src/mesa/swrast/s_aatriangle.c

   1 /* $Id: s_aatriangle.c,v 1.3 2000/11/13 20:02:57 keithw Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  3.5
   6  *
   7  * Copyright (C) 1999-2000  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 "s_aatriangle.h"
  34 #include "s_context.h"
  35 #include "s_span.h"
  36
  37
  38 /*
  39  * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2
  40  * vertices and the given Z values.
  41  */
  42 static INLINE void
  43 compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[],
  44               GLfloat z0, GLfloat z1, GLfloat z2, GLfloat plane[4])
  45 {
  46    const GLfloat px = v1[0] - v0[0];
  47    const GLfloat py = v1[1] - v0[1];
  48    const GLfloat pz = z1 - z0;
  49
  50    const GLfloat qx = v2[0] - v0[0];
  51    const GLfloat qy = v2[1] - v0[1];
  52    const GLfloat qz = z2 - z0;
  53
  54    const GLfloat a = py * qz - pz * qy;
  55    const GLfloat b = pz * qx - px * qz;
  56    const GLfloat c = px * qy - py * qx;
  57    const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0);
  58
  59    plane[0] = a;
  60    plane[1] = b;
  61    plane[2] = c;
  62    plane[3] = d;
  63 }
  64
  65
  66 /*
  67  * Compute coefficients of a plane with a constant Z value.
  68  */
  69 static INLINE void
  70 constant_plane(GLfloat value, GLfloat plane[4])
  71 {
  72    plane[0] = 0.0;
  73    plane[1] = 0.0;
  74    plane[2] = -1.0;
  75    plane[3] = value;
  76 }
  77
  78 #define CONSTANT_PLANE(VALUE, PLANE)    \
  79 do {                                    \
  80    PLANE[0] = 0.0F;                     \
  81    PLANE[1] = 0.0F;                     \
  82    PLANE[2] = -1.0F;                    \
  83    PLANE[3] = VALUE;                    \
  84 } while (0)
  85
  86
  87
  88 /*
  89  * Solve plane equation for Z at (X,Y).
  90  */
  91 static INLINE GLfloat
  92 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
  93 {
  94    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
  95    return z;
  96 }
  97
  98
  99 #define SOLVE_PLANE(X, Y, PLANE) \
 100    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 101
 102
 103 /*
 104  * Return 1 / solve_plane().
 105  */
 106 static INLINE GLfloat
 107 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 108 {
 109    GLfloat z = -plane[2] / (plane[3] + plane[0] * x + plane[1] * y);
 110    return z;
 111 }
 112
 113
 114
 115 /*
 116  * Solve plane and return clamped GLchan value.
 117  */
 118 static INLINE GLchan
 119 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 120 {
 121    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 122    if (z < 0.0F)
 123       return 0;
 124    else if (z > CHAN_MAXF)
 125       return CHAN_MAXF;
 126    return (GLchan) (GLint) z;
 127 }
 128
 129
 130
 131 /*
 132  * Compute how much (area) of the given pixel is inside the triangle.
 133  * Vertices MUST be specified in counter-clockwise order.
 134  * Return:  coverage in [0, 1].
 135  */
 136 static GLfloat
 137 compute_coveragef(const GLfloat v0[3], const GLfloat v1[3],
 138                   const GLfloat v2[3], GLint winx, GLint winy)
 139 {
 140    static const GLfloat samples[16][2] = {
 141       /* start with the four corners */
 142       { 0.00, 0.00 },
 143       { 0.75, 0.00 },
 144       { 0.00, 0.75 },
 145       { 0.75, 0.75 },
 146       /* continue with interior samples */
 147       { 0.25, 0.00 },
 148       { 0.50, 0.00 },
 149       { 0.00, 0.25 },
 150       { 0.25, 0.25 },
 151       { 0.50, 0.25 },
 152       { 0.75, 0.25 },
 153       { 0.00, 0.50 },
 154       { 0.25, 0.50 },
 155       { 0.50, 0.50 },
 156       { 0.75, 0.50 },
 157       { 0.25, 0.75 },
 158       { 0.50, 0.75 }
 159    };
 160    const GLfloat x = (GLfloat) winx;
 161    const GLfloat y = (GLfloat) winy;
 162    const GLfloat dx0 = v1[0] - v0[0];
 163    const GLfloat dy0 = v1[1] - v0[1];
 164    const GLfloat dx1 = v2[0] - v1[0];
 165    const GLfloat dy1 = v2[1] - v1[1];
 166    const GLfloat dx2 = v0[0] - v2[0];
 167    const GLfloat dy2 = v0[1] - v2[1];
 168    GLint stop = 4, i;
 169    GLfloat insideCount = 16.0F;
 170
 171 #ifdef DEBUG
 172    {
 173       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 174       assert(area >= 0.0);
 175    }
 176 #endif
 177
 178    for (i = 0; i < stop; i++) {
 179       const GLfloat sx = x + samples[i][0];
 180       const GLfloat sy = y + samples[i][1];
 181       const GLfloat fx0 = sx - v0[0];
 182       const GLfloat fy0 = sy - v0[1];
 183       const GLfloat fx1 = sx - v1[0];
 184       const GLfloat fy1 = sy - v1[1];
 185       const GLfloat fx2 = sx - v2[0];
 186       const GLfloat fy2 = sy - v2[1];
 187       /* cross product determines if sample is inside or outside each edge */
 188       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 189       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 190       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 191       /* Check if the sample is exactly on an edge.  If so, let cross be a
 192        * positive or negative value depending on the direction of the edge.
