src/mesa/pipe/draw/draw_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
   8  * "Software"), to deal in the Software without restriction, including
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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
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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_private.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          stage->next->tri( stage->next, &header );
 185
 186          header.v[1]->edgeflag = tmp1;
 187          header.v[2]->edgeflag = tmp2;
 188       }
 189    }
 190 }
 191
 192
 193
 194
 195 /* Clip a triangle against the viewport and user clip planes.
 196  */
 197 static void
 198 do_clip_tri( struct draw_stage *stage,
 199              struct prim_header *header,
 200              unsigned clipmask )
 201 {
 202    struct clipper *clipper = clipper_stage( stage );
 203    struct vertex_header *a[MAX_CLIPPED_VERTICES];
 204    struct vertex_header *b[MAX_CLIPPED_VERTICES];
 205    struct vertex_header **inlist = a;
 206    struct vertex_header **outlist = b;
 207    unsigned tmpnr = 0;
 208    unsigned n = 3;
 209    unsigned i;
 210
 211    inlist[0] = header->v[0];
 212    inlist[1] = header->v[1];
 213    inlist[2] = header->v[2];
 214
 215    while (clipmask && n >= 3) {
 216       const unsigned plane_idx = ffs(clipmask)-1;
 217       const float *plane = clipper->plane[plane_idx];
 218       struct vertex_header *vert_prev = inlist[0];
 219       float dp_prev = dot4( vert_prev->clip, plane );
 220       unsigned outcount = 0;
 221
 222       clipmask &= ~(1<<plane_idx);
 223
 224       inlist[n] = inlist[0]; /* prevent rotation of vertices */
 225
 226       for (i = 1; i <= n; i++) {
 227          struct vertex_header *vert = inlist[i];
 228
 229          float dp = dot4( vert->clip, plane );
 230
 231          if (!IS_NEGATIVE(dp_prev)) {
 232             outlist[outcount++] = vert_prev;
 233          }
 234
 235          if (DIFFERENT_SIGNS(dp, dp_prev)) {
 236             struct vertex_header *new_vert = clipper->stage.tmp[tmpnr++];
 237             outlist[outcount++] = new_vert;
 238
 239             if (IS_NEGATIVE(dp)) {
 240                /* Going out of bounds.  Avoid division by zero as we
 241                 * know dp != dp_prev from DIFFERENT_SIGNS, above.
 242                 */
 243                float t = dp / (dp - dp_prev);
 244                interp( clipper, new_vert, t, vert, vert_prev );
 245
 246                /* Force edgeflag true in this case:
 247                 */
 248                new_vert->edgeflag = 1;
 249             } else {
 250                /* Coming back in.
 251                 */
 252                float t = dp_prev / (dp_prev - dp);
 253                interp( clipper, new_vert, t, vert_prev, vert );
 254
 255                /* Copy starting vert's edgeflag:
 256                 */
 257                new_vert->edgeflag = vert_prev->edgeflag;
 258             }
 259          }
 260
 261          vert_prev = vert;
 262          dp_prev = dp;
 263       }
 264
 265       {
 266          struct vertex_header **tmp = inlist;
 267          inlist = outlist;
 268          outlist = tmp;
 269          n = outcount;
 270       }
 271    }
 272
 273    /* If flat-shading, copy color to new provoking vertex.
 274     */
 275    if (clipper->flat && inlist[0] != header->v[2]) {
 276       if (1) {
 277          inlist[0] = dup_vert(stage, inlist[0], tmpnr++);
 278       }
 279
 280       copy_colors(stage, inlist[0], header->v[2]);
 281    }
 282
 283
 284
 285    /* Emit the polygon as triangles to the setup stage:
 286     */
 287    if (n >= 3)
 288       emit_poly( stage, inlist, n, header );
 289 }
 290
 291
 292 /* Clip a line against the viewport and user clip planes.
