src/mesa/swrast/s_aatriangle.c

   1 /* $Id: s_aatriangle.c,v 1.27 2003/01/20 15:20:27 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  5.1
   6  *
   7  * Copyright (C) 1999-2003  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 "glheader.h"
  34 #include "colormac.h"
  35 #include "macros.h"
  36 #include "imports.h"
  37 #include "mmath.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    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 136    if (z < 0.0F)
 137       return 0;
 138    else if (z > CHAN_MAXF)
 139       return (GLchan) CHAN_MAXF;
 140    return (GLchan) (GLint) z;
 141 }
 142
 143
 144
 145 /*
 146  * Compute how much (area) of the given pixel is inside the triangle.
 147  * Vertices MUST be specified in counter-clockwise order.
 148  * Return:  coverage in [0, 1].
 149  */
 150 static GLfloat
 151 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 152                   const GLfloat v2[3], GLint winx, GLint winy)
 153 {
 154    /* Given a position [0,3]x[0,3] return the sub-pixel sample position.
 155     * Contributed by Ray Tice.
 156     *
 157     * Jitter sample positions -
 158     * - average should be .5 in x & y for each column
 159     * - each of the 16 rows and columns should be used once
 160     * - the rectangle formed by the first four points
 161     *   should contain the other points
 162     * - the distrubition should be fairly even in any given direction
 163     *
 164     * The pattern drawn below isn't optimal, but it's better than a regular
 165     * grid.  In the drawing, the center of each subpixel is surrounded by
 166     * four dots.  The "x" marks the jittered position relative to the
 167     * subpixel center.
 168     */
 169 #define POS(a, b) (0.5+a*4+b)/16
 170    static const GLfloat samples[16][2] = {
 171       /* start with the four corners */
 172       { POS(0, 2), POS(0, 0) },
 173       { POS(3, 3), POS(0, 2) },
 174       { POS(0, 0), POS(3, 1) },
 175       { POS(3, 1), POS(3, 3) },
 176       /* continue with interior samples */
 177       { POS(1, 1), POS(0, 1) },
 178       { POS(2, 0), POS(0, 3) },
 179       { POS(0, 3), POS(1, 3) },
 180       { POS(1, 2), POS(1, 0) },
 181       { POS(2, 3), POS(1, 2) },
 182       { POS(3, 2), POS(1, 1) },
 183       { POS(0, 1), POS(2, 2) },
 184       { POS(1, 0), POS(2, 1) },
 185       { POS(2, 1), POS(2, 3) },
 186       { POS(3, 0), POS(2, 0) },
 187       { POS(1, 3), POS(3, 0) },
 188       { POS(2, 2), POS(3, 2) }
 189    };
 190
 191    const GLfloat x = (GLfloat) winx;
 192    const GLfloat y = (GLfloat) winy;
 193    const GLfloat dx0 = v1[0] - v0[0];
 194    const GLfloat dy0 = v1[1] - v0[1];
 195    const GLfloat dx1 = v2[0] - v1[0];
 196    const GLfloat dy1 = v2[1] - v1[1];
 197    const GLfloat dx2 = v0[0] - v2[0];
 198    const GLfloat dy2 = v0[1] - v2[1];
 199    GLint stop = 4, i;
 200    GLfloat insideCount = 16.0F;
 201
 202 #ifdef DEBUG
 203    {
 204       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 205       ASSERT(area >= 0.0);
 206    }
 207 #endif
 208
 209    for (i = 0; i < stop; i++) {
 210       const GLfloat sx = x + samples[i][0];
 211       const GLfloat sy = y + samples[i][1];
 212       const GLfloat fx0 = sx - v0[0];
 213       const GLfloat fy0 = sy - v0[1];
 214       const GLfloat fx1 = sx - v1[0];
 215       const GLfloat fy1 = sy - v1[1];
 216       const GLfloat fx2 = sx - v2[0];
 217       const GLfloat fy2 = sy - v2[1];
 218       /* cross product determines if sample is inside or outside each edge */
 219       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 220       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 221       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 222       /* Check if the sample is exactly on an edge.  If so, let cross be a
 223        * positive or negative value depending on the direction of the edge.
