src/gallium/drivers/llvmpipe/lp_setup_tri.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
  22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27
  28 /*
  29  * Binning code for triangles
  30  */
  31
  32 #include "util/u_math.h"
  33 #include "util/u_memory.h"
  34 #include "util/u_rect.h"
  35 #include "lp_perf.h"
  36 #include "lp_setup_context.h"
  37 #include "lp_setup_coef.h"
  38 #include "lp_rast.h"
  39 #include "lp_state_fs.h"
  40
  41 #define NUM_CHANNELS 4
  42
  43
  44
  45 static INLINE int
  46 subpixel_snap(float a)
  47 {
  48    return util_iround(FIXED_ONE * a);
  49 }
  50
  51 static INLINE float
  52 fixed_to_float(int a)
  53 {
  54    return a * (1.0 / FIXED_ONE);
  55 }
  56
  57
  58
  59
  60
  61
  62
  63 /**
  64  * Alloc space for a new triangle plus the input.a0/dadx/dady arrays
  65  * immediately after it.
  66  * The memory is allocated from the per-scene pool, not per-tile.
  67  * \param tri_size  returns number of bytes allocated
  68  * \param nr_inputs  number of fragment shader inputs
  69  * \return pointer to triangle space
  70  */
  71 struct lp_rast_triangle *
  72 lp_setup_alloc_triangle(struct lp_scene *scene,
  73                         unsigned nr_inputs,
  74                         unsigned nr_planes,
  75                         unsigned *tri_size)
  76 {
  77    unsigned input_array_sz = NUM_CHANNELS * (nr_inputs + 1) * sizeof(float);
  78    struct lp_rast_triangle *tri;
  79    unsigned tri_bytes, bytes;
  80    char *inputs;
  81
  82    tri_bytes = align(Offset(struct lp_rast_triangle, plane[nr_planes]), 16);
  83    bytes = tri_bytes + (3 * input_array_sz);
  84
  85    tri = lp_scene_alloc_aligned( scene, bytes, 16 );
  86
  87    if (tri) {
  88       inputs = ((char *)tri) + tri_bytes;
  89       tri->inputs.a0   = (float (*)[4]) inputs;
  90       tri->inputs.dadx = (float (*)[4]) (inputs + input_array_sz);
  91       tri->inputs.dady = (float (*)[4]) (inputs + 2 * input_array_sz);
  92
  93       *tri_size = bytes;
  94    }
  95
  96    return tri;
  97 }
  98
  99 void
 100 lp_setup_print_vertex(struct lp_setup_context *setup,
 101                       const char *name,
 102                       const float (*v)[4])
 103 {
 104    int i, j;
 105
 106    debug_printf("   wpos (%s[0]) xyzw %f %f %f %f\n",
 107                 name,
 108                 v[0][0], v[0][1], v[0][2], v[0][3]);
 109
 110    for (i = 0; i < setup->fs.nr_inputs; i++) {
 111       const float *in = v[setup->fs.input[i].src_index];
 112
 113       debug_printf("  in[%d] (%s[%d]) %s%s%s%s ",
 114                    i,
 115                    name, setup->fs.input[i].src_index,
 116                    (setup->fs.input[i].usage_mask & 0x1) ? "x" : " ",
 117                    (setup->fs.input[i].usage_mask & 0x2) ? "y" : " ",
 118                    (setup->fs.input[i].usage_mask & 0x4) ? "z" : " ",
 119                    (setup->fs.input[i].usage_mask & 0x8) ? "w" : " ");
 120
 121       for (j = 0; j < 4; j++)
 122          if (setup->fs.input[i].usage_mask & (1<<j))
 123             debug_printf("%.5f ", in[j]);
 124
 125       debug_printf("\n");
 126    }
 127 }
 128
 129
 130 /**
 131  * Print triangle vertex attribs (for debug).
