src/gallium/auxiliary/draw/draw_pipe_clip.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
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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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  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,
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  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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  26  **************************************************************************/
  27
  28 /**
  29  * \brief  Clipping stage
  30  *
  31  * \author  Keith Whitwell <keith@tungstengraphics.com>
  32  */
  33
  34
  35 #include "pipe/p_util.h"
  36 #include "pipe/p_shader_tokens.h"
  37
  38 #include "draw_context.h"
  39 #include "draw_vs.h"
  40
  41
  42 #ifndef IS_NEGATIVE
  43 #define IS_NEGATIVE(X) ((X) < 0.0)
  44 #endif
  45
  46 #ifndef DIFFERENT_SIGNS
  47 #define DIFFERENT_SIGNS(x, y) ((x) * (y) <= 0.0F && (x) - (y) != 0.0F)
  48 #endif
  49
  50 #ifndef MAX_CLIPPED_VERTICES
  51 #define MAX_CLIPPED_VERTICES ((2 * (6 + PIPE_MAX_CLIP_PLANES))+1)
  52 #endif
  53
  54
  55
  56 struct clipper {
  57    struct draw_stage stage;      /**< base class */
  58
  59    /* Basically duplicate some of the flatshading logic here:
  60     */
  61    boolean flat;
  62    uint num_color_attribs;
  63    uint color_attribs[4];  /* front/back primary/secondary colors */
  64
  65    float (*plane)[4];
  66 };
  67
  68
  69 /* This is a bit confusing:
  70  */
  71 static INLINE struct clipper *clipper_stage( struct draw_stage *stage )
  72 {
  73    return (struct clipper *)stage;
  74 }
  75
  76
  77 #define LINTERP(T, OUT, IN) ((OUT) + (T) * ((IN) - (OUT)))
  78
  79
  80 /* All attributes are float[4], so this is easy:
  81  */
  82 static void interp_attr( float *fdst,
  83                          float t,
  84                          const float *fin,
  85                          const float *fout )
  86 {
  87    fdst[0] = LINTERP( t, fout[0], fin[0] );
  88    fdst[1] = LINTERP( t, fout[1], fin[1] );
  89    fdst[2] = LINTERP( t, fout[2], fin[2] );
  90    fdst[3] = LINTERP( t, fout[3], fin[3] );
  91 }
  92
  93 static void copy_colors( struct draw_stage *stage,
  94                          struct vertex_header *dst,
  95                          const struct vertex_header *src )
  96 {
  97    const struct clipper *clipper = clipper_stage(stage);
  98    uint i;
  99    for (i = 0; i < clipper->num_color_attribs; i++) {
 100       const uint attr = clipper->color_attribs[i];
 101       COPY_4FV(dst->data[attr], src->data[attr]);
 102    }
 103 }
 104
 105
 106
 107 /* Interpolate between two vertices to produce a third.
 108  */
 109 static void interp( const struct clipper *clip,
 110                     struct vertex_header *dst,
 111                     float t,
 112                     const struct vertex_header *out,
 113                     const struct vertex_header *in )
 114 {
 115    const unsigned nr_attrs = clip->stage.draw->num_vs_outputs;
 116    unsigned j;
 117
 118    /* Vertex header.
 119     */
 120    {
 121       dst->clipmask = 0;
 122       dst->edgeflag = 0;
 123       dst->pad = 0;
 124       dst->vertex_id = UNDEFINED_VERTEX_ID;
 125    }
 126
 127    /* Clip coordinates:  interpolate normally
 128     */
 129    {
 130       interp_attr(dst->clip, t, in->clip, out->clip);
 131    }
 132
 133    /* Do the projective divide and insert window coordinates:
 134     */
 135    {
 136       const float *pos = dst->clip;
 137       const float *scale = clip->stage.draw->viewport.scale;
 138       const float *trans = clip->stage.draw->viewport.translate;
 139       const float oow = 1.0f / pos[3];
 140
 141       dst->data[0][0] = pos[0] * oow * scale[0] + trans[0];
 142       dst->data[0][1] = pos[1] * oow * scale[1] + trans[1];
 143       dst->data[0][2] = pos[2] * oow * scale[2] + trans[2];
 144       dst->data[0][3] = oow;
 145    }
 146
 147    /* Other attributes
 148     * Note: start at 1 to skip winpos (data[0]) since we just computed
 149     * it above.
