src/mesa/swrast/s_aaline.c

   1 /*
   2  * Mesa 3-D graphics library
   3  *
   4  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included
  14  * in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  17  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  22  * OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 #include "c99_math.h"
  27 #include "main/glheader.h"
  28 #include "main/macros.h"
  29 #include "main/mtypes.h"
  30 #include "main/teximage.h"
  31 #include "swrast/s_aaline.h"
  32 #include "swrast/s_context.h"
  33 #include "swrast/s_span.h"
  34 #include "swrast/swrast.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_RGBA - always enabled */
  64    GLfloat rPlane[4], gPlane[4], bPlane[4], aPlane[4];
  65    /* DO_ATTRIBS */
  66    GLfloat wPlane[4];
  67    GLfloat attrPlane[VARYING_SLOT_MAX][4][4];
  68    GLfloat lambda[VARYING_SLOT_MAX];
  69    GLfloat texWidth[VARYING_SLOT_MAX];
  70    GLfloat texHeight[VARYING_SLOT_MAX];
  71
  72    SWspan span;
  73 };
  74
  75
  76
  77 /*
  78  * Compute the equation of a plane used to interpolate line fragment data
  79  * such as color, Z, texture coords, etc.
  80  * Input: (x0, y0) and (x1,y1) are the endpoints of the line.
  81  *        z0, and z1 are the end point values to interpolate.
  82  * Output:  plane - the plane equation.
  83  *
  84  * Note: we don't really have enough parameters to specify a plane.
  85  * We take the endpoints of the line and compute a plane such that
  86  * the cross product of the line vector and the plane normal is
  87  * parallel to the projection plane.
  88  */
  89 static void
  90 compute_plane(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
  91               GLfloat z0, GLfloat z1, GLfloat plane[4])
  92 {
  93 #if 0
  94    /* original */
  95    const GLfloat px = x1 - x0;
  96    const GLfloat py = y1 - y0;
  97    const GLfloat pz = z1 - z0;
  98    const GLfloat qx = -py;
  99    const GLfloat qy = px;
 100    const GLfloat qz = 0;
 101    const GLfloat a = py * qz - pz * qy;
 102    const GLfloat b = pz * qx - px * qz;
 103    const GLfloat c = px * qy - py * qx;
 104    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 105    plane[0] = a;
 106    plane[1] = b;
 107    plane[2] = c;
 108    plane[3] = d;
 109 #else
 110    /* simplified */
 111    const GLfloat px = x1 - x0;
 112    const GLfloat py = y1 - y0;
 113    const GLfloat pz = z0 - z1;
 114    const GLfloat a = pz * px;
 115    const GLfloat b = pz * py;
 116    const GLfloat c = px * px + py * py;
 117    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 118    if (a == 0.0F && b == 0.0F && c == 0.0F && d == 0.0F) {
 119       plane[0] = 0.0F;
 120       plane[1] = 0.0F;
 121       plane[2] = 1.0F;
 122       plane[3] = 0.0F;
 123    }
 124    else {
 125       plane[0] = a;
 126       plane[1] = b;
 127       plane[2] = c;
 128       plane[3] = d;
 129    }
 130 #endif
 131 }
 132
 133
 134 static inline void
 135 constant_plane(GLfloat value, GLfloat plane[4])
 136 {
 137    plane[0] = 0.0F;
 138    plane[1] = 0.0F;
 139    plane[2] = -1.0F;
 140    plane[3] = value;
 141 }
 142
 143
 144 static inline GLfloat
 145 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 146 {
 147    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 148    return z;
 149 }
 150
 151 #define SOLVE_PLANE(X, Y, PLANE) \
 152    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 153
 154
 155 /*
 156  * Return 1 / solve_plane().
 157  */
 158 static inline GLfloat
 159 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 160 {
 161    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 162    if (denom == 0.0F)
 163       return 0.0F;
 164    else
 165       return -plane[2] / denom;
 166 }
 167
 168
 169 /*
 170  * Solve plane and return clamped GLchan value.
