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 "util/imports.h"
  29 #include "main/macros.h"
  30 #include "main/mtypes.h"
  31 #include "main/teximage.h"
  32 #include "swrast/s_aaline.h"
  33 #include "swrast/s_context.h"
  34 #include "swrast/s_span.h"
  35 #include "swrast/swrast.h"
  36
  37
  38 #define SUB_PIXEL 4
  39
  40
  41 /*
  42  * Info about the AA line we're rendering
  43  */
  44 struct LineInfo
  45 {
  46    GLfloat x0, y0;        /* start */
  47    GLfloat x1, y1;        /* end */
  48    GLfloat dx, dy;        /* direction vector */
  49    GLfloat len;           /* length */
  50    GLfloat halfWidth;     /* half of line width */
  51    GLfloat xAdj, yAdj;    /* X and Y adjustment for quad corners around line */
  52    /* for coverage computation */
  53    GLfloat qx0, qy0;      /* quad vertices */
  54    GLfloat qx1, qy1;
  55    GLfloat qx2, qy2;
  56    GLfloat qx3, qy3;
  57    GLfloat ex0, ey0;      /* quad edge vectors */
  58    GLfloat ex1, ey1;
  59    GLfloat ex2, ey2;
  60    GLfloat ex3, ey3;
  61
  62    /* DO_Z */
  63    GLfloat zPlane[4];
  64    /* DO_RGBA - always enabled */
  65    GLfloat rPlane[4], gPlane[4], bPlane[4], aPlane[4];
  66    /* DO_ATTRIBS */
  67    GLfloat wPlane[4];
  68    GLfloat attrPlane[VARYING_SLOT_MAX][4][4];
  69    GLfloat lambda[VARYING_SLOT_MAX];
  70    GLfloat texWidth[VARYING_SLOT_MAX];
  71    GLfloat texHeight[VARYING_SLOT_MAX];
  72
  73    SWspan span;
  74 };
  75
  76
  77
  78 /*
  79  * Compute the equation of a plane used to interpolate line fragment data
  80  * such as color, Z, texture coords, etc.
  81  * Input: (x0, y0) and (x1,y1) are the endpoints of the line.
  82  *        z0, and z1 are the end point values to interpolate.
  83  * Output:  plane - the plane equation.
  84  *
  85  * Note: we don't really have enough parameters to specify a plane.
  86  * We take the endpoints of the line and compute a plane such that
  87  * the cross product of the line vector and the plane normal is
  88  * parallel to the projection plane.
  89  */
  90 static void
  91 compute_plane(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
  92               GLfloat z0, GLfloat z1, GLfloat plane[4])
  93 {
  94 #if 0
  95    /* original */
  96    const GLfloat px = x1 - x0;
  97    const GLfloat py = y1 - y0;
  98    const GLfloat pz = z1 - z0;
  99    const GLfloat qx = -py;
 100    const GLfloat qy = px;
 101    const GLfloat qz = 0;
 102    const GLfloat a = py * qz - pz * qy;
 103    const GLfloat b = pz * qx - px * qz;
 104    const GLfloat c = px * qy - py * qx;
 105    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 106    plane[0] = a;
 107    plane[1] = b;
 108    plane[2] = c;
 109    plane[3] = d;
 110 #else
 111    /* simplified */
 112    const GLfloat px = x1 - x0;
 113    const GLfloat py = y1 - y0;
 114    const GLfloat pz = z0 - z1;
 115    const GLfloat a = pz * px;
 116    const GLfloat b = pz * py;
 117    const GLfloat c = px * px + py * py;
 118    const GLfloat d = -(a * x0 + b * y0 + c * z0);
 119    if (a == 0.0F && b == 0.0F && c == 0.0F && d == 0.0F) {
 120       plane[0] = 0.0F;
 121       plane[1] = 0.0F;
 122       plane[2] = 1.0F;
 123       plane[3] = 0.0F;
 124    }
 125    else {
 126       plane[0] = a;
 127       plane[1] = b;
 128       plane[2] = c;
 129       plane[3] = d;
 130    }
 131 #endif
 132 }
 133
 134
 135 static inline void
 136 constant_plane(GLfloat value, GLfloat plane[4])
 137 {
 138    plane[0] = 0.0F;
 139    plane[1] = 0.0F;
 140    plane[2] = -1.0F;
 141    plane[3] = value;
 142 }
 143
 144
 145 static inline GLfloat
 146 solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
 147 {
 148    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 149    return z;
 150 }
 151
 152 #define SOLVE_PLANE(X, Y, PLANE) \
 153    ((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
 154
 155
 156 /*
 157  * Return 1 / solve_plane().
