src/mesa/swrast/s_aaline.c

   1 /* $Id: s_aaline.c,v 1.14 2002/04/19 14:05:50 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  4.1
   6  *
   7  * Copyright (C) 1999-2002  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_UNITS][4];
  73    GLfloat tPlane[MAX_TEXTURE_UNITS][4];
  74    GLfloat uPlane[MAX_TEXTURE_UNITS][4];
  75    GLfloat vPlane[MAX_TEXTURE_UNITS][4];
  76    GLfloat lambda[MAX_TEXTURE_UNITS];
  77    GLfloat texWidth[MAX_TEXTURE_UNITS], texHeight[MAX_TEXTURE_UNITS];
  78
  79    struct sw_span *span;
  80 };
  81
  82
  83
  84 /*
  85  * Compute the equation of a plane used to interpolate line fragment data
  86  * such as color, Z, texture coords, etc.
  87  * Input: (x0, y0) and (x1,y1) are the endpoints of the line.
  88  *        z0, and z1 are the end point values to interpolate.
  89  * Output:  plane - the plane equation.
  90  *
  91  * Note: we don't really have enough parameters to specify a plane.
  92  * We take the endpoints of the line and compute a plane such that
  93  * the cross product of the line vector and the plane normal is
  94  * parallel to the projection plane.
  95  */
  96 static void
  97 compute_plane(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
  98               GLfloat z0, GLfloat z1, GLfloat plane[4])
  99 {
 100 #if 0
 101    /* original */
 102    const GLfloat px = x1 - x0;
 103    const GLfloat py = y1 - y0;
 104    const GLfloat pz = z1 - z0;
 105    const GLfloat qx = -py;
 106    const GLfloat qy = px;
 107    const GLfloat qz = 0;
 108    const GLfloat a = py * qz - pz * qy;
 109    const GLfloat b = pz * qx - px * qz;
 110    const GLfloat c = px * qy - py * qx;
 111    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 112    plane[0] = a;
 113    plane[1] = b;
 114    plane[2] = c;
 115    plane[3] = d;
 116 #else
 117    /* simplified */
 118    const GLfloat px = x1 - x0;
 119    const GLfloat py = y1 - y0;
 120    const GLfloat pz = z0 - z1;
 121    const GLfloat a = pz * px;
 122    const GLfloat b = pz * py;
 123    const GLfloat c = px * px + py * py;
 124    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 125    if (a == 0.0 && b == 0.0 && c == 0.0 && d == 0.0) {
 126       plane[0] = 0.0;
 127       plane[1] = 0.0;
 128       plane[2] = 1.0;
 129       plane[3] = 0.0;
 130    }
 131    else {
 132       plane[0] = a;
 133       plane[1] = b;
 134       plane[2] = c;
 135       plane[3] = d;
 136    }
 137 #endif
 138 }
 139
 140
 141 static INLINE void
 142 constant_plane(GLfloat value, GLfloat plane[4])
 143 {
 144    plane[0] = 0.0;
 145    plane[1] = 0.0;
 146    plane[2] = -1.0;
 147    plane[3] = value;
 148 }
 149
 150
 151 static INLINE GLfloat
 152 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 153 {
 154    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 155    return z;
 156 }
 157
 158 #define SOLVE_PLANE(X, Y, PLANE) \
 159    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 160
 161
 162 /*
 163  * Return 1 / solve_plane().
 164  */
 165 static INLINE GLfloat
 166 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 167 {
 168    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 169    if (denom == 0.0)
 170       return 0.0;
 171    else
 172       return -plane[2] / denom;
 173 }
 174
 175
 176 /*
 177  * Solve plane and return clamped GLchan value.
 178  */
 179 static INLINE GLchan
 180 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 181 {
 182    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 183    if (z < 0.0F)
 184       return 0;
 185    else if (z > CHAN_MAXF)
 186       return (GLchan) CHAN_MAXF;
 187    return (GLchan) (GLint) z;
 188 }
 189
 190
 191 /*
 192  * Compute mipmap level of detail.
