src/mesa/swrast/s_aatriangle.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  5.1
   4  *
   5  * Copyright (C) 1999-2003  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 /*
  27  * Antialiased Triangle rasterizers
  28  */
  29
  30
  31 #include "glheader.h"
  32 #include "context.h"
  33 #include "colormac.h"
  34 #include "context.h"
  35 #include "macros.h"
  36 #include "imports.h"
  37 #include "nvfragprog.h"
  38 #include "s_aatriangle.h"
  39 #include "s_context.h"
  40 #include "s_span.h"
  41
  42
  43 /*
  44  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  45  * vertices and the given Z values.
  46  * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
  47  */
  48 static INLINE void
  49 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  50               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  51 {
  52    const GLfloat px = v1[0] - v0[0];
  53    const GLfloat py = v1[1] - v0[1];
  54    const GLfloat pz = z1 - z0;
  55
  56    const GLfloat qx = v2[0] - v0[0];
  57    const GLfloat qy = v2[1] - v0[1];
  58    const GLfloat qz = z2 - z0;
  59
  60    /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
  61    const GLfloat a = py * qz - pz * qy;
  62    const GLfloat b = pz * qx - px * qz;
  63    const GLfloat c = px * qy - py * qx;
  64    /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
  65       on the distance of plane from origin and arbitrary "w" parallel
  66       to the plane. */
  67    /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
  68       which is equal to "-d" below. */
  69    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  70
  71    plane[0] = a;
  72    plane[1] = b;
  73    plane[2] = c;
  74    plane[3] = d;
  75 }
  76
  77
  78 /*
  79  * Compute coefficients of a plane with a constant Z value.
  80  */
  81 static INLINE void
  82 constant_plane(GLfloat value, GLfloat plane[4])
  83 {
  84    plane[0] = 0.0;
  85    plane[1] = 0.0;
  86    plane[2] = -1.0;
  87    plane[3] = value;
  88 }
  89
  90 #define CONSTANT_PLANE(VALUE, PLANE)    \
  91 do {                                    \
  92    PLANE[0] = 0.0F;                     \
  93    PLANE[1] = 0.0F;                     \
  94    PLANE[2] = -1.0F;                    \
  95    PLANE[3] = VALUE;                    \
  96 } while (0)
  97
  98
  99
 100 /*
 101  * Solve plane equation for Z at (X,Y).
 102  */
 103 static INLINE GLfloat
 104 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 105 {
 106    ASSERT(plane[2] != 0.0F);
 107    return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 108 }
 109
 110
 111 #define SOLVE_PLANE(X, Y, PLANE) \
 112    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 113
 114
 115 /*
 116  * Return 1 / solve_plane().
 117  */
 118 static INLINE GLfloat
 119 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 120 {
 121    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 122    if (denom == 0.0F)
 123       return 0.0F;
 124    else
 125       return -plane[2] / denom;
 126 }
 127
 128
 129 /*
 130  * Solve plane and return clamped GLchan value.
 131  */
 132 static INLINE GLchan
 133 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 134 {
 135    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 136 #if CHAN_TYPE == GL_FLOAT
 137    return CLAMP(z, 0.0F, CHAN_MAXF);
 138 #else
 139    if (z < 0)
 140       return 0;
 141    else if (z > CHAN_MAX)
 142       return CHAN_MAX;
 143    return (GLchan) IROUND_POS(z);
 144 #endif
 145 }
 146
 147
 148
 149 /*
 150  * Compute how much (area) of the given pixel is inside the triangle.
 151  * Vertices MUST be specified in counter-clockwise order.
 152  * Return:  coverage in [0, 1].
 153  */
 154 static GLfloat
 155 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 156                   const GLfloat v2[3], GLint winx, GLint winy)
 157 {
 158    /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
 159     * Contributed by Ray Tice.
 160     *
 161     * Jitter sample positions -
 162     * - average should be .5 in x & y for each column
 163     * - each of the 16 rows and columns should be used once
 164     * - the rectangle formed by the first four points
 165     *   should contain the other points
 166     * - the distrubition should be fairly even in any given direction
 167     *
 168     * The pattern drawn below isn't optimal, but it's better than a regular
 169     * grid.  In the drawing, the center of each subpixel is surrounded by
 170     * four dots.  The "x" marks the jittered position relative to the
 171     * subpixel center.
