src/gallium/drivers/llvmpipe/lp_setup_tri.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
   5  *
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  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
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  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_setup_context *setup,
  45                            struct lp_rast_triangle *tri,
  46                            unsigned slot,
  47                            const float value,
  48                            unsigned i )
  49 {
  50    tri->inputs.a0[slot][i] = value;
  51    tri->inputs.dadx[slot][i] = 0.0f;
  52    tri->inputs.dady[slot][i] = 0.0f;
  53 }
  54
  55
  56 /**
  57  * Compute a0, dadx and dady for a linearly interpolated coefficient,
  58  * for a triangle.
  59  */
  60 static void linear_coef( struct lp_setup_context *setup,
  61                          struct lp_rast_triangle *tri,
  62                          float oneoverarea,
  63                          unsigned slot,
  64                          const float (*v1)[4],
  65                          const float (*v2)[4],
  66                          const float (*v3)[4],
  67                          unsigned vert_attr,
  68                          unsigned i)
  69 {
  70    float a1 = v1[vert_attr][i];
  71    float a2 = v2[vert_attr][i];
  72    float a3 = v3[vert_attr][i];
  73
  74    float da12 = a1 - a2;
  75    float da31 = a3 - a1;
  76    float dadx = (da12 * tri->dy31 - tri->dy12 * da31) * oneoverarea;
  77    float dady = (da31 * tri->dx12 - tri->dx31 * da12) * oneoverarea;
  78
  79    tri->inputs.dadx[slot][i] = dadx;
  80    tri->inputs.dady[slot][i] = dady;
  81
  82    /* calculate a0 as the value which would be sampled for the
  83     * fragment at (0,0), taking into account that we want to sample at
  84     * pixel centers, in other words (0.5, 0.5).
  85     *
  86     * this is neat but unfortunately not a good way to do things for
  87     * triangles with very large values of dadx or dady as it will
  88     * result in the subtraction and re-addition from a0 of a very
  89     * large number, which means we'll end up loosing a lot of the
  90     * fractional bits and precision from a0.  the way to fix this is
  91     * to define a0 as the sample at a pixel center somewhere near vmin
  92     * instead - i'll switch to this later.
  93     */
  94    tri->inputs.a0[slot][i] = (a1 -
  95                               (dadx * (v1[0][0] - setup->pixel_offset) +
  96                                dady * (v1[0][1] - setup->pixel_offset)));
  97 }
  98
  99
 100 /**
 101  * Compute a0, dadx and dady for a perspective-corrected interpolant,
 102  * for a triangle.
 103  * We basically multiply the vertex value by 1/w before computing
 104  * the plane coefficients (a0, dadx, dady).
 105  * Later, when we compute the value at a particular fragment position we'll
 106  * divide the interpolated value by the interpolated W at that fragment.
 107  */
 108 static void perspective_coef( struct lp_setup_context *setup,
 109                               struct lp_rast_triangle *tri,
 110                               float oneoverarea,
 111                               unsigned slot,
 112                               const float (*v1)[4],
 113                               const float (*v2)[4],
 114                               const float (*v3)[4],
 115                               unsigned vert_attr,
 116                               unsigned i)
 117 {
 118    /* premultiply by 1/w  (v[0][3] is always 1/w):
 119     */
 120    float a1 = v1[vert_attr][i] * v1[0][3];
 121    float a2 = v2[vert_attr][i] * v2[0][3];
 122    float a3 = v3[vert_attr][i] * v3[0][3];
 123    float da12 = a1 - a2;
 124    float da31 = a3 - a1;
 125    float dadx = (da12 * tri->dy31 - tri->dy12 * da31) * oneoverarea;
 126    float dady = (da31 * tri->dx12 - tri->dx31 * da12) * oneoverarea;
 127
 128    tri->inputs.dadx[slot][i] = dadx;
 129    tri->inputs.dady[slot][i] = dady;
 130    tri->inputs.a0[slot][i] = (a1 -
 131                               (dadx * (v1[0][0] - setup->pixel_offset) +
 132                                dady * (v1[0][1] - setup->pixel_offset)));
 133 }
 134
 135
 136 /**
 137  * Special coefficient setup for gl_FragCoord.
 138  * X and Y are trivial
 139  * Z and W are copied from position_coef which should have already been computed.
 140  * We could do a bit less work if we'd examine gl_FragCoord's swizzle mask.
