text: #include "engine.h"
  #include "SDL_thread.h"
  
  enum
  {
      PVS_HIDE_GEOM = 1<<0,
      PVS_HIDE_BB   = 1<<1
  };
  
  struct pvsnode
  {
      bvec edges;
      uchar flags;
      uint children;
  };
  
  static vector<pvsnode> origpvsnodes;
  
  static bool mergepvsnodes(pvsnode &p, pvsnode *children)
  {
      loopi(7) if(children[i].flags!=children[7].flags) return false;
      bvec bbs[4];
      loop(x, 2) loop(y, 2)
      {
          const bvec &lo = children[octaindex(2, x, y, 0)].edges,
                     &hi = children[octaindex(2, x, y, 1)].edges;
          if(lo.x!=0xFF && (lo.x&0x11 || lo.y&0x11 || lo.z&0x11)) return false;
          if(hi.x!=0xFF && (hi.x&0x11 || hi.y&0x11 || hi.z&0x11)) return false;
  
  #define MERGEBBS(res, coord, row, col) \
          if(lo.coord==0xFF) \
          { \
              if(hi.coord!=0xFF) \
              { \
                  res.coord = ((hi.coord&~0x11)>>1) + 0x44; \
                  res.row = hi.row; \
                  res.col = hi.col; \
              } \
          } \
          else if(hi.coord==0xFF) \
          { \
              res.coord = (lo.coord&0xEE)>>1; \
              res.row = lo.row; \
              res.col = lo.col; \
          } \
          else if(lo.row!=hi.row || lo.col!=hi.col || (lo.coord&0xF0)!=0x80 || (hi.coord&0xF)!=0) return false; \
          else \
          { \
              res.coord = ((lo.coord&~0xF1)>>1) | (((hi.coord&~0x1F)>>1) + 0x40); \
              res.row = lo.row; \
              res.col = lo.col; \
          }
  
          bvec &res = bbs[x + 2*y];
          MERGEBBS(res, z, x, y);
          res.x = lo.x;
          res.y = lo.y;
      }
      loop(x, 2)
      {
          bvec &lo = bbs[x], &hi = bbs[x+2];
          MERGEBBS(lo, y, x, z);
      }
      bvec &lo = bbs[0], &hi = bbs[1];
      MERGEBBS(p.edges, x, y, z);
  
      return true;
  }
  
  static void genpvsnodes(cube *c, int parent = 0, const ivec &co = ivec(0, 0, 0), int size = worldsize/2)
  {
      int index = origpvsnodes.length();
      loopi(8)
      {
          ivec o(i, co.x, co.y, co.z, size);
          pvsnode &n = origpvsnodes.add();
          n.flags = 0;
          n.children = 0;
          if(c[i].children || isempty(c[i]) || c[i].material&MAT_ALPHA) memset(n.edges.v, 0xFF, 3);
          else loopk(3)
          {
              uint face = c[i].faces[k];
              if(face==F_SOLID) n.edges[k] = 0x80;
              else
              {
                  uchar low = max(max(face&0xF, (face>>8)&0xF), max((face>>16)&0xF, (face>>24)&0xF)),
                        high = min(min((face>>4)&0xF, (face>>12)&0xF), min((face>>20)&0xF, (face>>28)&0xF));
                  if(size<8)
                  {
                      if(low&((8/size)-1)) { low += 8/size - (low&((8/size)-1)); }
                      if(high&((8/size)-1)) high &= ~(8/size-1);
                  }
                  if(low >= high) { memset(n.edges.v, 0xFF, 3); break; }
                  n.edges[k] = low | (high<<4);
              }
          }
      }
      int branches = 0;
      loopi(8) if(c[i].children)
      {
          ivec o(i, co.x, co.y, co.z, size);
          genpvsnodes(c[i].children, index+i, o, size>>1);
          if(origpvsnodes[index+i].children) branches++;
      }
      if(!branches && mergepvsnodes(origpvsnodes[parent], &origpvsnodes[index])) origpvsnodes.setsize(index);
      else origpvsnodes[parent].children = index;
  }
  
  struct shaftplane
  {
      float r, c, offset;
      uchar rnear, cnear, rfar, cfar;
  };
  
  struct usvec
  {
      union
      {
          struct { ushort x, y, z; };
          ushort v[3];
      };
  