 193        */
 194       if (cross0 == 0.0F)
 195          cross0 = dx0 + dy0;
 196       if (cross1 == 0.0F)
 197          cross1 = dx1 + dy1;
 198       if (cross2 == 0.0F)
 199          cross2 = dx2 + dy2;
 200       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 201          /* point is outside triangle */
 202          insideCount -= 1.0F;
 203          stop = 16;
 204       }
 205    }
 206    if (stop == 4)
 207       return 1.0F;
 208    else
 209       return insideCount * (1.0F / 16.0F);
 210 }
 211
 212
 213
 214 /*
 215  * Compute how much (area) of the given pixel is inside the triangle.
 216  * Vertices MUST be specified in counter-clockwise order.
 217  * Return:  coverage in [0, 15].
 218  */
 219 static GLint
 220 compute_coveragei(const GLfloat v0[3], const GLfloat v1[3],
 221                   const GLfloat v2[3], GLint winx, GLint winy)
 222 {
 223    /* NOTE: 15 samples instead of 16.
 224     * A better sample distribution could be used.
 225     */
 226    static const GLfloat samples[15][2] = {
 227       /* start with the four corners */
 228       { 0.00, 0.00 },
 229       { 0.75, 0.00 },
 230       { 0.00, 0.75 },
 231       { 0.75, 0.75 },
 232       /* continue with interior samples */
 233       { 0.25, 0.00 },
 234       { 0.50, 0.00 },
 235       { 0.00, 0.25 },
 236       { 0.25, 0.25 },
 237       { 0.50, 0.25 },
 238       { 0.75, 0.25 },
 239       { 0.00, 0.50 },
 240       { 0.25, 0.50 },
 241       /*{ 0.50, 0.50 },*/
 242       { 0.75, 0.50 },
 243       { 0.25, 0.75 },
 244       { 0.50, 0.75 }
 245    };
 246    const GLfloat x = (GLfloat) winx;
 247    const GLfloat y = (GLfloat) winy;
 248    const GLfloat dx0 = v1[0] - v0[0];
 249    const GLfloat dy0 = v1[1] - v0[1];
 250    const GLfloat dx1 = v2[0] - v1[0];
 251    const GLfloat dy1 = v2[1] - v1[1];
 252    const GLfloat dx2 = v0[0] - v2[0];
 253    const GLfloat dy2 = v0[1] - v2[1];
 254    GLint stop = 4, i;
 255    GLint insideCount = 15;
 256
 257 #ifdef DEBUG
 258    {
 259       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 260       assert(area >= 0.0);
 261    }
 262 #endif
 263
 264    for (i = 0; i < stop; i++) {
 265       const GLfloat sx = x + samples[i][0];
 266       const GLfloat sy = y + samples[i][1];
 267       const GLfloat fx0 = sx - v0[0];
 268       const GLfloat fy0 = sy - v0[1];
 269       const GLfloat fx1 = sx - v1[0];
 270       const GLfloat fy1 = sy - v1[1];
 271       const GLfloat fx2 = sx - v2[0];
 272       const GLfloat fy2 = sy - v2[1];
 273       /* cross product determines if sample is inside or outside each edge */
 274       GLfloat cross0 = (dx0 * fy0 - dy0 * fx0);
 275       GLfloat cross1 = (dx1 * fy1 - dy1 * fx1);
 276       GLfloat cross2 = (dx2 * fy2 - dy2 * fx2);
 277       /* Check if the sample is exactly on an edge.  If so, let cross be a
 278        * positive or negative value depending on the direction of the edge.