 141  */
 142 static void
 143 setup_fragcoord_coef(struct lp_setup_context *setup,
 144                      struct lp_rast_triangle *tri,
 145                      float oneoverarea,
 146                      unsigned slot,
 147                      const float (*v1)[4],
 148                      const float (*v2)[4],
 149                      const float (*v3)[4])
 150 {
 151    /*X*/
 152    tri->inputs.a0[slot][0] = 0.0;
 153    tri->inputs.dadx[slot][0] = 1.0;
 154    tri->inputs.dady[slot][0] = 0.0;
 155    /*Y*/
 156    tri->inputs.a0[slot][1] = 0.0;
 157    tri->inputs.dadx[slot][1] = 0.0;
 158    tri->inputs.dady[slot][1] = 1.0;
 159    /*Z*/
 160    linear_coef(setup, tri, oneoverarea, slot, v1, v2, v3, 0, 2);
 161    /*W*/
 162    linear_coef(setup, tri, oneoverarea, slot, v1, v2, v3, 0, 3);
 163 }
 164
 165
 166 static void setup_facing_coef( struct lp_setup_context *setup,
 167                                struct lp_rast_triangle *tri,
 168                                unsigned slot,
 169                                boolean frontface )
 170 {
 171    constant_coef( setup, tri, slot, 1.0f - frontface, 0 );
 172    constant_coef( setup, tri, slot, 0.0f, 1 ); /* wasted */
 173    constant_coef( setup, tri, slot, 0.0f, 2 ); /* wasted */
 174    constant_coef( setup, tri, slot, 0.0f, 3 ); /* wasted */
 175 }
 176
 177
 178 /**
 179  * Compute the tri->coef[] array dadx, dady, a0 values.
 180  */
 181 static void setup_tri_coefficients( struct lp_setup_context *setup,
 182                                     struct lp_rast_triangle *tri,
 183                                     float oneoverarea,
 184                                     const float (*v1)[4],
 185                                     const float (*v2)[4],
 186                                     const float (*v3)[4],
 187                                     boolean frontface)
 188 {
 189    unsigned slot;
 190
 191    /* The internal position input is in slot zero:
 192     */
 193    setup_fragcoord_coef(setup, tri, oneoverarea, 0, v1, v2, v3);
 194
 195    /* setup interpolation for all the remaining attributes:
 196     */
 197    for (slot = 0; slot < setup->fs.nr_inputs; slot++) {
 198       unsigned vert_attr = setup->fs.input[slot].src_index;
 199       unsigned i;
 200
 201       switch (setup->fs.input[slot].interp) {
 202       case LP_INTERP_CONSTANT:
 203          for (i = 0; i < NUM_CHANNELS; i++)
 204             constant_coef(setup, tri, slot+1, v3[vert_attr][i], i);
 205          break;
 206
 207       case LP_INTERP_LINEAR:
 208          for (i = 0; i < NUM_CHANNELS; i++)
 209             linear_coef(setup, tri, oneoverarea, slot+1, v1, v2, v3, vert_attr, i);
 210          break;
 211
 212       case LP_INTERP_PERSPECTIVE:
 213          for (i = 0; i < NUM_CHANNELS; i++)
 214             perspective_coef(setup, tri, oneoverarea, slot+1, v1, v2, v3, vert_attr, i);
 215          break;
 216
 217       case LP_INTERP_POSITION:
 218          /* XXX: fix me - duplicates the values in slot zero.
 219           */
 220          setup_fragcoord_coef(setup, tri, oneoverarea, slot+1, v1, v2, v3);
 221          break;
 222
 223       case LP_INTERP_FACING:
 224          setup_facing_coef(setup, tri, slot+1, frontface);
 225          break;
 226
 227       default:
 228          assert(0);
 229       }
 230    }
 231 }
 232
 233
 234
 235 static INLINE int subpixel_snap( float a )
 236 {
 237    return util_iround(FIXED_ONE * a - (FIXED_ONE / 2));
 238 }
 239
 240
 241
 242 /**
 243  * Alloc space for a new triangle plus the input.a0/dadx/dady arrays
 244  * immediately after it.
 245  * The memory is allocated from the per-scene pool, not per-tile.
