src/mesa/swrast/s_aaline.c

   1 /* $Id: s_aaline.c,v 1.9 2001/05/10 17:41:41 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 #include "glheader.h"
  29 #include "swrast/s_aaline.h"
  30 #include "swrast/s_pb.h"
  31 #include "swrast/s_context.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
  80
  81
  82 /*
  83  * Compute the equation of a plane used to interpolate line fragment data
  84  * such as color, Z, texture coords, etc.
  85  * Input: (x0, y0) and (x1,y1) are the endpoints of the line.
  86  *        z0, and z1 are the end point values to interpolate.
  87  * Output:  plane - the plane equation.
  88  *
  89  * Note: we don't really have enough parameters to specify a plane.
  90  * We take the endpoints of the line and compute a plane such that
  91  * the cross product of the line vector and the plane normal is
  92  * parallel to the projection plane.
  93  */
  94 static void
  95 compute_plane(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
  96               GLfloat z0, GLfloat z1, GLfloat plane[4])
  97 {
  98 #if 0
  99    /* original */
 100    const GLfloat px = x1 - x0;
 101    const GLfloat py = y1 - y0;
 102    const GLfloat pz = z1 - z0;
 103    const GLfloat qx = -py;
 104    const GLfloat qy = px;
 105    const GLfloat qz = 0;
 106    const GLfloat a = py * qz - pz * qy;
 107    const GLfloat b = pz * qx - px * qz;
 108    const GLfloat c = px * qy - py * qx;
 109    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 110    plane[0] = a;
 111    plane[1] = b;
 112    plane[2] = c;
 113    plane[3] = d;
 114 #else
 115    /* simplified */
 116    const GLfloat px = x1 - x0;
 117    const GLfloat py = y1 - y0;
 118    const GLfloat pz = z0 - z1;
 119    const GLfloat a = pz * px;
 120    const GLfloat b = pz * py;
 121    const GLfloat c = px * px + py * py;
 122    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 123    if (a == 0.0 && b == 0.0 && c == 0.0 && d == 0.0) {
 124       plane[0] = 0.0;
 125       plane[1] = 0.0;
 126       plane[2] = 1.0;
 127       plane[3] = 0.0;
 128    }
 129    else {
 130       plane[0] = a;
 131       plane[1] = b;
 132       plane[2] = c;
 133       plane[3] = d;
 134    }
 135 #endif
 136 }
 137
 138
 139 static INLINE void
 140 constant_plane(GLfloat value, GLfloat plane[4])
 141 {
 142    plane[0] = 0.0;
 143    plane[1] = 0.0;
 144    plane[2] = -1.0;
 145    plane[3] = value;
 146 }
 147
 148
 149 static INLINE GLfloat
 150 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 151 {
 152    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 153    return z;
 154 }
 155
 156 #define SOLVE_PLANE(X, Y, PLANE) \
 157    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 158
 159
 160 /*
 161  * Return 1 / solve_plane().
 162  */
 163 static INLINE GLfloat
 164 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 165 {
 166    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 167    if (denom == 0.0)
 168       return 0.0;
 169    else
 170       return -plane[2] / denom;
 171 }
 172
 173
 174 /*
 175  * Solve plane and return clamped GLchan value.
 176  */
 177 static INLINE GLchan
 178 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 179 {
 180    GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2] + 0.5F;
 181    if (z < 0.0F)
 182       return 0;
 183    else if (z > CHAN_MAXF)
 184       return (GLchan) CHAN_MAXF;
 185    return (GLchan) (GLint) z;
 186 }
 187
 188
 189 /*
 190  * Compute mipmap level of detail.
 191  */
 192 static INLINE GLfloat
 193 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 194                GLfloat invQ, GLfloat width, GLfloat height)
 195 {
 196    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 197    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 198    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 199    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 200    GLfloat r1 = dudx * dudx + dudy * dudy;
 201    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 202    GLfloat rho2 = r1 + r2;
 203    /* return log base 2 of rho */
 204    if (rho2 == 0.0F)
 205       return 0.0;
 206    else
 207       return log(rho2) * 1.442695 * 0.5;       /* 1.442695 = 1/log(2) */
 208 }
 209
 210
 211
 212
 213 /*
 214  * Fill in the samples[] array with the (x,y) subpixel positions of
 215  * xSamples * ySamples sample positions.