 224        */
 225       if (cross0 == 0.0F)
 226          cross0 = dx0 + dy0;
 227       if (cross1 == 0.0F)
 228          cross1 = dx1 + dy1;
 229       if (cross2 == 0.0F)
 230          cross2 = dx2 + dy2;
 231       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 232          /* point is outside triangle */
 233          insideCount -= 1.0F;
 234          stop = 16;
 235       }
 236    }
 237    if (stop == 4)
 238       return 1.0F;
 239    else
 240       return insideCount * (1.0F / 16.0F);
 241 }
 242
 243
 244
 245 /*
 246  * Compute how much (area) of the given pixel is inside the triangle.
 247  * Vertices MUST be specified in counter-clockwise order.
 248  * Return:  coverage in [0, 15].
 249  */
 250 static GLint
 251 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 252                   const GLfloat v2[3], GLint winx, GLint winy)
 253 {
 254    /* NOTE: 15 samples instead of 16. */
 255    static const GLfloat samples[15][2] = {
 256       /* start with the four corners */
 257       { POS(0, 2), POS(0, 0) },
 258       { POS(3, 3), POS(0, 2) },
 259       { POS(0, 0), POS(3, 1) },
 260       { POS(3, 1), POS(3, 3) },
 261       /* continue with interior samples */
 262       { POS(1, 1), POS(0, 1) },
 263       { POS(2, 0), POS(0, 3) },
 264       { POS(0, 3), POS(1, 3) },
 265       { POS(1, 2), POS(1, 0) },
 266       { POS(2, 3), POS(1, 2) },
 267       { POS(3, 2), POS(1, 1) },
 268       { POS(0, 1), POS(2, 2) },
 269       { POS(1, 0), POS(2, 1) },
 270       { POS(2, 1), POS(2, 3) },
 271       { POS(3, 0), POS(2, 0) },
 272       { POS(1, 3), POS(3, 0) }
 273    };
 274    const GLfloat x = (GLfloat) winx;
 275    const GLfloat y = (GLfloat) winy;
 276    const GLfloat dx0 = v1[0] - v0[0];
 277    const GLfloat dy0 = v1[1] - v0[1];
 278    const GLfloat dx1 = v2[0] - v1[0];
 279    const GLfloat dy1 = v2[1] - v1[1];
 280    const GLfloat dx2 = v0[0] - v2[0];
 281    const GLfloat dy2 = v0[1] - v2[1];
 282    GLint stop = 4, i;
 283    GLint insideCount = 15;
 284
 285 #ifdef DEBUG
 286    {
 287       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 288       ASSERT(area >= 0.0);
 289    }
 290 #endif
 291
 292    for (i = 0; i < stop; i++) {
 293       const GLfloat sx = x + samples[i][0];
 294       const GLfloat sy = y + samples[i][1];
 295       const GLfloat fx0 = sx - v0[0];
 296       const GLfloat fy0 = sy - v0[1];
 297       const GLfloat fx1 = sx - v1[0];
 298       const GLfloat fy1 = sy - v1[1];
 299       const GLfloat fx2 = sx - v2[0];
 300       const GLfloat fy2 = sy - v2[1];
 301       /* cross product determines if sample is inside or outside each edge */
 302       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 303       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 304       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 305       /* Check if the sample is exactly on an edge.  If so, let cross be a
 306        * positive or negative value depending on the direction of the edge.
 307        */
 308       if (cross0 == 0.0F)
 309          cross0 = dx0 + dy0;
 310       if (cross1 == 0.0F)
 311          cross1 = dx1 + dy1;
 312       if (cross2 == 0.0F)
 313          cross2 = dx2 + dy2;
 314       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 315          /* point is outside triangle */
 316          insideCount--;
 317          stop = 15;
 318       }
 319    }
 320    if (stop == 4)
 321       return 15;
 322    else
 323       return insideCount;
 324 }
 325
 326
 327
 328 static void
 329 rgba_aa_tri(GLcontext *ctx,
 330             const SWvertex *v0,
 331             const SWvertex *v1,
 332             const SWvertex *v2)
 333 {
 334 #define DO_Z
 335 #define DO_FOG
 336 #define DO_RGBA
 337 #include "s_aatritemp.h"
 338 }
 339
 340
 341 static void
 342 index_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_INDEX
 350 #include "s_aatritemp.h"
 351 }
 352
 353
 354 /*
 355  * Compute mipmap level of detail.
