src/mesa/swrast/s_aatriangle.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.3
   4  *
   5  * Copyright (C) 1999-2004  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 "s_aatriangle.h"
  38 #include "s_context.h"
  39 #include "s_span.h"
  40
  41
  42 /*
  43  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  44  * vertices and the given Z values.
  45  * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
  46  */
  47 static INLINE void
  48 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  49               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  50 {
  51    const GLfloat px = v1[0] - v0[0];
  52    const GLfloat py = v1[1] - v0[1];
  53    const GLfloat pz = z1 - z0;
  54
  55    const GLfloat qx = v2[0] - v0[0];
  56    const GLfloat qy = v2[1] - v0[1];
  57    const GLfloat qz = z2 - z0;
  58
  59    /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
  60    const GLfloat a = py * qz - pz * qy;
  61    const GLfloat b = pz * qx - px * qz;
  62    const GLfloat c = px * qy - py * qx;
  63    /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
  64       on the distance of plane from origin and arbitrary "w" parallel
  65       to the plane. */
  66    /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
  67       which is equal to "-d" below. */
  68    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  69
  70    plane[0] = a;
  71    plane[1] = b;
  72    plane[2] = c;
  73    plane[3] = d;
  74 }
  75
  76
  77 /*
  78  * Compute coefficients of a plane with a constant Z value.
  79  */
  80 static INLINE void
  81 constant_plane(GLfloat value, GLfloat plane[4])
  82 {
  83    plane[0] = 0.0;
  84    plane[1] = 0.0;
  85    plane[2] = -1.0;
  86    plane[3] = value;
  87 }
  88
  89 #define CONSTANT_PLANE(VALUE, PLANE)    \
  90 do {                                    \
  91    PLANE[0] = 0.0F;                     \
  92    PLANE[1] = 0.0F;                     \
  93    PLANE[2] = -1.0F;                    \
  94    PLANE[3] = VALUE;                    \
  95 } while (0)
  96
  97
  98
  99 /*
 100  * Solve plane equation for Z at (X,Y).
 101  */
 102 static INLINE GLfloat
 103 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 104 {
 105    ASSERT(plane[2] != 0.0F);
 106    return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 107 }
 108
 109
 110 #define SOLVE_PLANE(X, Y, PLANE) \
 111    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 112
 113
 114 /*
 115  * Return 1 / solve_plane().
 116  */
 117 static INLINE GLfloat
 118 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 119 {
 120    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 121    if (denom == 0.0F)
 122       return 0.0F;
 123    else
 124       return -plane[2] / denom;
 125 }
 126
 127
 128 /*
 129  * Solve plane and return clamped GLchan value.
 130  */
 131 static INLINE GLchan
 132 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 133 {
 134    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 135 #if CHAN_TYPE == GL_FLOAT
 136    return CLAMP(z, 0.0F, CHAN_MAXF);
 137 #else
 138    if (z < 0)
 139       return 0;
 140    else if (z > CHAN_MAX)
 141       return CHAN_MAX;
 142    return (GLchan) IROUND_POS(z);
 143 #endif
 144 }
 145
 146
 147
 148 /*
 149  * Compute how much (area) of the given pixel is inside the triangle.
 150  * Vertices MUST be specified in counter-clockwise order.
 151  * Return:  coverage in [0, 1].
 152  */
 153 static GLfloat
 154 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 155                   const GLfloat v2[3], GLint winx, GLint winy)
 156 {
 157    /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
 158     * Contributed by Ray Tice.
 159     *
 160     * Jitter sample positions -
 161     * - average should be .5 in x & y for each column
 162     * - each of the 16 rows and columns should be used once
 163     * - the rectangle formed by the first four points
 164     *   should contain the other points
 165     * - the distrubition should be fairly even in any given direction
 166     *
 167     * The pattern drawn below isn't optimal, but it's better than a regular
 168     * grid.  In the drawing, the center of each subpixel is surrounded by
 169     * four dots.  The "x" marks the jittered position relative to the
 170     * subpixel center.
