src/mesa/swrast/s_points.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  7.1
   4  *
   5  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 #include "glheader.h"
  27 #include "colormac.h"
  28 #include "context.h"
  29 #include "macros.h"
  30 #include "texstate.h"
  31 #include "s_context.h"
  32 #include "s_feedback.h"
  33 #include "s_points.h"
  34 #include "s_span.h"
  35
  36
  37 /**
  38  * Used to cull points with invalid coords
  39  */
  40 #define CULL_INVALID(V)                              \
  41    do {                                              \
  42       float tmp = (V)->attrib[FRAG_ATTRIB_WPOS][0]   \
  43                 + (V)->attrib[FRAG_ATTRIB_WPOS][1];  \
  44       if (IS_INF_OR_NAN(tmp))                        \
  45          return;                                     \
  46    } while(0)
  47
  48
  49 /**
  50  * Draw a point sprite
  51  */
  52 static void
  53 sprite_point(GLcontext *ctx, const SWvertex *vert)
  54 {
  55    SWcontext *swrast = SWRAST_CONTEXT(ctx);
  56    SWspan span;
  57    GLfloat size;
  58    GLuint tCoords[MAX_TEXTURE_COORD_UNITS + 1];
  59    GLuint numTcoords = 0;
  60    GLfloat t0, dtdy;
  61
  62    CULL_INVALID(vert);
  63
  64    /* z coord */
  65    if (ctx->DrawBuffer->Visual.depthBits <= 16)
  66       span.z = FloatToFixed(vert->attrib[FRAG_ATTRIB_WPOS][2] + 0.5F);
  67    else
  68       span.z = (GLuint) (vert->attrib[FRAG_ATTRIB_WPOS][2] + 0.5F);
  69    span.zStep = 0;
  70
  71    /* compute size */
  72    if (ctx->Point._Attenuated || ctx->VertexProgram.PointSizeEnabled) {
  73       /* use vertex's point size */
  74       /* first, clamp attenuated size to the user-specifed range */
  75       size = CLAMP(vert->pointSize, ctx->Point.MinSize, ctx->Point.MaxSize);
  76    }
  77    else {
  78       /* use constant point size */
  79       size = ctx->Point.Size;
  80    }
  81    /* clamp to non-AA implementation limits */
  82    size = CLAMP(size, ctx->Const.MinPointSize, ctx->Const.MaxPointSize);
  83
  84    /* span init */
  85    INIT_SPAN(span, GL_POINT);
  86    span.interpMask = SPAN_Z | SPAN_RGBA;
  87
  88    span.red   = ChanToFixed(vert->color[0]);
  89    span.green = ChanToFixed(vert->color[1]);
  90    span.blue  = ChanToFixed(vert->color[2]);
  91    span.alpha = ChanToFixed(vert->color[3]);
  92    span.redStep = 0;
  93    span.greenStep = 0;
  94    span.blueStep = 0;
  95    span.alphaStep = 0;
  96
  97    /* need these for fragment programs */
  98    span.attrStart[FRAG_ATTRIB_WPOS][3] = 1.0F;
  99    span.attrStepX[FRAG_ATTRIB_WPOS][3] = 0.0F;
 100    span.attrStepY[FRAG_ATTRIB_WPOS][3] = 0.0F;
 101
 102    {
 103       GLfloat s, r, dsdx;
 104
 105       /* texcoord / pointcoord interpolants */
 106       s = 0.0;
 107       dsdx = 1.0 / size;
 108       if (ctx->Point.SpriteOrigin == GL_LOWER_LEFT) {
 109          t0 = 0.0;
 110          dtdy = 1.0 / size;
 111       }
 112       else {
 113          /* GL_UPPER_LEFT */
 114          t0 = 1.0;
 115          dtdy = -1.0 / size;
 116       }
 117
 118       ATTRIB_LOOP_BEGIN
 119          if (attr >= FRAG_ATTRIB_TEX0 && attr < FRAG_ATTRIB_VAR0) {
 120             const GLuint u = attr - FRAG_ATTRIB_TEX0;
 121             /* a texcoord */
 122             if (ctx->Point.CoordReplace[u]) {
 123                tCoords[numTcoords++] = attr;
 124
 125                if (ctx->Point.SpriteRMode == GL_ZERO)
 126                   r = 0.0F;