 293  */
 294 static void
 295 do_clip_line( struct draw_stage *stage,
 296               struct prim_header *header,
 297               unsigned clipmask )
 298 {
 299    const struct clipper *clipper = clipper_stage( stage );
 300    struct vertex_header *v0 = header->v[0];
 301    struct vertex_header *v1 = header->v[1];
 302    const float *pos0 = v0->clip;
 303    const float *pos1 = v1->clip;
 304    float t0 = 0.0F;
 305    float t1 = 0.0F;
 306    struct prim_header newprim;
 307
 308    while (clipmask) {
 309       const unsigned plane_idx = ffs(clipmask)-1;
 310       const float *plane = clipper->plane[plane_idx];
 311       const float dp0 = dot4( pos0, plane );
 312       const float dp1 = dot4( pos1, plane );
 313
 314       if (dp1 < 0.0F) {
 315          float t = dp1 / (dp1 - dp0);
 316          t1 = MAX2(t1, t);
 317       }
 318
 319       if (dp0 < 0.0F) {
 320          float t = dp0 / (dp0 - dp1);
 321          t0 = MAX2(t0, t);
 322       }
 323
 324       if (t0 + t1 >= 1.0F)
 325          return; /* discard */
 326
 327       clipmask &= ~(1 << plane_idx);  /* turn off this plane's bit */
 328    }
 329
 330    if (v0->clipmask) {
 331       interp( clipper, stage->tmp[0], t0, v0, v1 );
 332
 333       if (clipper->flat)
 334          copy_colors(stage, stage->tmp[0], v0);
 335
 336       newprim.v[0] = stage->tmp[0];
 337    }
 338    else {
 339       newprim.v[0] = v0;
 340    }
 341
 342    if (v1->clipmask) {
 343       interp( clipper, stage->tmp[1], t1, v1, v0 );
 344       newprim.v[1] = stage->tmp[1];
 345    }
 346    else {
 347       newprim.v[1] = v1;
 348    }
 349
 350    stage->next->line( stage->next, &newprim );
 351 }
 352
 353
 354 static void
 355 clip_point( struct draw_stage *stage,
 356             struct prim_header *header )
 357 {
 358    if (header->v[0]->clipmask == 0)
 359       stage->next->point( stage->next, header );
 360 }
 361
 362
 363 static void
 364 clip_line( struct draw_stage *stage,
 365            struct prim_header *header )
 366 {
 367    unsigned clipmask = (header->v[0]->clipmask |
 368                         header->v[1]->clipmask);
 369
 370    if (clipmask == 0) {
 371       /* no clipping needed */
 372       stage->next->line( stage->next, header );
 373    }
 374    else if ((header->v[0]->clipmask &
 375              header->v[1]->clipmask) == 0) {
 376       do_clip_line(stage, header, clipmask);
 377    }
 378    /* else, totally clipped */
 379 }
 380
 381
 382 static void
 383 clip_tri( struct draw_stage *stage,
 384           struct prim_header *header )
 385 {
 386    unsigned clipmask = (header->v[0]->clipmask |
 387                         header->v[1]->clipmask |
 388                         header->v[2]->clipmask);
 389
 390    if (clipmask == 0) {
 391       /* no clipping needed */
 392       stage->next->tri( stage->next, header );
 393    }
 394    else if ((header->v[0]->clipmask &
 395              header->v[1]->clipmask &
 396              header->v[2]->clipmask) == 0) {
 397       do_clip_tri(stage, header, clipmask);
 398    }
 399 }
 400
 401 /* Update state.  Could further delay this until we hit the first
 402  * primitive that really requires clipping.
 403  */
 404 static void
 405 clip_init_state( struct draw_stage *stage )
 406 {
 407    struct clipper *clipper = clipper_stage( stage );
 408
 409    clipper->flat = stage->draw->rasterizer->flatshade;
 410
 411    if (clipper->flat) {
 412       const struct pipe_shader_state *vs = stage->draw->vertex_shader->state;
 413       uint i;
 414
 415       clipper->num_color_attribs = 0;
 416       for (i = 0; i < vs->num_outputs; i++) {
 417          if (vs->output_semantic_name[i] == TGSI_SEMANTIC_COLOR ||
 418              vs->output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
 419             clipper->color_attribs[clipper->num_color_attribs++] = i;
 420          }
 421       }
 422    }
 423
 424    stage->tri = clip_tri;
 425    stage->line = clip_line;
 426 }
 427
 428
 429
 430 static void clip_first_tri( struct draw_stage *stage,
 431                             struct prim_header *header )
 432 {
 433    clip_init_state( stage );
 434    stage->tri( stage, header );
 435 }
 436
 437 static void clip_first_line( struct draw_stage *stage,
 438                              struct prim_header *header )
 439 {
 440    clip_init_state( stage );
 441    stage->line( stage, header );
 442 }
 443
 444
 445 static void clip_flush( struct draw_stage *stage,
 446                              unsigned flags )
 447 {
 448    stage->tri = clip_first_tri;
 449    stage->line = clip_first_line;
 450    stage->next->flush( stage->next, flags );
 451 }
 452
 453
 454 static void clip_reset_stipple_counter( struct draw_stage *stage )
 455 {
 456    stage->next->reset_stipple_counter( stage->next );
 457 }
 458
 459
 460 static void clip_destroy( struct draw_stage *stage )
 461 {
 462    draw_free_tmps( stage );
 463    FREE( stage );
 464 }
 465
 466
 467 /**
 468  * Allocate a new clipper stage.
 469  * \return pointer to new stage object
 470  */
 471 struct draw_stage *draw_clip_stage( struct draw_context *draw )
 472 {
 473    struct clipper *clipper = CALLOC_STRUCT(clipper);
 474
 475    draw_alloc_tmps( &clipper->stage, MAX_CLIPPED_VERTICES+1 );
 476
 477    clipper->stage.draw = draw;
 478    clipper->stage.point = clip_point;
 479    clipper->stage.line = clip_first_line;
 480    clipper->stage.tri = clip_first_tri;
 481    clipper->stage.flush = clip_flush;
 482    clipper->stage.reset_stipple_counter = clip_reset_stipple_counter;
 483    clipper->stage.destroy = clip_destroy;
 484
 485    clipper->plane = draw->plane;
 486
 487    return &clipper->stage;
 488 }