 132  */
 133 void
 134 lp_setup_print_triangle(struct lp_setup_context *setup,
 135                         const float (*v0)[4],
 136                         const float (*v1)[4],
 137                         const float (*v2)[4])
 138 {
 139    debug_printf("triangle\n");
 140
 141    {
 142       const float ex = v0[0][0] - v2[0][0];
 143       const float ey = v0[0][1] - v2[0][1];
 144       const float fx = v1[0][0] - v2[0][0];
 145       const float fy = v1[0][1] - v2[0][1];
 146
 147       /* det = cross(e,f).z */
 148       const float det = ex * fy - ey * fx;
 149       if (det < 0.0f)
 150          debug_printf("   - ccw\n");
 151       else if (det > 0.0f)
 152          debug_printf("   - cw\n");
 153       else
 154          debug_printf("   - zero area\n");
 155    }
 156
 157    lp_setup_print_vertex(setup, "v0", v0);
 158    lp_setup_print_vertex(setup, "v1", v1);
 159    lp_setup_print_vertex(setup, "v2", v2);
 160 }
 161
 162
 163 #define MAX_PLANES 8
 164 static unsigned
 165 lp_rast_tri_tab[MAX_PLANES+1] = {
 166    0,               /* should be impossible */
 167    LP_RAST_OP_TRIANGLE_1,
 168    LP_RAST_OP_TRIANGLE_2,
 169    LP_RAST_OP_TRIANGLE_3,
 170    LP_RAST_OP_TRIANGLE_4,
 171    LP_RAST_OP_TRIANGLE_5,
 172    LP_RAST_OP_TRIANGLE_6,
 173    LP_RAST_OP_TRIANGLE_7,
 174    LP_RAST_OP_TRIANGLE_8
 175 };
 176
 177
 178
 179 /**
 180  * The primitive covers the whole tile- shade whole tile.
 181  *
 182  * \param tx, ty  the tile position in tiles, not pixels
 183  */
 184 static boolean
 185 lp_setup_whole_tile(struct lp_setup_context *setup,
 186                     const struct lp_rast_shader_inputs *inputs,
 187                     int tx, int ty)
 188 {
 189    struct lp_scene *scene = setup->scene;
 190
 191    LP_COUNT(nr_fully_covered_64);
 192
 193    /* if variant is opaque and scissor doesn't effect the tile */
 194    if (inputs->opaque) {
 195       if (!scene->fb.zsbuf) {
 196          /*
 197           * All previous rendering will be overwritten so reset the bin.
 198           */
 199          lp_scene_bin_reset( scene, tx, ty );
 200       }
 201
 202       LP_COUNT(nr_shade_opaque_64);
 203       return lp_scene_bin_cmd_with_state( scene, tx, ty,
 204                                           setup->fs.stored,
 205                                           LP_RAST_OP_SHADE_TILE_OPAQUE,
 206                                           lp_rast_arg_inputs(inputs) );
 207    } else {
 208       LP_COUNT(nr_shade_64);
 209       return lp_scene_bin_cmd_with_state( scene, tx, ty,
 210                                           setup->fs.stored,
 211                                           LP_RAST_OP_SHADE_TILE,
 212                                           lp_rast_arg_inputs(inputs) );
 213    }
 214 }
 215
 216
 217 /**
 218  * Do basic setup for triangle rasterization and determine which
 219  * framebuffer tiles are touched.  Put the triangle in the scene's
 220  * bins for the tiles which we overlap.
 221  */
 222 static boolean
 223 do_triangle_ccw(struct lp_setup_context *setup,
 224                 const float (*v0)[4],
 225                 const float (*v1)[4],
 226                 const float (*v2)[4],
 227                 boolean frontfacing )
 228 {
 229    struct lp_scene *scene = setup->scene;
 230    struct lp_rast_triangle *tri;
 231    int x[3];
 232    int y[3];
 233    struct u_rect bbox;
 234    unsigned tri_bytes;
 235    int i;
 236    int nr_planes = 3;
 237
 238    if (0)
 239       lp_setup_print_triangle(setup, v0, v1, v2);
 240
 241    if (setup->scissor_test) {
 242       nr_planes = 7;
 243    }
 244    else {
 245       nr_planes = 3;
 246    }
 247
 248    /* x/y positions in fixed point */
 249    x[0] = subpixel_snap(v0[0][0] - setup->pixel_offset);
 250    x[1] = subpixel_snap(v1[0][0] - setup->pixel_offset);
 251    x[2] = subpixel_snap(v2[0][0] - setup->pixel_offset);
 252    y[0] = subpixel_snap(v0[0][1] - setup->pixel_offset);
 253    y[1] = subpixel_snap(v1[0][1] - setup->pixel_offset);
 254    y[2] = subpixel_snap(v2[0][1] - setup->pixel_offset);
 255
 256
 257    /* Bounding rectangle (in pixels) */
 258    {
 259       /* Yes this is necessary to accurately calculate bounding boxes
 260        * with the two fill-conventions we support.  GL (normally) ends
 261        * up needing a bottom-left fill convention, which requires
 262        * slightly different rounding.