 127                else if (ctx->Point.SpriteRMode == GL_S)
 128                   r = vert->attrib[attr][0];
 129                else /* GL_R */
 130                   r = vert->attrib[attr][2];
 131
 132                span.attrStart[attr][0] = s;
 133                span.attrStart[attr][1] = 0.0; /* overwritten below */
 134                span.attrStart[attr][2] = r;
 135                span.attrStart[attr][3] = 1.0;
 136
 137                span.attrStepX[attr][0] = dsdx;
 138                span.attrStepX[attr][1] = 0.0;
 139                span.attrStepX[attr][2] = 0.0;
 140                span.attrStepX[attr][3] = 0.0;
 141
 142                span.attrStepY[attr][0] = 0.0;
 143                span.attrStepY[attr][1] = dtdy;
 144                span.attrStepY[attr][2] = 0.0;
 145                span.attrStepY[attr][3] = 0.0;
 146
 147                continue;
 148             }
 149          }
 150          else if (attr == FRAG_ATTRIB_FOGC) {
 151             /* GLSL gl_PointCoord is stored in fog.zw */
 152             span.attrStart[FRAG_ATTRIB_FOGC][2] = 0.0;
 153             span.attrStart[FRAG_ATTRIB_FOGC][3] = 0.0; /* t0 set below */
 154             span.attrStepX[FRAG_ATTRIB_FOGC][2] = dsdx;
 155             span.attrStepX[FRAG_ATTRIB_FOGC][3] = 0.0;
 156             span.attrStepY[FRAG_ATTRIB_FOGC][2] = 0.0;
 157             span.attrStepY[FRAG_ATTRIB_FOGC][3] = dtdy;
 158             tCoords[numTcoords++] = FRAG_ATTRIB_FOGC;
 159             continue;
 160          }
 161          /* use vertex's texcoord/attrib */
 162          COPY_4V(span.attrStart[attr], vert->attrib[attr]);
 163          ASSIGN_4V(span.attrStepX[attr], 0, 0, 0, 0);
 164          ASSIGN_4V(span.attrStepY[attr], 0, 0, 0, 0);
 165       ATTRIB_LOOP_END;
 166    }
 167
 168    /* compute pos, bounds and render */
 169    {
 170       const GLfloat x = vert->attrib[FRAG_ATTRIB_WPOS][0];
 171       const GLfloat y = vert->attrib[FRAG_ATTRIB_WPOS][1];
 172       GLint iSize = (GLint) (size + 0.5F);
 173       GLint xmin, xmax, ymin, ymax, iy;
 174       GLint iRadius;
 175       GLfloat tcoord = t0;
 176
 177       iSize = MAX2(1, iSize);
 178       iRadius = iSize / 2;
 179
 180       if (iSize & 1) {
 181          /* odd size */
 182          xmin = (GLint) (x - iRadius);
 183          xmax = (GLint) (x + iRadius);
 184          ymin = (GLint) (y - iRadius);
 185          ymax = (GLint) (y + iRadius);
 186       }
 187       else {
 188          /* even size */
 189          xmin = (GLint) x - iRadius + 1;
 190          xmax = xmin + iSize - 1;
 191          ymin = (GLint) y - iRadius + 1;
 192          ymax = ymin + iSize - 1;
 193       }
 194
 195       /* render spans */
 196       for (iy = ymin; iy <= ymax; iy++) {
 197          GLuint i;
 198          /* setup texcoord T for this row */
 199          for (i = 0; i < numTcoords; i++) {
 200             if (tCoords[i] == FRAG_ATTRIB_FOGC)
 201                span.attrStart[FRAG_ATTRIB_FOGC][3] = tcoord;
 202             else
 203                span.attrStart[tCoords[i]][1] = tcoord;
 204          }
 205
 206          /* these might get changed by span clipping */
 207          span.x = xmin;
 208          span.y = iy;
 209          span.end = xmax - xmin + 1;
 210
 211          _swrast_write_rgba_span(ctx, &span);
 212
 213          tcoord += dtdy;
 214       }
 215    }
 216 }
 217
 218
 219 /**
 220  * Draw smooth/antialiased point.  RGB or CI mode.
