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
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  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 "lp_perf.h"
  35 #include "lp_setup_context.h"
  36 #include "lp_rast.h"
  37
  38 #define NUM_CHANNELS 4
  39
  40
  41 /**
  42  * Compute a0 for a constant-valued coefficient (GL_FLAT shading).
  43  */
  44 static void constant_coef( struct lp_rast_triangle *tri,
  45                            unsigned slot,
  46                            const float value,
  47                            unsigned i )
  48 {
  49    tri->inputs.a0[slot][i] = value;
  50    tri->inputs.dadx[slot][i] = 0.0f;
  51    tri->inputs.dady[slot][i] = 0.0f;
  52 }
  53
  54
  55 /**
  56  * Compute a0, dadx and dady for a linearly interpolated coefficient,
  57  * for a triangle.
  58  */
  59 static void linear_coef( struct lp_rast_triangle *tri,
  60                          float oneoverarea,
  61                          unsigned slot,
  62                          const float (*v1)[4],
  63                          const float (*v2)[4],
  64                          const float (*v3)[4],
  65                          unsigned vert_attr,
  66                          unsigned i)
  67 {
  68    float a1 = v1[vert_attr][i];
  69    float a2 = v2[vert_attr][i];
  70    float a3 = v3[vert_attr][i];
  71
  72    float da12 = a1 - a2;
  73    float da31 = a3 - a1;
  74    float dadx = (da12 * tri->dy31 - tri->dy12 * da31) * oneoverarea;
  75    float dady = (da31 * tri->dx12 - tri->dx31 * da12) * oneoverarea;
  76
  77    tri->inputs.dadx[slot][i] = dadx;
  78    tri->inputs.dady[slot][i] = dady;
  79
  80    /* calculate a0 as the value which would be sampled for the
  81     * fragment at (0,0), taking into account that we want to sample at
  82     * pixel centers, in other words (0.5, 0.5).
  83     *
  84     * this is neat but unfortunately not a good way to do things for
  85     * triangles with very large values of dadx or dady as it will
  86     * result in the subtraction and re-addition from a0 of a very
  87     * large number, which means we'll end up loosing a lot of the
  88     * fractional bits and precision from a0.  the way to fix this is
  89     * to define a0 as the sample at a pixel center somewhere near vmin
  90     * instead - i'll switch to this later.
  91     */
  92    tri->inputs.a0[slot][i] = (a1 -
  93                               (dadx * (v1[0][0] - 0.5f) +
  94                                dady * (v1[0][1] - 0.5f)));
  95 }
  96
  97
  98 /**
  99  * Compute a0, dadx and dady for a perspective-corrected interpolant,
 100  * for a triangle.
 101  * We basically multiply the vertex value by 1/w before computing
 102  * the plane coefficients (a0, dadx, dady).
 103  * Later, when we compute the value at a particular fragment position we'll
 104  * divide the interpolated value by the interpolated W at that fragment.
 105  */
 106 static void perspective_coef( struct lp_rast_triangle *tri,
 107                               float oneoverarea,
 108                               unsigned slot,
 109                               const float (*v1)[4],
 110                               const float (*v2)[4],
 111                               const float (*v3)[4],
 112                               unsigned vert_attr,
 113                               unsigned i)
 114 {
 115    /* premultiply by 1/w  (v[0][3] is always 1/w):
 116     */
 117    float a1 = v1[vert_attr][i] * v1[0][3];
 118    float a2 = v2[vert_attr][i] * v2[0][3];
 119    float a3 = v3[vert_attr][i] * v3[0][3];
 120    float da12 = a1 - a2;
 121    float da31 = a3 - a1;
 122    float dadx = (da12 * tri->dy31 - tri->dy12 * da31) * oneoverarea;
 123    float dady = (da31 * tri->dx12 - tri->dx31 * da12) * oneoverarea;
 124
 125    tri->inputs.dadx[slot][i] = dadx;
 126    tri->inputs.dady[slot][i] = dady;
 127    tri->inputs.a0[slot][i] = (a1 -
 128                               (dadx * (v1[0][0] - 0.5f) +
 129                                dady * (v1[0][1] - 0.5f)));
 130 }
 131
 132
 133 /**
 134  * Special coefficient setup for gl_FragCoord.