 193  */
 194 static INLINE GLfloat
 195 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 196                GLfloat invQ, GLfloat width, GLfloat height)
 197 {
 198    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 199    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 200    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 201    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 202    GLfloat r1 = dudx * dudx + dudy * dudy;
 203    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 204    GLfloat rho2 = r1 + r2;
 205    /* return log base 2 of rho */
 206    if (rho2 == 0.0F)
 207       return 0.0;
 208    else
 209       return (GLfloat) (log(rho2) * 1.442695 * 0.5);/* 1.442695 = 1/log(2) */
 210 }
 211
 212
 213
 214
 215 /*
 216  * Fill in the samples[] array with the (x,y) subpixel positions of
 217  * xSamples * ySamples sample positions.
 218  * Note that the four corner samples are put into the first four
 219  * positions of the array.  This allows us to optimize for the common
 220  * case of all samples being inside the polygon.
 221  */
 222 static void
 223 make_sample_table(GLint xSamples, GLint ySamples, GLfloat samples[][2])
 224 {
 225    const GLfloat dx = 1.0F / (GLfloat) xSamples;
 226    const GLfloat dy = 1.0F / (GLfloat) ySamples;
 227    GLint x, y;
 228    GLint i;
 229
 230    i = 4;
 231    for (x = 0; x < xSamples; x++) {
 232       for (y = 0; y < ySamples; y++) {
 233          GLint j;
 234          if (x == 0 && y == 0) {
 235             /* lower left */
 236             j = 0;
 237          }
 238          else if (x == xSamples - 1 && y == 0) {
 239             /* lower right */
 240             j = 1;
 241          }
 242          else if (x == 0 && y == ySamples - 1) {
 243             /* upper left */
 244             j = 2;
 245          }
 246          else if (x == xSamples - 1 && y == ySamples - 1) {
 247             /* upper right */
 248             j = 3;
 249          }
 250          else {
 251             j = i++;
 252          }
 253          samples[j][0] = x * dx + 0.5F * dx;
 254          samples[j][1] = y * dy + 0.5F * dy;
 255       }
 256    }
 257 }
 258
 259
 260
 261 /*
 262  * Compute how much of the given pixel's area is inside the rectangle
 263  * defined by vertices v0, v1, v2, v3.
 264  * Vertices MUST be specified in counter-clockwise order.
 265  * Return:  coverage in [0, 1].
 266  */
 267 static GLfloat
 268 compute_coveragef(const struct LineInfo *info,
 269                   GLint winx, GLint winy)
 270 {
 271    static GLfloat samples[SUB_PIXEL * SUB_PIXEL][2];
 272    static GLboolean haveSamples = GL_FALSE;
 273    const GLfloat x = (GLfloat) winx;
 274    const GLfloat y = (GLfloat) winy;
 275    GLint stop = 4, i;
 276    GLfloat insideCount = SUB_PIXEL * SUB_PIXEL;
 277
 278    if (!haveSamples) {
 279       make_sample_table(SUB_PIXEL, SUB_PIXEL, samples);
 280       haveSamples = GL_TRUE;
 281    }
 282
 283 #if 0 /*DEBUG*/
 284    {
 285       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 286       assert(area >= 0.0);
 287    }
 288 #endif
 289
 290    for (i = 0; i < stop; i++) {
 291       const GLfloat sx = x + samples[i][0];
 292       const GLfloat sy = y + samples[i][1];
 293       const GLfloat fx0 = sx - info->qx0;
 294       const GLfloat fy0 = sy - info->qy0;
 295       const GLfloat fx1 = sx - info->qx1;
 296       const GLfloat fy1 = sy - info->qy1;
 297       const GLfloat fx2 = sx - info->qx2;
 298       const GLfloat fy2 = sy - info->qy2;
 299       const GLfloat fx3 = sx - info->qx3;
 300       const GLfloat fy3 = sy - info->qy3;
 301       /* cross product determines if sample is inside or outside each edge */
 302       GLfloat cross0 = (info->ex0 * fy0 - info->ey0 * fx0);
 303       GLfloat cross1 = (info->ex1 * fy1 - info->ey1 * fx1);
 304       GLfloat cross2 = (info->ex2 * fy2 - info->ey2 * fx2);
 305       GLfloat cross3 = (info->ex3 * fy3 - info->ey3 * fx3);
 306       /* Check if the sample is exactly on an edge.  If so, let cross be a
 307        * positive or negative value depending on the direction of the edge.
