rockbox/apps/plugins/doom/r_segs.c

/* 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
static fixed_t R_ScaleFromGlobalAngle (angle_t visangle)
{
   int   anglea = ANG90 + (visangle-viewangle);
   int   angleb = ANG90 + (visangle-rw_normalangle);
   int   sinea = finesine[anglea>>ANGLETOFINESHIFT];
   int   sineb = finesine[angleb>>ANGLETOFINESHIFT];
   fixed_t  num = FixedMul(projection,sineb);
   int   den = FixedMul(rw_distance,sinea);

   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[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++;
}