      ushort &operator[](int i) { return v[i]; }
      ushort operator[](int i) const { return v[i]; }
  
      ivec toivec() const { return ivec(x, y, z); }
  };
  
  struct shaftbb
  {
      union
      {
          ushort v[6];
          struct { usvec min, max; };
      };
  
      shaftbb() {}
      shaftbb(const ivec &o, int size)
      {
          min.x = o.x;
          min.y = o.y;
          min.z = o.z;
          max.x = o.x + size;
          max.y = o.y + size;
          max.z = o.z + size;
      }
      shaftbb(const ivec &o, int size, const bvec &edges)
      {
          min.x = o.x + (size*(edges.x&0xF))/8;
          min.y = o.y + (size*(edges.y&0xF))/8;
          min.z = o.z + (size*(edges.z&0xF))/8;
          max.x = o.x + (size*(edges.x>>4))/8;
          max.y = o.y + (size*(edges.y>>4))/8;
          max.z = o.z + (size*(edges.z>>4))/8;
      }
  
      ushort &operator[](int i) { return v[i]; }
      ushort operator[](int i) const { return v[i]; }
  
      bool contains(const shaftbb &o) const
      {
          return min.x<=o.min.x && min.y<=o.min.y && min.z<=o.min.z &&
                 max.x>=o.max.x && max.y>=o.max.y && max.z>=o.max.z;
      }
  
      bool outside(const ivec &o, int size) const
      {
          return o.x>=max.x || o.y>=max.y || o.z>=max.z ||
                 o.x+size<=min.x || o.y+size<=min.y || o.z+size<=min.z;
      }
  
      bool outside(const shaftbb &o) const
      {
          return o.min.x>max.x || o.min.y>max.y || o.min.z>max.z ||
                 o.max.x<min.x || o.max.y<min.y || o.max.z<min.z;
      }
  
      bool notinside(const shaftbb &o) const
      {
          return o.min.x<min.x || o.min.y<min.y || o.min.z<min.z ||
                 o.max.x>max.x || o.max.y>max.y || o.max.z>max.z;
      }
  };
  
  struct shaft
  {
      shaftbb bounds;
      shaftplane planes[8];
      int numplanes;
  
      shaft(const shaftbb &from, const shaftbb &to)
      {
          calcshaft(from, to);
      }
  
      void calcshaft(const shaftbb &from, const shaftbb &to)
      {
          uchar match = 0, color = 0;
          loopi(3)
          {
              if(to.min[i] < from.min[i]) { color |= 1<<i; bounds.min[i] = 0; }
              else if(to.min[i] > from.min[i]) bounds.min[i] = to.min[i]+1;
              else { match |= 1<<i; bounds.min[i] = to.min[i]; }
  
              if(to.max[i] > from.max[i]) { color |= 8<<i; bounds.max[i] = USHRT_MAX; }
              else if(to.max[i] < from.max[i]) bounds.max[i] = to.max[i]-1;
              else { match |= 8<<i; bounds.max[i] = to.max[i]; }
          }
          numplanes = 0;
          loopi(5) if(!(match&(1<<i))) for(int j = i+1; j<6; j++) if(!(match&(1<<j)) && i+3!=j && ((color>>i)^(color>>j))&1)
          {
              int r = i%3, c = j%3, d = (r+1)%3;
              if(d==c) d = (c+1)%3;
              shaftplane &p = planes[numplanes++];
              p.r = from[j] - to[j];
              if(i<3 ? p.r >= 0 : p.r < 0)
              {
                  p.r = -p.r;
                  p.c = from[i] - to[i];
              }
              else p.c = to[i] - from[i];
              p.offset = -(from[i]*p.r + from[j]*p.c);
              p.rnear = p.r >= 0 ? r : 3+r;
              p.cnear = p.c >= 0 ? c : 3+c;
              p.rfar = p.r < 0 ? r : 3+r;
              p.cfar = p.c < 0 ? c : 3+c;
          }
      }
  
      bool outside(const shaftbb &o) const
      {
          if(bounds.outside(o)) return true;
  
          for(const shaftplane *p = planes; p < &planes[numplanes]; p++)
          {
              if(o[p->rnear]*p->r + o[p->cnear]*p->c + p->offset > 0) return true;
          }
          return false;
      }
  
