src/mesa/swrast/s_aaline.c

   1 /* $Id: s_aaline.c,v 1.18 2003/02/27 23:37:53 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  5.0.1
   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 #include "glheader.h"
  29 #include "swrast/s_aaline.h"
  30 #include "swrast/s_context.h"
  31 #include "swrast/s_span.h"
  32 #include "swrast/swrast.h"
  33 #include "mtypes.h"
  34 #include "mmath.h"
  35
  36
  37 #define SUB_PIXEL 4
  38
  39
  40 /*
  41  * Info about the AA line we're rendering
  42  */
  43 struct LineInfo
  44 {
  45    GLfloat x0, y0;        /* start */
  46    GLfloat x1, y1;        /* end */
  47    GLfloat dx, dy;        /* direction vector */
  48    GLfloat len;           /* length */
  49    GLfloat halfWidth;     /* half of line width */
  50    GLfloat xAdj, yAdj;    /* X and Y adjustment for quad corners around line */
  51    /* for coverage computation */
  52    GLfloat qx0, qy0;      /* quad vertices */
  53    GLfloat qx1, qy1;
  54    GLfloat qx2, qy2;
  55    GLfloat qx3, qy3;
  56    GLfloat ex0, ey0;      /* quad edge vectors */
  57    GLfloat ex1, ey1;
  58    GLfloat ex2, ey2;
  59    GLfloat ex3, ey3;
  60
  61    /* DO_Z */
  62    GLfloat zPlane[4];
  63    /* DO_FOG */
  64    GLfloat fPlane[4];
  65    /* DO_RGBA */
  66    GLfloat rPlane[4], gPlane[4], bPlane[4], aPlane[4];
  67    /* DO_INDEX */
  68    GLfloat iPlane[4];
  69    /* DO_SPEC */
  70    GLfloat srPlane[4], sgPlane[4], sbPlane[4];
  71    /* DO_TEX or DO_MULTITEX */
  72    GLfloat sPlane[MAX_TEXTURE_COORD_UNITS][4];
  73    GLfloat tPlane[MAX_TEXTURE_COORD_UNITS][4];
  74    GLfloat uPlane[MAX_TEXTURE_COORD_UNITS][4];
  75    GLfloat vPlane[MAX_TEXTURE_COORD_UNITS][4];
  76    GLfloat lambda[MAX_TEXTURE_COORD_UNITS];
  77    GLfloat texWidth[MAX_TEXTURE_COORD_UNITS];
  78    GLfloat texHeight[MAX_TEXTURE_COORD_UNITS];
  79
  80    struct sw_span span;
  81 };
  82
  83
  84
  85 /*
  86  * Compute the equation of a plane used to interpolate line fragment data
  87  * such as color, Z, texture coords, etc.
  88  * Input: (x0, y0) and (x1,y1) are the endpoints of the line.
  89  *        z0, and z1 are the end point values to interpolate.
  90  * Output:  plane - the plane equation.
  91  *
  92  * Note: we don't really have enough parameters to specify a plane.
  93  * We take the endpoints of the line and compute a plane such that
  94  * the cross product of the line vector and the plane normal is
  95  * parallel to the projection plane.
  96  */
  97 static void
  98 compute_plane(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
  99               GLfloat z0, GLfloat z1, GLfloat plane[4])
 100 {
 101 #if 0
 102    /* original */
 103    const GLfloat px = x1 - x0;
 104    const GLfloat py = y1 - y0;
 105    const GLfloat pz = z1 - z0;
 106    const GLfloat qx = -py;
 107    const GLfloat qy = px;
 108    const GLfloat qz = 0;
 109    const GLfloat a = py * qz - pz * qy;
 110    const GLfloat b = pz * qx - px * qz;
 111    const GLfloat c = px * qy - py * qx;
 112    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 113    plane[0] = a;
 114    plane[1] = b;
 115    plane[2] = c;
 116    plane[3] = d;
 117 #else
 118    /* simplified */
 119    const GLfloat px = x1 - x0;
 120    const GLfloat py = y1 - y0;
 121    const GLfloat pz = z0 - z1;
 122    const GLfloat a = pz * px;
 123    const GLfloat b = pz * py;
 124    const GLfloat c = px * px + py * py;
 125    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 126    if (a == 0.0 && b == 0.0 && c == 0.0 && d == 0.0) {
 127       plane[0] = 0.0;
 128       plane[1] = 0.0;
 129       plane[2] = 1.0;
 130       plane[3] = 0.0;
 131    }
 132    else {
 133       plane[0] = a;
 134       plane[1] = b;
 135       plane[2] = c;
 136       plane[3] = d;
 137    }
 138 #endif
 139 }
 140
 141
 142 static INLINE void
 143 constant_plane(GLfloat value, GLfloat plane[4])
 144 {
 145    plane[0] = 0.0;
 146    plane[1] = 0.0;
 147    plane[2] = -1.0;
 148    plane[3] = value;
 149 }
 150
 151
 152 static INLINE GLfloat
 153 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 154 {
 155    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 156    return z;
 157 }
 158
 159 #define SOLVE_PLANE(X, Y, PLANE) \
 160    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 161
 162
 163 /*
 164  * Return 1 / solve_plane().