 221  */
 222 static void
 223 smooth_point(GLcontext *ctx, const SWvertex *vert)
 224 {
 225    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 226    const GLboolean ciMode = !ctx->Visual.rgbMode;
 227    SWspan span;
 228    GLfloat size, alphaAtten;
 229
 230    CULL_INVALID(vert);
 231
 232    /* z coord */
 233    if (ctx->DrawBuffer->Visual.depthBits <= 16)
 234       span.z = FloatToFixed(vert->attrib[FRAG_ATTRIB_WPOS][2] + 0.5F);
 235    else
 236       span.z = (GLuint) (vert->attrib[FRAG_ATTRIB_WPOS][2] + 0.5F);
 237    span.zStep = 0;
 238
 239    /* compute size */
 240    if (ctx->Point._Attenuated || ctx->VertexProgram.PointSizeEnabled) {
 241       /* use vertex's point size */
 242       /* first, clamp attenuated size to the user-specifed range */
 243       size = CLAMP(vert->pointSize, ctx->Point.MinSize, ctx->Point.MaxSize);
 244    }
 245    else {
 246       /* use constant point size */
 247       size = ctx->Point.Size;
 248    }
 249    /* clamp to AA implementation limits */
 250    size = CLAMP(size, ctx->Const.MinPointSizeAA, ctx->Const.MaxPointSizeAA);
 251
 252    /* alpha attenuation / fade factor */
 253    if (ctx->Multisample.Enabled) {
 254       if (vert->pointSize >= ctx->Point.Threshold) {
 255          alphaAtten = 1.0F;
 256       }
 257       else {
 258          GLfloat dsize = vert->pointSize / ctx->Point.Threshold;
 259          alphaAtten = dsize * dsize;
 260       }
 261    }
 262    else {
 263       alphaAtten = 1.0;
 264    }
 265    (void) alphaAtten; /* not used */
 266
 267    /* span init */
 268    INIT_SPAN(span, GL_POINT);
 269    span.interpMask = SPAN_Z | SPAN_RGBA;
 270    span.arrayMask = SPAN_COVERAGE | SPAN_MASK;
 271
 272    span.red   = ChanToFixed(vert->color[0]);
 273    span.green = ChanToFixed(vert->color[1]);
 274    span.blue  = ChanToFixed(vert->color[2]);
 275    span.alpha = ChanToFixed(vert->color[3]);
 276    span.redStep = 0;
 277    span.greenStep = 0;
 278    span.blueStep = 0;
 279    span.alphaStep = 0;
 280
 281    /* need these for fragment programs */
 282    span.attrStart[FRAG_ATTRIB_WPOS][3] = 1.0F;
 283    span.attrStepX[FRAG_ATTRIB_WPOS][3] = 0.0F;
 284    span.attrStepY[FRAG_ATTRIB_WPOS][3] = 0.0F;
 285
 286    ATTRIB_LOOP_BEGIN
 287       COPY_4V(span.attrStart[attr], vert->attrib[attr]);
 288       ASSIGN_4V(span.attrStepX[attr], 0, 0, 0, 0);
 289       ASSIGN_4V(span.attrStepY[attr], 0, 0, 0, 0);
 290    ATTRIB_LOOP_END
 291
 292    /* compute pos, bounds and render */
 293    {
 294       const GLfloat x = vert->attrib[FRAG_ATTRIB_WPOS][0];
 295       const GLfloat y = vert->attrib[FRAG_ATTRIB_WPOS][1];
 296       const GLfloat radius = 0.5F * size;
 297       const GLfloat rmin = radius - 0.7071F;  /* 0.7071 = sqrt(2)/2 */
 298       const GLfloat rmax = radius + 0.7071F;
 299       const GLfloat rmin2 = MAX2(0.0F, rmin * rmin);
 300       const GLfloat rmax2 = rmax * rmax;