 246  * \param tri_size  returns number of bytes allocated
 247  * \param nr_inputs  number of fragment shader inputs
 248  * \return pointer to triangle space
 249  */
 250 static INLINE struct lp_rast_triangle *
 251 alloc_triangle(struct lp_scene *scene, unsigned nr_inputs, unsigned *tri_size)
 252 {
 253    unsigned input_array_sz = NUM_CHANNELS * (nr_inputs + 1) * sizeof(float);
 254    struct lp_rast_triangle *tri;
 255    unsigned bytes;
 256    char *inputs;
 257
 258    assert(sizeof(*tri) % 16 == 0);
 259
 260    bytes = sizeof(*tri) + (3 * input_array_sz);
 261
 262    tri = lp_scene_alloc_aligned( scene, bytes, 16 );
 263
 264    inputs = (char *) (tri + 1);
 265    tri->inputs.a0   = (float (*)[4]) inputs;
 266    tri->inputs.dadx = (float (*)[4]) (inputs + input_array_sz);
 267    tri->inputs.dady = (float (*)[4]) (inputs + 2 * input_array_sz);
 268
 269    *tri_size = bytes;
 270
 271    return tri;
 272 }
 273
 274
 275 /**
 276  * Print triangle vertex attribs (for debug).
 277  */
 278 static void
 279 print_triangle(struct lp_setup_context *setup,
 280                const float (*v1)[4],
 281                const float (*v2)[4],
 282                const float (*v3)[4])
 283 {
 284    uint i;
 285
 286    debug_printf("llvmpipe triangle\n");
 287    for (i = 0; i < setup->fs.nr_inputs; i++) {
 288       debug_printf("  v1[%d]:  %f %f %f %f\n", i,
 289                    v1[i][0], v1[i][1], v1[i][2], v1[i][3]);
 290    }
 291    for (i = 0; i < setup->fs.nr_inputs; i++) {
 292       debug_printf("  v2[%d]:  %f %f %f %f\n", i,
 293                    v2[i][0], v2[i][1], v2[i][2], v2[i][3]);
 294    }
 295    for (i = 0; i < setup->fs.nr_inputs; i++) {
 296       debug_printf("  v3[%d]:  %f %f %f %f\n", i,
 297                    v3[i][0], v3[i][1], v3[i][2], v3[i][3]);
 298    }
 299 }
 300
 301
 302 /**
 303  * Do basic setup for triangle rasterization and determine which
 304  * framebuffer tiles are touched.  Put the triangle in the scene's
 305  * bins for the tiles which we overlap.
 306  */
 307 static void
 308 do_triangle_ccw(struct lp_setup_context *setup,
 309                 const float (*v1)[4],
 310                 const float (*v2)[4],
 311                 const float (*v3)[4],
 312                 boolean frontfacing )
 313 {
 314    /* x/y positions in fixed point */
 315    const int x1 = subpixel_snap(v1[0][0] + 0.5 - setup->pixel_offset);
 316    const int x2 = subpixel_snap(v2[0][0] + 0.5 - setup->pixel_offset);
 317    const int x3 = subpixel_snap(v3[0][0] + 0.5 - setup->pixel_offset);
 318    const int y1 = subpixel_snap(v1[0][1] + 0.5 - setup->pixel_offset);
 319    const int y2 = subpixel_snap(v2[0][1] + 0.5 - setup->pixel_offset);
 320    const int y3 = subpixel_snap(v3[0][1] + 0.5 - setup->pixel_offset);
 321
 322    struct lp_scene *scene = lp_setup_get_current_scene(setup);
 323    struct lp_rast_triangle *tri;
 324    int area;
 325    float oneoverarea;
 326    int minx, maxx, miny, maxy;
 327    unsigned tri_bytes;
 328
 329    if (0)
 330       print_triangle(setup, v1, v2, v3);
 331
 332    tri = alloc_triangle(scene, setup->fs.nr_inputs, &tri_bytes);
 333
 334 #ifdef DEBUG
 335    tri->v[0][0] = v1[0][0];
 336    tri->v[1][0] = v2[0][0];
 337    tri->v[2][0] = v3[0][0];
 338    tri->v[0][1] = v1[0][1];
 339    tri->v[1][1] = v2[0][1];
 340    tri->v[2][1] = v3[0][1];
 341 #endif
 342
 343    tri->dx12 = x1 - x2;
 344    tri->dx23 = x2 - x3;
 345    tri->dx31 = x3 - x1;
 346
 347    tri->dy12 = y1 - y2;
 348    tri->dy23 = y2 - y3;
 349    tri->dy31 = y3 - y1;
 350
 351    area = (tri->dx12 * tri->dy31 - tri->dx31 * tri->dy12);
 352
 353    LP_COUNT(nr_tris);
 354
 355    /* Cull non-ccw and zero-sized triangles.
