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 static unsigned
 164 lp_rast_tri_tab[9] = {
 165    0,               /* should be impossible */
 166    LP_RAST_OP_TRIANGLE_1,
 167    LP_RAST_OP_TRIANGLE_2,
 168    LP_RAST_OP_TRIANGLE_3,
 169    LP_RAST_OP_TRIANGLE_4,
 170    LP_RAST_OP_TRIANGLE_5,
 171    LP_RAST_OP_TRIANGLE_6,
 172    LP_RAST_OP_TRIANGLE_7,
 173    LP_RAST_OP_TRIANGLE_8
 174 };
 175
 176
 177
 178 /**
 179  * The primitive covers the whole tile- shade whole tile.
 180  *
 181  * \param tx, ty  the tile position in tiles, not pixels
 182  */
 183 static boolean
 184 lp_setup_whole_tile(struct lp_setup_context *setup,
 185                     const struct lp_rast_shader_inputs *inputs,
 186                     int tx, int ty)
 187 {
 188    struct lp_scene *scene = setup->scene;
 189
 190    LP_COUNT(nr_fully_covered_64);
 191
 192    /* if variant is opaque and scissor doesn't effect the tile */
 193    if (inputs->opaque) {
 194       if (!scene->fb.zsbuf) {
 195          /*
 196           * All previous rendering will be overwritten so reset the bin.
 197           */
 198          lp_scene_bin_reset( scene, tx, ty );
 199       }
 200
 201       LP_COUNT(nr_shade_opaque_64);
 202       return lp_scene_bin_command( scene, tx, ty,
 203                                    LP_RAST_OP_SHADE_TILE_OPAQUE,
 204                                    lp_rast_arg_inputs(inputs) );
 205    } else {
 206       LP_COUNT(nr_shade_64);
 207       return lp_scene_bin_command( scene, tx, ty,
 208                                    LP_RAST_OP_SHADE_TILE,
 209                                    lp_rast_arg_inputs(inputs) );
 210    }
 211 }
 212
 213
 214 /**
 215  * Do basic setup for triangle rasterization and determine which
 216  * framebuffer tiles are touched.  Put the triangle in the scene's
 217  * bins for the tiles which we overlap.
 218  */
 219 static boolean
 220 do_triangle_ccw(struct lp_setup_context *setup,
 221                 const float (*v0)[4],
 222                 const float (*v1)[4],
 223                 const float (*v2)[4],
 224                 boolean frontfacing )
 225 {
 226    struct lp_scene *scene = setup->scene;
 227    struct lp_rast_triangle *tri;
 228    int x[3];
 229    int y[3];
 230    int area;
 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    area = (tri->plane[0].dcdy * tri->plane[2].dcdx -
 315            tri->plane[2].dcdy * tri->plane[0].dcdx);
 316
 317    LP_COUNT(nr_tris);
 318
 319    /* Cull non-ccw and zero-sized triangles.
 320     *
 321     * XXX: subject to overflow??
 322     */
 323    if (area <= 0) {
 324       lp_scene_putback_data( scene, tri_bytes );
 325       LP_COUNT(nr_culled_tris);
 326       return TRUE;
 327    }
 328
 329    /* Setup parameter interpolants:
 330     */
 331    lp_setup_tri_coef( setup, &tri->inputs, v0, v1, v2, frontfacing );
 332
 333    tri->inputs.facing = frontfacing ? 1.0F : -1.0F;
 334    tri->inputs.disable = FALSE;
 335    tri->inputs.opaque = setup->fs.current.variant->opaque;
 336    tri->inputs.state = setup->fs.stored;
 337
 338
 339    for (i = 0; i < 3; i++) {
 340       struct lp_rast_plane *plane = &tri->plane[i];
 341
 342       /* half-edge constants, will be interated over the whole render
 343        * target.
 344        */
 345       plane->c = plane->dcdx * x[i] - plane->dcdy * y[i];
 346
 347       /* correct for top-left vs. bottom-left fill convention.
 348        *
 349        * note that we're overloading gl_rasterization_rules to mean
 350        * both (0.5,0.5) pixel centers *and* bottom-left filling
 351        * convention.
 352        *
 353        * GL actually has a top-left filling convention, but GL's
 354        * notion of "top" differs from gallium's...
 355        *
 356        * Also, sometimes (in FBO cases) GL will render upside down
 357        * to its usual method, in which case it will probably want
 358        * to use the opposite, top-left convention.