 165  */
 166 static INLINE GLfloat
 167 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 168 {
 169    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 170    if (denom == 0.0)
 171       return 0.0;
 172    else
 173       return -plane[2] / denom;
 174 }
 175
 176
 177 /*
 178  * Solve plane and return clamped GLchan value.
 179  */
 180 static INLINE GLchan
 181 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 182 {
 183    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 184    if (z < 0.0F)
 185       return 0;
 186    else if (z > CHAN_MAXF)
 187       return (GLchan) CHAN_MAXF;
 188    return (GLchan) z;
 189 }
 190
 191
 192 /*
 193  * Compute mipmap level of detail.
 194  */
 195 static INLINE GLfloat
 196 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 197                GLfloat invQ, GLfloat width, GLfloat height)
 198 {
 199    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 200    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 201    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 202    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 203    GLfloat r1 = dudx * dudx + dudy * dudy;
 204    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 205    GLfloat rho2 = r1 + r2;
 206    /* return log base 2 of rho */
 207    if (rho2 == 0.0F)
 208       return 0.0;
 209    else
 210       return (GLfloat) (log(rho2) * 1.442695 * 0.5);/* 1.442695 = 1/log(2) */
 211 }
 212
 213
 214
 215
 216 /*
 217  * Fill in the samples[] array with the (x,y) subpixel positions of
 218  * xSamples * ySamples sample positions.
 219  * Note that the four corner samples are put into the first four
 220  * positions of the array.  This allows us to optimize for the common
 221  * case of all samples being inside the polygon.
 222  */
 223 static void
 224 make_sample_table(GLint xSamples, GLint ySamples, GLfloat samples[][2])
 225 {
 226    const GLfloat dx = 1.0F / (GLfloat) xSamples;
 227    const GLfloat dy = 1.0F / (GLfloat) ySamples;
 228    GLint x, y;
 229    GLint i;
 230
 231    i = 4;
 232    for (x = 0; x < xSamples; x++) {
 233       for (y = 0; y < ySamples; y++) {
 234          GLint j;
 235          if (x == 0 && y == 0) {
 236             /* lower left */
 237             j = 0;
 238          }
 239          else if (x == xSamples - 1 && y == 0) {
 240             /* lower right */
 241             j = 1;
 242          }
 243          else if (x == 0 && y == ySamples - 1) {
 244             /* upper left */
 245             j = 2;
 246          }
 247          else if (x == xSamples - 1 && y == ySamples - 1) {
 248             /* upper right */
 249             j = 3;
 250          }
 251          else {
 252             j = i++;
 253          }
 254          samples[j][0] = x * dx + 0.5F * dx;
 255          samples[j][1] = y * dy + 0.5F * dy;
 256       }
 257    }
 258 }
 259
 260
 261
 262 /*
 263  * Compute how much of the given pixel's area is inside the rectangle
 264  * defined by vertices v0, v1, v2, v3.
 265  * Vertices MUST be specified in counter-clockwise order.
 266  * Return:  coverage in [0, 1].
 267  */
 268 static GLfloat
 269 compute_coveragef(const struct LineInfo *info,
 270                   GLint winx, GLint winy)
 271 {
 272    static GLfloat samples[SUB_PIXEL * SUB_PIXEL][2];
 273    static GLboolean haveSamples = GL_FALSE;
 274    const GLfloat x = (GLfloat) winx;
 275    const GLfloat y = (GLfloat) winy;
 276    GLint stop = 4, i;
 277    GLfloat insideCount = SUB_PIXEL * SUB_PIXEL;
 278
 279    if (!haveSamples) {
 280       make_sample_table(SUB_PIXEL, SUB_PIXEL, samples);
 281       haveSamples = GL_TRUE;
 282    }
 283
 284 #if 0 /*DEBUG*/
 285    {
 286       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 287       assert(area >= 0.0);
 288    }
 289 #endif
 290
 291    for (i = 0; i < stop; i++) {
 292       const GLfloat sx = x + samples[i][0];
 293       const GLfloat sy = y + samples[i][1];
 294       const GLfloat fx0 = sx - info->qx0;
 295       const GLfloat fy0 = sy - info->qy0;
 296       const GLfloat fx1 = sx - info->qx1;
 297       const GLfloat fy1 = sy - info->qy1;
 298       const GLfloat fx2 = sx - info->qx2;
 299       const GLfloat fy2 = sy - info->qy2;
 300       const GLfloat fx3 = sx - info->qx3;
 301       const GLfloat fy3 = sy - info->qy3;
 302       /* cross product determines if sample is inside or outside each edge */
 303       GLfloat cross0 = (info->ex0 * fy0 - info->ey0 * fx0);
 304       GLfloat cross1 = (info->ex1 * fy1 - info->ey1 * fx1);
 305       GLfloat cross2 = (info->ex2 * fy2 - info->ey2 * fx2);
 306       GLfloat cross3 = (info->ex3 * fy3 - info->ey3 * fx3);
 307       /* Check if the sample is exactly on an edge.  If so, let cross be a
 308        * positive or negative value depending on the direction of the edge.