 135  * X and Y are trivial
 136  * Z and W are copied from position_coef which should have already been computed.
 137  * We could do a bit less work if we'd examine gl_FragCoord's swizzle mask.
 138  */
 139 static void
 140 setup_fragcoord_coef(struct lp_rast_triangle *tri,
 141                      float oneoverarea,
 142                      unsigned slot,
 143                      const float (*v1)[4],
 144                      const float (*v2)[4],
 145                      const float (*v3)[4])
 146 {
 147    /*X*/
 148    tri->inputs.a0[slot][0] = 0.0;
 149    tri->inputs.dadx[slot][0] = 1.0;
 150    tri->inputs.dady[slot][0] = 0.0;
 151    /*Y*/
 152    tri->inputs.a0[slot][1] = 0.0;
 153    tri->inputs.dadx[slot][1] = 0.0;
 154    tri->inputs.dady[slot][1] = 1.0;
 155    /*Z*/
 156    linear_coef(tri, oneoverarea, slot, v1, v2, v3, 0, 2);
 157    /*W*/
 158    linear_coef(tri, oneoverarea, slot, v1, v2, v3, 0, 3);
 159 }
 160
 161
 162 static void setup_facing_coef( struct lp_rast_triangle *tri,
 163                                unsigned slot,
 164                                boolean frontface )
 165 {
 166    constant_coef( tri, slot, 1.0f - frontface, 0 );
 167    constant_coef( tri, slot, 0.0f, 1 ); /* wasted */
 168    constant_coef( tri, slot, 0.0f, 2 ); /* wasted */
 169    constant_coef( tri, slot, 0.0f, 3 ); /* wasted */
 170 }
 171
 172
 173 /**
 174  * Compute the tri->coef[] array dadx, dady, a0 values.
 175  */
 176 static void setup_tri_coefficients( struct setup_context *setup,
 177                                     struct lp_rast_triangle *tri,
 178                                     float oneoverarea,
 179                                     const float (*v1)[4],
 180                                     const float (*v2)[4],
 181                                     const float (*v3)[4],
 182                                     boolean frontface)
 183 {
 184    unsigned slot;
 185
 186    /* The internal position input is in slot zero:
 187     */
 188    setup_fragcoord_coef(tri, oneoverarea, 0, v1, v2, v3);
 189
 190    /* setup interpolation for all the remaining attributes:
 191     */
 192    for (slot = 0; slot < setup->fs.nr_inputs; slot++) {
 193       unsigned vert_attr = setup->fs.input[slot].src_index;
 194       unsigned i;
 195
 196       switch (setup->fs.input[slot].interp) {
 197       case LP_INTERP_CONSTANT:
 198          for (i = 0; i < NUM_CHANNELS; i++)
 199             constant_coef(tri, slot+1, v3[vert_attr][i], i);
 200          break;
 201
 202       case LP_INTERP_LINEAR:
 203          for (i = 0; i < NUM_CHANNELS; i++)
 204             linear_coef(tri, oneoverarea, slot+1, v1, v2, v3, vert_attr, i);
 205          break;
 206
 207       case LP_INTERP_PERSPECTIVE:
 208          for (i = 0; i < NUM_CHANNELS; i++)
 209             perspective_coef(tri, oneoverarea, slot+1, v1, v2, v3, vert_attr, i);
 210          break;
 211
 212       case LP_INTERP_POSITION:
 213          /* XXX: fix me - duplicates the values in slot zero.
