src/mesa/swrast/s_aatriangle.c

   1 /* $Id: s_aatriangle.c,v 1.14 2001/05/10 17:41:41 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  3.5
   6  *
   7  * Copyright (C) 1999-2001  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 "mmath.h"
  34 #include "s_aatriangle.h"
  35 #include "s_context.h"
  36 #include "s_span.h"
  37
  38
  39 /*
  40  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  41  * vertices and the given Z values.
  42  */
  43 static INLINE void
  44 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  45               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  46 {
  47    const GLfloat px = v1[0] - v0[0];
  48    const GLfloat py = v1[1] - v0[1];
  49    const GLfloat pz = z1 - z0;
  50
  51    const GLfloat qx = v2[0] - v0[0];
  52    const GLfloat qy = v2[1] - v0[1];
  53    const GLfloat qz = z2 - z0;
  54
  55    const GLfloat a = py * qz - pz * qy;
  56    const GLfloat b = pz * qx - px * qz;
  57    const GLfloat c = px * qy - py * qx;
  58    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  59
  60    plane[0] = a;
  61    plane[1] = b;
  62    plane[2] = c;
  63    plane[3] = d;
  64 }
  65
  66
  67 /*
  68  * Compute coefficients of a plane with a constant Z value.
  69  */
  70 static INLINE void
  71 constant_plane(GLfloat value, GLfloat plane[4])
  72 {
  73    plane[0] = 0.0;
  74    plane[1] = 0.0;
  75    plane[2] = -1.0;
  76    plane[3] = value;
  77 }
  78
  79 #define CONSTANT_PLANE(VALUE, PLANE)    \
  80 do {                                    \
  81    PLANE[0] = 0.0F;                     \
  82    PLANE[1] = 0.0F;                     \
  83    PLANE[2] = -1.0F;                    \
  84    PLANE[3] = VALUE;                    \
  85 } while (0)
  86
  87
  88
  89 /*
  90  * Solve plane equation for Z at (X,Y).
  91  */
  92 static INLINE GLfloat
  93 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
  94 {
  95    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
  96    return z;
  97 }
  98
  99
 100 #define SOLVE_PLANE(X, Y, PLANE) \
 101    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 102
 103
 104 /*
 105  * Return 1 / solve_plane().
 106  */
 107 static INLINE GLfloat
 108 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 109 {
 110    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 111    if (denom == 0.0F)
 112       return 0.0F;
 113    else
 114       return -plane[2] / denom;
 115 }
 116
 117
 118
 119 /*
 120  * Solve plane and return clamped GLchan value.
 121  */
 122 static INLINE GLchan
 123 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 124 {
 125    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 126    if (z < 0.0F)
 127       return 0;
 128    else if (z > CHAN_MAXF)
 129       return (GLchan) CHAN_MAXF;
 130    return (GLchan) (GLint) z;
 131 }
 132
 133
 134
 135 /*
 136  * Compute how much (area) of the given pixel is inside the triangle.
 137  * Vertices MUST be specified in counter-clockwise order.
 138  * Return:  coverage in [0, 1].
 139  */
 140 static GLfloat
 141 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 142                   const GLfloat v2[3], GLint winx, GLint winy)
 143 {
 144 #define B 0.125
 145    static const GLfloat samples[16][2] = {
 146       /* start with the four corners */
 147       { 0.00+B, 0.00+B },
 148       { 0.75+B, 0.00+B },
 149       { 0.00+B, 0.75+B },
 150       { 0.75+B, 0.75+B },
 151       /* continue with interior samples */
 152       { 0.25+B, 0.00+B },
 153       { 0.50+B, 0.00+B },
 154       { 0.00+B, 0.25+B },
 155       { 0.25+B, 0.25+B },
 156       { 0.50+B, 0.25+B },
 157       { 0.75+B, 0.25+B },
 158       { 0.00+B, 0.50+B },
 159       { 0.25+B, 0.50+B },
 160       { 0.50+B, 0.50+B },
 161       { 0.75+B, 0.50+B },
 162       { 0.25+B, 0.75+B },
 163       { 0.50+B, 0.75+B }
 164    };
 165    const GLfloat x = (GLfloat) winx;
 166    const GLfloat y = (GLfloat) winy;
 167    const GLfloat dx0 = v1[0] - v0[0];
 168    const GLfloat dy0 = v1[1] - v0[1];
 169    const GLfloat dx1 = v2[0] - v1[0];
 170    const GLfloat dy1 = v2[1] - v1[1];
 171    const GLfloat dx2 = v0[0] - v2[0];
 172    const GLfloat dy2 = v0[1] - v2[1];
 173    GLint stop = 4, i;
 174    GLfloat insideCount = 16.0F;
 175
 176 #ifdef DEBUG
 177    {
 178       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 179       assert(area >= 0.0);
 180    }
 181 #endif
 182
 183    for (i = 0; i < stop; i++) {
 184       const GLfloat sx = x + samples[i][0];
 185       const GLfloat sy = y + samples[i][1];
 186       const GLfloat fx0 = sx - v0[0];
 187       const GLfloat fy0 = sy - v0[1];
 188       const GLfloat fx1 = sx - v1[0];
 189       const GLfloat fy1 = sy - v1[1];
 190       const GLfloat fx2 = sx - v2[0];
 191       const GLfloat fy2 = sy - v2[1];
 192       /* cross product determines if sample is inside or outside each edge */
 193       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 194       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 195       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 196       /* Check if the sample is exactly on an edge.  If so, let cross be a
 197        * positive or negative value depending on the direction of the edge.
