src/mesa/swrast/s_aatriangle.c

   1 /* $Id: s_aatriangle.c,v 1.23 2002/03/16 18:02:07 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  4.1
   6  *
   7  * Copyright (C) 1999-2002  Brian Paul   All Rights Reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a
  10  * copy of this software and associated documentation files (the "Software"),
  11  * to deal in the Software without restriction, including without limitation
  12  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  13  * and/or sell copies of the Software, and to permit persons to whom the
  14  * Software is furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included
  17  * in all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  20  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  23  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 /*
  29  * Antialiased Triangle rasterizers
  30  */
  31
  32
  33 #include "macros.h"
  34 #include "mem.h"
  35 #include "mmath.h"
  36 #include "s_aatriangle.h"
  37 #include "s_context.h"
  38 #include "s_span.h"
  39
  40
  41 /*
  42  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  43  * vertices and the given Z values.
  44  * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0.
  45  */
  46 static INLINE void
  47 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  48               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  49 {
  50    const GLfloat px = v1[0] - v0[0];
  51    const GLfloat py = v1[1] - v0[1];
  52    const GLfloat pz = z1 - z0;
  53
  54    const GLfloat qx = v2[0] - v0[0];
  55    const GLfloat qy = v2[1] - v0[1];
  56    const GLfloat qz = z2 - z0;
  57
  58    /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */
  59    const GLfloat a = py * qz - pz * qy;
  60    const GLfloat b = pz * qx - px * qz;
  61    const GLfloat c = px * qy - py * qx;
  62    /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending
  63       on the distance of plane from origin and arbitrary "w" parallel
  64       to the plane. */
  65    /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)",
  66       which is equal to "-d" below. */
  67    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  68
  69    plane[0] = a;
  70    plane[1] = b;
  71    plane[2] = c;
  72    plane[3] = d;
  73 }
  74
  75
  76 /*
  77  * Compute coefficients of a plane with a constant Z value.
  78  */
  79 static INLINE void
  80 constant_plane(GLfloat value, GLfloat plane[4])
  81 {
  82    plane[0] = 0.0;
  83    plane[1] = 0.0;
  84    plane[2] = -1.0;
  85    plane[3] = value;
  86 }
  87
  88 #define CONSTANT_PLANE(VALUE, PLANE)    \
  89 do {                                    \
  90    PLANE[0] = 0.0F;                     \
  91    PLANE[1] = 0.0F;                     \
  92    PLANE[2] = -1.0F;                    \
  93    PLANE[3] = VALUE;                    \
  94 } while (0)
  95
  96
  97
  98 /*
  99  * Solve plane equation for Z at (X,Y).
 100  */
 101 static INLINE GLfloat
 102 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 103 {
 104    ASSERT(plane[2] != 0.0F);
 105    return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 106 }
 107
 108
 109 #define SOLVE_PLANE(X, Y, PLANE) \
 110    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 111
 112
 113 /*
 114  * Return 1 / solve_plane().
 115  */
 116 static INLINE GLfloat
 117 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 118 {
 119    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 120    if (denom == 0.0F)
 121       return 0.0F;
 122    else
 123       return -plane[2] / denom;
 124 }
 125
 126
 127 /*
 128  * Solve plane and return clamped GLchan value.
 129  */
 130 static INLINE GLchan
 131 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 132 {
 133    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 134    if (z < 0.0F)
 135       return 0;
 136    else if (z > CHAN_MAXF)
 137       return (GLchan) CHAN_MAXF;
 138    return (GLchan) (GLint) z;
 139 }
 140
 141
 142
 143 /*
 144  * Compute how much (area) of the given pixel is inside the triangle.
 145  * Vertices MUST be specified in counter-clockwise order.
 146  * Return:  coverage in [0, 1].
 147  */
 148 static GLfloat
 149 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 150                   const GLfloat v2[3], GLint winx, GLint winy)
 151 {
 152    /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
 153     * Contributed by Ray Tice.
 154     *
 155     * Jitter sample positions -
 156     * - average should be .5 in x & y for each column
 157     * - each of the 16 rows and columns should be used once
 158     * - the rectangle formed by the first four points
 159     *   should contain the other points
 160     * - the distrubition should be fairly even in any given direction
 161     *
 162     * The pattern drawn below isn't optimal, but it's better than a regular
 163     * grid.  In the drawing, the center of each subpixel is surrounded by
 164     * four dots.  The "x" marks the jittered position relative to the
 165     * subpixel center.