 356     *
 357     * XXX: subject to overflow??
 358     */
 359    if (area <= 0) {
 360       lp_scene_putback_data( scene, tri_bytes );
 361       LP_COUNT(nr_culled_tris);
 362       return;
 363    }
 364
 365    /* Bounding rectangle (in pixels) */
 366    minx = (MIN3(x1, x2, x3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 367    maxx = (MAX3(x1, x2, x3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 368    miny = (MIN3(y1, y2, y3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 369    maxy = (MAX3(y1, y2, y3) + (FIXED_ONE-1)) >> FIXED_ORDER;
 370
 371    if (setup->scissor_test) {
 372       minx = MAX2(minx, setup->scissor.current.minx);
 373       maxx = MIN2(maxx, setup->scissor.current.maxx);
 374       miny = MAX2(miny, setup->scissor.current.miny);
 375       maxy = MIN2(maxy, setup->scissor.current.maxy);
 376    }
 377
 378    if (miny == maxy ||
 379        minx == maxx) {
 380       lp_scene_putback_data( scene, tri_bytes );
 381       LP_COUNT(nr_culled_tris);
 382       return;
 383    }
 384
 385    /*
 386     */
 387    oneoverarea = ((float)FIXED_ONE) / (float)area;
 388
 389    /* Setup parameter interpolants:
 390     */
 391    setup_tri_coefficients( setup, tri, oneoverarea, v1, v2, v3, frontfacing );
 392
 393    tri->inputs.facing = frontfacing ? 1.0F : -1.0F;
 394
 395    /* half-edge constants, will be interated over the whole render target.
 396     */
 397    tri->c1 = tri->dy12 * x1 - tri->dx12 * y1;
 398    tri->c2 = tri->dy23 * x2 - tri->dx23 * y2;
 399    tri->c3 = tri->dy31 * x3 - tri->dx31 * y3;
 400
 401    /* correct for top-left fill convention:
 402     */
 403    if (tri->dy12 < 0 || (tri->dy12 == 0 && tri->dx12 > 0)) tri->c1++;
 404    if (tri->dy23 < 0 || (tri->dy23 == 0 && tri->dx23 > 0)) tri->c2++;
 405    if (tri->dy31 < 0 || (tri->dy31 == 0 && tri->dx31 > 0)) tri->c3++;
 406
 407    tri->dy12 *= FIXED_ONE;
 408    tri->dy23 *= FIXED_ONE;
 409    tri->dy31 *= FIXED_ONE;
 410
 411    tri->dx12 *= FIXED_ONE;
 412    tri->dx23 *= FIXED_ONE;
 413    tri->dx31 *= FIXED_ONE;
 414
 415    /* find trivial reject offsets for each edge for a single-pixel
 416     * sized block.  These will be scaled up at each recursive level to
 417     * match the active blocksize.  Scaling in this way works best if
 418     * the blocks are square.
 419     */
 420    tri->eo1 = 0;
 421    if (tri->dy12 < 0) tri->eo1 -= tri->dy12;
 422    if (tri->dx12 > 0) tri->eo1 += tri->dx12;
 423
 424    tri->eo2 = 0;
 425    if (tri->dy23 < 0) tri->eo2 -= tri->dy23;
 426    if (tri->dx23 > 0) tri->eo2 += tri->dx23;
 427
 428    tri->eo3 = 0;
 429    if (tri->dy31 < 0) tri->eo3 -= tri->dy31;
 430    if (tri->dx31 > 0) tri->eo3 += tri->dx31;
 431
 432    /* Calculate trivial accept offsets from the above.
 433     */
 434    tri->ei1 = tri->dx12 - tri->dy12 - tri->eo1;
 435    tri->ei2 = tri->dx23 - tri->dy23 - tri->eo2;
 436    tri->ei3 = tri->dx31 - tri->dy31 - tri->eo3;
 437
 438    /* Fill in the inputs.step[][] arrays.
 439     * We've manually unrolled some loops here.