 216  * Note that the four corner samples are put into the first four
 217  * positions of the array.  This allows us to optimize for the common
 218  * case of all samples being inside the polygon.
 219  */
 220 static void
 221 make_sample_table(GLint xSamples, GLint ySamples, GLfloat samples[][2])
 222 {
 223    const GLfloat dx = 1.0F / (GLfloat) xSamples;
 224    const GLfloat dy = 1.0F / (GLfloat) ySamples;
 225    GLint x, y;
 226    GLint i;
 227
 228    i = 4;
 229    for (x = 0; x < xSamples; x++) {
 230       for (y = 0; y < ySamples; y++) {
 231          GLint j;
 232          if (x == 0 && y == 0) {
 233             /* lower left */
 234             j = 0;
 235          }
 236          else if (x == xSamples - 1 && y == 0) {
 237             /* lower right */
 238             j = 1;
 239          }
 240          else if (x == 0 && y == ySamples - 1) {
 241             /* upper left */
 242             j = 2;
 243          }
 244          else if (x == xSamples - 1 && y == ySamples - 1) {
 245             /* upper right */
 246             j = 3;
 247          }
 248          else {
 249             j = i++;
 250          }
 251          samples[j][0] = x * dx + 0.5 * dx;
 252          samples[j][1] = y * dy + 0.5 * dy;
 253       }
 254    }
 255 }
 256
 257
 258
 259 /*
 260  * Compute how much of the given pixel's area is inside the rectangle
 261  * defined by vertices v0, v1, v2, v3.
 262  * Vertices MUST be specified in counter-clockwise order.
 263  * Return:  coverage in [0, 1].
 264  */
 265 static GLfloat
 266 compute_coveragef(const struct LineInfo *info,
 267                   GLint winx, GLint winy)
 268 {
 269    static GLfloat samples[SUB_PIXEL * SUB_PIXEL][2];
 270    static GLboolean haveSamples = GL_FALSE;
 271    const GLfloat x = (GLfloat) winx;
 272    const GLfloat y = (GLfloat) winy;
 273    GLint stop = 4, i;
 274    GLfloat insideCount = SUB_PIXEL * SUB_PIXEL;
 275
 276    if (!haveSamples) {
 277       make_sample_table(SUB_PIXEL, SUB_PIXEL, samples);
 278       haveSamples = GL_TRUE;
 279    }
 280
 281 #if 0 /*DEBUG*/
 282    {
 283       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 284       assert(area >= 0.0);
 285    }
 286 #endif
 287
 288    for (i = 0; i < stop; i++) {
 289       const GLfloat sx = x + samples[i][0];
 290       const GLfloat sy = y + samples[i][1];
 291       const GLfloat fx0 = sx - info->qx0;
 292       const GLfloat fy0 = sy - info->qy0;
 293       const GLfloat fx1 = sx - info->qx1;
 294       const GLfloat fy1 = sy - info->qy1;
 295       const GLfloat fx2 = sx - info->qx2;
 296       const GLfloat fy2 = sy - info->qy2;
 297       const GLfloat fx3 = sx - info->qx3;
 298       const GLfloat fy3 = sy - info->qy3;
 299       /* cross product determines if sample is inside or outside each edge */
 300       GLfloat cross0 = (info->ex0 * fy0 - info->ey0 * fx0);
 301       GLfloat cross1 = (info->ex1 * fy1 - info->ey1 * fx1);
 302       GLfloat cross2 = (info->ex2 * fy2 - info->ey2 * fx2);
 303       GLfloat cross3 = (info->ex3 * fy3 - info->ey3 * fx3);
 304       /* Check if the sample is exactly on an edge.  If so, let cross be a
 305        * positive or negative value depending on the direction of the edge.
