summaryrefslogtreecommitdiffstats
path: root/apps/plugins/doom/r_segs.c
blob: f3bd81e9218e4f4f086ceb25a7ead55c0c363ed8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
/* Emacs style mode select   -*- C++ -*-
 *-----------------------------------------------------------------------------
 *
 *
 *  PrBoom a Doom port merged with LxDoom and LSDLDoom
 *  based on BOOM, a modified and improved DOOM engine
 *  Copyright (C) 1999 by
 *  id Software, Chi Hoang, Lee Killough, Jim Flynn, Rand Phares, Ty Halderman
 *  Copyright (C) 1999-2000 by
 *  Jess Haas, Nicolas Kalkhof, Colin Phipps, Florian Schulze
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 *  02111-1307, USA.
 *
 * DESCRIPTION:
 *      All the clipping: columns, horizontal spans, sky columns.
 *
 *-----------------------------------------------------------------------------*/
//
// 4/25/98, 5/2/98 killough: reformatted, beautified

#include "doomstat.h"
#include "r_main.h"
#include "r_bsp.h"
#include "r_plane.h"
#include "r_things.h"
#include "r_draw.h"
#include "w_wad.h"
//#include "lprintf.h"
#include "rockmacros.h"

// OPTIMIZE: closed two sided lines as single sided

// killough 1/6/98: replaced globals with statics where appropriate

// True if any of the segs textures might be visible.
boolean  segtextured;
boolean  markfloor;      // False if the back side is the same plane.
boolean  markceiling;
static boolean  maskedtexture;
static int      toptexture;
static int      bottomtexture;
static int      midtexture;

static fixed_t  toptexheight, midtexheight, bottomtexheight; // cph

angle_t  rw_normalangle;// angle to line origin
int  rw_angle1;
fixed_t  rw_distance;
lighttable_t** walllights;

//
// regular wall
//
int      rw_x;
int      rw_stopx;
static angle_t  rw_centerangle;
static fixed_t  rw_offset;
static fixed_t  rw_scale;
static fixed_t  rw_scalestep;
static fixed_t  rw_midtexturemid;
static fixed_t  rw_toptexturemid;
static fixed_t  rw_bottomtexturemid;
static int      worldtop;
static int      worldbottom;
static int      worldhigh;
static int      worldlow;
static fixed_t  pixhigh;
static fixed_t  pixlow;
static fixed_t  pixhighstep;
static fixed_t  pixlowstep;
static fixed_t  topfrac;
static fixed_t  topstep;
static fixed_t  bottomfrac;
static fixed_t  bottomstep;
static short    *maskedtexturecol;

//
// R_ScaleFromGlobalAngle
// Returns the texture mapping scale
//  for the current line (horizontal span)
//  at the given angle.
// rw_distance must be calculated first.
//
// killough 5/2/98: reformatted, cleaned up
// CPhipps - moved here from r_main.c

static fixed_t R_ScaleFromGlobalAngle(angle_t visangle)
{
   int     anglea = ANG90 + (visangle-viewangle);
   int     angleb = ANG90 + (visangle-rw_normalangle);
   int     den = FixedMul(rw_distance, finesine[anglea>>ANGLETOFINESHIFT]);
   // proff 11/06/98: Changed for high-res
   fixed_t num = FixedMul(projectiony, finesine[angleb>>ANGLETOFINESHIFT]);
   return den > num>>16 ? (num = FixedDiv(num, den)) > 64*FRACUNIT ?
       64*FRACUNIT : num < 256 ? 256 : num : 64*FRACUNIT;
}

//
// R_RenderMaskedSegRange
//

int fake_contrast IBSS_ATTR;

void R_RenderMaskedSegRange(drawseg_t *ds, int x1, int x2)
{
   column_t *col;
   int      lightnum;
   int      texnum;
   sector_t tempsec;      // killough 4/13/98

   // Calculate light table.
   // Use different light tables
   //   for horizontal / vertical / diagonal. Diagonal?

   curline = ds->curline;  // OPTIMIZE: get rid of LIGHTSEGSHIFT globally

   // killough 4/11/98: draw translucent 2s normal textures

   colfunc = R_DrawColumn;
   if (curline->linedef->tranlump >= 0 && general_translucency)
   {
      colfunc = R_DrawTLColumn;
      tranmap = main_tranmap;
      if (curline->linedef->tranlump > 0)
         tranmap = W_CacheLumpNum(curline->linedef->tranlump-1);
   }