 263        */
 264       int adj = (setup->pixel_offset != 0) ? 1 : 0;
 265
 266       bbox.x0 = (MIN3(x[0], x[1], x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
 267       bbox.x1 = (MAX3(x[0], x[1], x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
 268       bbox.y0 = (MIN3(y[0], y[1], y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
 269       bbox.y1 = (MAX3(y[0], y[1], y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
 270
 271       /* Inclusive coordinates:
 272        */
 273       bbox.x1--;
 274       bbox.y1--;
 275    }
 276
 277    if (bbox.x1 < bbox.x0 ||
 278        bbox.y1 < bbox.y0) {
 279       if (0) debug_printf("empty bounding box\n");
 280       LP_COUNT(nr_culled_tris);
 281       return TRUE;
 282    }
 283
 284    if (!u_rect_test_intersection(&setup->draw_region, &bbox)) {
 285       if (0) debug_printf("offscreen\n");
 286       LP_COUNT(nr_culled_tris);
 287       return TRUE;
 288    }
 289
 290    u_rect_find_intersection(&setup->draw_region, &bbox);
 291
 292    tri = lp_setup_alloc_triangle(scene,
 293                                  setup->fs.nr_inputs,
 294                                  nr_planes,
 295                                  &tri_bytes);
 296    if (!tri)
 297       return FALSE;
 298
 299 #ifdef DEBUG
 300    tri->v[0][0] = v0[0][0];
 301    tri->v[1][0] = v1[0][0];
 302    tri->v[2][0] = v2[0][0];
 303    tri->v[0][1] = v0[0][1];
 304    tri->v[1][1] = v1[0][1];
 305    tri->v[2][1] = v2[0][1];
 306 #endif
 307
 308    tri->plane[0].dcdy = x[0] - x[1];
 309    tri->plane[1].dcdy = x[1] - x[2];
 310    tri->plane[2].dcdy = x[2] - x[0];
 311
 312    tri->plane[0].dcdx = y[0] - y[1];
 313    tri->plane[1].dcdx = y[1] - y[2];
 314    tri->plane[2].dcdx = y[2] - y[0];
 315
 316    LP_COUNT(nr_tris);
 317
 318    /* Setup parameter interpolants:
 319     */
 320    lp_setup_tri_coef( setup, &tri->inputs, v0, v1, v2, frontfacing );
 321
 322    tri->inputs.facing = frontfacing ? 1.0F : -1.0F;
 323    tri->inputs.disable = FALSE;
 324    tri->inputs.opaque = setup->fs.current.variant->opaque;
 325
 326
 327    for (i = 0; i < 3; i++) {
 328       struct lp_rast_plane *plane = &tri->plane[i];
 329
 330       /* half-edge constants, will be interated over the whole render
 331        * target.
 332        */
 333       plane->c = plane->dcdx * x[i] - plane->dcdy * y[i];
 334
 335       /* correct for top-left vs. bottom-left fill convention.
 336        *
 337        * note that we're overloading gl_rasterization_rules to mean
 338        * both (0.5,0.5) pixel centers *and* bottom-left filling
 339        * convention.
 340        *
 341        * GL actually has a top-left filling convention, but GL's
 342        * notion of "top" differs from gallium's...
 343        *
 344        * Also, sometimes (in FBO cases) GL will render upside down
 345        * to its usual method, in which case it will probably want
 346        * to use the opposite, top-left convention.
 347        */
 348       if (plane->dcdx < 0) {
 349          /* both fill conventions want this - adjust for left edges */
 350          plane->c++;
 351       }
 352       else if (plane->dcdx == 0) {
 353          if (setup->pixel_offset == 0) {
 354             /* correct for top-left fill convention:
 355              */
 356             if (plane->dcdy > 0) plane->c++;
 357          }
 358          else {
 359             /* correct for bottom-left fill convention:
 360              */
 361             if (plane->dcdy < 0) plane->c++;
 362          }
 363       }
 364
 365       plane->dcdx *= FIXED_ONE;
 366       plane->dcdy *= FIXED_ONE;
 367
 368       /* find trivial reject offsets for each edge for a single-pixel
 369        * sized block.  These will be scaled up at each recursive level to
 370        * match the active blocksize.  Scaling in this way works best if
 371        * the blocks are square.
 372        */
 373       plane->eo = 0;
 374       if (plane->dcdx < 0) plane->eo -= plane->dcdx;
 375       if (plane->dcdy > 0) plane->eo += plane->dcdy;
 376
 377       /* Calculate trivial accept offsets from the above.