 359        */
 360       if (plane->dcdx < 0) {
 361          /* both fill conventions want this - adjust for left edges */
 362          plane->c++;
 363       }
 364       else if (plane->dcdx == 0) {
 365          if (setup->pixel_offset == 0) {
 366             /* correct for top-left fill convention:
 367              */
 368             if (plane->dcdy > 0) plane->c++;
 369          }
 370          else {
 371             /* correct for bottom-left fill convention:
 372              */
 373             if (plane->dcdy < 0) plane->c++;
 374          }
 375       }
 376
 377       plane->dcdx *= FIXED_ONE;
 378       plane->dcdy *= FIXED_ONE;
 379
 380       /* find trivial reject offsets for each edge for a single-pixel
 381        * sized block.  These will be scaled up at each recursive level to
 382        * match the active blocksize.  Scaling in this way works best if
 383        * the blocks are square.
 384        */
 385       plane->eo = 0;
 386       if (plane->dcdx < 0) plane->eo -= plane->dcdx;
 387       if (plane->dcdy > 0) plane->eo += plane->dcdy;
 388
 389       /* Calculate trivial accept offsets from the above.
 390        */
 391       plane->ei = plane->dcdy - plane->dcdx - plane->eo;
 392    }
 393
 394
 395    /*
 396     * When rasterizing scissored tris, use the intersection of the
 397     * triangle bounding box and the scissor rect to generate the
 398     * scissor planes.
 399     *
 400     * This permits us to cut off the triangle "tails" that are present
 401     * in the intermediate recursive levels caused when two of the
 402     * triangles edges don't diverge quickly enough to trivially reject
 403     * exterior blocks from the triangle.
 404     *
 405     * It's not really clear if it's worth worrying about these tails,
 406     * but since we generate the planes for each scissored tri, it's
 407     * free to trim them in this case.
 408     *
 409     * Note that otherwise, the scissor planes only vary in 'C' value,
 410     * and even then only on state-changes.  Could alternatively store
 411     * these planes elsewhere.
 412     */
 413    if (nr_planes == 7) {
 414       tri->plane[3].dcdx = -1;
 415       tri->plane[3].dcdy = 0;
 416       tri->plane[3].c = 1-bbox.x0;
 417       tri->plane[3].ei = 0;
 418       tri->plane[3].eo = 1;
 419
 420       tri->plane[4].dcdx = 1;
 421       tri->plane[4].dcdy = 0;
 422       tri->plane[4].c = bbox.x1+1;
 423       tri->plane[4].ei = -1;
 424       tri->plane[4].eo = 0;
 425
 426       tri->plane[5].dcdx = 0;
 427       tri->plane[5].dcdy = 1;
 428       tri->plane[5].c = 1-bbox.y0;
 429       tri->plane[5].ei = 0;
 430       tri->plane[5].eo = 1;
 431
 432       tri->plane[6].dcdx = 0;
 433       tri->plane[6].dcdy = -1;
 434       tri->plane[6].c = bbox.y1+1;
 435       tri->plane[6].ei = -1;
 436       tri->plane[6].eo = 0;
 437    }
 438
 439    return lp_setup_bin_triangle( setup, tri, &bbox, nr_planes );
 440 }
 441
 442 /*
 443  * Round to nearest less or equal power of two of the input.
 444  *
 445  * Undefined if no bit set exists, so code should check against 0 first.