 171  */
 172 static inline GLchan
 173 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 174 {
 175    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 176 #if CHAN_TYPE == GL_FLOAT
 177    return CLAMP(z, 0.0F, CHAN_MAXF);
 178 #else
 179    if (z < 0)
 180       return 0;
 181    else if (z > CHAN_MAX)
 182       return CHAN_MAX;
 183    return (GLchan) lroundf(z);
 184 #endif
 185 }
 186
 187
 188 /*
 189  * Compute mipmap level of detail.
 190  */
 191 static inline GLfloat
 192 compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
 193                GLfloat invQ, GLfloat width, GLfloat height)
 194 {
 195    GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
 196    GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
 197    GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
 198    GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
 199    GLfloat r1 = dudx * dudx + dudy * dudy;
 200    GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
 201    GLfloat rho2 = r1 + r2;
 202    /* return log base 2 of rho */
 203    if (rho2 == 0.0F)
 204       return 0.0;
 205    else
 206       return logf(rho2) * 1.442695f * 0.5f;/* 1.442695 = 1/log(2) */
 207 }
 208
 209
 210
 211
 212 /*
 213  * Fill in the samples[] array with the (x,y) subpixel positions of
 214  * xSamples * ySamples sample positions.
 215  * Note that the four corner samples are put into the first four
 216  * positions of the array.  This allows us to optimize for the common
 217  * case of all samples being inside the polygon.
 218  */
 219 static void
 220 make_sample_table(GLint xSamples, GLint ySamples, GLfloat samples[][2])
 221 {
 222    const GLfloat dx = 1.0F / (GLfloat) xSamples;
 223    const GLfloat dy = 1.0F / (GLfloat) ySamples;
 224    GLint x, y;
 225    GLint i;
 226
 227    i = 4;
 228    for (x = 0; x < xSamples; x++) {
 229       for (y = 0; y < ySamples; y++) {
 230          GLint j;
 231          if (x == 0 && y == 0) {
 232             /* lower left */
 233             j = 0;
 234          }
 235          else if (x == xSamples - 1 && y == 0) {
 236             /* lower right */
 237             j = 1;
 238          }
 239          else if (x == 0 && y == ySamples - 1) {
 240             /* upper left */
 241             j = 2;
 242          }
 243          else if (x == xSamples - 1 && y == ySamples - 1) {
 244             /* upper right */
 245             j = 3;
 246          }
 247          else {
 248             j = i++;
 249          }
 250          samples[j][0] = x * dx + 0.5F * dx;
 251          samples[j][1] = y * dy + 0.5F * dy;
 252       }
 253    }
 254 }
 255
 256
 257
 258 /*
 259  * Compute how much of the given pixel's area is inside the rectangle
 260  * defined by vertices v0, v1, v2, v3.
 261  * Vertices MUST be specified in counter-clockwise order.
 262  * Return:  coverage in [0, 1].
 263  */
 264 static GLfloat
 265 compute_coveragef(const struct LineInfo *info,
 266                   GLint winx, GLint winy)
 267 {
 268    static GLfloat samples[SUB_PIXEL * SUB_PIXEL][2];
 269    static GLboolean haveSamples = GL_FALSE;
 270    const GLfloat x = (GLfloat) winx;
 271    const GLfloat y = (GLfloat) winy;
 272    GLint stop = 4, i;
 273    GLfloat insideCount = SUB_PIXEL * SUB_PIXEL;
 274
 275    if (!haveSamples) {
 276       make_sample_table(SUB_PIXEL, SUB_PIXEL, samples);
 277       haveSamples = GL_TRUE;
 278    }
 279
 280 #if 0 /*DEBUG*/
 281    {
 282       const GLfloat area = dx0 * dy1 - dx1 * dy0;
 283       assert(area >= 0.0);
 284    }
 285 #endif
 286
 287    for (i = 0; i < stop; i++) {
 288       const GLfloat sx = x + samples[i][0];
 289       const GLfloat sy = y + samples[i][1];
 290       const GLfloat fx0 = sx - info->qx0;
 291       const GLfloat fy0 = sy - info->qy0;
 292       const GLfloat fx1 = sx - info->qx1;
 293       const GLfloat fy1 = sy - info->qy1;
 294       const GLfloat fx2 = sx - info->qx2;
 295       const GLfloat fy2 = sy - info->qy2;
 296       const GLfloat fx3 = sx - info->qx3;
 297       const GLfloat fy3 = sy - info->qy3;
 298       /* cross product determines if sample is inside or outside each edge */
 299       GLfloat cross0 = (info->ex0 * fy0 - info->ey0 * fx0);
 300       GLfloat cross1 = (info->ex1 * fy1 - info->ey1 * fx1);
 301       GLfloat cross2 = (info->ex2 * fy2 - info->ey2 * fx2);
 302       GLfloat cross3 = (info->ex3 * fy3 - info->ey3 * fx3);
 303       /* Check if the sample is exactly on an edge.  If so, let cross be a
 304        * positive or negative value depending on the direction of the edge.