 301       const GLfloat cscale = 1.0F / (rmax2 - rmin2);
 302       const GLint xmin = (GLint) (x - radius);
 303       const GLint xmax = (GLint) (x + radius);
 304       const GLint ymin = (GLint) (y - radius);
 305       const GLint ymax = (GLint) (y + radius);
 306       GLint ix, iy;
 307
 308       for (iy = ymin; iy <= ymax; iy++) {
 309
 310          /* these might get changed by span clipping */
 311          span.x = xmin;
 312          span.y = iy;
 313          span.end = xmax - xmin + 1;
 314
 315          /* compute coverage for each pixel in span */
 316          for (ix = xmin; ix <= xmax; ix++) {
 317             const GLfloat dx = ix - x + 0.5F;
 318             const GLfloat dy = iy - y + 0.5F;
 319             const GLfloat dist2 = dx * dx + dy * dy;
 320             GLfloat coverage;
 321
 322             if (dist2 < rmax2) {
 323                if (dist2 >= rmin2) {
 324                   /* compute partial coverage */
 325                   coverage = 1.0F - (dist2 - rmin2) * cscale;
 326                   if (ciMode) {
 327                      /* coverage in [0,15] */
 328                      coverage *= 15.0;
 329                   }
 330                }
 331                else {
 332                   /* full coverage */
 333                   coverage = 1.0F;
 334                }
 335                span.array->mask[ix - xmin] = 1;
 336             }
 337             else {
 338                /* zero coverage - fragment outside the radius */
 339                coverage = 0.0;
 340                span.array->mask[ix - xmin] = 0;
 341             }
 342             span.array->coverage[ix - xmin] = coverage;
 343          }
 344
 345          /* render span */
 346          _swrast_write_rgba_span(ctx, &span);
 347
 348       }
 349    }
 350 }
 351
 352
 353 /**
 354  * Draw large (size >= 1) non-AA point.  RGB or CI mode.
 355  */
 356 static void
 357 large_point(GLcontext *ctx, const SWvertex *vert)
 358 {
 359    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 360    const GLboolean ciMode = !ctx->Visual.rgbMode;
 361    SWspan span;
 362    GLfloat size;
 363
 364    CULL_INVALID(vert);
 365
 366    /* z coord */
 367    if (ctx->DrawBuffer->Visual.depthBits <= 16)
 368       span.z = FloatToFixed(vert->attrib[FRAG_ATTRIB_WPOS][2] + 0.5F);
 369    else
 370       span.z = (GLuint) (vert->attrib[FRAG_ATTRIB_WPOS][2] + 0.5F);
 371    span.zStep = 0;
 372
 373    /* compute size */
 374    if (ctx->Point._Attenuated || ctx->VertexProgram.PointSizeEnabled) {
 375       /* use vertex's point size */
 376       /* first, clamp attenuated size to the user-specifed range */
 377       size = CLAMP(vert->pointSize, ctx->Point.MinSize, ctx->Point.MaxSize);
 378    }
 379    else {
 380       /* use constant point size */
 381       size = ctx->Point.Size;
 382    }
 383    /* clamp to non-AA implementation limits */
 384    size = CLAMP(size, ctx->Const.MinPointSize, ctx->Const.MaxPointSize);