 171     */
 172 #define POS(a, b) (0.5+a*4+b)/16
 173    static const GLfloat samples[16][2] = {
 174       /* start with the four corners */
 175       { POS(0, 2), POS(0, 0) },
 176       { POS(3, 3), POS(0, 2) },
 177       { POS(0, 0), POS(3, 1) },
 178       { POS(3, 1), POS(3, 3) },
 179       /* continue with interior samples */
 180       { POS(1, 1), POS(0, 1) },
 181       { POS(2, 0), POS(0, 3) },
 182       { POS(0, 3), POS(1, 3) },
 183       { POS(1, 2), POS(1, 0) },
 184       { POS(2, 3), POS(1, 2) },
 185       { POS(3, 2), POS(1, 1) },
 186       { POS(0, 1), POS(2, 2) },
 187       { POS(1, 0), POS(2, 1) },
 188       { POS(2, 1), POS(2, 3) },
 189       { POS(3, 0), POS(2, 0) },
 190       { POS(1, 3), POS(3, 0) },
 191       { POS(2, 2), POS(3, 2) }
 192    };
 193
 194    const GLfloat x = (GLfloat) winx;
 195    const GLfloat y = (GLfloat) winy;
 196    const GLfloat dx0 = v1[0] - v0[0];
 197    const GLfloat dy0 = v1[1] - v0[1];
 198    const GLfloat dx1 = v2[0] - v1[0];
 199    const GLfloat dy1 = v2[1] - v1[1];
 200    const GLfloat dx2 = v0[0] - v2[0];
 201    const GLfloat dy2 = v0[1] - v2[1];
 202    GLint stop = 4, i;
 203    GLfloat insideCount = 16.0F;
 204
 205 #ifdef DEBUG
 206    {
 207       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 208       ASSERT(area >= 0.0);
 209    }
 210 #endif
 211
 212    for (i = 0; i < stop; i++) {
 213       const GLfloat sx = x + samples[i][0];
 214       const GLfloat sy = y + samples[i][1];
 215       /* cross product determines if sample is inside or outside each edge */
 216       GLfloat cross = (dx0 * (sy - v0[1]) - dy0 * (sx - v0[0]));
 217       /* Check if the sample is exactly on an edge.  If so, let cross be a
 218        * positive or negative value depending on the direction of the edge.
 219        */
 220       if (cross == 0.0F)
 221          cross = dx0 + dy0;
 222       if (cross < 0.0F) {
 223          /* sample point is outside first edge */
 224          insideCount -= 1.0F;
 225          stop = 16;
 226       }
 227       else {
 228          /* sample point is inside first edge */
 229          cross = (dx1 * (sy - v1[1]) - dy1 * (sx - v1[0]));
 230          if (cross == 0.0F)
 231             cross = dx1 + dy1;
 232          if (cross < 0.0F) {
 233             /* sample point is outside second edge */
 234             insideCount -= 1.0F;
 235             stop = 16;
 236          }
 237          else {
 238             /* sample point is inside first and second edges */
 239             cross = (dx2 * (sy - v2[1]) -  dy2 * (sx - v2[0]));
 240             if (cross == 0.0F)
 241                cross = dx2 + dy2;
 242             if (cross < 0.0F) {
 243                /* sample point is outside third edge */
 244                insideCount -= 1.0F;
 245                stop = 16;
 246             }
 247          }
 248       }
 249    }
 250    if (stop == 4)
 251       return 1.0F;
 252    else
 253       return insideCount * (1.0F / 16.0F);
 254 }
 255
 256
 257
 258 /*
 259  * Compute how much (area) of the given pixel is inside the triangle.
 260  * Vertices MUST be specified in counter-clockwise order.
 261  * Return:  coverage in [0, 15].