      bool inside(const shaftbb &o) const
      {
          if(bounds.notinside(o)) return false;
  
          for(const shaftplane *p = planes; p < &planes[numplanes]; p++)
          {
              if(o[p->rfar]*p->r + o[p->cfar]*p->c + p->offset > 0) return false;
          }
          return true;
      }
  };
  
  struct pvsdata
  {
      int offset, len;
  
      pvsdata() {}
      pvsdata(int offset, int len) : offset(offset), len(len) {}
  };
  
  static vector<uchar> pvsbuf;
  
  static inline uint hthash(const pvsdata &k)
  {
      uint h = 5381;
      loopi(k.len) h = ((h<<5)+h)^pvsbuf[k.offset+i];
      return h;
  }
  
  static inline bool htcmp(const pvsdata &x, const pvsdata &y)
  {
      return x.len==y.len && !memcmp(&pvsbuf[x.offset], &pvsbuf[y.offset], x.len);
  }
  
  static SDL_mutex *pvsmutex = NULL;
  static hashtable<pvsdata, int> pvscompress;
  static vector<pvsdata> pvs;
  
  static SDL_mutex *viewcellmutex = NULL;
  struct viewcellrequest
  {
      int *result;
      ivec o;
      int size;
  };
  static vector<viewcellrequest> viewcellrequests;
  
  static bool genpvs_canceled = false;
  static int numviewcells = 0;
  
  VAR(maxpvsblocker, 1, 512, 1<<16);
  VAR(pvsleafsize, 1, 64, 1024);
  
  #define MAXWATERPVS 32
  
  static struct
  {
      int height;
      vector<materialsurface *> matsurfs;
  } waterplanes[MAXWATERPVS];
  static vector<materialsurface *> waterfalls;
  uint numwaterplanes = 0;
  
  struct pvsworker
  {
      pvsworker() : thread(NULL), pvsnodes(new pvsnode[origpvsnodes.length()])
      {
      }
      ~pvsworker()
      {
          delete[] pvsnodes;
      }
  
      SDL_Thread *thread;
      pvsnode *pvsnodes;
  
      shaftbb viewcellbb;
  
      pvsnode *levels[32];
      int curlevel;
      ivec origin;
  
      void resetlevels()
      {
          curlevel = worldscale;
          levels[curlevel] = &pvsnodes[0];
          origin = ivec(0, 0, 0);
      }
  
      int hasvoxel(const ivec &p, int coord, int dir, int ocoord = 0, int odir = 0, int *omin = NULL)
      {
          uint diff = (origin.x^p.x)|(origin.y^p.y)|(origin.z^p.z);
          if(diff >= uint(worldsize)) return 0;
          diff >>= curlevel;
          while(diff)
          {
              curlevel++;
              diff >>= 1;
          }
  
          pvsnode *cur = levels[curlevel];
          while(cur->children && !(cur->flags&PVS_HIDE_BB))
          {
              cur = &pvsnodes[cur->children];
              curlevel--;
              cur += ((p.z>>(curlevel-2))&4) | ((p.y>>(curlevel-1))&2) | ((p.x>>curlevel)&1);
              levels[curlevel] = cur;
          }
  
          origin = ivec(p.x&(~0<<curlevel), p.y&(~0<<curlevel), p.z&(~0<<curlevel));
  
          if(cur->flags&PVS_HIDE_BB || cur->edges==bvec(0x80, 0x80, 0x80))
          {
              if(omin)
              {
                  int step = origin[ocoord] + (odir<<curlevel) - p[ocoord] + odir - 1;
                  if(odir ? step < *omin : step > *omin) *omin = step;
              }
              return origin[coord] + (dir<<curlevel) - p[coord] + dir - 1;
          }
  
          if(cur->edges.x==0xFF) return 0;
          ivec bbp(p);
          bbp.sub(origin);
          ivec bbmin, bbmax;
          bbmin.x = ((cur->edges.x&0xF)<<curlevel)/8;
          if(bbp.x < bbmin.x) return 0;
          bbmax.x = ((cur->edges.x>>4)<<curlevel)/8;
          if(bbp.x >= bbmax.x) return 0;
          bbmin.y = ((cur->edges.y&0xF)<<curlevel)/8;
          if(bbp.y < bbmin.y) return 0;
          bbmax.y = ((cur->edges.y>>4)<<curlevel)/8;
          if(bbp.y >= bbmax.y) return 0;
          bbmin.z = ((cur->edges.z&0xF)<<curlevel)/8;
          if(bbp.z < bbmin.z) return 0;
          bbmax.z = ((cur->edges.z>>4)<<curlevel)/8;
          if(bbp.z >= bbmax.z) return 0;
  
