src/mesa/swrast/s_aatriangle.c

   1 /* $Id: s_aatriangle.c,v 1.6 2001/01/23 23:39:37 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    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    GLfloat z = -plane[2] / (plane[3] + plane[0] * x + plane[1] * y);
 111    return z;
 112 }
 113
 114
 115
 116 /*
 117  * Solve plane and return clamped GLchan value.
 118  */
 119 static INLINE GLchan
 120 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 121 {
 122    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 123    if (z < 0.0F)
 124       return 0;
 125    else if (z > CHAN_MAXF)
 126       return CHAN_MAXF;
 127    return (GLchan) (GLint) z;
 128 }
 129
 130
 131
 132 /*
 133  * Compute how much (area) of the given pixel is inside the triangle.
 134  * Vertices MUST be specified in counter-clockwise order.
 135  * Return:  coverage in [0, 1].
 136  */
 137 static GLfloat
 138 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 139                   const GLfloat v2[3], GLint winx, GLint winy)
 140 {
 141    static const GLfloat samples[16][2] = {
 142       /* start with the four corners */
 143       { 0.00, 0.00 },
 144       { 0.75, 0.00 },
 145       { 0.00, 0.75 },
 146       { 0.75, 0.75 },
 147       /* continue with interior samples */
 148       { 0.25, 0.00 },
 149       { 0.50, 0.00 },
 150       { 0.00, 0.25 },
 151       { 0.25, 0.25 },
 152       { 0.50, 0.25 },
 153       { 0.75, 0.25 },
 154       { 0.00, 0.50 },
 155       { 0.25, 0.50 },
 156       { 0.50, 0.50 },
 157       { 0.75, 0.50 },
 158       { 0.25, 0.75 },
 159       { 0.50, 0.75 }
 160    };
 161    const GLfloat x = (GLfloat) winx;
 162    const GLfloat y = (GLfloat) winy;
 163    const GLfloat dx0 = v1[0] - v0[0];
 164    const GLfloat dy0 = v1[1] - v0[1];
 165    const GLfloat dx1 = v2[0] - v1[0];
 166    const GLfloat dy1 = v2[1] - v1[1];
 167    const GLfloat dx2 = v0[0] - v2[0];
 168    const GLfloat dy2 = v0[1] - v2[1];
 169    GLint stop = 4, i;
 170    GLfloat insideCount = 16.0F;
 171
 172 #ifdef DEBUG
 173    {
 174       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 175       assert(area >= 0.0);
 176    }
 177 #endif
 178
 179    for (i = 0; i < stop; i++) {
 180       const GLfloat sx = x + samples[i][0];
 181       const GLfloat sy = y + samples[i][1];
 182       const GLfloat fx0 = sx - v0[0];
 183       const GLfloat fy0 = sy - v0[1];
 184       const GLfloat fx1 = sx - v1[0];
 185       const GLfloat fy1 = sy - v1[1];
 186       const GLfloat fx2 = sx - v2[0];
 187       const GLfloat fy2 = sy - v2[1];
 188       /* cross product determines if sample is inside or outside each edge */
 189       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 190       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 191       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 192       /* Check if the sample is exactly on an edge.  If so, let cross be a
 193        * positive or negative value depending on the direction of the edge.
 194        */
 195       if (cross0 == 0.0F)
 196          cross0 = dx0 + dy0;
 197       if (cross1 == 0.0F)
 198          cross1 = dx1 + dy1;
 199       if (cross2 == 0.0F)
 200          cross2 = dx2 + dy2;
 201       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 202          /* point is outside triangle */
 203          insideCount -= 1.0F;
 204          stop = 16;
 205       }
 206    }
 207    if (stop == 4)
 208       return 1.0F;
 209    else
 210       return insideCount * (1.0F / 16.0F);
 211 }
 212
 213
 214
 215 /*
 216  * Compute how much (area) of the given pixel is inside the triangle.
 217  * Vertices MUST be specified in counter-clockwise order.
 218  * Return:  coverage in [0, 15].
 219  */
 220 static GLint
 221 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 222                   const GLfloat v2[3], GLint winx, GLint winy)
 223 {
 224    /* NOTE: 15 samples instead of 16.
 225     * A better sample distribution could be used.
 226     */
 227    static const GLfloat samples[15][2] = {
 228       /* start with the four corners */
 229       { 0.00, 0.00 },
 230       { 0.75, 0.00 },
 231       { 0.00, 0.75 },
 232       { 0.75, 0.75 },
 233       /* continue with interior samples */
 234       { 0.25, 0.00 },
 235       { 0.50, 0.00 },
 236       { 0.00, 0.25 },
 237       { 0.25, 0.25 },
 238       { 0.50, 0.25 },
 239       { 0.75, 0.25 },
 240       { 0.00, 0.50 },
 241       { 0.25, 0.50 },
 242       /*{ 0.50, 0.50 },*/
 243       { 0.75, 0.50 },
 244       { 0.25, 0.75 },
 245       { 0.50, 0.75 }
 246    };
 247    const GLfloat x = (GLfloat) winx;
 248    const GLfloat y = (GLfloat) winy;
 249    const GLfloat dx0 = v1[0] - v0[0];
 250    const GLfloat dy0 = v1[1] - v0[1];
 251    const GLfloat dx1 = v2[0] - v1[0];
 252    const GLfloat dy1 = v2[1] - v1[1];
 253    const GLfloat dx2 = v0[0] - v2[0];
 254    const GLfloat dy2 = v0[1] - v2[1];
 255    GLint stop = 4, i;
 256    GLint insideCount = 15;
 257
 258 #ifdef DEBUG
 259    {
 260       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 261       assert(area >= 0.0);
 262    }
 263 #endif
 264
 265    for (i = 0; i < stop; i++) {
 266       const GLfloat sx = x + samples[i][0];
 267       const GLfloat sy = y + samples[i][1];
 268       const GLfloat fx0 = sx - v0[0];
 269       const GLfloat fy0 = sy - v0[1];
 270       const GLfloat fx1 = sx - v1[0];
 271       const GLfloat fy1 = sy - v1[1];
 272       const GLfloat fx2 = sx - v2[0];
 273       const GLfloat fy2 = sy - v2[1];
 274       /* cross product determines if sample is inside or outside each edge */
 275       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 276       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 277       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 278       /* Check if the sample is exactly on an edge.  If so, let cross be a
 279        * positive or negative value depending on the direction of the edge.
