src/mesa/swrast/s_aaline.c

   1 /* $Id: s_aaline.c,v 1.20 2003/03/01 01:50:25 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 "imports.h"
  30 #include "swrast/s_aaline.h"
  31 #include "swrast/s_context.h"
  32 #include "swrast/s_span.h"
  33 #include "swrast/swrast.h"
  34 #include "mtypes.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    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 184 #if CHAN_TYPE == GL_FLOAT
 185    return CLAMP(z, 0.0F, CHAN_MAXF);
 186 #else
 187    if (z < 0)
 188       return 0;
 189    else if (z > CHAN_MAX)
 190       return CHAN_MAX;
 191    return (GLchan) IROUND_POS(z);
 192 #endif
 193 }
 194
 195
 196 /*
 197  * Compute mipmap level of detail.
 198  */
 199 static INLINE GLfloat
 200 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 201                GLfloat invQ, GLfloat width, GLfloat height)
 202 {
 203    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 204    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 205    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 206    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 207    GLfloat r1 = dudx * dudx + dudy * dudy;
 208    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 209    GLfloat rho2 = r1 + r2;
 210    /* return log base 2 of rho */
 211    if (rho2 == 0.0F)
 212       return 0.0;
 213    else
 214       return (GLfloat) (log(rho2) * 1.442695 * 0.5);/* 1.442695 = 1/log(2) */
 215 }
 216
 217
 218
 219
 220 /*
 221  * Fill in the samples[] array with the (x,y) subpixel positions of
 222  * xSamples * ySamples sample positions.
 223  * Note that the four corner samples are put into the first four
 224  * positions of the array.  This allows us to optimize for the common
 225  * case of all samples being inside the polygon.
 226  */
 227 static void
 228 make_sample_table(GLint xSamples, GLint ySamples, GLfloat samples[][2])
 229 {
 230    const GLfloat dx = 1.0F / (GLfloat) xSamples;
 231    const GLfloat dy = 1.0F / (GLfloat) ySamples;
 232    GLint x, y;
 233    GLint i;
 234
 235    i = 4;
 236    for (x = 0; x < xSamples; x++) {
 237       for (y = 0; y < ySamples; y++) {
 238          GLint j;
 239          if (x == 0 && y == 0) {
 240             /* lower left */
 241             j = 0;
 242          }
 243          else if (x == xSamples - 1 && y == 0) {
 244             /* lower right */
 245             j = 1;
 246          }
 247          else if (x == 0 && y == ySamples - 1) {
 248             /* upper left */
 249             j = 2;
 250          }
 251          else if (x == xSamples - 1 && y == ySamples - 1) {
 252             /* upper right */
 253             j = 3;
 254          }
 255          else {
 256             j = i++;
 257          }
 258          samples[j][0] = x * dx + 0.5F * dx;
 259          samples[j][1] = y * dy + 0.5F * dy;
 260       }
 261    }
 262 }
 263
 264
 265
 266 /*
 267  * Compute how much of the given pixel's area is inside the rectangle
 268  * defined by vertices v0, v1, v2, v3.
 269  * Vertices MUST be specified in counter-clockwise order.
 270  * Return:  coverage in [0, 1].
 271  */
 272 static GLfloat
 273 compute_coveragef(const struct LineInfo *info,
 274                   GLint winx, GLint winy)
 275 {
 276    static GLfloat samples[SUB_PIXEL * SUB_PIXEL][2];
 277    static GLboolean haveSamples = GL_FALSE;
 278    const GLfloat x = (GLfloat) winx;
 279    const GLfloat y = (GLfloat) winy;
 280    GLint stop = 4, i;
 281    GLfloat insideCount = SUB_PIXEL * SUB_PIXEL;
 282
 283    if (!haveSamples) {
 284       make_sample_table(SUB_PIXEL, SUB_PIXEL, samples);
 285       haveSamples = GL_TRUE;
 286    }
 287
 288 #if 0 /*DEBUG*/
 289    {
 290       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 291       assert(area >= 0.0);
 292    }
 293 #endif
 294
 295    for (i = 0; i < stop; i++) {
 296       const GLfloat sx = x + samples[i][0];
 297       const GLfloat sy = y + samples[i][1];
 298       const GLfloat fx0 = sx - info->qx0;
 299       const GLfloat fy0 = sy - info->qy0;
 300       const GLfloat fx1 = sx - info->qx1;
 301       const GLfloat fy1 = sy - info->qy1;
 302       const GLfloat fx2 = sx - info->qx2;
 303       const GLfloat fy2 = sy - info->qy2;
 304       const GLfloat fx3 = sx - info->qx3;
 305       const GLfloat fy3 = sy - info->qy3;
 306       /* cross product determines if sample is inside or outside each edge */
 307       GLfloat cross0 = (info->ex0 * fy0 - info->ey0 * fx0);
 308       GLfloat cross1 = (info->ex1 * fy1 - info->ey1 * fx1);
 309       GLfloat cross2 = (info->ex2 * fy2 - info->ey2 * fx2);
 310       GLfloat cross3 = (info->ex3 * fy3 - info->ey3 * fx3);
 311       /* Check if the sample is exactly on an edge.  If so, let cross be a
 312        * positive or negative value depending on the direction of the edge.