 308        */
 309       if (cross0 == 0.0F)
 310          cross0 = info->ex0 + info->ey0;
 311       if (cross1 == 0.0F)
 312          cross1 = info->ex1 + info->ey1;
 313       if (cross2 == 0.0F)
 314          cross2 = info->ex2 + info->ey2;
 315       if (cross3 == 0.0F)
 316          cross3 = info->ex3 + info->ey3;
 317       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F || cross3 < 0.0F) {
 318          /* point is outside quadrilateral */
 319          insideCount -= 1.0F;
 320          stop = SUB_PIXEL * SUB_PIXEL;
 321       }
 322    }
 323    if (stop == 4)
 324       return 1.0F;
 325    else
 326       return insideCount * (1.0F / (SUB_PIXEL * SUB_PIXEL));
 327 }
 328
 329
 330
 331 typedef void (*plot_func)(GLcontext *ctx, struct LineInfo *line,
 332                           int ix, int iy);
 333
 334
 335
 336 /*
 337  * Draw an AA line segment (called many times per line when stippling)
 338  */
 339 static void
 340 segment(GLcontext *ctx,
 341         struct LineInfo *line,
 342         plot_func plot,
 343         GLfloat t0, GLfloat t1)
 344 {
 345    const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
 346    const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
 347    /* compute the actual segment's endpoints */
 348    const GLfloat x0 = line->x0 + t0 * line->dx;
 349    const GLfloat y0 = line->y0 + t0 * line->dy;
 350    const GLfloat x1 = line->x0 + t1 * line->dx;
 351    const GLfloat y1 = line->y0 + t1 * line->dy;
 352
 353    /* compute vertices of the line-aligned quadrilateral */
 354    line->qx0 = x0 - line->yAdj;
 355    line->qy0 = y0 + line->xAdj;
 356    line->qx1 = x0 + line->yAdj;
 357    line->qy1 = y0 - line->xAdj;
 358    line->qx2 = x1 + line->yAdj;
 359    line->qy2 = y1 - line->xAdj;
 360    line->qx3 = x1 - line->yAdj;
 361    line->qy3 = y1 + line->xAdj;
 362    /* compute the quad's edge vectors (for coverage calc) */
 363    line->ex0 = line->qx1 - line->qx0;
 364    line->ey0 = line->qy1 - line->qy0;
 365    line->ex1 = line->qx2 - line->qx1;
 366    line->ey1 = line->qy2 - line->qy1;
 367    line->ex2 = line->qx3 - line->qx2;
 368    line->ey2 = line->qy3 - line->qy2;
 369    line->ex3 = line->qx0 - line->qx3;
 370    line->ey3 = line->qy0 - line->qy3;
 371
 372    if (absDx > absDy) {
 373       /* X-major line */
 374       GLfloat dydx = line->dy / line->dx;
 375       GLfloat xLeft, xRight, yBot, yTop;
 376       GLint ix, ixRight;
 377       if (x0 < x1) {
 378          xLeft = x0 - line->halfWidth;
 379          xRight = x1 + line->halfWidth;
 380          if (line->dy >= 0.0) {
 381             yBot = y0 - 3.0F * line->halfWidth;
 382             yTop = y0 + line->halfWidth;
 383          }
 384          else {
 385             yBot = y0 - line->halfWidth;
 386             yTop = y0 + 3.0F * line->halfWidth;
 387          }
 388       }
 389       else {
 390          xLeft = x1 - line->halfWidth;
 391          xRight = x0 + line->halfWidth;
 392          if (line->dy <= 0.0) {
 393             yBot = y1 - 3.0F * line->halfWidth;
 394             yTop = y1 + line->halfWidth;
 395          }
 396          else {
 397             yBot = y1 - line->halfWidth;
 398             yTop = y1 + 3.0F * line->halfWidth;
 399          }
 400       }
 401
 402       /* scan along the line, left-to-right */
 403       ixRight = (GLint) (xRight + 1.0F);
 404
 405       /*printf("avg span height: %g\n", yTop - yBot);*/
 406       for (ix = (GLint) xLeft; ix < ixRight; ix++) {
 407          const GLint iyBot = (GLint) yBot;
 408          const GLint iyTop = (GLint) (yTop + 1.0F);
