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_command( scene, tx, ty,
 204                                    LP_RAST_OP_SHADE_TILE_OPAQUE,
 205                                    lp_rast_arg_inputs(inputs) );
 206    } else {
 207       LP_COUNT(nr_shade_64);
 208       return lp_scene_bin_command( scene, tx, ty,
 209                                    LP_RAST_OP_SHADE_TILE,
 210                                    lp_rast_arg_inputs(inputs) );
 211    }
 212 }
 213
 214
 215 /**
 216  * Do basic setup for triangle rasterization and determine which
 217  * framebuffer tiles are touched.  Put the triangle in the scene's
 218  * bins for the tiles which we overlap.
 219  */
 220 static boolean
 221 do_triangle_ccw(struct lp_setup_context *setup,
 222                 const float (*v0)[4],
 223                 const float (*v1)[4],
 224                 const float (*v2)[4],
 225                 boolean frontfacing )
 226 {
 227    struct lp_scene *scene = setup->scene;
 228    struct lp_rast_triangle *tri;
 229    int x[3];
 230    int y[3];
 231    struct u_rect bbox;
 232    unsigned tri_bytes;
 233    int i;
 234    int nr_planes = 3;
 235
 236    if (0)
 237       lp_setup_print_triangle(setup, v0, v1, v2);
 238
 239    if (setup->scissor_test) {
 240       nr_planes = 7;
 241    }
 242    else {
 243       nr_planes = 3;
 244    }
 245
 246    /* x/y positions in fixed point */
 247    x[0] = subpixel_snap(v0[0][0] - setup->pixel_offset);
 248    x[1] = subpixel_snap(v1[0][0] - setup->pixel_offset);
 249    x[2] = subpixel_snap(v2[0][0] - setup->pixel_offset);
 250    y[0] = subpixel_snap(v0[0][1] - setup->pixel_offset);
 251    y[1] = subpixel_snap(v1[0][1] - setup->pixel_offset);
 252    y[2] = subpixel_snap(v2[0][1] - setup->pixel_offset);
 253
 254
 255    /* Bounding rectangle (in pixels) */
 256    {
 257       /* Yes this is necessary to accurately calculate bounding boxes
 258        * with the two fill-conventions we support.  GL (normally) ends
 259        * up needing a bottom-left fill convention, which requires
 260        * slightly different rounding.
 261        */
 262       int adj = (setup->pixel_offset != 0) ? 1 : 0;
 263
 264       bbox.x0 = (MIN3(x[0], x[1], x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
 265       bbox.x1 = (MAX3(x[0], x[1], x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
 266       bbox.y0 = (MIN3(y[0], y[1], y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
 267       bbox.y1 = (MAX3(y[0], y[1], y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
 268
 269       /* Inclusive coordinates:
 270        */
 271       bbox.x1--;
 272       bbox.y1--;
 273    }
 274
 275    if (bbox.x1 < bbox.x0 ||
 276        bbox.y1 < bbox.y0) {
 277       if (0) debug_printf("empty bounding box\n");
 278       LP_COUNT(nr_culled_tris);
 279       return TRUE;
 280    }
 281
 282    if (!u_rect_test_intersection(&setup->draw_region, &bbox)) {
 283       if (0) debug_printf("offscreen\n");
 284       LP_COUNT(nr_culled_tris);
 285       return TRUE;
 286    }
 287
 288    u_rect_find_intersection(&setup->draw_region, &bbox);
 289
 290    tri = lp_setup_alloc_triangle(scene,
 291                                  setup->fs.nr_inputs,
 292                                  nr_planes,
 293                                  &tri_bytes);
 294    if (!tri)
 295       return FALSE;
 296
 297 #ifdef DEBUG
 298    tri->v[0][0] = v0[0][0];
 299    tri->v[1][0] = v1[0][0];
 300    tri->v[2][0] = v2[0][0];
 301    tri->v[0][1] = v0[0][1];
 302    tri->v[1][1] = v1[0][1];
 303    tri->v[2][1] = v2[0][1];
 304 #endif
 305
 306    tri->plane[0].dcdy = x[0] - x[1];
 307    tri->plane[1].dcdy = x[1] - x[2];
 308    tri->plane[2].dcdy = x[2] - x[0];
 309
 310    tri->plane[0].dcdx = y[0] - y[1];
 311    tri->plane[1].dcdx = y[1] - y[2];
 312    tri->plane[2].dcdx = y[2] - y[0];
 313
 314    LP_COUNT(nr_tris);
 315
 316    /* Setup parameter interpolants:
 317     */
 318    lp_setup_tri_coef( setup, &tri->inputs, v0, v1, v2, frontfacing );
 319
 320    tri->inputs.facing = frontfacing ? 1.0F : -1.0F;
 321    tri->inputs.disable = FALSE;
 322    tri->inputs.opaque = setup->fs.current.variant->opaque;
 323    tri->inputs.state = setup->fs.stored;
 324
 325
 326    for (i = 0; i < 3; i++) {
 327       struct lp_rast_plane *plane = &tri->plane[i];
 328
 329       /* half-edge constants, will be interated over the whole render
 330        * target.