 356  * XXX we should really include the R coordinate in this computation
 357  * in order to do 3-D texture mipmapping.
 358  */
 359 static INLINE GLfloat
 360 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 361                const GLfloat qPlane[4], GLfloat cx, GLfloat cy,
 362                GLfloat invQ, GLfloat texWidth, GLfloat texHeight)
 363 {
 364    const GLfloat s = solve_plane(cx, cy, sPlane);
 365    const GLfloat t = solve_plane(cx, cy, tPlane);
 366    const GLfloat invQ_x1 = solve_plane_recip(cx+1.0F, cy, qPlane);
 367    const GLfloat invQ_y1 = solve_plane_recip(cx, cy+1.0F, qPlane);
 368    const GLfloat s_x1 = s - sPlane[0] / sPlane[2];
 369    const GLfloat s_y1 = s - sPlane[1] / sPlane[2];
 370    const GLfloat t_x1 = t - tPlane[0] / tPlane[2];
 371    const GLfloat t_y1 = t - tPlane[1] / tPlane[2];
 372    GLfloat dsdx = s_x1 * invQ_x1 - s * invQ;
 373    GLfloat dsdy = s_y1 * invQ_y1 - s * invQ;
 374    GLfloat dtdx = t_x1 * invQ_x1 - t * invQ;
 375    GLfloat dtdy = t_y1 * invQ_y1 - t * invQ;
 376    GLfloat maxU, maxV, rho, lambda;
 377    dsdx = FABSF(dsdx);
 378    dsdy = FABSF(dsdy);
 379    dtdx = FABSF(dtdx);
 380    dtdy = FABSF(dtdy);
 381    maxU = MAX2(dsdx, dsdy) * texWidth;
 382    maxV = MAX2(dtdx, dtdy) * texHeight;
 383    rho = MAX2(maxU, maxV);
 384    lambda = LOG2(rho);
 385    return lambda;
 386 }
 387
 388
 389 static void
 390 tex_aa_tri(GLcontext *ctx,
 391            const SWvertex *v0,
 392            const SWvertex *v1,
 393            const SWvertex *v2)
 394 {
 395 #define DO_Z
 396 #define DO_FOG
 397 #define DO_RGBA
 398 #define DO_TEX
 399 #include "s_aatritemp.h"
 400 }
 401
 402
 403 static void
 404 spec_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 #define DO_SPEC
 414 #include "s_aatritemp.h"
 415 }
 416
 417
 418 static void
 419 multitex_aa_tri(GLcontext *ctx,
 420                 const SWvertex *v0,
 421                 const SWvertex *v1,
 422                 const SWvertex *v2)
 423 {
 424 #define DO_Z
 425 #define DO_FOG
 426 #define DO_RGBA
 427 #define DO_MULTITEX
 428 #include "s_aatritemp.h"
 429 }
 430
 431 static void
 432 spec_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 #define DO_SPEC
 442 #include "s_aatritemp.h"
 443 }
 444
 445
 446 /*
 447  * Examine GL state and set swrast->Triangle to an
 448  * appropriate antialiased triangle rasterizer function.
 449  */
 450 void
 451 _mesa_set_aa_triangle_function(GLcontext *ctx)
 452 {
 453    ASSERT(ctx->Polygon.SmoothFlag);
 454
 455    if (ctx->Texture._EnabledUnits != 0) {
 456       if (ctx->_TriangleCaps & DD_SEPARATE_SPECULAR) {
 457          if (ctx->Texture._EnabledUnits > 1) {
 458             SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;
 459          }
 460          else {
 461             SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;
 462          }
 463       }
 464       else {
 465          if (ctx->Texture._EnabledUnits > 1) {
 466             SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;
 467          }
 468          else {
 469             SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;
 470          }
 471       }
 472    }
 473    else if (ctx->Visual.rgbMode) {
 474       SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 475    }
 476    else {
 477       SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 478    }
 479
 480    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 481 }