 279        */
 280       if (cross0 == 0.0F)
 281          cross0 = dx0 + dy0;
 282       if (cross1 == 0.0F)
 283          cross1 = dx1 + dy1;
 284       if (cross2 == 0.0F)
 285          cross2 = dx2 + dy2;
 286       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F) {
 287          /* point is outside triangle */
 288          insideCount--;
 289          stop = 15;
 290       }
 291    }
 292    if (stop == 4)
 293       return 15;
 294    else
 295       return insideCount;
 296 }
 297
 298
 299
 300 static void
 301 rgba_aa_tri(GLcontext *ctx,
 302             SWvertex *v0,
 303             SWvertex *v1,
 304             SWvertex *v2)
 305 {
 306 #define DO_Z
 307 #define DO_RGBA
 308 #include "s_aatritemp.h"
 309 }
 310
 311
 312 static void
 313 index_aa_tri(GLcontext *ctx,
 314              SWvertex *v0,
 315              SWvertex *v1,
 316              SWvertex *v2)
 317 {
 318 #define DO_Z
 319 #define DO_INDEX
 320 #include "s_aatritemp.h"
 321 }
 322
 323
 324 /*
 325  * Compute mipmap level of detail.
 326  */
 327 static INLINE GLfloat
 328 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 329                GLfloat invQ, GLfloat width, GLfloat height)
 330 {
 331    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 332    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 333    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 334    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 335    GLfloat r1 = dudx * dudx + dudy * dudy;
 336    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 337    GLfloat rho2 = r1 + r2;
 338    /* return log base 2 of rho */
 339    return log(rho2) * 1.442695 * 0.5;       /* 1.442695 = 1/log(2) */
 340 }
 341
 342
 343 static void
 344 tex_aa_tri(GLcontext *ctx,
 345            SWvertex *v0,
 346            SWvertex *v1,
 347            SWvertex *v2)
 348 {
 349 #define DO_Z
 350 #define DO_RGBA
 351 #define DO_TEX
 352 #include "s_aatritemp.h"
 353 }
 354
 355
 356 static void
 357 spec_tex_aa_tri(GLcontext *ctx,
 358                 SWvertex *v0,
 359                 SWvertex *v1,
 360                 SWvertex *v2)
 361 {
 362 #define DO_Z
 363 #define DO_RGBA
 364 #define DO_TEX
 365 #define DO_SPEC
 366 #include "s_aatritemp.h"
 367 }
 368
 369
 370 static void
 371 multitex_aa_tri(GLcontext *ctx,
 372                 SWvertex *v0,
 373                 SWvertex *v1,
 374                 SWvertex *v2)
 375 {
 376 #define DO_Z
 377 #define DO_RGBA
 378 #define DO_MULTITEX
 379 #include "s_aatritemp.h"
 380 }
 381
 382 static void
 383 spec_multitex_aa_tri(GLcontext *ctx,
 384                      SWvertex *v0,
 385                      SWvertex *v1,
 386                      SWvertex *v2)
 387 {
 388 #define DO_Z
 389 #define DO_RGBA
 390 #define DO_MULTITEX
 391 #define DO_SPEC
 392 #include "s_aatritemp.h"
 393 }
 394
 395
 396 /*
 397  * Examine GL state and set ctx->Driver.TriangleFunc to an
 398  * appropriate antialiased triangle rasterizer function.
 399  */
 400 void
 401 _mesa_set_aa_triangle_function(GLcontext *ctx)
 402 {
 403    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 404    ASSERT(ctx->Polygon.SmoothFlag);
 405
 406    if (ctx->Texture._ReallyEnabled) {
 407       if (ctx->Light.Enabled &&
 408           (ctx->Light.Model.ColorControl == GL_SEPARATE_SPECULAR_COLOR ||
 409            ctx->Fog.ColorSumEnabled)) {
 410          if (swrast->_MultiTextureEnabled) {
 411             SWRAST_CONTEXT(ctx)->Triangle = spec_multitex_aa_tri;
 412          }
 413          else {
 414             SWRAST_CONTEXT(ctx)->Triangle = spec_tex_aa_tri;
 415          }
 416       }
 417       else {
 418          if (swrast->_MultiTextureEnabled) {
 419             SWRAST_CONTEXT(ctx)->Triangle = multitex_aa_tri;
 420          }
 421          else {
 422             SWRAST_CONTEXT(ctx)->Triangle = tex_aa_tri;
 423          }
 424       }
 425    }
 426    else {
 427       if (ctx->Visual.RGBAflag) {
 428          SWRAST_CONTEXT(ctx)->Triangle = rgba_aa_tri;
 429       }
 430       else {
 431          SWRAST_CONTEXT(ctx)->Triangle = index_aa_tri;
 432       }
 433    }
 434    ASSERT(SWRAST_CONTEXT(ctx)->Triangle);
 435 }