 331        */
 332       plane->c = plane->dcdx * x[i] - plane->dcdy * y[i];
 333
 334       /* correct for top-left vs. bottom-left fill convention.
 335        *
 336        * note that we're overloading gl_rasterization_rules to mean
 337        * both (0.5,0.5) pixel centers *and* bottom-left filling
 338        * convention.
 339        *
 340        * GL actually has a top-left filling convention, but GL's
 341        * notion of "top" differs from gallium's...
 342        *
 343        * Also, sometimes (in FBO cases) GL will render upside down
 344        * to its usual method, in which case it will probably want
 345        * to use the opposite, top-left convention.
 346        */
 347       if (plane->dcdx < 0) {
 348          /* both fill conventions want this - adjust for left edges */
 349          plane->c++;
 350       }
 351       else if (plane->dcdx == 0) {
 352          if (setup->pixel_offset == 0) {
 353             /* correct for top-left fill convention:
 354              */
 355             if (plane->dcdy > 0) plane->c++;
 356          }
 357          else {
 358             /* correct for bottom-left fill convention:
 359              */
 360             if (plane->dcdy < 0) plane->c++;
 361          }
 362       }
 363
 364       plane->dcdx *= FIXED_ONE;
 365       plane->dcdy *= FIXED_ONE;
 366
 367       /* find trivial reject offsets for each edge for a single-pixel
 368        * sized block.  These will be scaled up at each recursive level to
 369        * match the active blocksize.  Scaling in this way works best if
 370        * the blocks are square.
 371        */
 372       plane->eo = 0;
 373       if (plane->dcdx < 0) plane->eo -= plane->dcdx;
 374       if (plane->dcdy > 0) plane->eo += plane->dcdy;
 375
 376       /* Calculate trivial accept offsets from the above.
 377        */
 378       plane->ei = plane->dcdy - plane->dcdx - plane->eo;
 379    }
 380
 381
 382    /*
 383     * When rasterizing scissored tris, use the intersection of the
 384     * triangle bounding box and the scissor rect to generate the
 385     * scissor planes.
 386     *
 387     * This permits us to cut off the triangle "tails" that are present
 388     * in the intermediate recursive levels caused when two of the
 389     * triangles edges don't diverge quickly enough to trivially reject
 390     * exterior blocks from the triangle.
 391     *
 392     * It's not really clear if it's worth worrying about these tails,
 393     * but since we generate the planes for each scissored tri, it's
 394     * free to trim them in this case.
 395     *
 396     * Note that otherwise, the scissor planes only vary in 'C' value,
 397     * and even then only on state-changes.  Could alternatively store
 398     * these planes elsewhere.