   // killough 4/11/98: end translucent 2s normal code

   frontsector = curline->frontsector;
   backsector = curline->backsector;

   texnum = texturetranslation[curline->sidedef->midtexture];

   // killough 4/13/98: get correct lightlevel for 2s normal textures
   lightnum = (R_FakeFlat(frontsector, &tempsec, NULL, NULL, false)
               ->lightlevel >> LIGHTSEGSHIFT)+extralight;

   /* cph - ...what is this for? adding contrast to rooms?
    * It looks crap in outdoor areas */
   if (fake_contrast)
   {
      if (curline->v1->y == curline->v2->y)
         lightnum--;
      else
         if (curline->v1->x == curline->v2->x)
            lightnum++;
   }

   walllights = lightnum >= LIGHTLEVELS ? scalelight[LIGHTLEVELS-1] :
                lightnum <  0           ? scalelight[0] : scalelight[lightnum];

   maskedtexturecol = ds->maskedtexturecol;

   rw_scalestep = ds->scalestep;
   spryscale = ds->scale1 + (x1 - ds->x1)*rw_scalestep;
   mfloorclip = ds->sprbottomclip;
   mceilingclip = ds->sprtopclip;

   // find positioning
   if (curline->linedef->flags & ML_DONTPEGBOTTOM)
   {
      dc_texturemid = frontsector->floorheight > backsector->floorheight
                      ? frontsector->floorheight : backsector->floorheight;
      dc_texturemid = dc_texturemid + textureheight[texnum] - viewz;
   }
   else
   {
      dc_texturemid =frontsector->ceilingheight<backsector->ceilingheight
                     ? frontsector->ceilingheight : backsector->ceilingheight;
      dc_texturemid = dc_texturemid - viewz;
   }

   dc_texturemid += curline->sidedef->rowoffset;

   if (fixedcolormap)
      dc_colormap = fixedcolormap;

   // draw the columns
   for (dc_x = x1 ; dc_x <= x2 ; dc_x++, spryscale += rw_scalestep)
      if (maskedtexturecol[dc_x] != SHRT_MAX)
      {
         if (!fixedcolormap)      // calculate lighting
         {
            unsigned index = spryscale>>LIGHTSCALESHIFT;

            if (index >=  MAXLIGHTSCALE )
               index = MAXLIGHTSCALE-1;

            dc_colormap = walllights[index];
         }

         // killough 3/2/98:
         //
         // This calculation used to overflow and cause crashes in Doom:
         //
         // sprtopscreen = centeryfrac - FixedMul(dc_texturemid, spryscale);
         //
         // This code fixes it, by using double-precision intermediate
         // arithmetic and by skipping the drawing of 2s normals whose
         // mapping to screen coordinates is totally out of range:

         {
            int_64_t t = ((int_64_t) centeryfrac << FRACBITS) -
                         (int_64_t) dc_texturemid * spryscale;
            if (t + (int_64_t) textureheight[texnum] * spryscale < 0 ||
                  t > (int_64_t) SCREENHEIGHT << FRACBITS*2)
               continue;        // skip if the texture is out of screen's range
            sprtopscreen = (long)(t >> FRACBITS);
         }

         dc_iscale = 0xffffffffu / (unsigned) spryscale;

         // killough 1/25/98: here's where Medusa came in, because
         // it implicitly assumed that the column was all one patch.
         // Originally, Doom did not construct complete columns for
         // multipatched textures, so there were no header or trailer
         // bytes in the column referred to below, which explains
         // the Medusa effect. The fix is to construct true columns
         // when forming multipatched textures (see r_data.c).