 378        */
 379       plane->ei = plane->dcdy - plane->dcdx - plane->eo;
 380    }
 381
 382
 383    /*
 384     * When rasterizing scissored tris, use the intersection of the
 385     * triangle bounding box and the scissor rect to generate the
 386     * scissor planes.
 387     *
 388     * This permits us to cut off the triangle "tails" that are present
 389     * in the intermediate recursive levels caused when two of the
 390     * triangles edges don't diverge quickly enough to trivially reject
 391     * exterior blocks from the triangle.
 392     *
 393     * It's not really clear if it's worth worrying about these tails,
 394     * but since we generate the planes for each scissored tri, it's
 395     * free to trim them in this case.
 396     *
 397     * Note that otherwise, the scissor planes only vary in 'C' value,
 398     * and even then only on state-changes.  Could alternatively store
 399     * these planes elsewhere.
 400     */
 401    if (nr_planes == 7) {
 402       tri->plane[3].dcdx = -1;
 403       tri->plane[3].dcdy = 0;
 404       tri->plane[3].c = 1-bbox.x0;
 405       tri->plane[3].ei = 0;
 406       tri->plane[3].eo = 1;
 407
 408       tri->plane[4].dcdx = 1;
 409       tri->plane[4].dcdy = 0;
 410       tri->plane[4].c = bbox.x1+1;
 411       tri->plane[4].ei = -1;
 412       tri->plane[4].eo = 0;
 413
 414       tri->plane[5].dcdx = 0;
 415       tri->plane[5].dcdy = 1;
 416       tri->plane[5].c = 1-bbox.y0;
 417       tri->plane[5].ei = 0;
 418       tri->plane[5].eo = 1;
 419
 420       tri->plane[6].dcdx = 0;
 421       tri->plane[6].dcdy = -1;
 422       tri->plane[6].c = bbox.y1+1;
 423       tri->plane[6].ei = -1;
 424       tri->plane[6].eo = 0;
 425    }
 426
 427    return lp_setup_bin_triangle( setup, tri, &bbox, nr_planes );
 428 }
 429
 430 /*
 431  * Round to nearest less or equal power of two of the input.
 432  *
 433  * Undefined if no bit set exists, so code should check against 0 first.
 434  */
 435 static INLINE uint32_t
 436 floor_pot(uint32_t n)
 437 {
 438 #if defined(PIPE_CC_GCC) && defined(PIPE_ARCH_X86)
 439    if (n == 0)
 440       return 0;
 441
 442    __asm__("bsr %1,%0"
 443           : "=r" (n)
 444           : "rm" (n));
 445    return 1 << n;
 446 #else
 447    n |= (n >>  1);
 448    n |= (n >>  2);
 449    n |= (n >>  4);
 450    n |= (n >>  8);
 451    n |= (n >> 16);
 452    return n - (n >> 1);
 453 #endif
 454 }
 455
 456
 457 boolean
 458 lp_setup_bin_triangle( struct lp_setup_context *setup,
 459                        struct lp_rast_triangle *tri,
 460                        const struct u_rect *bbox,
 461                        int nr_planes )
 462 {
 463    struct lp_scene *scene = setup->scene;
 464    int i;
 465
 466    /* What is the largest power-of-two boundary this triangle crosses:
 467     */
 468    int dx = floor_pot((bbox->x0 ^ bbox->x1) |
 469                       (bbox->y0 ^ bbox->y1));
 470
 471    /* The largest dimension of the rasterized area of the triangle
 472     * (aligned to a 4x4 grid), rounded down to the nearest power of two:
 473     */
 474    int sz = floor_pot((bbox->x1 - (bbox->x0 & ~3)) |
 475                       (bbox->y1 - (bbox->y0 & ~3)));
 476
 477    /* Determine which tile(s) intersect the triangle's bounding box
 478     */
 479    if (dx < TILE_SIZE)
 480    {
 481       int ix0 = bbox->x0 / TILE_SIZE;
 482       int iy0 = bbox->y0 / TILE_SIZE;
 483       int px = bbox->x0 & 63 & ~3;
 484       int py = bbox->y0 & 63 & ~3;
 485       int mask = px | (py << 8);
 486
 487       assert(iy0 == bbox->y1 / TILE_SIZE &&
 488              ix0 == bbox->x1 / TILE_SIZE);
 489
 490       if (nr_planes == 3) {
 491          if (sz < 4)
 492          {
 493             /* Triangle is contained in a single 4x4 stamp:
 494              */
 495             return lp_scene_bin_cmd_with_state( scene, ix0, iy0,
 496                                                 setup->fs.stored,
 497                                                 LP_RAST_OP_TRIANGLE_3_4,
 498                                                 lp_rast_arg_triangle(tri, mask) );
 499          }
 500
 501          if (sz < 16)
 502          {
 503             /* Triangle is contained in a single 16x16 block:
 504              */
 505             return lp_scene_bin_cmd_with_state( scene, ix0, iy0,
 506                                                 setup->fs.stored,
 507                                                 LP_RAST_OP_TRIANGLE_3_16,
