags);

       w = edge1.x + fixmul(h, edge1.dx) - ftofix(vt2->x);
       if (w) _triangle_deltas_f(bmp, w, &s1, &info, vt2, flags);
      }

      /* draws part between y1 and y2 */
      if (_fill_3d_edge_structure_f(&edge2, vt1, vt2, flags, bmp))
       draw_triangle_part(bmp, edge2.top, edge2.bottom, &edge1, &edge2, drawer, flags, color, &info);

      /* draws part between y2 and y3 */
      if (_fill_3d_edge_structure_f(&edge2, vt2, vt3, flags, bmp))
       draw_triangle_part(bmp, edge2.top, edge2.bottom, &edge1, &edge2, drawer, flags, color, &info);

      bmp_unwrite_line(bmp);
      release_bitmap(bmp);
   }

   /* reset fpu mode */
   #ifdef ALLEGRO_DOS
      if (flags & (INTERP_Z | INTERP_FLOAT_UV))
       _control87(old87, MCW_PC | MCW_RC);
   #endif
}



/* quad3d:
 *  Draws a 3d quad.
 */
void _soft_quad3d(BITMAP *bmp, int type, BITMAP *texture, V3D *v1, V3D *v2, V3D *v3, V3D *v4)
{
   #if (defined ALLEGRO_GCC) && (defined ALLEGRO_I386)
      ASSERT(bmp);

      /* dodgy assumption alert! See comments for triangle() */
      polygon3d(bmp, type, texture, 4, &v1);

   #else

      V3D *vertex[4];
      ASSERT(bmp);

      vertex[0] = v1;
      vertex[1] = v2;
      vertex[2] = v3;
      vertex[3] = v4;
      polygon3d(bmp, type, texture, 4, vertex);

   #endif
}



/* quad3d_f:
 *  Draws a 3d quad.
 */
void _soft_quad3d_f(BITMAP *bmp, int type, BITMAP *texture, V3D_f *v1, V3D_f *v2, V3D_f *v3, V3D_f *v4)
{
   #if (defined ALLEGRO_GCC) && (defined ALLEGRO_I386)
      ASSERT(bmp);

      /* dodgy assumption alert! See comments for triangle() */
      polygon3d_f(bmp, type, texture, 4, &v1);

   #else

      V3D_f *vertex[4];
      ASSERT(bmp);

      vertex[0] = v1;
      vertex[1] = v2;
      vertex[2] = v3;
      vertex[3] = v4;
      polygon3d_f(bmp, type, texture, 4, vertex);

   #endif
}



/* create_zbuffer:
 *  Creates a new Z-buffer the size of the given bitmap.
 */
ZBUFFER *create_zbuffer(BITMAP *bmp)
{
   ASSERT(bmp);
   return create_bitmap_ex(32, bmp->w, bmp->h);
}



/* clear_zbuffer:
 *  Clears the given z-buffer, z is the value written in the z-buffer
 *  - it is 1/(z coordinate), z=0 meaning far away.
 */
void clear_zbuffer(ZBUFFER *zbuf, float z)
{
   union {
      float zf;
      long zi;
   } _zbuf_clip;
   ASSERT(zbuf);

   _zbuf_clip.zf = z;
   clear_to_color(zbuf, _zbuf_clip.zi);
}



/* destroy_zbuffer:
 *  Destroys the given z-buffer.
 */
void destroy_zbuffer(ZBUFFER *zbuf)
{
   if (zbuf) {
      if (zbuf == _zbuffer)
       _zbuffer = NULL;
      destroy_bitmap(zbuf);
   }
}



/* set_zbuffer:
 *  Makes polygon drawing routines use the given BITMAP as z-buffer.
 */
void set_zbuffer(ZBUFFER *zbuf)
{
   ASSERT(zbuf);
   _zbuffer = zbuf;
}



/* create_sub_zbuffer:
 *  Creates a new sub-z-buffer of the given z-buffer. A sub-z-buffer is
 *  exactly like a sub-bitmap, buf for z-buffers.
 */
ZBUFFER *create_sub_zbuffer(ZBUFFER *parent, int x, int y, int width, int height)
{
   ASSERT(parent);
   /* For now, just use the code for BITMAPs. */
   return create_sub_bitmap(parent, x, y, width, height);
}

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