 198        */
 199       if (cross0 == 0.0F)
 200          cross0 = dx0 + dy0;
 201       if (cross1 == 0.0F)
 202          cross1 = dx1 + dy1;
 203       if (cross2 == 0.0F)
 204          cross2 = dx2 + dy2;
 205       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 206          /* point is outside triangle */
 207          insideCount -= 1.0F;
 208          stop = 16;
 209       }
 210    }
 211    if (stop == 4)
 212       return 1.0F;
 213    else
 214       return insideCount * (1.0F / 16.0F);
 215 }
 216
 217
 218
 219 /*
 220  * Compute how much (area) of the given pixel is inside the triangle.
 221  * Vertices MUST be specified in counter-clockwise order.
 222  * Return:  coverage in [0, 15].
 223  */
 224 static GLint
 225 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 226                   const GLfloat v2[3], GLint winx, GLint winy)
 227 {
 228    /* NOTE: 15 samples instead of 16.
 229     * A better sample distribution could be used.
 230     */
 231    static const GLfloat samples[15][2] = {
 232       /* start with the four corners */
 233       { 0.00+B, 0.00+B },
 234       { 0.75+B, 0.00+B },
 235       { 0.00+B, 0.75+B },
 236       { 0.75+B, 0.75+B },
 237       /* continue with interior samples */
 238       { 0.25+B, 0.00+B },
 239       { 0.50+B, 0.00+B },
 240       { 0.00+B, 0.25+B },
 241       { 0.25+B, 0.25+B },
 242       { 0.50+B, 0.25+B },
 243       { 0.75+B, 0.25+B },
 244       { 0.00+B, 0.50+B },
 245       { 0.25+B, 0.50+B },
 246       /*{ 0.50, 0.50 },*/
 247       { 0.75+B, 0.50+B },
 248       { 0.25+B, 0.75+B },
 249       { 0.50+B, 0.75+B }
 250    };
 251    const GLfloat x = (GLfloat) winx;
 252    const GLfloat y = (GLfloat) winy;
 253    const GLfloat dx0 = v1[0] - v0[0];
 254    const GLfloat dy0 = v1[1] - v0[1];
 255    const GLfloat dx1 = v2[0] - v1[0];
 256    const GLfloat dy1 = v2[1] - v1[1];
 257    const GLfloat dx2 = v0[0] - v2[0];
 258    const GLfloat dy2 = v0[1] - v2[1];
 259    GLint stop = 4, i;
 260    GLint insideCount = 15;
 261
 262 #ifdef DEBUG
 263    {
 264       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 265       assert(area >= 0.0);
 266    }
 267 #endif
 268
 269    for (i = 0; i < stop; i++) {
 270       const GLfloat sx = x + samples[i][0];
 271       const GLfloat sy = y + samples[i][1];
 272       const GLfloat fx0 = sx - v0[0];
 273       const GLfloat fy0 = sy - v0[1];
 274       const GLfloat fx1 = sx - v1[0];
 275       const GLfloat fy1 = sy - v1[1];
 276       const GLfloat fx2 = sx - v2[0];
 277       const GLfloat fy2 = sy - v2[1];
 278       /* cross product determines if sample is inside or outside each edge */
 279       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 280       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 281       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 282       /* Check if the sample is exactly on an edge.  If so, let cross be a
 283        * positive or negative value depending on the direction of the edge.