 309        */
 310       if (cross0 == 0.0F)
 311          cross0 = info->ex0 + info->ey0;
 312       if (cross1 == 0.0F)
 313          cross1 = info->ex1 + info->ey1;
 314       if (cross2 == 0.0F)
 315          cross2 = info->ex2 + info->ey2;
 316       if (cross3 == 0.0F)
 317          cross3 = info->ex3 + info->ey3;
 318       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F || cross3 < 0.0F) {
 319          /* point is outside quadrilateral */
 320          insideCount -= 1.0F;
 321          stop = SUB_PIXEL * SUB_PIXEL;
 322       }
 323    }
 324    if (stop == 4)
 325       return 1.0F;
 326    else
 327       return insideCount * (1.0F / (SUB_PIXEL * SUB_PIXEL));
 328 }
 329
 330
 331
 332 typedef void (*plot_func)(GLcontext *ctx, struct LineInfo *line,
 333                           int ix, int iy);
 334
 335
 336
 337 /*
 338  * Draw an AA line segment (called many times per line when stippling)
 339  */
 340 static void
 341 segment(GLcontext *ctx,
 342         struct LineInfo *line,
 343         plot_func plot,
 344         GLfloat t0, GLfloat t1)
 345 {
 346    const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
 347    const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
 348    /* compute the actual segment's endpoints */
 349    const GLfloat x0 = line->x0 + t0 * line->dx;
 350    const GLfloat y0 = line->y0 + t0 * line->dy;
 351    const GLfloat x1 = line->x0 + t1 * line->dx;
 352    const GLfloat y1 = line->y0 + t1 * line->dy;
 353
 354    /* compute vertices of the line-aligned quadrilateral */
 355    line->qx0 = x0 - line->yAdj;
 356    line->qy0 = y0 + line->xAdj;
 357    line->qx1 = x0 + line->yAdj;
 358    line->qy1 = y0 - line->xAdj;
 359    line->qx2 = x1 + line->yAdj;
 360    line->qy2 = y1 - line->xAdj;
 361    line->qx3 = x1 - line->yAdj;
 362    line->qy3 = y1 + line->xAdj;
 363    /* compute the quad's edge vectors (for coverage calc) */
 364    line->ex0 = line->qx1 - line->qx0;
 365    line->ey0 = line->qy1 - line->qy0;
 366    line->ex1 = line->qx2 - line->qx1;
 367    line->ey1 = line->qy2 - line->qy1;
 368    line->ex2 = line->qx3 - line->qx2;
 369    line->ey2 = line->qy3 - line->qy2;
 370    line->ex3 = line->qx0 - line->qx3;
 371    line->ey3 = line->qy0 - line->qy3;
 372
 373    if (absDx > absDy) {
 374       /* X-major line */
 375       GLfloat dydx = line->dy / line->dx;
 376       GLfloat xLeft, xRight, yBot, yTop;
 377       GLint ix, ixRight;
 378       if (x0 < x1) {
 379          xLeft = x0 - line->halfWidth;
 380          xRight = x1 + line->halfWidth;
 381          if (line->dy >= 0.0) {
 382             yBot = y0 - 3.0F * line->halfWidth;
 383             yTop = y0 + line->halfWidth;
 384          }
 385          else {
 386             yBot = y0 - line->halfWidth;
 387             yTop = y0 + 3.0F * line->halfWidth;
 388          }
 389       }
 390       else {
 391          xLeft = x1 - line->halfWidth;
 392          xRight = x0 + line->halfWidth;
 393          if (line->dy <= 0.0) {
 394             yBot = y1 - 3.0F * line->halfWidth;
 395             yTop = y1 + line->halfWidth;
 396          }
 397          else {
 398             yBot = y1 - line->halfWidth;
 399             yTop = y1 + 3.0F * line->halfWidth;
 400          }
 401       }
 402
 403       /* scan along the line, left-to-right */
 404       ixRight = (GLint) (xRight + 1.0F);
 405
 406       /*printf("avg span height: %g\n", yTop - yBot);*/
 407       for (ix = (GLint) xLeft; ix < ixRight; ix++) {
 408          const GLint iyBot = (GLint) yBot;
 409          const GLint iyTop = (GLint) (yTop + 1.0F);