 172     */
 173 #define POS(a, b) (0.5+a*4+b)/16
 174    static const GLfloat samples[16][2] = {
 175       /* start with the four corners */
 176       { POS(0, 2), POS(0, 0) },
 177       { POS(3, 3), POS(0, 2) },
 178       { POS(0, 0), POS(3, 1) },
 179       { POS(3, 1), POS(3, 3) },
 180       /* continue with interior samples */
 181       { POS(1, 1), POS(0, 1) },
 182       { POS(2, 0), POS(0, 3) },
 183       { POS(0, 3), POS(1, 3) },
 184       { POS(1, 2), POS(1, 0) },
 185       { POS(2, 3), POS(1, 2) },
 186       { POS(3, 2), POS(1, 1) },
 187       { POS(0, 1), POS(2, 2) },
 188       { POS(1, 0), POS(2, 1) },
 189       { POS(2, 1), POS(2, 3) },
 190       { POS(3, 0), POS(2, 0) },
 191       { POS(1, 3), POS(3, 0) },
 192       { POS(2, 2), POS(3, 2) }
 193    };
 194
 195    const GLfloat x = (GLfloat) winx;
 196    const GLfloat y = (GLfloat) winy;
 197    const GLfloat dx0 = v1[0] - v0[0];
 198    const GLfloat dy0 = v1[1] - v0[1];
 199    const GLfloat dx1 = v2[0] - v1[0];
 200    const GLfloat dy1 = v2[1] - v1[1];
 201    const GLfloat dx2 = v0[0] - v2[0];
 202    const GLfloat dy2 = v0[1] - v2[1];
 203    GLint stop = 4, i;
 204    GLfloat insideCount = 16.0F;
 205
 206 #ifdef DEBUG
 207    {
 208       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 209       ASSERT(area >= 0.0);
 210    }
 211 #endif
 212
 213    for (i = 0; i < stop; i++) {
 214       const GLfloat sx = x + samples[i][0];
 215       const GLfloat sy = y + samples[i][1];
 216       /* cross product determines if sample is inside or outside each edge */
 217       GLfloat cross = (dx0 * (sy - v0[1]) - dy0 * (sx - v0[0]));
 218       /* Check if the sample is exactly on an edge.  If so, let cross be a
 219        * positive or negative value depending on the direction of the edge.
 220        */
 221       if (cross == 0.0F)
 222          cross = dx0 + dy0;
 223       if (cross < 0.0F) {
 224          /* sample point is outside first edge */
 225          insideCount -= 1.0F;
 226          stop = 16;
 227       }
 228       else {
 229          /* sample point is inside first edge */
 230          cross = (dx1 * (sy - v1[1]) - dy1 * (sx - v1[0]));
 231          if (cross == 0.0F)
 232             cross = dx1 + dy1;
 233          if (cross < 0.0F) {
 234             /* sample point is outside second edge */
 235             insideCount -= 1.0F;
 236             stop = 16;
 237          }
 238          else {
 239             /* sample point is inside first and second edges */
 240             cross = (dx2 * (sy - v2[1]) -  dy2 * (sx - v2[0]));
 241             if (cross == 0.0F)
 242                cross = dx2 + dy2;
 243             if (cross < 0.0F) {
 244                /* sample point is outside third edge */
 245                insideCount -= 1.0F;
 246                stop = 16;
 247             }
 248          }
 249       }
 250    }
 251    if (stop == 4)
 252       return 1.0F;
 253    else
 254       return insideCount * (1.0F / 16.0F);
 255 }
 256
 257
 258
 259 /*
 260  * Compute how much (area) of the given pixel is inside the triangle.
 261  * Vertices MUST be specified in counter-clockwise order.
 262  * Return:  coverage in [0, 15].