 214           */
 215          setup_fragcoord_coef(tri, oneoverarea, slot+1, v1, v2, v3);
 216          break;
 217
 218       case LP_INTERP_FACING:
 219          setup_facing_coef(tri, slot+1, frontface);
 220          break;
 221
 222       default:
 223          assert(0);
 224       }
 225    }
 226 }
 227
 228
 229
 230 static inline int subpixel_snap( float a )
 231 {
 232    return util_iround(FIXED_ONE * a - (FIXED_ONE / 2));
 233 }
 234
 235
 236
 237 /**
 238  * Alloc space for a new triangle plus the input.a0/dadx/dady arrays
 239  * immediately after it.
 240  * The memory is allocated from the per-scene pool, not per-tile.
 241  * \param tri_size  returns number of bytes allocated
 242  * \param nr_inputs  number of fragment shader inputs
 243  * \return pointer to triangle space
 244  */
 245 static INLINE struct lp_rast_triangle *
 246 alloc_triangle(struct lp_scene *scene, unsigned nr_inputs, unsigned *tri_size)
 247 {
 248    unsigned input_array_sz = NUM_CHANNELS * (nr_inputs + 1) * sizeof(float);
 249    struct lp_rast_triangle *tri;
 250    unsigned bytes;
 251    char *inputs;
 252
 253    assert(sizeof(*tri) % 16 == 0);
 254
 255    bytes = sizeof(*tri) + (3 * input_array_sz);
 256
 257    tri = lp_scene_alloc_aligned( scene, bytes, 16 );
 258
 259    inputs = (char *) (tri + 1);
 260    tri->inputs.a0   = (float (*)[4]) inputs;
 261    tri->inputs.dadx = (float (*)[4]) (inputs + input_array_sz);
 262    tri->inputs.dady = (float (*)[4]) (inputs + 2 * input_array_sz);
 263
 264    *tri_size = bytes;
 265
 266    return tri;
 267 }
 268
 269
 270
 271 /**
 272  * Do basic setup for triangle rasterization and determine which
 273  * framebuffer tiles are touched.  Put the triangle in the scene's
 274  * bins for the tiles which we overlap.
 275  */
 276 static void
 277 do_triangle_ccw(struct setup_context *setup,
 278                 const float (*v1)[4],
 279                 const float (*v2)[4],
 280                 const float (*v3)[4],
 281                 boolean frontfacing )
 282 {
 283    /* x/y positions in fixed point */
 284    const int x1 = subpixel_snap(v1[0][0]);
 285    const int x2 = subpixel_snap(v2[0][0]);
 286    const int x3 = subpixel_snap(v3[0][0]);
 287    const int y1 = subpixel_snap(v1[0][1]);
 288    const int y2 = subpixel_snap(v2[0][1]);
 289    const int y3 = subpixel_snap(v3[0][1]);
 290
 291    struct lp_scene *scene = lp_setup_get_current_scene(setup);
 292    struct lp_rast_triangle *tri;
 293    int area;
 294    float oneoverarea;
 295    int minx, maxx, miny, maxy;
 296    unsigned tri_bytes;
 297
 298    tri = alloc_triangle(scene, setup->fs.nr_inputs, &tri_bytes);
 299
 300    tri->dx12 = x1 - x2;
 301    tri->dx23 = x2 - x3;
 302    tri->dx31 = x3 - x1;
 303
 304    tri->dy12 = y1 - y2;
 305    tri->dy23 = y2 - y3;
 306    tri->dy31 = y3 - y1;
 307
 308    area = (tri->dx12 * tri->dy31 - tri->dx31 * tri->dy12);
 309
 310    LP_COUNT(nr_tris);
 311
 312    /* Cull non-ccw and zero-sized triangles.
 313     *
 314     * XXX: subject to overflow??