 166     */
 167 #define POS(a, b) (0.5+a*4+b)/16
 168    static const GLfloat samples[16][2] = {
 169       /* start with the four corners */
 170       { POS(0, 2), POS(0, 0) },
 171       { POS(3, 3), POS(0, 2) },
 172       { POS(0, 0), POS(3, 1) },
 173       { POS(3, 1), POS(3, 3) },
 174       /* continue with interior samples */
 175       { POS(1, 1), POS(0, 1) },
 176       { POS(2, 0), POS(0, 3) },
 177       { POS(0, 3), POS(1, 3) },
 178       { POS(1, 2), POS(1, 0) },
 179       { POS(2, 3), POS(1, 2) },
 180       { POS(3, 2), POS(1, 1) },
 181       { POS(0, 1), POS(2, 2) },
 182       { POS(1, 0), POS(2, 1) },
 183       { POS(2, 1), POS(2, 3) },
 184       { POS(3, 0), POS(2, 0) },
 185       { POS(1, 3), POS(3, 0) },
 186       { POS(2, 2), POS(3, 2) }
 187    };
 188
 189    const GLfloat x = (GLfloat) winx;
 190    const GLfloat y = (GLfloat) winy;
 191    const GLfloat dx0 = v1[0] - v0[0];
 192    const GLfloat dy0 = v1[1] - v0[1];
 193    const GLfloat dx1 = v2[0] - v1[0];
 194    const GLfloat dy1 = v2[1] - v1[1];
 195    const GLfloat dx2 = v0[0] - v2[0];
 196    const GLfloat dy2 = v0[1] - v2[1];
 197    GLint stop = 4, i;
 198    GLfloat insideCount = 16.0F;
 199
 200 #ifdef DEBUG
 201    {
 202       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 203       ASSERT(area >= 0.0);
 204    }
 205 #endif
 206
 207    for (i = 0; i < stop; i++) {
 208       const GLfloat sx = x + samples[i][0];
 209       const GLfloat sy = y + samples[i][1];
 210       const GLfloat fx0 = sx - v0[0];
 211       const GLfloat fy0 = sy - v0[1];
 212       const GLfloat fx1 = sx - v1[0];
 213       const GLfloat fy1 = sy - v1[1];
 214       const GLfloat fx2 = sx - v2[0];
 215       const GLfloat fy2 = sy - v2[1];
 216       /* cross product determines if sample is inside or outside each edge */
 217       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 218       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 219       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 220       /* Check if the sample is exactly on an edge.  If so, let cross be a
 221        * positive or negative value depending on the direction of the edge.
 222        */
 223       if (cross0 == 0.0F)
 224          cross0 = dx0 + dy0;
 225       if (cross1 == 0.0F)
 226          cross1 = dx1 + dy1;
 227       if (cross2 == 0.0F)
 228          cross2 = dx2 + dy2;
 229       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 230          /* point is outside triangle */
 231          insideCount -= 1.0F;
 232          stop = 16;
 233       }
 234    }
 235    if (stop == 4)
 236       return 1.0F;
 237    else
 238       return insideCount * (1.0F / 16.0F);
 239 }
 240
 241
 242
 243 /*
 244  * Compute how much (area) of the given pixel is inside the triangle.
 245  * Vertices MUST be specified in counter-clockwise order.
 246  * Return:  coverage in [0, 15].
 247  */
 248 static GLint
 249 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 250                   const GLfloat v2[3], GLint winx, GLint winy)
 251 {
 252    /* NOTE: 15 samples instead of 16. */
 253    static const GLfloat samples[15][2] = {
 254       /* start with the four corners */
 255       { POS(0, 2), POS(0, 0) },
 256       { POS(3, 3), POS(0, 2) },
 257       { POS(0, 0), POS(3, 1) },
 258       { POS(3, 1), POS(3, 3) },
 259       /* continue with interior samples */
 260       { POS(1, 1), POS(0, 1) },
 261       { POS(2, 0), POS(0, 3) },
 262       { POS(0, 3), POS(1, 3) },
 263       { POS(1, 2), POS(1, 0) },
 264       { POS(2, 3), POS(1, 2) },
 265       { POS(3, 2), POS(1, 1) },
 266       { POS(0, 1), POS(2, 2) },
 267       { POS(1, 0), POS(2, 1) },
 268       { POS(2, 1), POS(2, 3) },
 269       { POS(3, 0), POS(2, 0) },
 270       { POS(1, 3), POS(3, 0) }
 271    };
 272    const GLfloat x = (GLfloat) winx;
 273    const GLfloat y = (GLfloat) winy;
 274    const GLfloat dx0 = v1[0] - v0[0];
 275    const GLfloat dy0 = v1[1] - v0[1];
 276    const GLfloat dx1 = v2[0] - v1[0];
 277    const GLfloat dy1 = v2[1] - v1[1];
 278    const GLfloat dx2 = v0[0] - v2[0];
 279    const GLfloat dy2 = v0[1] - v2[1];
 280    GLint stop = 4, i;
 281    GLint insideCount = 15;
 282
 283 #ifdef DEBUG
 284    {
 285       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 286       ASSERT(area >= 0.0);
 287    }
 288 #endif
 289
 290    for (i = 0; i < stop; i++) {
 291       const GLfloat sx = x + samples[i][0];
 292       const GLfloat sy = y + samples[i][1];
 293       const GLfloat fx0 = sx - v0[0];
 294       const GLfloat fy0 = sy - v0[1];
 295       const GLfloat fx1 = sx - v1[0];
 296       const GLfloat fy1 = sy - v1[1];
 297       const GLfloat fx2 = sx - v2[0];
 298       const GLfloat fy2 = sy - v2[1];
 299       /* cross product determines if sample is inside or outside each edge */
 300       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 301       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 302       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 303       /* Check if the sample is exactly on an edge.  If so, let cross be a
 304        * positive or negative value depending on the direction of the edge.