 306        */
 307       if (cross0 == 0.0F)
 308          cross0 = info->ex0 + info->ey0;
 309       if (cross1 == 0.0F)
 310          cross1 = info->ex1 + info->ey1;
 311       if (cross2 == 0.0F)
 312          cross2 = info->ex2 + info->ey2;
 313       if (cross3 == 0.0F)
 314          cross3 = info->ex3 + info->ey3;
 315       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F || cross3 < 0.0F) {
 316          /* point is outside quadrilateral */
 317          insideCount -= 1.0F;
 318          stop = SUB_PIXEL * SUB_PIXEL;
 319       }
 320    }
 321    if (stop == 4)
 322       return 1.0F;
 323    else
 324       return insideCount * (1.0F / (SUB_PIXEL * SUB_PIXEL));
 325 }
 326
 327
 328
 329 typedef void (*plot_func)(GLcontext *ctx, const struct LineInfo *line,
 330                           struct pixel_buffer *pb, int ix, int iy);
 331
 332
 333 /*
 334  * Draw an AA line segment (called many times per line when stippling)
 335  */
 336 static void
 337 segment(GLcontext *ctx,
 338         struct LineInfo *line,
 339         plot_func plot,
 340         struct pixel_buffer *pb,
 341         GLfloat t0, GLfloat t1)
 342 {
 343    const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
 344    const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
 345    /* compute the actual segment's endpoints */
 346    const GLfloat x0 = line->x0 + t0 * line->dx;
 347    const GLfloat y0 = line->y0 + t0 * line->dy;
 348    const GLfloat x1 = line->x0 + t1 * line->dx;
 349    const GLfloat y1 = line->y0 + t1 * line->dy;
 350
 351    /* compute vertices of the line-aligned quadrilateral */
 352    line->qx0 = x0 - line->yAdj;
 353    line->qy0 = y0 + line->xAdj;
 354    line->qx1 = x0 + line->yAdj;
 355    line->qy1 = y0 - line->xAdj;
 356    line->qx2 = x1 + line->yAdj;
 357    line->qy2 = y1 - line->xAdj;
 358    line->qx3 = x1 - line->yAdj;
 359    line->qy3 = y1 + line->xAdj;
 360    /* compute the quad's edge vectors (for coverage calc) */
 361    line->ex0 = line->qx1 - line->qx0;
 362    line->ey0 = line->qy1 - line->qy0;
 363    line->ex1 = line->qx2 - line->qx1;
 364    line->ey1 = line->qy2 - line->qy1;
 365    line->ex2 = line->qx3 - line->qx2;
 366    line->ey2 = line->qy3 - line->qy2;
 367    line->ex3 = line->qx0 - line->qx3;
 368    line->ey3 = line->qy0 - line->qy3;
 369
 370    if (absDx > absDy) {
 371       /* X-major line */
 372       GLfloat dydx = line->dy / line->dx;
 373       GLfloat xLeft, xRight, yBot, yTop;
 374       GLint ix, ixRight;
 375       if (x0 < x1) {
 376          xLeft = x0 - line->halfWidth;
 377          xRight = x1 + line->halfWidth;
 378          if (line->dy >= 0.0) {
 379             yBot = y0 - 3.0 * line->halfWidth;
 380             yTop = y0 + line->halfWidth;
 381          }
 382          else {
 383             yBot = y0 - line->halfWidth;
 384             yTop = y0 + 3.0 * line->halfWidth;
 385          }
 386       }
 387       else {
 388          xLeft = x1 - line->halfWidth;
 389          xRight = x0 + line->halfWidth;
 390          if (line->dy <= 0.0) {
 391             yBot = y1 - 3.0 * line->halfWidth;
 392             yTop = y1 + line->halfWidth;
 393          }
 394          else {
 395             yBot = y1 - line->halfWidth;
 396             yTop = y1 + 3.0 * line->halfWidth;
 397          }
 398       }
 399
 400       /* scan along the line, left-to-right */
 401       ixRight = (GLint) (xRight + 1.0F);
 402
 403       /*printf("avg span height: %g\n", yTop - yBot);*/