 305        */
 306       if (cross0 == 0.0F)
 307          cross0 = info->ex0 + info->ey0;
 308       if (cross1 == 0.0F)
 309          cross1 = info->ex1 + info->ey1;
 310       if (cross2 == 0.0F)
 311          cross2 = info->ex2 + info->ey2;
 312       if (cross3 == 0.0F)
 313          cross3 = info->ex3 + info->ey3;
 314       if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F || cross3 < 0.0F) {
 315          /* point is outside quadrilateral */
 316          insideCount -= 1.0F;
 317          stop = SUB_PIXEL * SUB_PIXEL;
 318       }
 319    }
 320    if (stop == 4)
 321       return 1.0F;
 322    else
 323       return insideCount * (1.0F / (SUB_PIXEL * SUB_PIXEL));
 324 }
 325
 326
 327 typedef void (*plot_func)(struct gl_context *ctx, struct LineInfo *line,
 328                           int ix, int iy);
 329
 330
 331
 332 /*
 333  * Draw an AA line segment (called many times per line when stippling)
 334  */
 335 static void
 336 segment(struct gl_context *ctx,
 337         struct LineInfo *line,
 338         plot_func plot,
 339         GLfloat t0, GLfloat t1)
 340 {
 341    const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
 342    const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
 343    /* compute the actual segment's endpoints */
 344    const GLfloat x0 = line->x0 + t0 * line->dx;
 345    const GLfloat y0 = line->y0 + t0 * line->dy;
 346    const GLfloat x1 = line->x0 + t1 * line->dx;
 347    const GLfloat y1 = line->y0 + t1 * line->dy;
 348
 349    /* compute vertices of the line-aligned quadrilateral */
 350    line->qx0 = x0 - line->yAdj;
 351    line->qy0 = y0 + line->xAdj;
 352    line->qx1 = x0 + line->yAdj;
 353    line->qy1 = y0 - line->xAdj;
 354    line->qx2 = x1 + line->yAdj;
 355    line->qy2 = y1 - line->xAdj;
 356    line->qx3 = x1 - line->yAdj;
 357    line->qy3 = y1 + line->xAdj;
 358    /* compute the quad's edge vectors (for coverage calc) */
 359    line->ex0 = line->qx1 - line->qx0;
 360    line->ey0 = line->qy1 - line->qy0;
 361    line->ex1 = line->qx2 - line->qx1;
 362    line->ey1 = line->qy2 - line->qy1;
 363    line->ex2 = line->qx3 - line->qx2;
 364    line->ey2 = line->qy3 - line->qy2;
 365    line->ex3 = line->qx0 - line->qx3;
 366    line->ey3 = line->qy0 - line->qy3;
 367
 368    if (absDx > absDy) {
 369       /* X-major line */
 370       GLfloat dydx = line->dy / line->dx;
 371       GLfloat xLeft, xRight, yBot, yTop;
 372       GLint ix, ixRight;
 373       if (x0 < x1) {
 374          xLeft = x0 - line->halfWidth;
 375          xRight = x1 + line->halfWidth;
 376          if (line->dy >= 0.0F) {
 377             yBot = y0 - 3.0F * line->halfWidth;
 378             yTop = y0 + line->halfWidth;
 379          }
 380          else {
 381             yBot = y0 - line->halfWidth;
 382             yTop = y0 + 3.0F * line->halfWidth;
 383          }
 384       }
 385       else {
 386          xLeft = x1 - line->halfWidth;
 387          xRight = x0 + line->halfWidth;
 388          if (line->dy <= 0.0F) {
 389             yBot = y1 - 3.0F * line->halfWidth;
 390             yTop = y1 + line->halfWidth;
 391          }
 392          else {
