git.mutantstargoat.com Git - dosdemo/blob - src/polytmpl.h

   1 static uint32_t SCANEDGE(struct pvertex *v0, struct pvertex *v1, struct pvertex *edge)
   2 {
   3         int i;
   4         int32_t x, dx, dy, slope;
   5 #ifdef GOURAUD
   6         int r, g, b, dr, dg, db;
   7         int32_t rslope, gslope, bslope;
   8 #endif
   9 #ifdef TEXMAP
  10         int32_t u, v, du, dv, uslope, vslope;
  11 #endif
  12         int32_t start_idx, end_idx;
  13
  14         if(v0->y > v1->y) {
  15                 struct pvertex *tmp = v0;
  16                 v0 = v1;
  17                 v1 = tmp;
  18         }
  19
  20         x = v0->x;
  21         dy = v1->y - v0->y;
  22         dx = v1->x - v0->x;
  23         slope = (dx << 8) / dy;
  24 #ifdef GOURAUD
  25         r = (v0->r << COLOR_SHIFT);
  26         g = (v0->g << COLOR_SHIFT);
  27         b = (v0->b << COLOR_SHIFT);
  28         dr = (v1->r << COLOR_SHIFT) - r;
  29         dg = (v1->g << COLOR_SHIFT) - g;
  30         db = (v1->b << COLOR_SHIFT) - b;
  31         rslope = (dr << 8) / dy;
  32         gslope = (dg << 8) / dy;
  33         bslope = (db << 8) / dy;
  34 #endif
  35 #ifdef TEXMAP
  36         u = v0->u;
  37         v = v0->v;
  38         du = v1->u - v0->u;
  39         dv = v1->v - v0->v;
  40         uslope = (du << 8) / dy;
  41         vslope = (dv << 8) / dy;
  42 #endif
  43
  44         start_idx = v0->y >> 8;
  45         end_idx = v1->y >> 8;
  46
  47         for(i=start_idx; i<end_idx; i++) {
  48                 edge[i].x = x;
  49                 x += slope;
  50 #ifdef GOURAUD
  51                 /* we'll store the color in the edge tables with COLOR_SHIFT extra bits of precision */
  52                 edge[i].r = r;
  53                 edge[i].g = g;
  54                 edge[i].b = b;
  55                 r += rslope;
  56                 g += gslope;
  57                 b += bslope;
  58 #endif
  59 #ifdef TEXMAP
  60                 edge[i].u = u;
  61                 edge[i].v = v;
  62                 u += uslope;
  63                 v += vslope;
  64 #endif
  65         }
  66
  67         return (uint32_t)start_idx | ((uint32_t)(end_idx - 1) << 16);
  68 }
  69
  70 void POLYFILL(struct pvertex *pv, int nverts)
  71 {
  72         int i;
  73         int topidx = 0, botidx = 0, sltop = pfill_fb.height, slbot = 0;
  74         struct pvertex *left, *right;
  75         uint16_t color;
  76         /* the following variables are used for interpolating horizontally accros scanlines */
  77 #if defined(GOURAUD) || defined(TEXMAP)
  78         int mid;
  79         int32_t dx, tmp;
  80 #else
  81         /* flat version, just pack the color now */
  82         color = PACK_RGB16(pv[0].r, pv[0].g, pv[0].b);
  83 #endif
  84 #ifdef GOURAUD
  85         int32_t r, g, b, dr, dg, db, rslope, gslope, bslope;
  86 #endif
  87 #ifdef TEXMAP
  88         int32_t u, v, du, dv, uslope, vslope;
  89 #endif
  90
  91         for(i=1; i<nverts; i++) {
  92                 if(pv[i].y < pv[topidx].y) topidx = i;
  93                 if(pv[i].y > pv[botidx].y) botidx = i;
  94         }
  95
  96         /* +1 to avoid crashing due to off-by-one rounding errors in the rasterization */
  97         left = alloca((pfill_fb.height + 1) * sizeof *left);
  98         right = alloca((pfill_fb.height + 1) * sizeof *right);
  99
 100         for(i=0; i<nverts; i++) {
 101                 int next = NEXTIDX(i);
 102                 int32_t y0 = pv[i].y;
 103                 int32_t y1 = pv[next].y;
 104
 105                 if((y0 >> 8) == (y1 >> 8)) {
 106                         /*if(y0 > y1) {*/
 107                                 int i0, i1;
 108                                 int idx = y0 >> 8;
 109                                 if(pv[i].x < pv[next].x) {
 110                                         i0 = i;
 111                                         i1 = next;
 112                                 } else {
 113                                         i0 = next;
 114                                         i1 = i;
 115                                 }
 116                                 left[idx].x = pv[i0].x;
 117                                 right[idx].x = pv[i1].x;
 118 #ifdef GOURAUD
 119                                 left[idx].r = pv[i0].r << COLOR_SHIFT;
 120                                 left[idx].g = pv[i0].g << COLOR_SHIFT;
 121                                 left[idx].b = pv[i0].b << COLOR_SHIFT;
 122                                 right[idx].r = pv[i1].r << COLOR_SHIFT;
 123                                 right[idx].g = pv[i1].g << COLOR_SHIFT;
 124                                 right[idx].b = pv[i1].b << COLOR_SHIFT;
 125 #endif
 126 #ifdef TEXMAP
 127                                 left[idx].u = pv[i0].u;
 128                                 left[idx].v = pv[i0].v;
 129                                 right[idx].u = pv[i1].u;
 130                                 right[idx].v = pv[i1].v;
 131 #endif
 132                                 if(idx > slbot) slbot = idx;
 133                                 if(idx < sltop) sltop = idx;
 134                         /*}*/
 135                 } else {
 136                         struct pvertex *edge = y0 > y1 ? left : right;
 137                         uint32_t res = SCANEDGE(pv + i, pv + next, edge);
 138                         uint32_t tmp = (res >> 16) & 0xffff;
 139                         if(tmp > slbot) slbot = tmp;
 140                         if((tmp = res & 0xffff) < sltop) {
 141                                 sltop = tmp;
 142                         }
 143                 }
 144         }
 145
 146         /* calculate the slopes of all attributes across the largest span out
 147          * of the three: middle, top, or bottom.