 262  */
 263 static GLint
 264 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 265                   const GLfloat v2[3], GLint winx, GLint winy)
 266 {
 267    /* NOTE: 15 samples instead of 16. */
 268    static const GLfloat samples[15][2] = {
 269       /* start with the four corners */
 270       { POS(0, 2), POS(0, 0) },
 271       { POS(3, 3), POS(0, 2) },
 272       { POS(0, 0), POS(3, 1) },
 273       { POS(3, 1), POS(3, 3) },
 274       /* continue with interior samples */
 275       { POS(1, 1), POS(0, 1) },
 276       { POS(2, 0), POS(0, 3) },
 277       { POS(0, 3), POS(1, 3) },
 278       { POS(1, 2), POS(1, 0) },
 279       { POS(2, 3), POS(1, 2) },
 280       { POS(3, 2), POS(1, 1) },
 281       { POS(0, 1), POS(2, 2) },
 282       { POS(1, 0), POS(2, 1) },
 283       { POS(2, 1), POS(2, 3) },
 284       { POS(3, 0), POS(2, 0) },
 285       { POS(1, 3), POS(3, 0) }
 286    };
 287    const GLfloat x = (GLfloat) winx;
 288    const GLfloat y = (GLfloat) winy;
 289    const GLfloat dx0 = v1[0] - v0[0];
 290    const GLfloat dy0 = v1[1] - v0[1];
 291    const GLfloat dx1 = v2[0] - v1[0];
 292    const GLfloat dy1 = v2[1] - v1[1];
 293    const GLfloat dx2 = v0[0] - v2[0];
 294    const GLfloat dy2 = v0[1] - v2[1];
 295    GLint stop = 4, i;
 296    GLint insideCount = 15;
 297
 298 #ifdef DEBUG
 299    {
 300       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 301       ASSERT(area >= 0.0);
 302    }
 303 #endif
 304
 305    for (i = 0; i < stop; i++) {
 306       const GLfloat sx = x + samples[i][0];
 307       const GLfloat sy = y + samples[i][1];
 308       const GLfloat fx0 = sx - v0[0];
 309       const GLfloat fy0 = sy - v0[1];
 310       const GLfloat fx1 = sx - v1[0];
 311       const GLfloat fy1 = sy - v1[1];
 312       const GLfloat fx2 = sx - v2[0];
 313       const GLfloat fy2 = sy - v2[1];
 314       /* cross product determines if sample is inside or outside each edge */
 315       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 316       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 317       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 318       /* Check if the sample is exactly on an edge.  If so, let cross be a
 319        * positive or negative value depending on the direction of the edge.
 320        */
 321       if (cross0 == 0.0F)
 322          cross0 = dx0 + dy0;
 323       if (cross1 == 0.0F)
 324          cross1 = dx1 + dy1;
 325       if (cross2 == 0.0F)
 326          cross2 = dx2 + dy2;
 327       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 328          /* point is outside triangle */
 329          insideCount--;
 330          stop = 15;
 331       }
 332    }
 333    if (stop == 4)
 334       return 15;
 335    else
 336       return insideCount;
 337 }
 338
 339
 340
 341 static void
 342 rgba_aa_tri(GLcontext *ctx,
 343             const SWvertex *v0,
 344             const SWvertex *v1,
 345             const SWvertex *v2)
 346 {
 347 #define DO_Z
 348 #define DO_FOG
 349 #define DO_RGBA
 350 #include "s_aatritemp.h"
 351 }
 352
 353
 354 static void
 355 index_aa_tri(GLcontext *ctx,
 356              const SWvertex *v0,
 357              const SWvertex *v1,
 358              const SWvertex *v2)
 359 {
 360 #define DO_Z
 361 #define DO_FOG
 362 #define DO_INDEX
 363 #include "s_aatritemp.h"
 364 }
 365
 366
 367 /*
 368  * Compute mipmap level of detail.
 369  * XXX we should really include the R coordinate in this computation
 370  * in order to do 3-D texture mipmapping.