 446  */
 447 static INLINE uint32_t
 448 floor_pot(uint32_t n)
 449 {
 450    assert(n);
 451 #if defined(PIPE_CC_GCC) && defined(PIPE_ARCH_X86)
 452    asm("bsr %1,%0"
 453        : "=r" (n)
 454        : "rm" (n));
 455    return 1 << n;
 456 #else
 457    n |= (n >>  1);
 458    n |= (n >>  2);
 459    n |= (n >>  4);
 460    n |= (n >>  8);
 461    n |= (n >> 16);
 462    return n - (n >> 1);
 463 #endif
 464 }
 465
 466
 467 boolean
 468 lp_setup_bin_triangle( struct lp_setup_context *setup,
 469                        struct lp_rast_triangle *tri,
 470                        const struct u_rect *bbox,
 471                        int nr_planes )
 472 {
 473    struct lp_scene *scene = setup->scene;
 474    int i;
 475
 476    /* What is the largest power-of-two boundary this triangle crosses:
 477     */
 478    int dx = floor_pot((bbox->x0 ^ bbox->x1) |
 479                       (bbox->y0 ^ bbox->y1));
 480
 481    /* The largest dimension of the rasterized area of the triangle
 482     * (aligned to a 4x4 grid), rounded down to the nearest power of two:
 483     */
 484    int sz = floor_pot((bbox->x1 - (bbox->x0 & ~3)) |
 485                       (bbox->y1 - (bbox->y0 & ~3)));
 486
 487    if (nr_planes == 3) {
 488       if (sz < 4 && dx < 64)
 489       {
 490          /* Triangle is contained in a single 4x4 stamp:
 491           */
 492          int mask = (bbox->x0 & 63 & ~3) | ((bbox->y0 & 63 & ~3) << 8);
 493
 494          return lp_scene_bin_command( scene,
 495                                       bbox->x0/64, bbox->y0/64,
 496                                       LP_RAST_OP_TRIANGLE_3_4,
 497                                       lp_rast_arg_triangle(tri, mask) );
 498       }
 499
 500       if (sz < 16 && dx < 64)
 501       {
 502          int mask = (bbox->x0 & 63 & ~3) | ((bbox->y0 & 63 & ~3) << 8);
 503
 504          /* Triangle is contained in a single 16x16 block:
 505           */
 506          return lp_scene_bin_command( scene,
 507                                       bbox->x0/64, bbox->y0/64,
 508                                       LP_RAST_OP_TRIANGLE_3_16,
 509                                       lp_rast_arg_triangle(tri, mask) );
 510       }
 511    }
 512
 513
 514    /* Determine which tile(s) intersect the triangle's bounding box
 515     */
 516    if (dx < TILE_SIZE)
 517    {
 518       int ix0 = bbox->x0 / TILE_SIZE;
 519       int iy0 = bbox->y0 / TILE_SIZE;
 520
 521       assert(iy0 == bbox->y1 / TILE_SIZE &&
 522              ix0 == bbox->x1 / TILE_SIZE);
 523
 524       /* Triangle is contained in a single tile:
 525        */
 526       return lp_scene_bin_command( scene, ix0, iy0,
 527                                    lp_rast_tri_tab[nr_planes],
 528                                    lp_rast_arg_triangle(tri, (1<<nr_planes)-1) );
 529    }
 530    else
 531    {
 532       int c[7];
 533       int ei[7];
 534       int eo[7];
 535       int xstep[7];
 536       int ystep[7];
 537       int x, y;
 538
 539       int ix0 = bbox->x0 / TILE_SIZE;
 540       int iy0 = bbox->y0 / TILE_SIZE;
 541       int ix1 = bbox->x1 / TILE_SIZE;
 542       int iy1 = bbox->y1 / TILE_SIZE;
 543
 544       for (i = 0; i < nr_planes; i++) {
 545          c[i] = (tri->plane[i].c +
 546                  tri->plane[i].dcdy * iy0 * TILE_SIZE -
 547                  tri->plane[i].dcdx * ix0 * TILE_SIZE);
 548
 549          ei[i] = tri->plane[i].ei << TILE_ORDER;
 550          eo[i] = tri->plane[i].eo << TILE_ORDER;
 551          xstep[i] = -(tri->plane[i].dcdx << TILE_ORDER);
 552          ystep[i] = tri->plane[i].dcdy << TILE_ORDER;
 553       }
 554
 555
 556
 557       /* Test tile-sized blocks against the triangle.
 558        * Discard blocks fully outside the tri.  If the block is fully
 559        * contained inside the tri, bin an lp_rast_shade_tile command.
 560        * Else, bin a lp_rast_triangle command.