 263  */
 264 static GLint
 265 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 266                   const GLfloat v2[3], GLint winx, GLint winy)
 267 {
 268    /* NOTE: 15 samples instead of 16. */
 269    static const GLfloat samples[15][2] = {
 270       /* start with the four corners */
 271       { POS(0, 2), POS(0, 0) },
 272       { POS(3, 3), POS(0, 2) },
 273       { POS(0, 0), POS(3, 1) },
 274       { POS(3, 1), POS(3, 3) },
 275       /* continue with interior samples */
 276       { POS(1, 1), POS(0, 1) },
 277       { POS(2, 0), POS(0, 3) },
 278       { POS(0, 3), POS(1, 3) },
 279       { POS(1, 2), POS(1, 0) },
 280       { POS(2, 3), POS(1, 2) },
 281       { POS(3, 2), POS(1, 1) },
 282       { POS(0, 1), POS(2, 2) },
 283       { POS(1, 0), POS(2, 1) },
 284       { POS(2, 1), POS(2, 3) },
 285       { POS(3, 0), POS(2, 0) },
 286       { POS(1, 3), POS(3, 0) }
 287    };
 288    const GLfloat x = (GLfloat) winx;
 289    const GLfloat y = (GLfloat) winy;
 290    const GLfloat dx0 = v1[0] - v0[0];
 291    const GLfloat dy0 = v1[1] - v0[1];
 292    const GLfloat dx1 = v2[0] - v1[0];
 293    const GLfloat dy1 = v2[1] - v1[1];
 294    const GLfloat dx2 = v0[0] - v2[0];
 295    const GLfloat dy2 = v0[1] - v2[1];
 296    GLint stop = 4, i;
 297    GLint insideCount = 15;
 298
 299 #ifdef DEBUG
 300    {
 301       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 302       ASSERT(area >= 0.0);
 303    }
 304 #endif
 305
 306    for (i = 0; i < stop; i++) {
 307       const GLfloat sx = x + samples[i][0];
 308       const GLfloat sy = y + samples[i][1];
 309       const GLfloat fx0 = sx - v0[0];
 310       const GLfloat fy0 = sy - v0[1];
 311       const GLfloat fx1 = sx - v1[0];
 312       const GLfloat fy1 = sy - v1[1];
 313       const GLfloat fx2 = sx - v2[0];
 314       const GLfloat fy2 = sy - v2[1];
 315       /* cross product determines if sample is inside or outside each edge */
 316       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 317       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 318       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 319       /* Check if the sample is exactly on an edge.  If so, let cross be a
 320        * positive or negative value depending on the direction of the edge.
 321        */
 322       if (cross0 == 0.0F)
 323          cross0 = dx0 + dy0;
 324       if (cross1 == 0.0F)
 325          cross1 = dx1 + dy1;
 326       if (cross2 == 0.0F)
 327          cross2 = dx2 + dy2;
 328       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 329          /* point is outside triangle */
 330          insideCount--;
 331          stop = 15;
 332       }
 333    }
 334    if (stop == 4)
 335       return 15;
 336    else
 337       return insideCount;
 338 }
 339
 340
 341
 342 static void
 343 rgba_aa_tri(GLcontext *ctx,
 344             const SWvertex *v0,
 345             const SWvertex *v1,
 346             const SWvertex *v2)
 347 {
 348 #define DO_Z
 349 #define DO_FOG
 350 #define DO_RGBA
 351 #include "s_aatritemp.h"
 352 }
 353
 354
 355 static void
 356 index_aa_tri(GLcontext *ctx,
 357              const SWvertex *v0,
 358              const SWvertex *v1,
 359              const SWvertex *v2)
 360 {
 361 #define DO_Z
 362 #define DO_FOG
 363 #define DO_INDEX
 364 #include "s_aatritemp.h"
 365 }
 366
 367
 368 /*
 369  * Compute mipmap level of detail.
 370  * XXX we should really include the R coordinate in this computation
 371  * in order to do 3-D texture mipmapping.