 371  */
 372 static INLINE GLfloat
 373 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 374                const GLfloat qPlane[4], GLfloat cx, GLfloat cy,
 375                GLfloat invQ, GLfloat texWidth, GLfloat texHeight)
 376 {
 377    const GLfloat s = solve_plane(cx, cy, sPlane);
 378    const GLfloat t = solve_plane(cx, cy, tPlane);
 379    const GLfloat invQ_x1 = solve_plane_recip(cx+1.0F, cy, qPlane);
 380    const GLfloat invQ_y1 = solve_plane_recip(cx, cy+1.0F, qPlane);
 381    const GLfloat s_x1 = s - sPlane[0] / sPlane[2];
 382    const GLfloat s_y1 = s - sPlane[1] / sPlane[2];
 383    const GLfloat t_x1 = t - tPlane[0] / tPlane[2];
 384    const GLfloat t_y1 = t - tPlane[1] / tPlane[2];
 385    GLfloat dsdx = s_x1 * invQ_x1 - s * invQ;
 386    GLfloat dsdy = s_y1 * invQ_y1 - s * invQ;
 387    GLfloat dtdx = t_x1 * invQ_x1 - t * invQ;
 388    GLfloat dtdy = t_y1 * invQ_y1 - t * invQ;
 389    GLfloat maxU, maxV, rho, lambda;
 390    dsdx = FABSF(dsdx);
 391    dsdy = FABSF(dsdy);
 392    dtdx = FABSF(dtdx);
 393    dtdy = FABSF(dtdy);
 394    maxU = MAX2(dsdx, dsdy) * texWidth;
 395    maxV = MAX2(dtdx, dtdy) * texHeight;
 396    rho = MAX2(maxU, maxV);
 397    lambda = LOG2(rho);
 398    return lambda;
 399 }
 400
 401
 402 static void
 403 tex_aa_tri(GLcontext *ctx,
 404            const SWvertex *v0,
 405            const SWvertex *v1,
 406            const SWvertex *v2)
 407 {
 408 #define DO_Z
 409 #define DO_FOG
 410 #define DO_RGBA
 411 #define DO_TEX
 412 #include "s_aatritemp.h"
 413 }
 414
 415
 416 static void
 417 spec_tex_aa_tri(GLcontext *ctx,
 418                 const SWvertex *v0,
 419                 const SWvertex *v1,
 420                 const SWvertex *v2)
 421 {
 422 #define DO_Z
 423 #define DO_FOG
 424 #define DO_RGBA
 425 #define DO_TEX
 426 #define DO_SPEC
 427 #include "s_aatritemp.h"
 428 }
 429
 430
 431 static void
 432 multitex_aa_tri(GLcontext *ctx,
 433                 const SWvertex *v0,
 434                 const SWvertex *v1,
 435                 const SWvertex *v2)
 436 {
 437 #define DO_Z
 438 #define DO_FOG
 439 #define DO_RGBA
 440 #define DO_MULTITEX
 441 #include "s_aatritemp.h"
 442 }
 443
 444 static void
 445 spec_multitex_aa_tri(GLcontext *ctx,
 446                      const SWvertex *v0,
 447                      const SWvertex *v1,
 448                      const SWvertex *v2)
 449 {
 450 #define DO_Z
 451 #define DO_FOG
 452 #define DO_RGBA
 453 #define DO_MULTITEX
 454 #define DO_SPEC
 455 #include "s_aatritemp.h"
 456 }
 457
 458
 459 /*
 460  * Examine GL state and set swrast->Triangle to an
 461  * appropriate antialiased triangle rasterizer function.
 462  */
 463 void
 464 _swrast_set_aa_triangle_function(GLcontext *ctx)
 465 {
 466    ASSERT(ctx->Polygon.SmoothFlag);
 467
 468    if (ctx->Texture._EnabledCoordUnits != 0) {
 469       if (NEED_SECONDARY_COLOR(ctx)) {
 470          if (ctx->Texture._EnabledCoordUnits > 1) {
 471             SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;
 472          }
 473          else {
 474             SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;
 475          }
 476       }
 477       else {
 478          if (ctx->Texture._EnabledCoordUnits > 1) {
 479             SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;
 480          }
 481          else {
 482             SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;
 483          }
 484       }
 485    }
 486    else if (ctx->Visual.rgbMode) {
 487       SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 488    }
 489    else {
 490       SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 491    }
 492
 493    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 494 }