 284        */
 285       if (cross0 == 0.0F)
 286          cross0 = dx0 + dy0;
 287       if (cross1 == 0.0F)
 288          cross1 = dx1 + dy1;
 289       if (cross2 == 0.0F)
 290          cross2 = dx2 + dy2;
 291       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 292          /* point is outside triangle */
 293          insideCount--;
 294          stop = 15;
 295       }
 296    }
 297    if (stop == 4)
 298       return 15;
 299    else
 300       return insideCount;
 301 }
 302
 303
 304
 305 static void
 306 rgba_aa_tri(GLcontext *ctx,
 307             const SWvertex *v0,
 308             const SWvertex *v1,
 309             const SWvertex *v2)
 310 {
 311 #define DO_Z
 312 #define DO_RGBA
 313 #include "s_aatritemp.h"
 314 }
 315
 316
 317 static void
 318 index_aa_tri(GLcontext *ctx,
 319              const SWvertex *v0,
 320              const SWvertex *v1,
 321              const SWvertex *v2)
 322 {
 323 #define DO_Z
 324 #define DO_INDEX
 325 #include "s_aatritemp.h"
 326 }
 327
 328
 329 /*
 330  * Compute mipmap level of detail.
 331  */
 332 static INLINE GLfloat
 333 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 334                GLfloat invQ, GLfloat width, GLfloat height)
 335 {
 336    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 337    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 338    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 339    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 340    GLfloat r1 = dudx * dudx + dudy * dudy;
 341    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 342    GLfloat rho2 = r1 + r2;
 343    /* return log base 2 of rho */
 344    if (rho2 == 0.0F)
 345       return 0.0;
 346    else
 347       return log(rho2) * 1.442695 * 0.5;       /* 1.442695 = 1/log(2) */
 348 }
 349
 350
 351 static void
 352 tex_aa_tri(GLcontext *ctx,
 353            const SWvertex *v0,
 354            const SWvertex *v1,
 355            const SWvertex *v2)
 356 {
 357 #define DO_Z
 358 #define DO_RGBA
 359 #define DO_TEX
 360 #include "s_aatritemp.h"
 361 }
 362
 363
 364 static void
 365 spec_tex_aa_tri(GLcontext *ctx,
 366                 const SWvertex *v0,
 367                 const SWvertex *v1,
 368                 const SWvertex *v2)
 369 {
 370 #define DO_Z
 371 #define DO_RGBA
 372 #define DO_TEX
 373 #define DO_SPEC
 374 #include "s_aatritemp.h"
 375 }
 376
 377
 378 static void
 379 multitex_aa_tri(GLcontext *ctx,
 380                 const SWvertex *v0,
 381                 const SWvertex *v1,
 382                 const SWvertex *v2)
 383 {
 384 #define DO_Z
 385 #define DO_RGBA
 386 #define DO_MULTITEX
 387 #include "s_aatritemp.h"
 388 }
 389
 390 static void
 391 spec_multitex_aa_tri(GLcontext *ctx,
 392                      const SWvertex *v0,
 393                      const SWvertex *v1,
 394                      const SWvertex *v2)
 395 {
 396 #define DO_Z
 397 #define DO_RGBA
 398 #define DO_MULTITEX
 399 #define DO_SPEC
 400 #include "s_aatritemp.h"
 401 }
 402
 403
 404 /*
 405  * Examine GL state and set swrast->Triangle to an
 406  * appropriate antialiased triangle rasterizer function.
 407  */
 408 void
 409 _mesa_set_aa_triangle_function(GLcontext *ctx)
 410 {
 411    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 412    ASSERT(ctx->Polygon.SmoothFlag);
 413
 414    if (ctx->Texture._ReallyEnabled) {
 415       if (ctx->_TriangleCaps & DD_SEPARATE_SPECULAR) {
 416          if (swrast->_MultiTextureEnabled) {
 417             SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;
 418          }
 419          else {
 420             SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;
 421          }
 422       }
 423       else {
 424          if (swrast->_MultiTextureEnabled) {
 425             SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;
 426          }
 427          else {
 428             SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;
 429          }
 430       }
 431    }
 432    else if (ctx->Visual.rgbMode) {
 433       SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 434    }
 435    else {
 436       SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 437    }
 438
 439    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 440 }