 399     */
 400    if (nr_planes == 7) {
 401       tri->plane[3].dcdx = -1;
 402       tri->plane[3].dcdy = 0;
 403       tri->plane[3].c = 1-bbox.x0;
 404       tri->plane[3].ei = 0;
 405       tri->plane[3].eo = 1;
 406
 407       tri->plane[4].dcdx = 1;
 408       tri->plane[4].dcdy = 0;
 409       tri->plane[4].c = bbox.x1+1;
 410       tri->plane[4].ei = -1;
 411       tri->plane[4].eo = 0;
 412
 413       tri->plane[5].dcdx = 0;
 414       tri->plane[5].dcdy = 1;
 415       tri->plane[5].c = 1-bbox.y0;
 416       tri->plane[5].ei = 0;
 417       tri->plane[5].eo = 1;
 418
 419       tri->plane[6].dcdx = 0;
 420       tri->plane[6].dcdy = -1;
 421       tri->plane[6].c = bbox.y1+1;
 422       tri->plane[6].ei = -1;
 423       tri->plane[6].eo = 0;
 424    }
 425
 426    return lp_setup_bin_triangle( setup, tri, &bbox, nr_planes );
 427 }
 428
 429 /*
 430  * Round to nearest less or equal power of two of the input.
 431  *
 432  * Undefined if no bit set exists, so code should check against 0 first.
 433  */
 434 static INLINE uint32_t
 435 floor_pot(uint32_t n)
 436 {
 437 #if defined(PIPE_CC_GCC) && defined(PIPE_ARCH_X86)
 438    if (n == 0)
 439       return 0;
 440
 441    __asm__("bsr %1,%0"
 442           : "=r" (n)
 443           : "rm" (n));
 444    return 1 << n;
 445 #else
 446    n |= (n >>  1);
 447    n |= (n >>  2);
 448    n |= (n >>  4);
 449    n |= (n >>  8);
 450    n |= (n >> 16);
 451    return n - (n >> 1);
 452 #endif
 453 }
 454
 455
 456 boolean
 457 lp_setup_bin_triangle( struct lp_setup_context *setup,
 458                        struct lp_rast_triangle *tri,
 459                        const struct u_rect *bbox,
 460                        int nr_planes )
 461 {
 462    struct lp_scene *scene = setup->scene;
 463    int i;
 464
 465    /* What is the largest power-of-two boundary this triangle crosses:
 466     */
 467    int dx = floor_pot((bbox->x0 ^ bbox->x1) |
 468                       (bbox->y0 ^ bbox->y1));
 469
 470    /* The largest dimension of the rasterized area of the triangle
 471     * (aligned to a 4x4 grid), rounded down to the nearest power of two:
 472     */
 473    int sz = floor_pot((bbox->x1 - (bbox->x0 & ~3)) |
 474                       (bbox->y1 - (bbox->y0 & ~3)));
 475
 476    if (nr_planes == 3) {
 477       if (sz < 4 && dx < 64)
 478       {
 479          /* Triangle is contained in a single 4x4 stamp:
 480           */
 481          int mask = (bbox->x0 & 63 & ~3) | ((bbox->y0 & 63 & ~3) << 8);
 482
 483          return lp_scene_bin_command( scene,
 484                                       bbox->x0/64, bbox->y0/64,
 485                                       LP_RAST_OP_TRIANGLE_3_4,
 486                                       lp_rast_arg_triangle(tri, mask) );
 487       }
 488
 489       if (sz < 16 && dx < 64)
 490       {
 491          int mask = (bbox->x0 & 63 & ~3) | ((bbox->y0 & 63 & ~3) << 8);
 492
 493          /* Triangle is contained in a single 16x16 block:
 494           */
 495          return lp_scene_bin_command( scene,
 496                                       bbox->x0/64, bbox->y0/64,
 497                                       LP_RAST_OP_TRIANGLE_3_16,
 498                                       lp_rast_arg_triangle(tri, mask) );
 499       }
 500    }
 501
 502
 503    /* Determine which tile(s) intersect the triangle's bounding box
 504     */
 505    if (dx < TILE_SIZE)
 506    {
 507       int ix0 = bbox->x0 / TILE_SIZE;
 508       int iy0 = bbox->y0 / TILE_SIZE;
 509
 510       assert(iy0 == bbox->y1 / TILE_SIZE &&
 511              ix0 == bbox->x1 / TILE_SIZE);
 512
 513       /* Triangle is contained in a single tile:
 514        */
 515       return lp_scene_bin_command( scene, ix0, iy0,