         // draw the texture
         col = (column_t *)((byte *)
                            R_GetColumn(texnum,maskedtexturecol[dc_x]) - 3);
         R_DrawMaskedColumn (col);
         maskedtexturecol[dc_x] = SHRT_MAX;
      }

   // Except for main_tranmap, mark others purgable at this point
   if (curline->linedef->tranlump > 0 && general_translucency)
      W_UnlockLumpNum(curline->linedef->tranlump-1); // cph - unlock it
}

//
// R_RenderSegLoop
// Draws zero, one, or two textures (and possibly a masked texture) for walls.
// Can draw or mark the starting pixel of floor and ceiling textures.
// CALLED: CORE LOOPING ROUTINE.
//

extern byte solidcol[MAX_SCREENWIDTH];
#define HEIGHTBITS 12
#define HEIGHTUNIT (1<<HEIGHTBITS)
static int didsolidcol; /* True if at least one column was marked solid */

static void R_RenderSegLoop (void)
{
   fixed_t  texturecolumn = 0;   // shut up compiler warning
   for ( ; rw_x < rw_stopx ; rw_x++)
   {

      // mark floor / ceiling areas

      int yh = bottomfrac>>HEIGHTBITS;
      int yl = (topfrac+HEIGHTUNIT-1)>>HEIGHTBITS;

      // no space above wall?
      int bottom,top = ceilingclip[rw_x]+1;

      if (yl < top)
         yl = top;

      if (markceiling)
      {
         bottom = yl-1;

         if (bottom >= floorclip[rw_x])
            bottom = floorclip[rw_x]-1;

         if (top <= bottom)
         {
            ceilingplane->top[rw_x] = top;
            ceilingplane->bottom[rw_x] = bottom;
         }
      }

      //      yh = bottomfrac>>HEIGHTBITS;

      bottom = floorclip[rw_x]-1;
      if (yh > bottom)
         yh = bottom;

      if (markfloor)
      {

         top  = yh < ceilingclip[rw_x] ? ceilingclip[rw_x] : yh;

         if (++top <= bottom)
         {
            floorplane->top[rw_x] = top;
            floorplane->bottom[rw_x] = bottom;
         }
      }

      // texturecolumn and lighting are independent of wall tiers
      if (segtextured)
      {
         unsigned index;

         // calculate texture offset
         angle_t angle =(rw_centerangle+xtoviewangle[rw_x])>>ANGLETOFINESHIFT;

         texturecolumn = rw_offset-FixedMul(finetangent[angle],rw_distance);
         texturecolumn >>= FRACBITS;
         // calculate lighting
         index = rw_scale>>LIGHTSCALESHIFT;

         if (index >=  MAXLIGHTSCALE )
            index = MAXLIGHTSCALE-1;

         dc_colormap = walllights[index];
         dc_x = rw_x;
         dc_iscale = 0xffffffffu / (unsigned)rw_scale;
      }

      // draw the wall tiers
      if (midtexture)
      {

         dc_yl = yl;     // single sided line
         dc_yh = yh;
         dc_texturemid = rw_midtexturemid;
         dc_source = R_GetColumn(midtexture, texturecolumn);
         dc_texheight = midtexheight;
         colfunc ();
         ceilingclip[rw_x] = viewheight;
         floorclip[rw_x] = -1;
      }
      else
      {

         // two sided line
         if (toptexture)
         {
            // top wall
            int mid = pixhigh>>HEIGHTBITS;
            pixhigh += pixhighstep;

            if (mid >= floorclip[rw_x])
               mid = floorclip[rw_x]-1;

            if (mid >= yl)
            {
               dc_yl = yl;
               dc_yh = mid;
               dc_texturemid = rw_toptexturemid;
               dc_source = R_GetColumn(toptexture,texturecolumn);
               dc_texheight = toptexheight;
               colfunc ();
               ceilingclip[rw_x] = mid;
            }
            else
               ceilingclip[rw_x] = yl-1;
         }
         else  // no top wall
         {

            if (markceiling)
               ceilingclip[rw_x] = yl-1;
         }

         if (bottomtexture)          // bottom wall
         {
            int mid = (pixlow+HEIGHTUNIT-1)>>HEIGHTBITS;
            pixlow += pixlowstep;

            // no space above wall?
            if (mid <= ceilingclip[rw_x])
               mid = ceilingclip[rw_x]+1;

            if (mid <= yh)
            {
               dc_yl = mid;
               dc_yh = yh;
               dc_texturemid = rw_bottomtexturemid;
               dc_source = R_GetColumn(bottomtexture,
                                       texturecolumn);
               dc_texheight = bottomtexheight;
               colfunc ();
               floorclip[rw_x] = mid;
            }
            else
               floorclip[rw_x] = yh+1;
         }
         else        // no bottom wall
         {
            if (markfloor)
               floorclip[rw_x] = yh+1;
         }