 315     */
 316    if (area <= 0) {
 317       lp_scene_putback_data( scene, tri_bytes );
 318       LP_COUNT(nr_culled_tris);
 319       return;
 320    }
 321
 322    /* Bounding rectangle (in pixels) */
 323    minx = (MIN3(x1, x2, x3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 324    maxx = (MAX3(x1, x2, x3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 325    miny = (MIN3(y1, y2, y3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 326    maxy = (MAX3(y1, y2, y3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 327
 328    if (setup->scissor_test) {
 329       minx = MAX2(minx, setup->scissor.current.minx);
 330       maxx = MIN2(maxx, setup->scissor.current.maxx);
 331       miny = MAX2(miny, setup->scissor.current.miny);
 332       maxy = MIN2(maxy, setup->scissor.current.maxy);
 333    }
 334
 335    if (miny == maxy ||
 336        minx == maxx) {
 337       lp_scene_putback_data( scene, tri_bytes );
 338       LP_COUNT(nr_culled_tris);
 339       return;
 340    }
 341
 342    /*
 343     */
 344    oneoverarea = ((float)FIXED_ONE) / (float)area;
 345
 346    /* Setup parameter interpolants:
 347     */
 348    setup_tri_coefficients( setup, tri, oneoverarea, v1, v2, v3, frontfacing );
 349
 350    /* half-edge constants, will be interated over the whole render target.
 351     */
 352    tri->c1 = tri->dy12 * x1 - tri->dx12 * y1;
 353    tri->c2 = tri->dy23 * x2 - tri->dx23 * y2;
 354    tri->c3 = tri->dy31 * x3 - tri->dx31 * y3;
 355
 356    /* correct for top-left fill convention:
 357     */
 358    if (tri->dy12 < 0 || (tri->dy12 == 0 && tri->dx12 > 0)) tri->c1++;
 359    if (tri->dy23 < 0 || (tri->dy23 == 0 && tri->dx23 > 0)) tri->c2++;
 360    if (tri->dy31 < 0 || (tri->dy31 == 0 && tri->dx31 > 0)) tri->c3++;
 361
 362    tri->dy12 *= FIXED_ONE;
 363    tri->dy23 *= FIXED_ONE;
 364    tri->dy31 *= FIXED_ONE;
 365
 366    tri->dx12 *= FIXED_ONE;
 367    tri->dx23 *= FIXED_ONE;
 368    tri->dx31 *= FIXED_ONE;
 369
 370    /* find trivial reject offsets for each edge for a single-pixel
 371     * sized block.  These will be scaled up at each recursive level to
 372     * match the active blocksize.  Scaling in this way works best if
 373     * the blocks are square.
 374     */
 375    tri->eo1 = 0;
 376    if (tri->dy12 < 0) tri->eo1 -= tri->dy12;
 377    if (tri->dx12 > 0) tri->eo1 += tri->dx12;
 378
 379    tri->eo2 = 0;
 380    if (tri->dy23 < 0) tri->eo2 -= tri->dy23;
 381    if (tri->dx23 > 0) tri->eo2 += tri->dx23;
 382
 383    tri->eo3 = 0;
 384    if (tri->dy31 < 0) tri->eo3 -= tri->dy31;
 385    if (tri->dx31 > 0) tri->eo3 += tri->dx31;
 386
 387    /* Calculate trivial accept offsets from the above.
 388     */
 389    tri->ei1 = tri->dx12 - tri->dy12 - tri->eo1;
 390    tri->ei2 = tri->dx23 - tri->dy23 - tri->eo2;
 391    tri->ei3 = tri->dx31 - tri->dy31 - tri->eo3;
 392
 393    /* Fill in the inputs.step[][] arrays.
 394     * We've manually unrolled some loops here.