 148          */
 149 #ifndef HIGH_QUALITY
 150 #if defined(GOURAUD) || defined(TEXMAP)
 151         mid = (sltop + slbot) >> 1;
 152         dx = right[mid].x - left[mid].x;
 153         if((tmp = right[sltop].x - left[sltop].x) > dx) {
 154                 dx = tmp;
 155                 mid = sltop;
 156         }
 157         if((tmp = right[slbot].x - left[slbot].x) > dx) {
 158                 dx = tmp;
 159                 mid = slbot;
 160         }
 161         if(!dx) dx = 256;       /* avoid division by zero */
 162 #endif
 163 #ifdef GOURAUD
 164         dr = right[mid].r - left[mid].r;
 165         dg = right[mid].g - left[mid].g;
 166         db = right[mid].b - left[mid].b;
 167         rslope = (dr << 8) / dx;
 168         gslope = (dg << 8) / dx;
 169         bslope = (db << 8) / dx;
 170 #endif
 171 #ifdef TEXMAP
 172         du = right[mid].u - left[mid].u;
 173         dv = right[mid].v - left[mid].v;
 174         uslope = (du << 8) / dx;
 175         vslope = (dv << 8) / dx;
 176 #endif
 177 #endif  /* !defined(HIGH_QUALITY) */
 178
 179         /* for each scanline ... */
 180         for(i=sltop; i<=slbot; i++) {
 181                 uint16_t *pixptr;
 182                 int32_t x;
 183
 184                 x = left[i].x;
 185                 pixptr = pfill_fb.pixels + i * pfill_fb.width + (x >> 8);
 186
 187 #ifdef GOURAUD
 188                 r = left[i].r;
 189                 g = left[i].g;
 190                 b = left[i].b;
 191 #endif
 192 #ifdef TEXMAP
 193                 u = left[i].u;
 194                 v = left[i].v;
 195 #endif
 196
 197 #if defined(HIGH_QUALITY) && (defined(GOURAUD) || defined(TEXMAP))
 198                 if(!(dx = right[i].x - left[i].x)) dx = 256;
 199
 200 #ifdef GOURAUD
 201                 dr = right[i].r - left[i].r;
 202                 dg = right[i].g - left[i].g;
 203                 db = right[i].b - left[i].b;
 204                 rslope = (dr << 8) / dx;
 205                 gslope = (dg << 8) / dx;
 206                 bslope = (db << 8) / dx;
 207 #endif
 208 #ifdef TEXMAP
 209                 du = right[i].u - left[i].u;
 210                 dv = right[i].v - left[i].v;
 211                 uslope = (du << 8) / dx;
 212                 vslope = (dv << 8) / dx;
 213 #endif
 214 #endif  /* HIGH_QUALITY */
 215
 216                 /* go across the scanline interpolating if necessary */
 217                 while(x <= right[i].x) {
 218 #if defined(GOURAUD) || defined(TEXMAP)
 219                         int cr, cg, cb;
 220 #endif
 221 #ifdef GOURAUD
 222                         /* we upped the color precision to while interpolating the
 223                          * edges, now drop the extra bits before packing
 224                          */
 225                         cr = r < 0 ? 0 : (r >> COLOR_SHIFT);
 226                         cg = g < 0 ? 0 : (g >> COLOR_SHIFT);
 227                         cb = b < 0 ? 0 : (b >> COLOR_SHIFT);
 228                         if(cr > 255) cr = 255;
 229                         if(cg > 255) cg = 255;
 230                         if(cb > 255) cb = 255;
 231                         r += rslope;
 232                         g += gslope;
 233                         b += bslope;
 234 #endif
 235 #ifdef TEXMAP
 236                         {
 237                                 int tx = (u >> (16 - pfill_tex.xshift)) & pfill_tex.xmask;
 238                                 int ty = (v >> (16 - pfill_tex.yshift)) & pfill_tex.ymask;
 239                                 uint16_t texel = pfill_tex.pixels[(ty << pfill_tex.xshift) + tx];
 240 #ifdef GOURAUD
 241                                 /* This is not correct, should be /255, but it's much faster
 242                                  * to shift by 8 (/256), and won't make a huge difference
 243                                  */
 244                                 cr = (cr * UNPACK_R16(texel)) >> 8;
 245                                 cg = (cg * UNPACK_G16(texel)) >> 8;
 246                                 cb = (cb * UNPACK_B16(texel)) >> 8;
 247 #else
 248                                 cr = UNPACK_R16(texel);
 249                                 cg = UNPACK_G16(texel);
 250                                 cb = UNPACK_B16(texel);
 251 #endif
 252                         }
 253                         u += uslope;
 254                         v += vslope;
 255 #endif
 256 #if defined(GOURAUD) || defined(TEXMAP)
 257                         color = PACK_RGB16(cr, cg, cb);
 258 #endif
 259
 260 #ifdef DEBUG_OVERDRAW
 261                         *pixptr++ += DEBUG_OVERDRAW;
 262 #else
 263                         *pixptr++ = color;
 264 #endif
 265                         x += 256;
 266                 }
 267         }
 268 }
 269