 150     */
 151    for (j = 1; j < nr_attrs; j++) {
 152       interp_attr(dst->data[j], t, in->data[j], out->data[j]);
 153    }
 154 }
 155
 156
 157 static void emit_poly( struct draw_stage *stage,
 158                        struct vertex_header **inlist,
 159                        unsigned n,
 160                        const struct prim_header *origPrim)
 161 {
 162    struct prim_header header;
 163    unsigned i;
 164
 165    /* later stages may need the determinant, but only the sign matters */
 166    header.det = origPrim->det;
 167
 168    for (i = 2; i < n; i++) {
 169       header.v[0] = inlist[i-1];
 170       header.v[1] = inlist[i];
 171       header.v[2] = inlist[0];  /* keep in v[2] for flatshading */
 172
 173       {
 174          unsigned tmp1 = header.v[1]->edgeflag;
 175          unsigned tmp2 = header.v[2]->edgeflag;
 176
 177          if (i != n-1) header.v[1]->edgeflag = 0;
 178          if (i != 2)   header.v[2]->edgeflag = 0;
 179
 180          header.edgeflags = ((header.v[0]->edgeflag << 0) |
 181                              (header.v[1]->edgeflag << 1) |
 182                              (header.v[2]->edgeflag << 2));
 183
 184          if (0) {
 185             const struct draw_vertex_shader *vs = stage->draw->vertex_shader;
 186             uint j, k;
 187             debug_printf("Clipped tri:\n");
 188             for (j = 0; j < 3; j++) {
 189                for (k = 0; k < vs->info.num_outputs; k++) {
 190                   debug_printf("  Vert %d: Attr %d:  %f %f %f %f\n", j, k,
 191                          header.v[j]->data[k][0],
 192                          header.v[j]->data[k][1],
 193                          header.v[j]->data[k][2],
 194                          header.v[j]->data[k][3]);
 195                }
 196             }
 197          }
 198
 199          stage->next->tri( stage->next, &header );
 200
 201          header.v[1]->edgeflag = tmp1;
 202          header.v[2]->edgeflag = tmp2;
 203       }
 204    }
 205 }
 206
 207
 208
 209
 210 /* Clip a triangle against the viewport and user clip planes.
 211  */
 212 static void
 213 do_clip_tri( struct draw_stage *stage,
 214              struct prim_header *header,
 215              unsigned clipmask )
 216 {
 217    struct clipper *clipper = clipper_stage( stage );
 218    struct vertex_header *a[MAX_CLIPPED_VERTICES];
 219    struct vertex_header *b[MAX_CLIPPED_VERTICES];
 220    struct vertex_header **inlist = a;
 221    struct vertex_header **outlist = b;
 222    unsigned tmpnr = 0;
 223    unsigned n = 3;
 224    unsigned i;
 225
 226    inlist[0] = header->v[0];
 227    inlist[1] = header->v[1];
 228    inlist[2] = header->v[2];
 229
 230    while (clipmask && n >= 3) {
 231       const unsigned plane_idx = ffs(clipmask)-1;
 232       const float *plane = clipper->plane[plane_idx];
 233       struct vertex_header *vert_prev = inlist[0];
 234       float dp_prev = dot4( vert_prev->clip, plane );
 235       unsigned outcount = 0;
 236
 237       clipmask &= ~(1<<plane_idx);
 238
 239       inlist[n] = inlist[0]; /* prevent rotation of vertices */
 240
 241       for (i = 1; i <= n; i++) {
 242          struct vertex_header *vert = inlist[i];
 243
 244          float dp = dot4( vert->clip, plane );
 245
 246          if (!IS_NEGATIVE(dp_prev)) {
 247             outlist[outcount++] = vert_prev;
 248          }
 249
 250          if (DIFFERENT_SIGNS(dp, dp_prev)) {
 251             struct vertex_header *new_vert = clipper->stage.tmp[tmpnr++];
 252             outlist[outcount++] = new_vert;
 253
 254             if (IS_NEGATIVE(dp)) {
 255                /* Going out of bounds.  Avoid division by zero as we
 256                 * know dp != dp_prev from DIFFERENT_SIGNS, above.