         // cph - if we completely blocked further sight through this column,
         // add this info to the solid columns array for r_bsp.c
         if ((markceiling || markfloor) &&
               (floorclip[rw_x] <= ceilingclip[rw_x] + 1))
         {
            solidcol[rw_x] = 1;
            didsolidcol = 1;
         }

         // save texturecol for backdrawing of masked mid texture
         if (maskedtexture)
            maskedtexturecol[rw_x] = texturecolumn;
      }

      rw_scale += rw_scalestep;
      topfrac += topstep;
      bottomfrac += bottomstep;
   }
}

// killough 5/2/98: move from r_main.c, made static, simplified

static fixed_t R_PointToDist(fixed_t x, fixed_t y)
{
   fixed_t dx = D_abs(x - viewx);
   fixed_t dy = D_abs(y - viewy);

   if (dy > dx)
   {
      fixed_t t = dx;
      dx = dy;
      dy = t;
   }

   return FixedDiv(dx, finesine[(tantoangle[FixedDiv(dy,dx) >> DBITS]
                                 + ANG90) >> ANGLETOFINESHIFT]);
}

//
// R_StoreWallRange
// A wall segment will be drawn
//  between start and stop pixels (inclusive).
//
void R_StoreWallRange(const int start, const int stop)
{
   fixed_t hyp;
   fixed_t sineval;
   angle_t distangle, offsetangle;

   if (ds_p == drawsegs+maxdrawsegs)   // killough 1/98 -- fix 2s line HOM
   {
      unsigned pos = ds_p - drawsegs; // jff 8/9/98 fix from ZDOOM1.14a
      unsigned newmax = maxdrawsegs ? maxdrawsegs*2 : 128; // killough
      drawsegs = realloc(drawsegs,newmax*sizeof(*drawsegs));
      ds_p = drawsegs + pos;          // jff 8/9/98 fix from ZDOOM1.14a
      maxdrawsegs = newmax;
   }

   if(curline->miniseg == false) // figgi -- skip minisegs
      curline->linedef->flags |= ML_MAPPED;


#ifdef RANGECHECK

   if (start >=viewwidth || start > stop)
      I_Error ("Bad R_RenderWallRange: %i to %i", start , stop);
#endif

   sidedef = curline->sidedef;
   linedef = curline->linedef;

   // mark the segment as visible for auto map
   linedef->flags |= ML_MAPPED;

   // calculate rw_distance for scale calculation
   rw_normalangle = curline->angle + ANG90;

   offsetangle = D_abs(rw_normalangle-rw_angle1);

   if (offsetangle > ANG90)
      offsetangle = ANG90;

   distangle = ANG90 - offsetangle;
   hyp = (viewx==curline->v1->x && viewy==curline->v1->y)?
         0 : R_PointToDist (curline->v1->x, curline->v1->y);
   sineval = finesine[distangle>>ANGLETOFINESHIFT];
   rw_distance = FixedMul(hyp, sineval);

   ds_p->x1 = rw_x = start;
   ds_p->x2 = stop;
   ds_p->curline = curline;
   rw_stopx = stop+1;

   {     // killough 1/6/98, 2/1/98: remove limit on openings
      extern short *openings;
      extern size_t maxopenings;
      size_t pos = lastopening - openings;
      size_t need = (rw_stopx - start)*4 + pos;
      if (need > maxopenings)
      {
         drawseg_t *ds;                //jff 8/9/98 needed for fix from ZDoom
         short *oldopenings = openings;
         short *oldlast = lastopening;

         do
            maxopenings = maxopenings ? maxopenings*2 : 16384;
         while (need > maxopenings);
         openings = realloc(openings, maxopenings * sizeof(*openings));
         lastopening = openings + pos;