 440     */
 441    {
 442       const int xstep1 = -tri->dy12;
 443       const int xstep2 = -tri->dy23;
 444       const int xstep3 = -tri->dy31;
 445       const int ystep1 = tri->dx12;
 446       const int ystep2 = tri->dx23;
 447       const int ystep3 = tri->dx31;
 448
 449 #define SETUP_STEP(i, x, y)                                \
 450       do {                                                 \
 451          tri->inputs.step[0][i] = x * xstep1 + y * ystep1; \
 452          tri->inputs.step[1][i] = x * xstep2 + y * ystep2; \
 453          tri->inputs.step[2][i] = x * xstep3 + y * ystep3; \
 454       } while (0)
 455
 456       SETUP_STEP(0, 0, 0);
 457       SETUP_STEP(1, 1, 0);
 458       SETUP_STEP(2, 0, 1);
 459       SETUP_STEP(3, 1, 1);
 460
 461       SETUP_STEP(4, 2, 0);
 462       SETUP_STEP(5, 3, 0);
 463       SETUP_STEP(6, 2, 1);
 464       SETUP_STEP(7, 3, 1);
 465
 466       SETUP_STEP(8, 0, 2);
 467       SETUP_STEP(9, 1, 2);
 468       SETUP_STEP(10, 0, 3);
 469       SETUP_STEP(11, 1, 3);
 470
 471       SETUP_STEP(12, 2, 2);
 472       SETUP_STEP(13, 3, 2);
 473       SETUP_STEP(14, 2, 3);
 474       SETUP_STEP(15, 3, 3);
 475 #undef STEP
 476    }
 477
 478    /*
 479     * All fields of 'tri' are now set.  The remaining code here is
 480     * concerned with binning.
 481     */
 482
 483    /* Convert to tile coordinates:
 484     */
 485    minx = minx / TILE_SIZE;
 486    miny = miny / TILE_SIZE;
 487    maxx = maxx / TILE_SIZE;
 488    maxy = maxy / TILE_SIZE;
 489
 490    /*
 491     * Clamp to framebuffer size
 492     */
 493    minx = MAX2(minx, 0);
 494    miny = MAX2(miny, 0);
 495    maxx = MIN2(maxx, scene->tiles_x - 1);
 496    maxy = MIN2(maxy, scene->tiles_y - 1);
 497
 498    /* Determine which tile(s) intersect the triangle's bounding box
 499     */
 500    if (miny == maxy && minx == maxx)
 501    {
 502       /* Triangle is contained in a single tile:
 503        */
 504       lp_scene_bin_command( scene, minx, miny, lp_rast_triangle,
 505                             lp_rast_arg_triangle(tri) );
 506    }
 507    else
 508    {
 509       int c1 = (tri->c1 +
 510                 tri->dx12 * miny * TILE_SIZE -
 511                 tri->dy12 * minx * TILE_SIZE);
 512       int c2 = (tri->c2 +
 513                 tri->dx23 * miny * TILE_SIZE -
 514                 tri->dy23 * minx * TILE_SIZE);
 515       int c3 = (tri->c3 +
 516                 tri->dx31 * miny * TILE_SIZE -
 517                 tri->dy31 * minx * TILE_SIZE);
 518
 519       int ei1 = tri->ei1 << TILE_ORDER;
 520       int ei2 = tri->ei2 << TILE_ORDER;
 521       int ei3 = tri->ei3 << TILE_ORDER;
 522
 523       int eo1 = tri->eo1 << TILE_ORDER;
 524       int eo2 = tri->eo2 << TILE_ORDER;
 525       int eo3 = tri->eo3 << TILE_ORDER;
 526
 527       int xstep1 = -(tri->dy12 << TILE_ORDER);
 528       int xstep2 = -(tri->dy23 << TILE_ORDER);
 529       int xstep3 = -(tri->dy31 << TILE_ORDER);
 530
 531       int ystep1 = tri->dx12 << TILE_ORDER;
 532       int ystep2 = tri->dx23 << TILE_ORDER;
 533       int ystep3 = tri->dx31 << TILE_ORDER;
 534       int x, y;
 535
 536
 537       /* Test tile-sized blocks against the triangle.
 538        * Discard blocks fully outside the tri.  If the block is fully
 539        * contained inside the tri, bin an lp_rast_shade_tile command.
 540        * Else, bin a lp_rast_triangle command.