 508                                                 lp_rast_arg_triangle(tri, mask) );
 509          }
 510       }
 511       else if (nr_planes == 4 && sz < 16)
 512       {
 513          return lp_scene_bin_cmd_with_state(scene, ix0, iy0,
 514                                             setup->fs.stored,
 515                                             LP_RAST_OP_TRIANGLE_4_16,
 516                                             lp_rast_arg_triangle(tri, mask) );
 517       }
 518
 519
 520       /* Triangle is contained in a single tile:
 521        */
 522       return lp_scene_bin_cmd_with_state( scene, ix0, iy0, setup->fs.stored,
 523                                           lp_rast_tri_tab[nr_planes],
 524                                           lp_rast_arg_triangle(tri, (1<<nr_planes)-1) );
 525    }
 526    else
 527    {
 528       int c[MAX_PLANES];
 529       int ei[MAX_PLANES];
 530       int eo[MAX_PLANES];
 531       int xstep[MAX_PLANES];
 532       int ystep[MAX_PLANES];
 533       int x, y;
 534
 535       int ix0 = bbox->x0 / TILE_SIZE;
 536       int iy0 = bbox->y0 / TILE_SIZE;
 537       int ix1 = bbox->x1 / TILE_SIZE;
 538       int iy1 = bbox->y1 / TILE_SIZE;
 539
 540       for (i = 0; i < nr_planes; i++) {
 541          c[i] = (tri->plane[i].c +
 542                  tri->plane[i].dcdy * iy0 * TILE_SIZE -
 543                  tri->plane[i].dcdx * ix0 * TILE_SIZE);
 544
 545          ei[i] = tri->plane[i].ei << TILE_ORDER;
 546          eo[i] = tri->plane[i].eo << TILE_ORDER;
 547          xstep[i] = -(tri->plane[i].dcdx << TILE_ORDER);
 548          ystep[i] = tri->plane[i].dcdy << TILE_ORDER;
 549       }
 550
 551
 552
 553       /* Test tile-sized blocks against the triangle.
 554        * Discard blocks fully outside the tri.  If the block is fully
 555        * contained inside the tri, bin an lp_rast_shade_tile command.
 556        * Else, bin a lp_rast_triangle command.
 557        */
 558       for (y = iy0; y <= iy1; y++)
 559       {
 560          boolean in = FALSE;  /* are we inside the triangle? */
 561          int cx[MAX_PLANES];
 562
 563          for (i = 0; i < nr_planes; i++)
 564             cx[i] = c[i];
 565
 566          for (x = ix0; x <= ix1; x++)
 567          {
 568             int out = 0;
 569             int partial = 0;
 570
 571             for (i = 0; i < nr_planes; i++) {
 572                int planeout = cx[i] + eo[i];
 573                int planepartial = cx[i] + ei[i] - 1;
 574                out |= (planeout >> 31);
 575                partial |= (planepartial >> 31) & (1<<i);
 576             }
 577
 578             if (out) {
 579                /* do nothing */
 580                if (in)
 581                   break;  /* exiting triangle, all done with this row */
 582                LP_COUNT(nr_empty_64);
 583             }
 584             else if (partial) {
 585                /* Not trivially accepted by at least one plane -
 586                 * rasterize/shade partial tile
 587                 */
 588                int count = util_bitcount(partial);
 589                in = TRUE;
 590
 591                if (!lp_scene_bin_cmd_with_state( scene, x, y,
 592                                                  setup->fs.stored,
 593                                                  lp_rast_tri_tab[count],
 594                                                  lp_rast_arg_triangle(tri, partial) ))
 595                   goto fail;
 596
 597                LP_COUNT(nr_partially_covered_64);
 598             }
 599             else {
 600                /* triangle covers the whole tile- shade whole tile */
 601                LP_COUNT(nr_fully_covered_64);
 602                in = TRUE;
 603                if (!lp_setup_whole_tile(setup, &tri->inputs, x, y))
 604                   goto fail;
 605             }
 606
 607             /* Iterate cx values across the region:
 608              */
 609             for (i = 0; i < nr_planes; i++)
 610                cx[i] += xstep[i];
 611          }
 612
 613          /* Iterate c values down the region:
 614           */
 615          for (i = 0; i < nr_planes; i++)
 616             c[i] += ystep[i];
 617       }
 618    }
 619
 620    return TRUE;
 621
 622 fail:
 623    /* Need to disable any partially binned triangle.  This is easier
 624     * than trying to locate all the triangle, shade-tile, etc,
 625     * commands which may have been binned.