 393             yBot = y1 - line->halfWidth;
 394             yTop = y1 + 3.0F * line->halfWidth;
 395          }
 396       }
 397
 398       /* scan along the line, left-to-right */
 399       ixRight = (GLint) (xRight + 1.0F);
 400
 401       /*printf("avg span height: %g\n", yTop - yBot);*/
 402       for (ix = (GLint) xLeft; ix < ixRight; ix++) {
 403          const GLint iyBot = (GLint) yBot;
 404          const GLint iyTop = (GLint) (yTop + 1.0F);
 405          GLint iy;
 406          /* scan across the line, bottom-to-top */
 407          for (iy = iyBot; iy < iyTop; iy++) {
 408             plot(ctx, line, ix, iy);
 409          }
 410          yBot += dydx;
 411          yTop += dydx;
 412       }
 413    }
 414    else {
 415       /* Y-major line */
 416       GLfloat dxdy = line->dx / line->dy;
 417       GLfloat yBot, yTop, xLeft, xRight;
 418       GLint iy, iyTop;
 419       if (y0 < y1) {
 420          yBot = y0 - line->halfWidth;
 421          yTop = y1 + line->halfWidth;
 422          if (line->dx >= 0.0F) {
 423             xLeft = x0 - 3.0F * line->halfWidth;
 424             xRight = x0 + line->halfWidth;
 425          }
 426          else {
 427             xLeft = x0 - line->halfWidth;
 428             xRight = x0 + 3.0F * line->halfWidth;
 429          }
 430       }
 431       else {
 432          yBot = y1 - line->halfWidth;
 433          yTop = y0 + line->halfWidth;
 434          if (line->dx <= 0.0F) {
 435             xLeft = x1 - 3.0F * line->halfWidth;
 436             xRight = x1 + line->halfWidth;
 437          }
 438          else {
 439             xLeft = x1 - line->halfWidth;
 440             xRight = x1 + 3.0F * line->halfWidth;
 441          }
 442       }
 443
 444       /* scan along the line, bottom-to-top */
 445       iyTop = (GLint) (yTop + 1.0F);
 446
 447       /*printf("avg span width: %g\n", xRight - xLeft);*/
 448       for (iy = (GLint) yBot; iy < iyTop; iy++) {
 449          const GLint ixLeft = (GLint) xLeft;
 450          const GLint ixRight = (GLint) (xRight + 1.0F);
 451          GLint ix;
 452          /* scan across the line, left-to-right */
 453          for (ix = ixLeft; ix < ixRight; ix++) {
 454             plot(ctx, line, ix, iy);
 455          }
 456          xLeft += dxdy;
 457          xRight += dxdy;
 458       }
 459    }
 460 }
 461
 462
 463 #define NAME(x) aa_rgba_##x
 464 #define DO_Z
 465 #include "s_aalinetemp.h"
 466
 467
 468 #define NAME(x)  aa_general_rgba_##x
 469 #define DO_Z
 470 #define DO_ATTRIBS
 471 #include "s_aalinetemp.h"
 472
 473
 474
 475 void
 476 _swrast_choose_aa_line_function(struct gl_context *ctx)
 477 {
 478    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 479
 480    assert(ctx->Line.SmoothFlag);
 481
 482    if (ctx->Texture._EnabledCoordUnits != 0
 483        || _swrast_use_fragment_program(ctx)
 484        || (ctx->Light.Enabled &&
 485            ctx->Light.Model.ColorControl == GL_SEPARATE_SPECULAR_COLOR)
 486        || ctx->Fog.ColorSumEnabled
 487        || swrast->_FogEnabled) {
 488       swrast->Line = aa_general_rgba_line;
 489    }
 490    else {
 491       swrast->Line = aa_rgba_line;
 492    }
 493 }