 257                 */
 258                float t = dp / (dp - dp_prev);
 259                interp( clipper, new_vert, t, vert, vert_prev );
 260
 261                /* Force edgeflag true in this case:
 262                 */
 263                new_vert->edgeflag = 1;
 264             } else {
 265                /* Coming back in.
 266                 */
 267                float t = dp_prev / (dp_prev - dp);
 268                interp( clipper, new_vert, t, vert_prev, vert );
 269
 270                /* Copy starting vert's edgeflag:
 271                 */
 272                new_vert->edgeflag = vert_prev->edgeflag;
 273             }
 274          }
 275
 276          vert_prev = vert;
 277          dp_prev = dp;
 278       }
 279
 280       {
 281          struct vertex_header **tmp = inlist;
 282          inlist = outlist;
 283          outlist = tmp;
 284          n = outcount;
 285       }
 286    }
 287
 288    /* If flat-shading, copy color to new provoking vertex.
 289     */
 290    if (clipper->flat && inlist[0] != header->v[2]) {
 291       if (1) {
 292          inlist[0] = dup_vert(stage, inlist[0], tmpnr++);
 293       }
 294
 295       copy_colors(stage, inlist[0], header->v[2]);
 296    }
 297
 298
 299
 300    /* Emit the polygon as triangles to the setup stage:
 301     */
 302    if (n >= 3)
 303       emit_poly( stage, inlist, n, header );
 304 }
 305
 306
 307 /* Clip a line against the viewport and user clip planes.
 308  */
 309 static void
 310 do_clip_line( struct draw_stage *stage,
 311               struct prim_header *header,
 312               unsigned clipmask )
 313 {
 314    const struct clipper *clipper = clipper_stage( stage );
 315    struct vertex_header *v0 = header->v[0];
 316    struct vertex_header *v1 = header->v[1];
 317    const float *pos0 = v0->clip;
 318    const float *pos1 = v1->clip;
 319    float t0 = 0.0F;
 320    float t1 = 0.0F;
 321    struct prim_header newprim;
 322
 323    while (clipmask) {
 324       const unsigned plane_idx = ffs(clipmask)-1;
 325       const float *plane = clipper->plane[plane_idx];
 326       const float dp0 = dot4( pos0, plane );
 327       const float dp1 = dot4( pos1, plane );
 328
 329       if (dp1 < 0.0F) {
 330          float t = dp1 / (dp1 - dp0);
 331          t1 = MAX2(t1, t);
 332       }
 333
 334       if (dp0 < 0.0F) {
 335          float t = dp0 / (dp0 - dp1);
 336          t0 = MAX2(t0, t);
 337       }
 338
 339       if (t0 + t1 >= 1.0F)
 340          return; /* discard */
 341
 342       clipmask &= ~(1 << plane_idx);  /* turn off this plane's bit */
 343    }
 344
 345    if (v0->clipmask) {
 346       interp( clipper, stage->tmp[0], t0, v0, v1 );
 347
 348       if (clipper->flat)
 349          copy_colors(stage, stage->tmp[0], v0);
 350
 351       newprim.v[0] = stage->tmp[0];
 352    }
 353    else {
 354       newprim.v[0] = v0;
 355    }
 356
 357    if (v1->clipmask) {
 358       interp( clipper, stage->tmp[1], t1, v1, v0 );
 359       newprim.v[1] = stage->tmp[1];
 360    }
 361    else {
 362       newprim.v[1] = v1;
 363    }
 364
 365    stage->next->line( stage->next, &newprim );
 366 }
 367
 368
 369 static void
 370 clip_point( struct draw_stage *stage,
 371             struct prim_header *header )
 372 {
 373    if (header->v[0]->clipmask == 0)
 374       stage->next->point( stage->next, header );
 375 }
 376
 377
 378 static void
 379 clip_line( struct draw_stage *stage,
 380            struct prim_header *header )
 381 {
 382    unsigned clipmask = (header->v[0]->clipmask |
 383                         header->v[1]->clipmask);