 410          GLint iy;
 411          /* scan across the line, bottom-to-top */
 412          for (iy = iyBot; iy < iyTop; iy++) {
 413             (*plot)(ctx, line, ix, iy);
 414          }
 415          yBot += dydx;
 416          yTop += dydx;
 417       }
 418    }
 419    else {
 420       /* Y-major line */
 421       GLfloat dxdy = line->dx / line->dy;
 422       GLfloat yBot, yTop, xLeft, xRight;
 423       GLint iy, iyTop;
 424       if (y0 < y1) {
 425          yBot = y0 - line->halfWidth;
 426          yTop = y1 + line->halfWidth;
 427          if (line->dx >= 0.0) {
 428             xLeft = x0 - 3.0F * line->halfWidth;
 429             xRight = x0 + line->halfWidth;
 430          }
 431          else {
 432             xLeft = x0 - line->halfWidth;
 433             xRight = x0 + 3.0F * line->halfWidth;
 434          }
 435       }
 436       else {
 437          yBot = y1 - line->halfWidth;
 438          yTop = y0 + line->halfWidth;
 439          if (line->dx <= 0.0) {
 440             xLeft = x1 - 3.0F * line->halfWidth;
 441             xRight = x1 + line->halfWidth;
 442          }
 443          else {
 444             xLeft = x1 - line->halfWidth;
 445             xRight = x1 + 3.0F * line->halfWidth;
 446          }
 447       }
 448
 449       /* scan along the line, bottom-to-top */
 450       iyTop = (GLint) (yTop + 1.0F);
 451
 452       /*printf("avg span width: %g\n", xRight - xLeft);*/
 453       for (iy = (GLint) yBot; iy < iyTop; iy++) {
 454          const GLint ixLeft = (GLint) xLeft;
 455          const GLint ixRight = (GLint) (xRight + 1.0F);
 456          GLint ix;
 457          /* scan across the line, left-to-right */
 458          for (ix = ixLeft; ix < ixRight; ix++) {
 459             (*plot)(ctx, line, ix, iy);
 460          }
 461          xLeft += dxdy;
 462          xRight += dxdy;
 463       }
 464    }
 465 }
 466
 467
 468 #define NAME(x) aa_ci_##x
 469 #define DO_Z
 470 #define DO_FOG
 471 #define DO_INDEX
 472 #include "s_aalinetemp.h"
 473
 474
 475 #define NAME(x) aa_rgba_##x
 476 #define DO_Z
 477 #define DO_FOG
 478 #define DO_RGBA
 479 #include "s_aalinetemp.h"
 480
 481
 482 #define NAME(x)  aa_tex_rgba_##x
 483 #define DO_Z
 484 #define DO_FOG
 485 #define DO_RGBA
 486 #define DO_TEX
 487 #include "s_aalinetemp.h"
 488
 489
 490 #define NAME(x)  aa_multitex_rgba_##x
 491 #define DO_Z
 492 #define DO_FOG
 493 #define DO_RGBA
 494 #define DO_MULTITEX
 495 #include "s_aalinetemp.h"
 496
 497
 498 #define NAME(x)  aa_multitex_spec_##x
 499 #define DO_Z
 500 #define DO_FOG
 501 #define DO_RGBA
 502 #define DO_MULTITEX
 503 #define DO_SPEC
 504 #include "s_aalinetemp.h"
 505
 506
 507
 508 void
 509 _swrast_choose_aa_line_function(GLcontext *ctx)
 510 {
 511    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 512
 513    ASSERT(ctx->Line.SmoothFlag);
 514
 515    if (ctx->Visual.rgbMode) {
 516       /* RGBA */
 517       if (ctx->Texture._EnabledUnits != 0) {
 518          if (ctx->Texture._EnabledUnits > 1) {
 519             /* Multitextured! */
 520             if (ctx->Light.Model.ColorControl==GL_SEPARATE_SPECULAR_COLOR ||
 521                 ctx->Fog.ColorSumEnabled)
 522                swrast->Line = aa_multitex_spec_line;
 523             else
 524                swrast->Line = aa_multitex_rgba_line;
 525          }
 526          else {
 527             swrast->Line = aa_tex_rgba_line;
 528          }
 529       }
 530       else {
 531          swrast->Line = aa_rgba_line;
 532       }
 533    }
 534    else {
 535       /* Color Index */
 536       swrast->Line = aa_ci_line;
 537    }
 538 }