 395     */
 396    {
 397       const int xstep1 = -tri->dy12;
 398       const int xstep2 = -tri->dy23;
 399       const int xstep3 = -tri->dy31;
 400       const int ystep1 = tri->dx12;
 401       const int ystep2 = tri->dx23;
 402       const int ystep3 = tri->dx31;
 403
 404 #define SETUP_STEP(i, x, y)                                \
 405       do {                                                 \
 406          tri->inputs.step[0][i] = x * xstep1 + y * ystep1; \
 407          tri->inputs.step[1][i] = x * xstep2 + y * ystep2; \
 408          tri->inputs.step[2][i] = x * xstep3 + y * ystep3; \
 409       } while (0)
 410
 411       SETUP_STEP(0, 0, 0);
 412       SETUP_STEP(1, 1, 0);
 413       SETUP_STEP(2, 0, 1);
 414       SETUP_STEP(3, 1, 1);
 415
 416       SETUP_STEP(4, 2, 0);
 417       SETUP_STEP(5, 3, 0);
 418       SETUP_STEP(6, 2, 1);
 419       SETUP_STEP(7, 3, 1);
 420
 421       SETUP_STEP(8, 0, 2);
 422       SETUP_STEP(9, 1, 2);
 423       SETUP_STEP(10, 0, 3);
 424       SETUP_STEP(11, 1, 3);
 425
 426       SETUP_STEP(12, 2, 2);
 427       SETUP_STEP(13, 3, 2);
 428       SETUP_STEP(14, 2, 3);
 429       SETUP_STEP(15, 3, 3);
 430 #undef STEP
 431    }
 432
 433    /*
 434     * All fields of 'tri' are now set.  The remaining code here is
 435     * concerned with binning.
 436     */
 437
 438    /* Convert to tile coordinates:
 439     */
 440    minx = minx / TILE_SIZE;
 441    miny = miny / TILE_SIZE;
 442    maxx = maxx / TILE_SIZE;
 443    maxy = maxy / TILE_SIZE;
 444
 445    /* Clamp maxx, maxy to framebuffer size
 446     */
 447    maxx = MIN2(maxx, scene->tiles_x - 1);
 448    maxy = MIN2(maxy, scene->tiles_y - 1);
 449
 450    /* Determine which tile(s) intersect the triangle's bounding box
 451     */
 452    if (miny == maxy && minx == maxx)
 453    {
 454       /* Triangle is contained in a single tile:
 455        */
 456       lp_scene_bin_command( scene, minx, miny, lp_rast_triangle,
 457                             lp_rast_arg_triangle(tri) );
 458    }
 459    else
 460    {
 461       int c1 = (tri->c1 +
 462                 tri->dx12 * miny * TILE_SIZE -
 463                 tri->dy12 * minx * TILE_SIZE);
 464       int c2 = (tri->c2 +
 465                 tri->dx23 * miny * TILE_SIZE -
 466                 tri->dy23 * minx * TILE_SIZE);
 467       int c3 = (tri->c3 +
 468                 tri->dx31 * miny * TILE_SIZE -
 469                 tri->dy31 * minx * TILE_SIZE);
 470
 471       int ei1 = tri->ei1 << TILE_ORDER;
 472       int ei2 = tri->ei2 << TILE_ORDER;
 473       int ei3 = tri->ei3 << TILE_ORDER;
 474
 475       int eo1 = tri->eo1 << TILE_ORDER;
 476       int eo2 = tri->eo2 << TILE_ORDER;
 477       int eo3 = tri->eo3 << TILE_ORDER;
 478
 479       int xstep1 = -(tri->dy12 << TILE_ORDER);
 480       int xstep2 = -(tri->dy23 << TILE_ORDER);
 481       int xstep3 = -(tri->dy31 << TILE_ORDER);
 482
 483       int ystep1 = tri->dx12 << TILE_ORDER;
 484       int ystep2 = tri->dx23 << TILE_ORDER;
 485       int ystep3 = tri->dx31 << TILE_ORDER;
 486       int x, y;
 487
 488
 489       /* Test tile-sized blocks against the triangle.
 490        * Discard blocks fully outside the tri.  If the block is fully
 491        * contained inside the tri, bin an lp_rast_shade_tile command.
 492        * Else, bin a lp_rast_triangle command.