 561        */
 562       for (y = iy0; y <= iy1; y++)
 563       {
 564          boolean in = FALSE;  /* are we inside the triangle? */
 565          int cx[7];
 566
 567          for (i = 0; i < nr_planes; i++)
 568             cx[i] = c[i];
 569
 570          for (x = ix0; x <= ix1; x++)
 571          {
 572             int out = 0;
 573             int partial = 0;
 574
 575             for (i = 0; i < nr_planes; i++) {
 576                int planeout = cx[i] + eo[i];
 577                int planepartial = cx[i] + ei[i] - 1;
 578                out |= (planeout >> 31);
 579                partial |= (planepartial >> 31) & (1<<i);
 580             }
 581
 582             if (out) {
 583                /* do nothing */
 584                if (in)
 585                   break;  /* exiting triangle, all done with this row */
 586                LP_COUNT(nr_empty_64);
 587             }
 588             else if (partial) {
 589                /* Not trivially accepted by at least one plane -
 590                 * rasterize/shade partial tile
 591                 */
 592                int count = util_bitcount(partial);
 593                in = TRUE;
 594                if (!lp_scene_bin_command( scene, x, y,
 595                                           lp_rast_tri_tab[count],
 596                                           lp_rast_arg_triangle(tri, partial) ))
 597                   goto fail;
 598
 599                LP_COUNT(nr_partially_covered_64);
 600             }
 601             else {
 602                /* triangle covers the whole tile- shade whole tile */
 603                LP_COUNT(nr_fully_covered_64);
 604                in = TRUE;
 605                if (!lp_setup_whole_tile(setup, &tri->inputs, x, y))
 606                   goto fail;
 607             }
 608
 609             /* Iterate cx values across the region:
 610              */
 611             for (i = 0; i < nr_planes; i++)
 612                cx[i] += xstep[i];
 613          }
 614
 615          /* Iterate c values down the region:
 616           */
 617          for (i = 0; i < nr_planes; i++)
 618             c[i] += ystep[i];
 619       }
 620    }
 621
 622    return TRUE;
 623
 624 fail:
 625    /* Need to disable any partially binned triangle.  This is easier
 626     * than trying to locate all the triangle, shade-tile, etc,
 627     * commands which may have been binned.
 628     */
 629    tri->inputs.disable = TRUE;
 630    return FALSE;
 631 }
 632
 633
 634 /**
 635  * Draw triangle if it's CW, cull otherwise.
 636  */
 637 static void triangle_cw( struct lp_setup_context *setup,
 638                          const float (*v0)[4],
 639                          const float (*v1)[4],
 640                          const float (*v2)[4] )
 641 {
 642    if (!do_triangle_ccw( setup, v1, v0, v2, !setup->ccw_is_frontface ))
 643    {
 644       lp_setup_flush_and_restart(setup);
 645
 646       if (!do_triangle_ccw( setup, v1, v0, v2, !setup->ccw_is_frontface ))
 647          assert(0);
 648    }
 649 }
 650
 651
 652 /**
 653  * Draw triangle if it's CCW, cull otherwise.
 654  */
 655 static void triangle_ccw( struct lp_setup_context *setup,
 656                          const float (*v0)[4],
 657                          const float (*v1)[4],
 658                          const float (*v2)[4] )
 659 {
 660    if (!do_triangle_ccw( setup, v0, v1, v2, setup->ccw_is_frontface ))
 661    {
 662       lp_setup_flush_and_restart(setup);
 663       if (!do_triangle_ccw( setup, v0, v1, v2, setup->ccw_is_frontface ))
 664          assert(0);
 665    }
 666 }
 667
 668
 669
 670 /**
 671  * Draw triangle whether it's CW or CCW.
 672  */
 673 static void triangle_both( struct lp_setup_context *setup,
 674                            const float (*v0)[4],
 675                            const float (*v1)[4],
 676                            const float (*v2)[4] )
 677 {
 678    /* edge vectors e = v0 - v2, f = v1 - v2 */
 679    const float ex = v0[0][0] - v2[0][0];
 680    const float ey = v0[0][1] - v2[0][1];
 681    const float fx = v1[0][0] - v2[0][0];
 682    const float fy = v1[0][1] - v2[0][1];
 683
 684    /* det = cross(e,f).z */
 685    const float det = ex * fy - ey * fx;
 686    if (det < 0.0f)
 687       triangle_ccw( setup, v0, v1, v2 );
 688    else if (det > 0.0f)
 689       triangle_cw( setup, v0, v1, v2 );
 690 }
 691
 692
 693 static void triangle_nop( struct lp_setup_context *setup,
 694                           const float (*v0)[4],
 695                           const float (*v1)[4],
 696                           const float (*v2)[4] )
 697 {
 698 }
 699
 700
 701 void
 702 lp_setup_choose_triangle( struct lp_setup_context *setup )
 703 {
 704    switch (setup->cullmode) {
 705    case PIPE_FACE_NONE:
 706       setup->triangle = triangle_both;
 707       break;
 708    case PIPE_FACE_BACK:
 709       setup->triangle = setup->ccw_is_frontface ? triangle_ccw : triangle_cw;
 710       break;
 711    case PIPE_FACE_FRONT:
 712       setup->triangle = setup->ccw_is_frontface ? triangle_cw : triangle_ccw;
 713       break;
 714    default:
 715       setup->triangle = triangle_nop;
 716       break;
 717    }
 718 }