         // jff 8/9/98 borrowed fix for openings from ZDOOM1.14
         // [RH] We also need to adjust the openings pointers that
         //    were already stored in drawsegs.
         for (ds = drawsegs; ds < ds_p; ds++)
         {
#define ADJUST(p) if (ds->p + ds->x1 >= oldopenings && ds->p + ds->x1 <= oldlast)\
            ds->p = ds->p - oldopenings + openings;
            ADJUST (maskedtexturecol);
            ADJUST (sprtopclip);
            ADJUST (sprbottomclip);
         }
#undef ADJUST
      }
   }  // killough: end of code to remove limits on openings

   // calculate scale at both ends and step

   ds_p->scale1 = rw_scale =
                     R_ScaleFromGlobalAngle (viewangle + xtoviewangle[start]);

   if (stop > start)
   {
      ds_p->scale2 = R_ScaleFromGlobalAngle (viewangle + xtoviewangle[stop]);
      ds_p->scalestep = rw_scalestep = (ds_p->scale2-rw_scale) / (stop-start);
   }
   else
      ds_p->scale2 = ds_p->scale1;

   // calculate texture boundaries
   //  and decide if floor / ceiling marks are needed

   worldtop = frontsector->ceilingheight - viewz;
   worldbottom = frontsector->floorheight - viewz;

   midtexture = toptexture = bottomtexture = maskedtexture = 0;
   ds_p->maskedtexturecol = NULL;

   if (!backsector)
   {
      // single sided line
      midtexture = texturetranslation[sidedef->midtexture];
      midtexheight = (linedef->r_flags & RF_MID_TILE) ? 0 : textureheight[midtexture] >> FRACBITS;

      // a single sided line is terminal, so it must mark ends
      markfloor = markceiling = true;

      if (linedef->flags & ML_DONTPEGBOTTOM)
      {         // bottom of texture at bottom
         fixed_t vtop = frontsector->floorheight +
                        textureheight[sidedef->midtexture];
         rw_midtexturemid = vtop - viewz;
      }
      else        // top of texture at top
         rw_midtexturemid = worldtop;

      rw_midtexturemid += FixedMod(sidedef->rowoffset, textureheight[midtexture]);

      ds_p->silhouette = SIL_BOTH;
      ds_p->sprtopclip = screenheightarray;
      ds_p->sprbottomclip = negonearray;
      ds_p->bsilheight = INT_MAX;
      ds_p->tsilheight = INT_MIN;
   }
   else      // two sided line
   {
      ds_p->sprtopclip = ds_p->sprbottomclip = NULL;
      ds_p->silhouette = 0;

      if (linedef->r_flags & RF_CLOSED)
      { /* cph - closed 2S line e.g. door */
         // cph - killough's (outdated) comment follows - this deals with both
         // "automap fixes", his and mine
         // killough 1/17/98: this test is required if the fix
         // for the automap bug (r_bsp.c) is used, or else some
         // sprites will be displayed behind closed doors. That
         // fix prevents lines behind closed doors with dropoffs
         // from being displayed on the automap.

         ds_p->silhouette = SIL_BOTH;
         ds_p->sprbottomclip = negonearray;
         ds_p->bsilheight = INT_MAX;
         ds_p->sprtopclip = screenheightarray;
         ds_p->tsilheight = INT_MIN;

      }
      else
      { /* not solid - old code */

         if (frontsector->floorheight > backsector->floorheight)
         {
            ds_p->silhouette = SIL_BOTTOM;
            ds_p->bsilheight = frontsector->floorheight;
         }
         else
            if (backsector->floorheight > viewz)
            {
               ds_p->silhouette = SIL_BOTTOM;
               ds_p->bsilheight = INT_MAX;
            }

         if (frontsector->ceilingheight < backsector->ceilingheight)
         {
            ds_p->silhouette |= SIL_TOP;
            ds_p->tsilheight = frontsector->ceilingheight;
         }
         else
            if (backsector->ceilingheight < viewz)
            {
               ds_p->silhouette |= SIL_TOP;
               ds_p->tsilheight = INT_MIN;
            }
      }

      worldhigh = backsector->ceilingheight - viewz;
      worldlow = backsector->floorheight - viewz;

      // hack to allow height changes in outdoor areas
      if (frontsector->ceilingpic == skyflatnum
            && backsector->ceilingpic == skyflatnum)
         worldtop = worldhigh;

      markfloor = worldlow != worldbottom
                  || backsector->floorpic != frontsector->floorpic
                  || backsector->lightlevel != frontsector->lightlevel