 409          GLint iy;
 410          /* scan across the line, bottom-to-top */
 411          for (iy = iyBot; iy < iyTop; iy++) {
 412             (*plot)(ctx, line, ix, iy);
 413          }
 414          yBot += dydx;
 415          yTop += dydx;
 416       }
 417    }
 418    else {
 419       /* Y-major line */
 420       GLfloat dxdy = line->dx / line->dy;
 421       GLfloat yBot, yTop, xLeft, xRight;
 422       GLint iy, iyTop;
 423       if (y0 < y1) {
 424          yBot = y0 - line->halfWidth;
 425          yTop = y1 + line->halfWidth;
 426          if (line->dx >= 0.0) {
 427             xLeft = x0 - 3.0F * line->halfWidth;
 428             xRight = x0 + line->halfWidth;
 429          }
 430          else {
 431             xLeft = x0 - line->halfWidth;
 432             xRight = x0 + 3.0F * line->halfWidth;
 433          }
 434       }
 435       else {
 436          yBot = y1 - line->halfWidth;
 437          yTop = y0 + line->halfWidth;
 438          if (line->dx <= 0.0) {
 439             xLeft = x1 - 3.0F * line->halfWidth;
 440             xRight = x1 + line->halfWidth;
 441          }
 442          else {
 443             xLeft = x1 - line->halfWidth;
 444             xRight = x1 + 3.0F * line->halfWidth;
 445          }
 446       }
 447
 448       /* scan along the line, bottom-to-top */
 449       iyTop = (GLint) (yTop + 1.0F);
 450
 451       /*printf("avg span width: %g\n", xRight - xLeft);*/
 452       for (iy = (GLint) yBot; iy < iyTop; iy++) {
 453          const GLint ixLeft = (GLint) xLeft;
 454          const GLint ixRight = (GLint) (xRight + 1.0F);
 455          GLint ix;
 456          /* scan across the line, left-to-right */
 457          for (ix = ixLeft; ix < ixRight; ix++) {
 458             (*plot)(ctx, line, ix, iy);
 459          }
 460          xLeft += dxdy;
 461          xRight += dxdy;
 462       }
 463    }
 464 }
 465
 466
 467 #define NAME(x) aa_ci_##x
 468 #define DO_Z
 469 #define DO_FOG
 470 #define DO_INDEX
 471 #include "s_aalinetemp.h"
 472
 473
 474 #define NAME(x) aa_rgba_##x
 475 #define DO_Z
 476 #define DO_FOG
 477 #define DO_RGBA
 478 #include "s_aalinetemp.h"
 479
 480
 481 #define NAME(x)  aa_tex_rgba_##x
 482 #define DO_Z
 483 #define DO_FOG
 484 #define DO_RGBA
 485 #define DO_TEX
 486 #include "s_aalinetemp.h"
 487
 488
 489 #define NAME(x)  aa_multitex_rgba_##x
 490 #define DO_Z
 491 #define DO_FOG
 492 #define DO_RGBA
 493 #define DO_MULTITEX
 494 #include "s_aalinetemp.h"
 495
 496
 497 #define NAME(x)  aa_multitex_spec_##x
 498 #define DO_Z
 499 #define DO_FOG
 500 #define DO_RGBA
 501 #define DO_MULTITEX
 502 #define DO_SPEC
 503 #include "s_aalinetemp.h"
 504
 505
 506
 507 void
 508 _swrast_choose_aa_line_function(GLcontext *ctx)
 509 {
 510    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 511
 512    ASSERT(ctx->Line.SmoothFlag);
 513
 514    if (ctx->Visual.rgbMode) {
 515       /* RGBA */
 516       if (ctx->Texture._ReallyEnabled) {
 517          if (ctx->Texture._ReallyEnabled > TEXTURE0_ANY) {
 518             /* Multitextured! */
 519             if (ctx->Light.Model.ColorControl==GL_SEPARATE_SPECULAR_COLOR ||
 520                 ctx->Fog.ColorSumEnabled)
 521                swrast->Line = aa_multitex_spec_line;
 522             else
 523                swrast->Line = aa_multitex_rgba_line;
 524          }
 525          else {
 526             swrast->Line = aa_tex_rgba_line;
 527          }
 528       }
 529       else {
 530          swrast->Line = aa_rgba_line;
 531       }
 532    }
 533    else {
 534       /* Color Index */
 535       swrast->Line = aa_ci_line;
 536    }
 537 }