 516                                    lp_rast_tri_tab[nr_planes],
 517                                    lp_rast_arg_triangle(tri, (1<<nr_planes)-1) );
 518    }
 519    else
 520    {
 521       int c[MAX_PLANES];
 522       int ei[MAX_PLANES];
 523       int eo[MAX_PLANES];
 524       int xstep[MAX_PLANES];
 525       int ystep[MAX_PLANES];
 526       int x, y;
 527
 528       int ix0 = bbox->x0 / TILE_SIZE;
 529       int iy0 = bbox->y0 / TILE_SIZE;
 530       int ix1 = bbox->x1 / TILE_SIZE;
 531       int iy1 = bbox->y1 / TILE_SIZE;
 532
 533       for (i = 0; i < nr_planes; i++) {
 534          c[i] = (tri->plane[i].c +
 535                  tri->plane[i].dcdy * iy0 * TILE_SIZE -
 536                  tri->plane[i].dcdx * ix0 * TILE_SIZE);
 537
 538          ei[i] = tri->plane[i].ei << TILE_ORDER;
 539          eo[i] = tri->plane[i].eo << TILE_ORDER;
 540          xstep[i] = -(tri->plane[i].dcdx << TILE_ORDER);
 541          ystep[i] = tri->plane[i].dcdy << TILE_ORDER;
 542       }
 543
 544
 545
 546       /* Test tile-sized blocks against the triangle.
 547        * Discard blocks fully outside the tri.  If the block is fully
 548        * contained inside the tri, bin an lp_rast_shade_tile command.
 549        * Else, bin a lp_rast_triangle command.
 550        */
 551       for (y = iy0; y <= iy1; y++)
 552       {
 553          boolean in = FALSE;  /* are we inside the triangle? */
 554          int cx[MAX_PLANES];
 555
 556          for (i = 0; i < nr_planes; i++)
 557             cx[i] = c[i];
 558
 559          for (x = ix0; x <= ix1; x++)
 560          {
 561             int out = 0;
 562             int partial = 0;
 563
 564             for (i = 0; i < nr_planes; i++) {
 565                int planeout = cx[i] + eo[i];
 566                int planepartial = cx[i] + ei[i] - 1;
 567                out |= (planeout >> 31);
 568                partial |= (planepartial >> 31) & (1<<i);
 569             }
 570
 571             if (out) {
 572                /* do nothing */
 573                if (in)
 574                   break;  /* exiting triangle, all done with this row */
 575                LP_COUNT(nr_empty_64);
 576             }
 577             else if (partial) {
 578                /* Not trivially accepted by at least one plane -
 579                 * rasterize/shade partial tile
 580                 */
 581                int count = util_bitcount(partial);
 582                in = TRUE;
 583                if (!lp_scene_bin_command( scene, x, y,
 584                                           lp_rast_tri_tab[count],
 585                                           lp_rast_arg_triangle(tri, partial) ))
 586                   goto fail;
 587
 588                LP_COUNT(nr_partially_covered_64);
 589             }
 590             else {
 591                /* triangle covers the whole tile- shade whole tile */
 592                LP_COUNT(nr_fully_covered_64);
 593                in = TRUE;
 594                if (!lp_setup_whole_tile(setup, &tri->inputs, x, y))
 595                   goto fail;
 596             }
 597
 598             /* Iterate cx values across the region:
 599              */
 600             for (i = 0; i < nr_planes; i++)
 601                cx[i] += xstep[i];
 602          }
 603
 604          /* Iterate c values down the region:
 605           */
 606          for (i = 0; i < nr_planes; i++)
 607             c[i] += ystep[i];
 608       }
 609    }
 610
 611    return TRUE;
 612
 613 fail:
 614    /* Need to disable any partially binned triangle.  This is easier
 615     * than trying to locate all the triangle, shade-tile, etc,
 616     * commands which may have been binned.