                  // killough 3/7/98: Add checks for (x,y) offsets
                  || backsector->floor_xoffs != frontsector->floor_xoffs
                  || backsector->floor_yoffs != frontsector->floor_yoffs

                  // killough 4/15/98: prevent 2s normals
                  // from bleeding through deep water
                  || frontsector->heightsec != -1

                  // killough 4/17/98: draw floors if different light levels
                  || backsector->floorlightsec != frontsector->floorlightsec
                  ;

      markceiling = worldhigh != worldtop
                    || backsector->ceilingpic != frontsector->ceilingpic
                    || backsector->lightlevel != frontsector->lightlevel

                    // killough 3/7/98: Add checks for (x,y) offsets
                    || backsector->ceiling_xoffs != frontsector->ceiling_xoffs
                    || backsector->ceiling_yoffs != frontsector->ceiling_yoffs

                    // killough 4/15/98: prevent 2s normals
                    // from bleeding through fake ceilings
                    || (frontsector->heightsec != -1 &&
                        frontsector->ceilingpic!=skyflatnum)

                    // killough 4/17/98: draw ceilings if different light levels
                    || backsector->ceilinglightsec != frontsector->ceilinglightsec
                    ;

      if (backsector->ceilingheight <= frontsector->floorheight
            || backsector->floorheight >= frontsector->ceilingheight)
         markceiling = markfloor = true;   // closed door

      if (worldhigh < worldtop)   // top texture
      {
         toptexture = texturetranslation[sidedef->toptexture];
         toptexheight = (linedef->r_flags & RF_TOP_TILE) ? 0 : textureheight[toptexture] >> FRACBITS;
         rw_toptexturemid = linedef->flags & ML_DONTPEGTOP ? worldtop :
                            backsector->ceilingheight+textureheight[sidedef->toptexture]-viewz;
         rw_toptexturemid += FixedMod(sidedef->rowoffset, textureheight[toptexture]);
      }

      if (worldlow > worldbottom) // bottom texture
      {
         bottomtexture = texturetranslation[sidedef->bottomtexture];
         bottomtexheight = (linedef->r_flags & RF_BOT_TILE) ? 0 : textureheight[bottomtexture] >> FRACBITS;
         rw_bottomtexturemid = linedef->flags & ML_DONTPEGBOTTOM ? worldtop :
                               worldlow;
         rw_bottomtexturemid += FixedMod(sidedef->rowoffset, textureheight[bottomtexture]);
      }

      // allocate space for masked texture tables
      if (sidedef->midtexture)    // masked midtexture
      {
         maskedtexture = true;
         ds_p->maskedtexturecol = maskedtexturecol = lastopening - rw_x;
         lastopening += rw_stopx - rw_x;
      }
   }

   // calculate rw_offset (only needed for textured lines)
   segtextured = midtexture | toptexture | bottomtexture | maskedtexture;

   if (segtextured)
   {
      offsetangle = rw_normalangle-rw_angle1;

      if (offsetangle > ANG180)
         offsetangle = 0-offsetangle;

      if (offsetangle > ANG90)
         offsetangle = ANG90;

      sineval = finesine[offsetangle >>ANGLETOFINESHIFT];
      rw_offset = FixedMul (hyp, sineval);

      if (rw_normalangle-rw_angle1 < ANG180)
         rw_offset = -rw_offset;

      rw_offset += sidedef->textureoffset + curline->offset;

      rw_centerangle = ANG90 + viewangle - rw_normalangle;

      // calculate light table
      //  use different light tables
      //  for horizontal / vertical / diagonal
      // OPTIMIZE: get rid of LIGHTSEGSHIFT globally
      if (!fixedcolormap)
      {
         int lightnum = (frontsector->lightlevel >> LIGHTSEGSHIFT)+extralight;

         /* cph - ...what is this for? adding contrast to rooms?
          * It looks crap in outdoor areas */
         if (fake_contrast)
         {
            if (curline->v1->y == curline->v2->y)
               lightnum--;
            else if (curline->v1->x == curline->v2->x)
               lightnum++;
         }

         if (lightnum < 0)
            walllights = scalelight[0];
         else if (lightnum >= LIGHTLEVELS)
            walllights = scalelight[LIGHTLEVELS-1];
         else
            walllights = scalelight[lightnum];
      }
   }

   // if a floor / ceiling plane is on the wrong side of the view
   // plane, it is definitely invisible and doesn't need to be marked.