 313        */
 314       if (cross0 == 0.0F)
 315          cross0 = info->ex0 + info->ey0;
 316       if (cross1 == 0.0F)
 317          cross1 = info->ex1 + info->ey1;
 318       if (cross2 == 0.0F)
 319          cross2 = info->ex2 + info->ey2;
 320       if (cross3 == 0.0F)
 321          cross3 = info->ex3 + info->ey3;
 322       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F || cross3 < 0.0F) {
 323          /* point is outside quadrilateral */
 324          insideCount -= 1.0F;
 325          stop = SUB_PIXEL * SUB_PIXEL;
 326       }
 327    }
 328    if (stop == 4)
 329       return 1.0F;
 330    else
 331       return insideCount * (1.0F / (SUB_PIXEL * SUB_PIXEL));
 332 }
 333
 334
 335
 336 typedef void (*plot_func)(GLcontext *ctx, struct LineInfo *line,
 337                           int ix, int iy);
 338
 339
 340
 341 /*
 342  * Draw an AA line segment (called many times per line when stippling)
 343  */
 344 static void
 345 segment(GLcontext *ctx,
 346         struct LineInfo *line,
 347         plot_func plot,
 348         GLfloat t0, GLfloat t1)
 349 {
 350    const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
 351    const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
 352    /* compute the actual segment's endpoints */
 353    const GLfloat x0 = line->x0 + t0 * line->dx;
 354    const GLfloat y0 = line->y0 + t0 * line->dy;
 355    const GLfloat x1 = line->x0 + t1 * line->dx;
 356    const GLfloat y1 = line->y0 + t1 * line->dy;
 357
 358    /* compute vertices of the line-aligned quadrilateral */
 359    line->qx0 = x0 - line->yAdj;
 360    line->qy0 = y0 + line->xAdj;
 361    line->qx1 = x0 + line->yAdj;
 362    line->qy1 = y0 - line->xAdj;
 363    line->qx2 = x1 + line->yAdj;
 364    line->qy2 = y1 - line->xAdj;
 365    line->qx3 = x1 - line->yAdj;
 366    line->qy3 = y1 + line->xAdj;
 367    /* compute the quad's edge vectors (for coverage calc) */
 368    line->ex0 = line->qx1 - line->qx0;
 369    line->ey0 = line->qy1 - line->qy0;
 370    line->ex1 = line->qx2 - line->qx1;
 371    line->ey1 = line->qy2 - line->qy1;
 372    line->ex2 = line->qx3 - line->qx2;
 373    line->ey2 = line->qy3 - line->qy2;
 374    line->ex3 = line->qx0 - line->qx3;
 375    line->ey3 = line->qy0 - line->qy3;
 376
 377    if (absDx > absDy) {
 378       /* X-major line */
 379       GLfloat dydx = line->dy / line->dx;
 380       GLfloat xLeft, xRight, yBot, yTop;
 381       GLint ix, ixRight;
 382       if (x0 < x1) {
 383          xLeft = x0 - line->halfWidth;
 384          xRight = x1 + line->halfWidth;
 385          if (line->dy >= 0.0) {
 386             yBot = y0 - 3.0F * line->halfWidth;
 387             yTop = y0 + line->halfWidth;
 388          }
 389          else {
 390             yBot = y0 - line->halfWidth;
 391             yTop = y0 + 3.0F * line->halfWidth;
 392          }
 393       }
 394       else {
 395          xLeft = x1 - line->halfWidth;
 396          xRight = x0 + line->halfWidth;
 397          if (line->dy <= 0.0) {
 398             yBot = y1 - 3.0F * line->halfWidth;
 399             yTop = y1 + line->halfWidth;
 400          }
 401          else {
 402             yBot = y1 - line->halfWidth;
 403             yTop = y1 + 3.0F * line->halfWidth;
 404          }
 405       }
 406
 407       /* scan along the line, left-to-right */
 408       ixRight = (GLint) (xRight + 1.0F);
 409
 410       /*printf("avg span height: %g\n", yTop - yBot);*/
 411       for (ix = (GLint) xLeft; ix < ixRight; ix++) {
 412          const GLint iyBot = (GLint) yBot;
 413          const GLint iyTop = (GLint) (yTop + 1.0F);
