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