 617     */
 618    tri->inputs.disable = TRUE;
 619    return FALSE;
 620 }
 621
 622
 623 /**
 624  * Try to draw the triangle, restart the scene on failure.
 625  */
 626 static void retry_triangle_ccw( struct lp_setup_context *setup,
 627                                 const float (*v0)[4],
 628                                 const float (*v1)[4],
 629                                 const float (*v2)[4],
 630                                 boolean front)
 631 {
 632    if (!do_triangle_ccw( setup, v0, v1, v2, front ))
 633    {
 634       if (!lp_setup_flush_and_restart(setup))
 635          return;
 636
 637       if (!do_triangle_ccw( setup, v0, v1, v2, front ))
 638          return;
 639    }
 640 }
 641
 642 static INLINE float
 643 calc_area(const float (*v0)[4],
 644           const float (*v1)[4],
 645           const float (*v2)[4])
 646 {
 647    float dx01 = v0[0][0] - v1[0][0];
 648    float dy01 = v0[0][1] - v1[0][1];
 649    float dx20 = v2[0][0] - v0[0][0];
 650    float dy20 = v2[0][1] - v0[0][1];
 651    return dx01 * dy20 - dx20 * dy01;
 652 }
 653
 654
 655 /**
 656  * Draw triangle if it's CW, cull otherwise.
 657  */
 658 static void triangle_cw( struct lp_setup_context *setup,
 659                          const float (*v0)[4],
 660                          const float (*v1)[4],
 661                          const float (*v2)[4] )
 662 {
 663    float area = calc_area(v0, v1, v2);
 664
 665    if (area < 0.0f)
 666       retry_triangle_ccw(setup, v0, v2, v1, !setup->ccw_is_frontface);
 667 }
 668
 669
 670 static void triangle_ccw( struct lp_setup_context *setup,
 671                           const float (*v0)[4],
 672                           const float (*v1)[4],
 673                           const float (*v2)[4])
 674 {
 675    float area = calc_area(v0, v1, v2);
 676
 677    if (area > 0.0f)
 678       retry_triangle_ccw(setup, v0, v1, v2, setup->ccw_is_frontface);
 679 }
 680
 681 /**
 682  * Draw triangle whether it's CW or CCW.
 683  */
 684 static void triangle_both( struct lp_setup_context *setup,
 685                            const float (*v0)[4],
 686                            const float (*v1)[4],
 687                            const float (*v2)[4] )
 688 {
 689    float area = calc_area(v0, v1, v2);
 690
 691    if (area > 0.0f)
 692       retry_triangle_ccw( setup, v0, v1, v2, setup->ccw_is_frontface );
 693    else if (area < 0.0f)
 694       retry_triangle_ccw( setup, v0, v2, v1, !setup->ccw_is_frontface );
 695 }
 696
 697
 698 static void triangle_nop( struct lp_setup_context *setup,
 699                           const float (*v0)[4],
 700                           const float (*v1)[4],
 701                           const float (*v2)[4] )
 702 {
 703 }
 704
 705
 706 void
 707 lp_setup_choose_triangle( struct lp_setup_context *setup )
 708 {
 709    switch (setup->cullmode) {
 710    case PIPE_FACE_NONE:
 711       setup->triangle = triangle_both;
 712       break;
 713    case PIPE_FACE_BACK:
 714       setup->triangle = setup->ccw_is_frontface ? triangle_ccw : triangle_cw;
 715       break;
 716    case PIPE_FACE_FRONT:
 717       setup->triangle = setup->ccw_is_frontface ? triangle_cw : triangle_ccw;
 718       break;
 719    default:
 720       setup->triangle = triangle_nop;
 721       break;
 722    }
 723 }