 158  */
 159 static inline GLfloat
 160 solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
 161 {
 162    const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
 163    if (denom == 0.0F)
 164       return 0.0F;
 165    else
 166       return -plane[2] / denom;
 167 }
 168
 169
 170 /*
 171  * Solve plane and return clamped GLchan value.
 172  */
 173 static inline GLchan
 174 solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
 175 {
 176    const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
 177 #if CHAN_TYPE == GL_FLOAT
 178    return CLAMP(z, 0.0F, CHAN_MAXF);
 179 #else
 180    if (z < 0)
 181       return 0;
 182    else if (z > CHAN_MAX)
 183       return CHAN_MAX;
 184    return (GLchan) IROUND_POS(z);
 185 #endif
 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 logf(rho2) * 1.442695f * 0.5f;/* 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 + 0.5F * dx;
 252          samples[j][1] = y * dy + 0.5F * 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 typedef void (*plot_func)(struct gl_context *ctx, struct LineInfo *line,
 329                           int ix, int iy);
 330
 331
 332
 333 /*
 334  * Draw an AA line segment (called many times per line when stippling)
 335  */
 336 static void
 337 segment(struct gl_context *ctx,
 338         struct LineInfo *line,
 339         plot_func plot,
 340         GLfloat t0, GLfloat t1)
 341 {
 342    const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
 343    const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
 344    /* compute the actual segment's endpoints */
 345    const GLfloat x0 = line->x0 + t0 * line->dx;
 346    const GLfloat y0 = line->y0 + t0 * line->dy;
 347    const GLfloat x1 = line->x0 + t1 * line->dx;
 348    const GLfloat y1 = line->y0 + t1 * line->dy;
 349
 350    /* compute vertices of the line-aligned quadrilateral */
 351    line->qx0 = x0 - line->yAdj;
 352    line->qy0 = y0 + line->xAdj;
 353    line->qx1 = x0 + line->yAdj;
 354    line->qy1 = y0 - line->xAdj;
 355    line->qx2 = x1 + line->yAdj;
 356    line->qy2 = y1 - line->xAdj;
 357    line->qx3 = x1 - line->yAdj;
 358    line->qy3 = y1 + line->xAdj;
 359    /* compute the quad's edge vectors (for coverage calc) */
 360    line->ex0 = line->qx1 - line->qx0;
 361    line->ey0 = line->qy1 - line->qy0;
 362    line->ex1 = line->qx2 - line->qx1;
 363    line->ey1 = line->qy2 - line->qy1;
 364    line->ex2 = line->qx3 - line->qx2;
 365    line->ey2 = line->qy3 - line->qy2;
 366    line->ex3 = line->qx0 - line->qx3;
 367    line->ey3 = line->qy0 - line->qy3;
 368
 369    if (absDx > absDy) {
 370       /* X-major line */
 371       GLfloat dydx = line->dy / line->dx;
 372       GLfloat xLeft, xRight, yBot, yTop;
 373       GLint ix, ixRight;
 374       if (x0 < x1) {
 375          xLeft = x0 - line->halfWidth;
 376          xRight = x1 + line->halfWidth;
 377          if (line->dy >= 0.0F) {
 378             yBot = y0 - 3.0F * line->halfWidth;
 379             yTop = y0 + line->halfWidth;
 380          }
 381          else {
 382             yBot = y0 - line->halfWidth;
 383             yTop = y0 + 3.0F * line->halfWidth;
 384          }
 385       }
 386       else {
 387          xLeft = x1 - line->halfWidth;
 388          xRight = x0 + line->halfWidth;
 389          if (line->dy <= 0.0F) {