 372  */
 373 static INLINE GLfloat
 374 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 375                const GLfloat qPlane[4], GLfloat cx, GLfloat cy,
 376                GLfloat invQ, GLfloat texWidth, GLfloat texHeight)
 377 {
 378    const GLfloat s = solve_plane(cx, cy, sPlane);
 379    const GLfloat t = solve_plane(cx, cy, tPlane);
 380    const GLfloat invQ_x1 = solve_plane_recip(cx+1.0F, cy, qPlane);
 381    const GLfloat invQ_y1 = solve_plane_recip(cx, cy+1.0F, qPlane);
 382    const GLfloat s_x1 = s - sPlane[0] / sPlane[2];
 383    const GLfloat s_y1 = s - sPlane[1] / sPlane[2];
 384    const GLfloat t_x1 = t - tPlane[0] / tPlane[2];
 385    const GLfloat t_y1 = t - tPlane[1] / tPlane[2];
 386    GLfloat dsdx = s_x1 * invQ_x1 - s * invQ;
 387    GLfloat dsdy = s_y1 * invQ_y1 - s * invQ;
 388    GLfloat dtdx = t_x1 * invQ_x1 - t * invQ;
 389    GLfloat dtdy = t_y1 * invQ_y1 - t * invQ;
 390    GLfloat maxU, maxV, rho, lambda;
 391    dsdx = FABSF(dsdx);
 392    dsdy = FABSF(dsdy);
 393    dtdx = FABSF(dtdx);
 394    dtdy = FABSF(dtdy);
 395    maxU = MAX2(dsdx, dsdy) * texWidth;
 396    maxV = MAX2(dtdx, dtdy) * texHeight;
 397    rho = MAX2(maxU, maxV);
 398    lambda = LOG2(rho);
 399    return lambda;
 400 }
 401
 402
 403 static void
 404 tex_aa_tri(GLcontext *ctx,
 405            const SWvertex *v0,
 406            const SWvertex *v1,
 407            const SWvertex *v2)
 408 {
 409 #define DO_Z
 410 #define DO_FOG
 411 #define DO_RGBA
 412 #define DO_TEX
 413 #include "s_aatritemp.h"
 414 }
 415
 416
 417 static void
 418 spec_tex_aa_tri(GLcontext *ctx,
 419                 const SWvertex *v0,
 420                 const SWvertex *v1,
 421                 const SWvertex *v2)
 422 {
 423 #define DO_Z
 424 #define DO_FOG
 425 #define DO_RGBA
 426 #define DO_TEX
 427 #define DO_SPEC
 428 #include "s_aatritemp.h"
 429 }
 430
 431
 432 static void
 433 multitex_aa_tri(GLcontext *ctx,
 434                 const SWvertex *v0,
 435                 const SWvertex *v1,
 436                 const SWvertex *v2)
 437 {
 438 #define DO_Z
 439 #define DO_FOG
 440 #define DO_RGBA
 441 #define DO_MULTITEX
 442 #include "s_aatritemp.h"
 443 }
 444
 445 static void
 446 spec_multitex_aa_tri(GLcontext *ctx,
 447                      const SWvertex *v0,
 448                      const SWvertex *v1,
 449                      const SWvertex *v2)
 450 {
 451 #define DO_Z
 452 #define DO_FOG
 453 #define DO_RGBA
 454 #define DO_MULTITEX
 455 #define DO_SPEC
 456 #include "s_aatritemp.h"
 457 }
 458
 459
 460 /*
 461  * Examine GL state and set swrast->Triangle to an
 462  * appropriate antialiased triangle rasterizer function.
 463  */
 464 void
 465 _swrast_set_aa_triangle_function(GLcontext *ctx)
 466 {
 467    ASSERT(ctx->Polygon.SmoothFlag);
 468
 469    if (ctx->Texture._EnabledCoordUnits != 0) {
 470       if (NEED_SECONDARY_COLOR(ctx)) {
 471          if (ctx->Texture._EnabledCoordUnits > 1) {
 472             SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;
 473          }
 474          else {
 475             SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;
 476          }
 477       }
 478       else {
 479          if (ctx->Texture._EnabledCoordUnits > 1) {
 480             SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;
 481          }
 482          else {
 483             SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;
 484          }
 485       }
 486    }
 487    else if (ctx->Visual.rgbMode) {
 488       SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 489    }
 490    else {
 491       SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 492    }
 493
 494    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 495 }