 280        */
 281       if (cross0 == 0.0F)
 282          cross0 = dx0 + dy0;
 283       if (cross1 == 0.0F)
 284          cross1 = dx1 + dy1;
 285       if (cross2 == 0.0F)
 286          cross2 = dx2 + dy2;
 287       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 288          /* point is outside triangle */
 289          insideCount--;
 290          stop = 15;
 291       }
 292    }
 293    if (stop == 4)
 294       return 15;
 295    else
 296       return insideCount;
 297 }
 298
 299
 300
 301 static void
 302 rgba_aa_tri(GLcontext *ctx,
 303             const SWvertex *v0,
 304             const SWvertex *v1,
 305             const SWvertex *v2)
 306 {
 307 #define DO_Z
 308 #define DO_RGBA
 309 #include "s_aatritemp.h"
 310 }
 311
 312
 313 static void
 314 index_aa_tri(GLcontext *ctx,
 315              const SWvertex *v0,
 316              const SWvertex *v1,
 317              const SWvertex *v2)
 318 {
 319 #define DO_Z
 320 #define DO_INDEX
 321 #include "s_aatritemp.h"
 322 }
 323
 324
 325 /*
 326  * Compute mipmap level of detail.
 327  */
 328 static INLINE GLfloat
 329 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 330                GLfloat invQ, GLfloat width, GLfloat height)
 331 {
 332    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 333    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 334    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 335    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 336    GLfloat r1 = dudx * dudx + dudy * dudy;
 337    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 338    GLfloat rho2 = r1 + r2;
 339    /* return log base 2 of rho */
 340    return log(rho2) * 1.442695 * 0.5;       /* 1.442695 = 1/log(2) */
 341 }
 342
 343
 344 static void
 345 tex_aa_tri(GLcontext *ctx,
 346            const SWvertex *v0,
 347            const SWvertex *v1,
 348            const SWvertex *v2)
 349 {
 350 #define DO_Z
 351 #define DO_RGBA
 352 #define DO_TEX
 353 #include "s_aatritemp.h"
 354 }
 355
 356
 357 static void
 358 spec_tex_aa_tri(GLcontext *ctx,
 359                 const SWvertex *v0,
 360                 const SWvertex *v1,
 361                 const SWvertex *v2)
 362 {
 363 #define DO_Z
 364 #define DO_RGBA
 365 #define DO_TEX
 366 #define DO_SPEC
 367 #include "s_aatritemp.h"
 368 }
 369
 370
 371 static void
 372 multitex_aa_tri(GLcontext *ctx,
 373                 const SWvertex *v0,
 374                 const SWvertex *v1,
 375                 const SWvertex *v2)
 376 {
 377 #define DO_Z
 378 #define DO_RGBA
 379 #define DO_MULTITEX
 380 #include "s_aatritemp.h"
 381 }
 382
 383 static void
 384 spec_multitex_aa_tri(GLcontext *ctx,
 385                      const SWvertex *v0,
 386                      const SWvertex *v1,
 387                      const SWvertex *v2)
 388 {
 389 #define DO_Z
 390 #define DO_RGBA
 391 #define DO_MULTITEX
 392 #define DO_SPEC
 393 #include "s_aatritemp.h"
 394 }
 395
 396
 397 /*
 398  * Examine GL state and set ctx->Driver.TriangleFunc to an
 399  * appropriate antialiased triangle rasterizer function.
 400  */
 401 void
 402 _mesa_set_aa_triangle_function(GLcontext *ctx)
 403 {
 404    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 405    ASSERT(ctx->Polygon.SmoothFlag);
 406
 407    if (ctx->Texture._ReallyEnabled) {
 408       if (ctx->Light.Enabled &&
 409           (ctx->Light.Model.ColorControl == GL_SEPARATE_SPECULAR_COLOR ||
 410            ctx->Fog.ColorSumEnabled)) {
 411          if (swrast->_MultiTextureEnabled) {
 412             SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;
 413          }
 414          else {
 415             SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;
 416          }
 417       }
 418       else {
 419          if (swrast->_MultiTextureEnabled) {
 420             SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;
 421          }
 422          else {
 423             SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;
 424          }
 425       }
 426    }
 427    else {
 428       if (ctx->Visual.rgbMode) {
 429          SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 430       }
 431       else {
 432          SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 433       }
 434    }
 435    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 436 }