 390             yBot = y1 - 3.0F * line->halfWidth;
 391             yTop = y1 + line->halfWidth;
 392          }
 393          else {
 394             yBot = y1 - line->halfWidth;
 395             yTop = y1 + 3.0F * line->halfWidth;
 396          }
 397       }
 398
 399       /* scan along the line, left-to-right */
 400       ixRight = (GLint) (xRight + 1.0F);
 401
 402       /*printf("avg span height: %g\n", yTop - yBot);*/
 403       for (ix = (GLint) xLeft; ix < ixRight; ix++) {
 404          const GLint iyBot = (GLint) yBot;
 405          const GLint iyTop = (GLint) (yTop + 1.0F);
 406          GLint iy;
 407          /* scan across the line, bottom-to-top */
 408          for (iy = iyBot; iy < iyTop; iy++) {
 409             plot(ctx, line, ix, iy);
 410          }
 411          yBot += dydx;
 412          yTop += dydx;
 413       }
 414    }
 415    else {
 416       /* Y-major line */
 417       GLfloat dxdy = line->dx / line->dy;
 418       GLfloat yBot, yTop, xLeft, xRight;
 419       GLint iy, iyTop;
 420       if (y0 < y1) {
 421          yBot = y0 - line->halfWidth;
 422          yTop = y1 + line->halfWidth;
 423          if (line->dx >= 0.0F) {
 424             xLeft = x0 - 3.0F * line->halfWidth;
 425             xRight = x0 + line->halfWidth;
 426          }
 427          else {
 428             xLeft = x0 - line->halfWidth;
 429             xRight = x0 + 3.0F * line->halfWidth;
 430          }
 431       }
 432       else {
 433          yBot = y1 - line->halfWidth;
 434          yTop = y0 + line->halfWidth;
 435          if (line->dx <= 0.0F) {
 436             xLeft = x1 - 3.0F * line->halfWidth;
 437             xRight = x1 + line->halfWidth;
 438          }
 439          else {
 440             xLeft = x1 - line->halfWidth;
 441             xRight = x1 + 3.0F * line->halfWidth;
 442          }
 443       }
 444
 445       /* scan along the line, bottom-to-top */
 446       iyTop = (GLint) (yTop + 1.0F);
 447
 448       /*printf("avg span width: %g\n", xRight - xLeft);*/
 449       for (iy = (GLint) yBot; iy < iyTop; iy++) {
 450          const GLint ixLeft = (GLint) xLeft;
 451          const GLint ixRight = (GLint) (xRight + 1.0F);
 452          GLint ix;
 453          /* scan across the line, left-to-right */
 454          for (ix = ixLeft; ix < ixRight; ix++) {
 455             plot(ctx, line, ix, iy);
 456          }
 457          xLeft += dxdy;
 458          xRight += dxdy;
 459       }
 460    }
 461 }
 462
 463
 464 #define NAME(x) aa_rgba_##x
 465 #define DO_Z
 466 #include "s_aalinetemp.h"
 467
 468
 469 #define NAME(x)  aa_general_rgba_##x
 470 #define DO_Z
 471 #define DO_ATTRIBS
 472 #include "s_aalinetemp.h"
 473
 474
 475
 476 void
 477 _swrast_choose_aa_line_function(struct gl_context *ctx)
 478 {
 479    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 480
 481    assert(ctx->Line.SmoothFlag);
 482
 483    if (ctx->Texture._EnabledCoordUnits != 0
 484        || _swrast_use_fragment_program(ctx)
 485        || (ctx->Light.Enabled &&
 486            ctx->Light.Model.ColorControl == GL_SEPARATE_SPECULAR_COLOR)
 487        || ctx->Fog.ColorSumEnabled
 488        || swrast->_FogEnabled) {
 489       swrast->Line = aa_general_rgba_line;
 490    }
 491    else {
 492       swrast->Line = aa_rgba_line;
 493    }
 494 }