 404       for (ix = (GLint) xLeft; ix < ixRight; ix++) {
 405          const GLint iyBot = (GLint) yBot;
 406          const GLint iyTop = (GLint) (yTop + 1.0F);
 407          GLint iy;
 408          /* scan across the line, bottom-to-top */
 409          for (iy = iyBot; iy < iyTop; iy++) {
 410             (*plot)(ctx, line, pb, ix, iy);
 411          }
 412          yBot += dydx;
 413          yTop += dydx;
 414       }
 415    }
 416    else {
 417       /* Y-major line */
 418       GLfloat dxdy = line->dx / line->dy;
 419       GLfloat yBot, yTop, xLeft, xRight;
 420       GLint iy, iyTop;
 421       if (y0 < y1) {
 422          yBot = y0 - line->halfWidth;
 423          yTop = y1 + line->halfWidth;
 424          if (line->dx >= 0.0) {
 425             xLeft = x0 - 3.0 * line->halfWidth;
 426             xRight = x0 + line->halfWidth;
 427          }
 428          else {
 429             xLeft = x0 - line->halfWidth;
 430             xRight = x0 + 3.0 * line->halfWidth;
 431          }
 432       }
 433       else {
 434          yBot = y1 - line->halfWidth;
 435          yTop = y0 + line->halfWidth;
 436          if (line->dx <= 0.0) {
 437             xLeft = x1 - 3.0 * line->halfWidth;
 438             xRight = x1 + line->halfWidth;
 439          }
 440          else {
 441             xLeft = x1 - line->halfWidth;
 442             xRight = x1 + 3.0 * line->halfWidth;
 443          }
 444       }
 445
 446       /* scan along the line, bottom-to-top */
 447       iyTop = (GLint) (yTop + 1.0F);
 448
 449       /*printf("avg span width: %g\n", xRight - xLeft);*/
 450       for (iy = (GLint) yBot; iy < iyTop; iy++) {
 451          const GLint ixLeft = (GLint) xLeft;
 452          const GLint ixRight = (GLint) (xRight + 1.0F);
 453          GLint ix;
 454          /* scan across the line, left-to-right */
 455          for (ix = ixLeft; ix < ixRight; ix++) {
 456             (*plot)(ctx, line, pb, ix, iy);
 457          }
 458          xLeft += dxdy;
 459          xRight += dxdy;
 460       }
 461    }
 462 }
 463
 464
 465 #define NAME(x) aa_ci_##x
 466 #define DO_Z
 467 #define DO_FOG
 468 #define DO_INDEX
 469 #include "s_aalinetemp.h"
 470
 471
 472 #define NAME(x) aa_rgba_##x
 473 #define DO_Z
 474 #define DO_FOG
 475 #define DO_RGBA
 476 #include "s_aalinetemp.h"
 477
 478
 479 #define NAME(x)  aa_tex_rgba_##x
 480 #define DO_Z
 481 #define DO_FOG
 482 #define DO_RGBA
 483 #define DO_TEX
 484 #include "s_aalinetemp.h"
 485
 486
 487 #define NAME(x)  aa_multitex_rgba_##x
 488 #define DO_Z
 489 #define DO_RGBA
 490 #define DO_MULTITEX
 491 #define DO_SPEC
 492 #include "s_aalinetemp.h"
 493
 494
 495
 496 void
 497 _swrast_choose_aa_line_function(GLcontext *ctx)
 498 {
 499    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 500
 501    ASSERT(ctx->Line.SmoothFlag);
 502
 503    if (ctx->Visual.rgbMode) {
 504       /* RGBA */
 505       if (ctx->Texture._ReallyEnabled) {
 506          if (swrast->_MultiTextureEnabled
 507              || ctx->Light.Model.ColorControl==GL_SEPARATE_SPECULAR_COLOR
 508              || ctx->Fog.ColorSumEnabled)
 509             /* Multitextured! */
 510             swrast->Line = aa_multitex_rgba_line;
 511          else
 512             swrast->Line = aa_tex_rgba_line;
 513       }
 514       else {
 515          swrast->Line = aa_rgba_line;
 516       }
 517    }
 518    else {
 519       /* Color Index */
 520       swrast->Line = aa_ci_line;
 521    }
 522 }