 493        */
 494       for (y = miny; y <= maxy; y++)
 495       {
 496          int cx1 = c1;
 497          int cx2 = c2;
 498          int cx3 = c3;
 499          boolean in = FALSE;  /* are we inside the triangle? */
 500
 501          for (x = minx; x <= maxx; x++)
 502          {
 503             if (cx1 + eo1 < 0 ||
 504                 cx2 + eo2 < 0 ||
 505                 cx3 + eo3 < 0)
 506             {
 507                /* do nothing */
 508                LP_COUNT(nr_empty_64);
 509                if (in)
 510                   break;  /* exiting triangle, all done with this row */
 511             }
 512             else if (cx1 + ei1 > 0 &&
 513                      cx2 + ei2 > 0 &&
 514                      cx3 + ei3 > 0)
 515             {
 516                /* triangle covers the whole tile- shade whole tile */
 517                LP_COUNT(nr_fully_covered_64);
 518                in = TRUE;
 519                if(setup->fs.current.opaque) {
 520                   lp_scene_bin_reset( scene, x, y );
 521                   lp_scene_bin_command( scene, x, y,
 522                                         lp_rast_set_state,
 523                                         lp_rast_arg_state(setup->fs.stored) );
 524                }
 525                lp_scene_bin_command( scene, x, y,
 526                                      lp_rast_shade_tile,
 527                                      lp_rast_arg_inputs(&tri->inputs) );
 528             }
 529             else
 530             {
 531                /* rasterizer/shade partial tile */
 532                LP_COUNT(nr_partially_covered_64);
 533                in = TRUE;
 534                lp_scene_bin_command( scene, x, y,
 535                                      lp_rast_triangle,
 536                                      lp_rast_arg_triangle(tri) );
 537             }
 538
 539             /* Iterate cx values across the region:
 540              */
 541             cx1 += xstep1;
 542             cx2 += xstep2;
 543             cx3 += xstep3;
 544          }
 545
 546          /* Iterate c values down the region:
 547           */
 548          c1 += ystep1;
 549          c2 += ystep2;
 550          c3 += ystep3;
 551       }
 552    }
 553 }
 554
 555
 556 static void triangle_cw( struct setup_context *setup,
 557                          const float (*v0)[4],
 558                          const float (*v1)[4],
 559                          const float (*v2)[4] )
 560 {
 561    do_triangle_ccw( setup, v1, v0, v2, !setup->ccw_is_frontface );
 562 }
 563
 564
 565 static void triangle_ccw( struct setup_context *setup,
 566                          const float (*v0)[4],
 567                          const float (*v1)[4],
 568                          const float (*v2)[4] )
 569 {
 570    do_triangle_ccw( setup, v0, v1, v2, setup->ccw_is_frontface );
 571 }
 572
 573
 574 static void triangle_both( struct setup_context *setup,
 575                            const float (*v0)[4],
 576                            const float (*v1)[4],
 577                            const float (*v2)[4] )
 578 {
 579    /* edge vectors e = v0 - v2, f = v1 - v2 */
 580    const float ex = v0[0][0] - v2[0][0];
 581    const float ey = v0[0][1] - v2[0][1];
 582    const float fx = v1[0][0] - v2[0][0];
 583    const float fy = v1[0][1] - v2[0][1];
 584
 585    /* det = cross(e,f).z */
 586    if (ex * fy - ey * fx < 0.0f)
 587       triangle_ccw( setup, v0, v1, v2 );
 588    else
 589       triangle_cw( setup, v0, v1, v2 );
 590 }
 591
 592
 593 static void triangle_nop( struct setup_context *setup,
 594                           const float (*v0)[4],
 595                           const float (*v1)[4],
 596                           const float (*v2)[4] )
 597 {
 598 }
 599
 600
 601 void
 602 lp_setup_choose_triangle( struct setup_context *setup )
 603 {
 604    switch (setup->cullmode) {
 605    case PIPE_WINDING_NONE:
 606       setup->triangle = triangle_both;
 607       break;
 608    case PIPE_WINDING_CCW:
 609       setup->triangle = triangle_cw;
 610       break;
 611    case PIPE_WINDING_CW:
 612       setup->triangle = triangle_ccw;
 613       break;
 614    default:
 615       setup->triangle = triangle_nop;
 616       break;
 617    }
 618 }