 541        */
 542       for (y = miny; y <= maxy; y++)
 543       {
 544          int cx1 = c1;
 545          int cx2 = c2;
 546          int cx3 = c3;
 547          boolean in = FALSE;  /* are we inside the triangle? */
 548
 549          for (x = minx; x <= maxx; x++)
 550          {
 551             if (cx1 + eo1 < 0 ||
 552                 cx2 + eo2 < 0 ||
 553                 cx3 + eo3 < 0)
 554             {
 555                /* do nothing */
 556                LP_COUNT(nr_empty_64);
 557                if (in)
 558                   break;  /* exiting triangle, all done with this row */
 559             }
 560             else if (cx1 + ei1 > 0 &&
 561                      cx2 + ei2 > 0 &&
 562                      cx3 + ei3 > 0)
 563             {
 564                /* triangle covers the whole tile- shade whole tile */
 565                LP_COUNT(nr_fully_covered_64);
 566                in = TRUE;
 567                if(setup->fs.current.opaque) {
 568                   lp_scene_bin_reset( scene, x, y );
 569                   lp_scene_bin_command( scene, x, y,
 570                                         lp_rast_set_state,
 571                                         lp_rast_arg_state(setup->fs.stored) );
 572                }
 573                lp_scene_bin_command( scene, x, y,
 574                                      lp_rast_shade_tile,
 575                                      lp_rast_arg_inputs(&tri->inputs) );
 576             }
 577             else
 578             {
 579                /* rasterizer/shade partial tile */
 580                LP_COUNT(nr_partially_covered_64);
 581                in = TRUE;
 582                lp_scene_bin_command( scene, x, y,
 583                                      lp_rast_triangle,
 584                                      lp_rast_arg_triangle(tri) );
 585             }
 586
 587             /* Iterate cx values across the region:
 588              */
 589             cx1 += xstep1;
 590             cx2 += xstep2;
 591             cx3 += xstep3;
 592          }
 593
 594          /* Iterate c values down the region:
 595           */
 596          c1 += ystep1;
 597          c2 += ystep2;
 598          c3 += ystep3;
 599       }
 600    }
 601 }
 602
 603
 604 /**
 605  * Draw triangle if it's CW, cull otherwise.
 606  */
 607 static void triangle_cw( struct lp_setup_context *setup,
 608                          const float (*v0)[4],
 609                          const float (*v1)[4],
 610                          const float (*v2)[4] )
 611 {
 612    do_triangle_ccw( setup, v1, v0, v2, !setup->ccw_is_frontface );
 613 }
 614
 615
 616 /**
 617  * Draw triangle if it's CCW, cull otherwise.
 618  */
 619 static void triangle_ccw( struct lp_setup_context *setup,
 620                          const float (*v0)[4],
 621                          const float (*v1)[4],
 622                          const float (*v2)[4] )
 623 {
 624    do_triangle_ccw( setup, v0, v1, v2, setup->ccw_is_frontface );
 625 }
 626
 627
 628
 629 /**
 630  * Draw triangle whether it's CW or CCW.
 631  */
 632 static void triangle_both( struct lp_setup_context *setup,
 633                            const float (*v0)[4],
 634                            const float (*v1)[4],
 635                            const float (*v2)[4] )
 636 {
 637    /* edge vectors e = v0 - v2, f = v1 - v2 */
 638    const float ex = v0[0][0] - v2[0][0];
 639    const float ey = v0[0][1] - v2[0][1];
 640    const float fx = v1[0][0] - v2[0][0];
 641    const float fy = v1[0][1] - v2[0][1];
 642
 643    /* det = cross(e,f).z */
 644    if (ex * fy - ey * fx < 0.0f)
 645       triangle_ccw( setup, v0, v1, v2 );
 646    else
 647       triangle_cw( setup, v0, v1, v2 );
 648 }
 649
 650
 651 static void triangle_nop( struct lp_setup_context *setup,
 652                           const float (*v0)[4],
 653                           const float (*v1)[4],
 654                           const float (*v2)[4] )
 655 {
 656 }
 657
 658
 659 void
 660 lp_setup_choose_triangle( struct lp_setup_context *setup )
 661 {
 662    switch (setup->cullmode) {
 663    case PIPE_WINDING_NONE:
 664       setup->triangle = triangle_both;
 665       break;
 666    case PIPE_WINDING_CCW:
 667       setup->triangle = triangle_cw;
 668       break;
 669    case PIPE_WINDING_CW:
 670       setup->triangle = triangle_ccw;
 671       break;
 672    default:
 673       setup->triangle = triangle_nop;
 674       break;
 675    }
 676 }