 305        */
 306       if (cross0 == 0.0F)
 307          cross0 = dx0 + dy0;
 308       if (cross1 == 0.0F)
 309          cross1 = dx1 + dy1;
 310       if (cross2 == 0.0F)
 311          cross2 = dx2 + dy2;
 312       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 313          /* point is outside triangle */
 314          insideCount--;
 315          stop = 15;
 316       }
 317    }
 318    if (stop == 4)
 319       return 15;
 320    else
 321       return insideCount;
 322 }
 323
 324
 325
 326 static void
 327 rgba_aa_tri(GLcontext *ctx,
 328             const SWvertex *v0,
 329             const SWvertex *v1,
 330             const SWvertex *v2)
 331 {
 332 #define DO_Z
 333 #define DO_FOG
 334 #define DO_RGBA
 335 #include "s_aatritemp.h"
 336 }
 337
 338
 339 static void
 340 index_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_INDEX
 348 #include "s_aatritemp.h"
 349 }
 350
 351
 352 /*
 353  * Compute mipmap level of detail.
 354  * XXX we should really include the R coordinate in this computation
 355  * in order to do 3-D texture mipmapping.
 356  */
 357 static INLINE GLfloat
 358 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 359                const GLfloat qPlane[4], GLfloat cx, GLfloat cy,
 360                GLfloat invQ, GLfloat texWidth, GLfloat texHeight)
 361 {
 362    const GLfloat s = solve_plane(cx, cy, sPlane);
 363    const GLfloat t = solve_plane(cx, cy, tPlane);
 364    const GLfloat invQ_x1 = solve_plane_recip(cx+1.0, cy, qPlane);
 365    const GLfloat invQ_y1 = solve_plane_recip(cx, cy+1.0, qPlane);
 366    const GLfloat s_x1 = s - sPlane[0] / sPlane[2];
 367    const GLfloat s_y1 = s - sPlane[1] / sPlane[2];
 368    const GLfloat t_x1 = t - tPlane[0] / tPlane[2];
 369    const GLfloat t_y1 = t - tPlane[1] / tPlane[2];
 370    GLfloat dsdx = s_x1 * invQ_x1 - s * invQ;
 371    GLfloat dsdy = s_y1 * invQ_y1 - s * invQ;
 372    GLfloat dtdx = t_x1 * invQ_x1 - t * invQ;
 373    GLfloat dtdy = t_y1 * invQ_y1 - t * invQ;
 374    GLfloat maxU, maxV, rho, lambda;
 375    dsdx = FABSF(dsdx);
 376    dsdy = FABSF(dsdy);
 377    dtdx = FABSF(dtdx);
 378    dtdy = FABSF(dtdy);
 379    maxU = MAX2(dsdx, dsdy) * texWidth;
 380    maxV = MAX2(dtdx, dtdy) * texHeight;
 381    rho = MAX2(maxU, maxV);
 382    lambda = LOG2(rho);
 383    return lambda;
 384 }
 385
 386
 387 static void
 388 tex_aa_tri(GLcontext *ctx,
 389            const SWvertex *v0,
 390            const SWvertex *v1,
 391            const SWvertex *v2)
 392 {
 393 #define DO_Z
 394 #define DO_FOG
 395 #define DO_RGBA
 396 #define DO_TEX
 397 #include "s_aatritemp.h"
 398 }
 399
 400
 401 static void
 402 spec_tex_aa_tri(GLcontext *ctx,
 403                 const SWvertex *v0,
 404                 const SWvertex *v1,
 405                 const SWvertex *v2)
 406 {
 407 #define DO_Z
 408 #define DO_FOG
 409 #define DO_RGBA
 410 #define DO_TEX
 411 #define DO_SPEC
 412 #include "s_aatritemp.h"
 413 }
 414
 415
 416 static void
 417 multitex_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_MULTITEX
 426 #include "s_aatritemp.h"
 427 }
 428
 429 static void
 430 spec_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 #define DO_SPEC
 440 #include "s_aatritemp.h"
 441 }
 442
 443
 444 /*
 445  * Examine GL state and set swrast->Triangle to an
 446  * appropriate antialiased triangle rasterizer function.
 447  */
 448 void
 449 _mesa_set_aa_triangle_function(GLcontext *ctx)
 450 {
 451    ASSERT(ctx->Polygon.SmoothFlag);
 452
 453    if (ctx->Texture._ReallyEnabled) {
 454       if (ctx->_TriangleCaps & DD_SEPARATE_SPECULAR) {
 455          if (ctx->Texture._ReallyEnabled > TEXTURE0_ANY) {
 456             SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;
 457          }
 458          else {
 459             SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;
 460          }
 461       }
 462       else {
 463          if (ctx->Texture._ReallyEnabled > TEXTURE0_ANY) {
 464             SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;
 465          }
 466          else {
 467             SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;
 468          }
 469       }
 470    }
 471    else if (ctx->Visual.rgbMode) {
 472       SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 473    }
 474    else {
 475       SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 476    }
 477
 478    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 479 }