 626     */
 627    tri->inputs.disable = TRUE;
 628    return FALSE;
 629 }
 630
 631
 632 /**
 633  * Try to draw the triangle, restart the scene on failure.
 634  */
 635 static void retry_triangle_ccw( struct lp_setup_context *setup,
 636                                 const float (*v0)[4],
 637                                 const float (*v1)[4],
 638                                 const float (*v2)[4],
 639                                 boolean front)
 640 {
 641    if (!do_triangle_ccw( setup, v0, v1, v2, front ))
 642    {
 643       if (!lp_setup_flush_and_restart(setup))
 644          return;
 645
 646       if (!do_triangle_ccw( setup, v0, v1, v2, front ))
 647          return;
 648    }
 649 }
 650
 651 static INLINE float
 652 calc_area(const float (*v0)[4],
 653           const float (*v1)[4],
 654           const float (*v2)[4])
 655 {
 656    float dx01 = v0[0][0] - v1[0][0];
 657    float dy01 = v0[0][1] - v1[0][1];
 658    float dx20 = v2[0][0] - v0[0][0];
 659    float dy20 = v2[0][1] - v0[0][1];
 660    return dx01 * dy20 - dx20 * dy01;
 661 }
 662
 663
 664 /**
 665  * Draw triangle if it's CW, cull otherwise.
 666  */
 667 static void triangle_cw( struct lp_setup_context *setup,
 668                          const float (*v0)[4],
 669                          const float (*v1)[4],
 670                          const float (*v2)[4] )
 671 {
 672    float area = calc_area(v0, v1, v2);
 673
 674    if (area < 0.0f)
 675       retry_triangle_ccw(setup, v0, v2, v1, !setup->ccw_is_frontface);
 676 }
 677
 678
 679 static void triangle_ccw( struct lp_setup_context *setup,
 680                           const float (*v0)[4],
 681                           const float (*v1)[4],
 682                           const float (*v2)[4])
 683 {
 684    float area = calc_area(v0, v1, v2);
 685
 686    if (area > 0.0f)
 687       retry_triangle_ccw(setup, v0, v1, v2, setup->ccw_is_frontface);
 688 }
 689
 690 /**
 691  * Draw triangle whether it's CW or CCW.
 692  */
 693 static void triangle_both( struct lp_setup_context *setup,
 694                            const float (*v0)[4],
 695                            const float (*v1)[4],
 696                            const float (*v2)[4] )
 697 {
 698    float area = calc_area(v0, v1, v2);
 699
 700    if (area > 0.0f)
 701       retry_triangle_ccw( setup, v0, v1, v2, setup->ccw_is_frontface );
 702    else if (area < 0.0f)
 703       retry_triangle_ccw( setup, v0, v2, v1, !setup->ccw_is_frontface );
 704 }
 705
 706
 707 static void triangle_nop( struct lp_setup_context *setup,
 708                           const float (*v0)[4],
 709                           const float (*v1)[4],
 710                           const float (*v2)[4] )
 711 {
 712 }
 713
 714
 715 void
 716 lp_setup_choose_triangle( struct lp_setup_context *setup )
 717 {
 718    switch (setup->cullmode) {
 719    case PIPE_FACE_NONE:
 720       setup->triangle = triangle_both;
 721       break;
 722    case PIPE_FACE_BACK:
 723       setup->triangle = setup->ccw_is_frontface ? triangle_ccw : triangle_cw;
 724       break;
 725    case PIPE_FACE_FRONT:
 726       setup->triangle = setup->ccw_is_frontface ? triangle_cw : triangle_ccw;
 727       break;
 728    default:
 729       setup->triangle = triangle_nop;
 730       break;
 731    }
 732 }