 385
 386    /* span init */
 387    INIT_SPAN(span, GL_POINT);
 388    span.arrayMask = SPAN_XY;
 389
 390    if (ciMode) {
 391       span.interpMask = SPAN_Z | SPAN_INDEX;
 392       span.index = FloatToFixed(vert->attrib[FRAG_ATTRIB_CI][0]);
 393       span.indexStep = 0;
 394    }
 395    else {
 396       span.interpMask = SPAN_Z | SPAN_RGBA;
 397       span.red   = ChanToFixed(vert->color[0]);
 398       span.green = ChanToFixed(vert->color[1]);
 399       span.blue  = ChanToFixed(vert->color[2]);
 400       span.alpha = ChanToFixed(vert->color[3]);
 401       span.redStep = 0;
 402       span.greenStep = 0;
 403       span.blueStep = 0;
 404       span.alphaStep = 0;
 405    }
 406
 407    /* need these for fragment programs */
 408    span.attrStart[FRAG_ATTRIB_WPOS][3] = 1.0F;
 409    span.attrStepX[FRAG_ATTRIB_WPOS][3] = 0.0F;
 410    span.attrStepY[FRAG_ATTRIB_WPOS][3] = 0.0F;
 411
 412    ATTRIB_LOOP_BEGIN
 413       COPY_4V(span.attrStart[attr], vert->attrib[attr]);
 414       ASSIGN_4V(span.attrStepX[attr], 0, 0, 0, 0);
 415       ASSIGN_4V(span.attrStepY[attr], 0, 0, 0, 0);
 416    ATTRIB_LOOP_END
 417
 418    /* compute pos, bounds and render */
 419    {
 420       const GLfloat x = vert->attrib[FRAG_ATTRIB_WPOS][0];
 421       const GLfloat y = vert->attrib[FRAG_ATTRIB_WPOS][1];
 422       GLint iSize = (GLint) (size + 0.5F);
 423       GLint xmin, xmax, ymin, ymax, ix, iy;
 424       GLint iRadius;
 425
 426       iSize = MAX2(1, iSize);
 427       iRadius = iSize / 2;
 428
 429       if (iSize & 1) {
 430          /* odd size */
 431          xmin = (GLint) (x - iRadius);
 432          xmax = (GLint) (x + iRadius);
 433          ymin = (GLint) (y - iRadius);
 434          ymax = (GLint) (y + iRadius);
 435       }
 436       else {
 437          /* even size */
 438          xmin = (GLint) x - iRadius + 1;
 439          xmax = xmin + iSize - 1;
 440          ymin = (GLint) y - iRadius + 1;
 441          ymax = ymin + iSize - 1;
 442       }
 443
 444       /* generate fragments */
 445       span.end = 0;
 446       for (iy = ymin; iy <= ymax; iy++) {
 447          for (ix = xmin; ix <= xmax; ix++) {
 448             span.array->x[span.end] = ix;
 449             span.array->y[span.end] = iy;
 450             span.end++;
 451          }
 452       }
 453       assert(span.end <= MAX_WIDTH);
 454       _swrast_write_rgba_span(ctx, &span);
 455    }
 456 }
 457
 458
 459 /**
 460  * Draw size=1, single-pixel point
 461  */
 462 static void
 463 pixel_point(GLcontext *ctx, const SWvertex *vert)
 464 {
 465    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 466    const GLboolean ciMode = !ctx->Visual.rgbMode;
 467    /*
 468     * Note that unlike the other functions, we put single-pixel points
 469     * into a special span array in order to render as many points as
 470     * possible with a single _swrast_write_rgba_span() call.