 414          GLint iy;
 415          /* scan across the line, bottom-to-top */
 416          for (iy = iyBot; iy < iyTop; iy++) {
 417             (*plot)(ctx, line, ix, iy);
 418          }
 419          yBot += dydx;
 420          yTop += dydx;
 421       }
 422    }
 423    else {
 424       /* Y-major line */
 425       GLfloat dxdy = line->dx / line->dy;
 426       GLfloat yBot, yTop, xLeft, xRight;
 427       GLint iy, iyTop;
 428       if (y0 < y1) {
 429          yBot = y0 - line->halfWidth;
 430          yTop = y1 + line->halfWidth;
 431          if (line->dx >= 0.0) {
 432             xLeft = x0 - 3.0F * line->halfWidth;
 433             xRight = x0 + line->halfWidth;
 434          }
 435          else {
 436             xLeft = x0 - line->halfWidth;
 437             xRight = x0 + 3.0F * line->halfWidth;
 438          }
 439       }
 440       else {
 441          yBot = y1 - line->halfWidth;
 442          yTop = y0 + line->halfWidth;
 443          if (line->dx <= 0.0) {
 444             xLeft = x1 - 3.0F * line->halfWidth;
 445             xRight = x1 + line->halfWidth;
 446          }
 447          else {
 448             xLeft = x1 - line->halfWidth;
 449             xRight = x1 + 3.0F * line->halfWidth;
 450          }
 451       }
 452
 453       /* scan along the line, bottom-to-top */
 454       iyTop = (GLint) (yTop + 1.0F);
 455
 456       /*printf("avg span width: %g\n", xRight - xLeft);*/
 457       for (iy = (GLint) yBot; iy < iyTop; iy++) {
 458          const GLint ixLeft = (GLint) xLeft;
 459          const GLint ixRight = (GLint) (xRight + 1.0F);
 460          GLint ix;
 461          /* scan across the line, left-to-right */
 462          for (ix = ixLeft; ix < ixRight; ix++) {
 463             (*plot)(ctx, line, ix, iy);
 464          }
 465          xLeft += dxdy;
 466          xRight += dxdy;
 467       }
 468    }
 469 }
 470
 471
 472 #define NAME(x) aa_ci_##x
 473 #define DO_Z
 474 #define DO_FOG
 475 #define DO_INDEX
 476 #include "s_aalinetemp.h"
 477
 478
 479 #define NAME(x) aa_rgba_##x
 480 #define DO_Z
 481 #define DO_FOG
 482 #define DO_RGBA
 483 #include "s_aalinetemp.h"
 484
 485
 486 #define NAME(x)  aa_tex_rgba_##x
 487 #define DO_Z
 488 #define DO_FOG
 489 #define DO_RGBA
 490 #define DO_TEX
 491 #include "s_aalinetemp.h"
 492
 493
 494 #define NAME(x)  aa_multitex_rgba_##x
 495 #define DO_Z
 496 #define DO_FOG
 497 #define DO_RGBA
 498 #define DO_MULTITEX
 499 #include "s_aalinetemp.h"
 500
 501
 502 #define NAME(x)  aa_multitex_spec_##x
 503 #define DO_Z
 504 #define DO_FOG
 505 #define DO_RGBA
 506 #define DO_MULTITEX
 507 #define DO_SPEC
 508 #include "s_aalinetemp.h"
 509
 510
 511
 512 void
 513 _swrast_choose_aa_line_function(GLcontext *ctx)
 514 {
 515    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 516
 517    ASSERT(ctx->Line.SmoothFlag);
 518
 519    if (ctx->Visual.rgbMode) {
 520       /* RGBA */
 521       if (ctx->Texture._EnabledUnits != 0) {
 522          if (ctx->Texture._EnabledUnits > 1) {
 523             /* Multitextured! */
 524             if (ctx->Light.Model.ColorControl==GL_SEPARATE_SPECULAR_COLOR ||
 525                 ctx->Fog.ColorSumEnabled)
 526                swrast->Line = aa_multitex_spec_line;
 527             else
 528                swrast->Line = aa_multitex_rgba_line;
 529          }
 530          else {
 531             swrast->Line = aa_tex_rgba_line;
 532          }
 533       }
 534       else {
 535          swrast->Line = aa_rgba_line;
 536       }
 537    }
 538    else {
 539       /* Color Index */
 540       swrast->Line = aa_ci_line;
 541    }
 542 }