 384
 385    if (clipmask == 0) {
 386       /* no clipping needed */
 387       stage->next->line( stage->next, header );
 388    }
 389    else if ((header->v[0]->clipmask &
 390              header->v[1]->clipmask) == 0) {
 391       do_clip_line(stage, header, clipmask);
 392    }
 393    /* else, totally clipped */
 394 }
 395
 396
 397 static void
 398 clip_tri( struct draw_stage *stage,
 399           struct prim_header *header )
 400 {
 401    unsigned clipmask = (header->v[0]->clipmask |
 402                         header->v[1]->clipmask |
 403                         header->v[2]->clipmask);
 404
 405    if (clipmask == 0) {
 406       /* no clipping needed */
 407       stage->next->tri( stage->next, header );
 408    }
 409    else if ((header->v[0]->clipmask &
 410              header->v[1]->clipmask &
 411              header->v[2]->clipmask) == 0) {
 412       do_clip_tri(stage, header, clipmask);
 413    }
 414 }
 415
 416 /* Update state.  Could further delay this until we hit the first
 417  * primitive that really requires clipping.
 418  */
 419 static void
 420 clip_init_state( struct draw_stage *stage )
 421 {
 422    struct clipper *clipper = clipper_stage( stage );
 423
 424    clipper->flat = stage->draw->rasterizer->flatshade ? TRUE : FALSE;
 425
 426    if (clipper->flat) {
 427       const struct draw_vertex_shader *vs = stage->draw->vertex_shader;
 428       uint i;
 429
 430       clipper->num_color_attribs = 0;
 431       for (i = 0; i < vs->info.num_outputs; i++) {
 432          if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_COLOR ||
 433              vs->info.output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
 434             clipper->color_attribs[clipper->num_color_attribs++] = i;
 435          }
 436       }
 437    }
 438
 439    stage->tri = clip_tri;
 440    stage->line = clip_line;
 441 }
 442
 443
 444
 445 static void clip_first_tri( struct draw_stage *stage,
 446                             struct prim_header *header )
 447 {
 448    clip_init_state( stage );
 449    stage->tri( stage, header );
 450 }
 451
 452 static void clip_first_line( struct draw_stage *stage,
 453                              struct prim_header *header )
 454 {
 455    clip_init_state( stage );
 456    stage->line( stage, header );
 457 }
 458
 459
 460 static void clip_flush( struct draw_stage *stage,
 461                              unsigned flags )
 462 {
 463    stage->tri = clip_first_tri;
 464    stage->line = clip_first_line;
 465    stage->next->flush( stage->next, flags );
 466 }
 467
 468
 469 static void clip_reset_stipple_counter( struct draw_stage *stage )
 470 {
 471    stage->next->reset_stipple_counter( stage->next );
 472 }
 473
 474
 475 static void clip_destroy( struct draw_stage *stage )
 476 {
 477    draw_free_temp_verts( stage );
 478    FREE( stage );
 479 }
 480
 481
 482 /**
 483  * Allocate a new clipper stage.
 484  * \return pointer to new stage object
 485  */
 486 struct draw_stage *draw_clip_stage( struct draw_context *draw )
 487 {
 488    struct clipper *clipper = CALLOC_STRUCT(clipper);
 489
 490    draw_alloc_temp_verts( &clipper->stage, MAX_CLIPPED_VERTICES+1 );
 491
 492    clipper->stage.draw = draw;
 493    clipper->stage.point = clip_point;
 494    clipper->stage.line = clip_first_line;
 495    clipper->stage.tri = clip_first_tri;
 496    clipper->stage.flush = clip_flush;
 497    clipper->stage.reset_stipple_counter = clip_reset_stipple_counter;
 498    clipper->stage.destroy = clip_destroy;
 499
 500    clipper->plane = draw->plane;
 501
 502    return &clipper->stage;
 503 }