 471     */
 472    SWspan *span = &(swrast->PointSpan);
 473    GLuint count;
 474
 475    CULL_INVALID(vert);
 476
 477    /* Span init */
 478    span->interpMask = 0;
 479    span->arrayMask = SPAN_XY | SPAN_Z;
 480    if (ciMode)
 481       span->arrayMask |= SPAN_INDEX;
 482    else
 483       span->arrayMask |= SPAN_RGBA;
 484    /*span->arrayMask |= SPAN_LAMBDA;*/
 485    span->arrayAttribs = swrast->_ActiveAttribMask; /* we'll produce these vals */
 486
 487    /* need these for fragment programs */
 488    span->attrStart[FRAG_ATTRIB_WPOS][3] = 1.0F;
 489    span->attrStepX[FRAG_ATTRIB_WPOS][3] = 0.0F;
 490    span->attrStepY[FRAG_ATTRIB_WPOS][3] = 0.0F;
 491
 492    /* check if we need to flush */
 493    if (span->end >= MAX_WIDTH ||
 494        (swrast->_RasterMask & (BLEND_BIT | LOGIC_OP_BIT | MASKING_BIT))) {
 495       if (ciMode)
 496          _swrast_write_index_span(ctx, span);
 497       else
 498          _swrast_write_rgba_span(ctx, span);
 499       span->end = 0;
 500    }
 501
 502    count = span->end;
 503
 504    /* fragment attributes */
 505    if (ciMode) {
 506       span->array->index[count] = (GLuint) vert->attrib[FRAG_ATTRIB_CI][0];
 507    }
 508    else {
 509       span->array->rgba[count][RCOMP] = vert->color[0];
 510       span->array->rgba[count][GCOMP] = vert->color[1];
 511       span->array->rgba[count][BCOMP] = vert->color[2];
 512       span->array->rgba[count][ACOMP] = vert->color[3];
 513    }
 514    ATTRIB_LOOP_BEGIN
 515       COPY_4V(span->array->attribs[attr][count], vert->attrib[attr]);
 516    ATTRIB_LOOP_END
 517
 518    /* fragment position */
 519    span->array->x[count] = (GLint) vert->attrib[FRAG_ATTRIB_WPOS][0];
 520    span->array->y[count] = (GLint) vert->attrib[FRAG_ATTRIB_WPOS][1];
 521    span->array->z[count] = (GLint) (vert->attrib[FRAG_ATTRIB_WPOS][2] + 0.5F);
 522
 523    span->end = count + 1;
 524    ASSERT(span->end <= MAX_WIDTH);
 525 }
 526
 527
 528 /**
 529  * Add specular color to primary color, draw point, restore original
 530  * primary color.
 531  */
 532 void
 533 _swrast_add_spec_terms_point(GLcontext *ctx, const SWvertex *v0)
 534 {
 535    SWvertex *ncv0 = (SWvertex *) v0; /* cast away const */
 536    GLfloat rSum, gSum, bSum;
 537    GLchan cSave[4];
 538
 539    /* save */
 540    COPY_CHAN4(cSave, ncv0->color);
 541    /* sum */
 542    rSum = CHAN_TO_FLOAT(ncv0->color[0]) + ncv0->attrib[FRAG_ATTRIB_COL1][0];
 543    gSum = CHAN_TO_FLOAT(ncv0->color[1]) + ncv0->attrib[FRAG_ATTRIB_COL1][1];
 544    bSum = CHAN_TO_FLOAT(ncv0->color[2]) + ncv0->attrib[FRAG_ATTRIB_COL1][2];
 545    UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[0], rSum);
 546    UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[1], gSum);
 547    UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[2], bSum);
 548    /* draw */
 549    SWRAST_CONTEXT(ctx)->SpecPoint(ctx, ncv0);
 550    /* restore */
 551    COPY_CHAN4(ncv0->color, cSave);
 552 }
 553
 554
 555 /**
 556  * Examine current state to determine which point drawing function to use.
 557  */
 558 void
 559 _swrast_choose_point(GLcontext *ctx)
 560 {
 561    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 562
 563    if (ctx->RenderMode == GL_RENDER) {
 564       if (ctx->Point.PointSprite) {
 565          swrast->Point = sprite_point;
 566       }
 567       else if (ctx->Point.SmoothFlag) {
 568          swrast->Point = smooth_point;
 569       }
 570       else if (ctx->Point.Size > 1.0 ||
 571                ctx->Point._Attenuated ||
 572                ctx->VertexProgram.PointSizeEnabled) {
 573          swrast->Point = large_point;
 574       }
 575       else {
 576          swrast->Point = pixel_point;
 577       }
 578    }
 579    else if (ctx->RenderMode == GL_FEEDBACK) {
 580       swrast->Point = _swrast_feedback_point;
 581    }
 582    else {
 583       /* GL_SELECT mode */
 584       swrast->Point = _swrast_select_point;
 585    }
 586 }