   // killough 3/7/98: add deep water check
   if (frontsector->heightsec == -1)
   {
      if (frontsector->floorheight >= viewz)       // above view plane
         markfloor = false;
      if (frontsector->ceilingheight <= viewz &&
            frontsector->ceilingpic != skyflatnum)   // below view plane
         markceiling = false;
   }

   // calculate incremental stepping values for texture edges
   worldtop >>= 4;
   worldbottom >>= 4;

   topstep = -FixedMul (rw_scalestep, worldtop);
   topfrac = (centeryfrac>>4) - FixedMul (worldtop, rw_scale);

   bottomstep = -FixedMul (rw_scalestep,worldbottom);
   bottomfrac = (centeryfrac>>4) - FixedMul (worldbottom, rw_scale);

   if (backsector)
   {
      worldhigh >>= 4;
      worldlow >>= 4;

      if (worldhigh < worldtop)
      {
         pixhigh = (centeryfrac>>4) - FixedMul (worldhigh, rw_scale);
         pixhighstep = -FixedMul (rw_scalestep,worldhigh);
      }
      if (worldlow > worldbottom)
      {
         pixlow = (centeryfrac>>4) - FixedMul (worldlow, rw_scale);
         pixlowstep = -FixedMul (rw_scalestep,worldlow);
      }
   }

   // render it
   if (markceiling)
   {
      if (ceilingplane)   // killough 4/11/98: add NULL ptr checks
         ceilingplane = R_CheckPlane (ceilingplane, rw_x, rw_stopx-1);
      else
         markceiling = 0;
   }

   if (markfloor)
   {
      if (floorplane)     // killough 4/11/98: add NULL ptr checks
         /* cph 2003/04/18  - ceilingplane and floorplane might be the same
          * visplane (e.g. if both skies); R_CheckPlane doesn't know about
          * modifications to the plane that might happen in parallel with the check
          * being made, so we have to override it and split them anyway if that is
          * a possibility, otherwise the floor marking would overwrite the ceiling
          * marking, resulting in HOM. */
         if (markceiling && ceilingplane == floorplane)
            floorplane = R_DupPlane (floorplane, rw_x, rw_stopx-1);
         else
            floorplane = R_CheckPlane (floorplane, rw_x, rw_stopx-1);
      else
         markfloor = 0;
   }

   didsolidcol = 0;
   R_RenderSegLoop();

   /* cph - if a column was made solid by this wall, we _must_ save full clipping info */
   if (backsector && didsolidcol)
   {
      if (!(ds_p->silhouette & SIL_BOTTOM))
      {
         ds_p->silhouette |= SIL_BOTTOM;
         ds_p->bsilheight = backsector->floorheight;
      }
      if (!(ds_p->silhouette & SIL_TOP))
      {
         ds_p->silhouette |= SIL_TOP;
         ds_p->tsilheight = backsector->ceilingheight;
      }
   }

   // save sprite clipping info
   if ((ds_p->silhouette & SIL_TOP || maskedtexture) && !ds_p->sprtopclip)
   {
      memcpy (lastopening, ceilingclip+start, 2*(rw_stopx-start));
      ds_p->sprtopclip = lastopening - start;
      lastopening += rw_stopx - start;
   }
   if ((ds_p->silhouette & SIL_BOTTOM || maskedtexture) && !ds_p->sprbottomclip)
   {
      memcpy (lastopening, floorclip+start, 2*(rw_stopx-start));
      ds_p->sprbottomclip = lastopening - start;
      lastopening += rw_stopx - start;
   }
   if (maskedtexture && !(ds_p->silhouette & SIL_TOP))
   {
      ds_p->silhouette |= SIL_TOP;
      ds_p->tsilheight = INT_MIN;
   }
   if (maskedtexture && !(ds_p->silhouette & SIL_BOTTOM))
   {
      ds_p->silhouette |= SIL_BOTTOM;
      ds_p->bsilheight = INT_MAX;
   }
   ds_p++;
}