          if(omin)
          {
              int step = (odir ? bbmax[ocoord] : bbmin[ocoord]) - bbp[ocoord] + (odir - 1);
              if(odir ? step < *omin : step > *omin) *omin = step;
          }
          return (dir ? bbmax[coord] : bbmin[coord]) - bbp[coord] + (dir - 1);
      }
  
      void hidepvs(pvsnode &p)
      {
          if(p.children)
          {
              pvsnode *children = &pvsnodes[p.children];
              loopi(8) hidepvs(children[i]);
              p.flags |= PVS_HIDE_BB;
              return;
          }
          p.flags |= PVS_HIDE_BB;
          if(p.edges.x!=0xFF) p.flags |= PVS_HIDE_GEOM;
      }
  
      void shaftcullpvs(shaft &s, pvsnode &p, const ivec &co = ivec(0, 0, 0), int size = worldsize)
      {
          if(p.flags&PVS_HIDE_BB) return;
          shaftbb bb(co, size);
          if(s.outside(bb)) return;
          if(s.inside(bb)) { hidepvs(p); return; }
          if(p.children)
          {
              pvsnode *children = &pvsnodes[p.children];
              uchar flags = 0xFF;
              loopi(8)
              {
                  ivec o(i, co.x, co.y, co.z, size>>1);
                  shaftcullpvs(s, children[i], o, size>>1);
                  flags &= children[i].flags;
              }
              if(flags & PVS_HIDE_BB) p.flags |= PVS_HIDE_BB;
              return;
          }
          if(p.edges.x==0xFF) return;
          shaftbb geom(co, size, p.edges);
          if(s.inside(geom)) p.flags |= PVS_HIDE_GEOM;
      }
  
      queue<shaftbb, 32> prevblockers;
  
      struct cullorder
      {
          int index, dist;
  
          cullorder() {}
          cullorder(int index, int dist) : index(index), dist(dist) {}
      };
  
      void cullpvs(pvsnode &p, const ivec &co = ivec(0, 0, 0), int size = worldsize)
      {
          if(p.flags&(PVS_HIDE_BB | PVS_HIDE_GEOM) || genpvs_canceled) return;
          if(p.children && !(p.flags&PVS_HIDE_BB))
          {
              pvsnode *children = &pvsnodes[p.children];
              int csize = size>>1;
              ivec dmin = ivec(co).add(csize>>1).sub(viewcellbb.min.toivec().add(viewcellbb.max.toivec()).shr(1)), dmax = ivec(dmin).add(csize);
              dmin.mul(dmin);
              dmax.mul(dmax);
              ivec diff = ivec(dmax).sub(dmin);
              cullorder order[8];
              int dir = 0;
              if(diff.x < 0) { diff.x = -diff.x; dir |= 1; }
              if(diff.y < 0) { diff.y = -diff.y; dir |= 2; }
              if(diff.z < 0) { diff.z = -diff.z; dir |= 4; }
              order[0] = cullorder(0, 0);
              order[7] = cullorder(7, diff.x + diff.y + diff.z);
              order[1] = cullorder(1, diff.x);
              order[2] = cullorder(2, diff.y);
              order[3] = cullorder(4, diff.z);
              if(order[2].dist < order[1].dist) swap(order[1], order[2]);
              if(order[3].dist < order[2].dist) swap(order[2], order[3]);
              if(order[2].dist < order[1].dist) swap(order[1], order[2]);
              cullorder dxy(order[1].index|order[2].index, order[1].dist+order[2].dist),
                        dxz(order[1].index|order[3].index, order[1].dist+order[3].dist),
                        dyz(order[2].index|order[3].index, order[2].dist+order[3].dist);
              int j;
              for(j = 4; j > 0 && dxy.dist < order[j-1].dist; --j) order[j] = order[j-1]; order[j] = dxy;
              for(j = 5; j > 0 && dxz.dist < order[j-1].dist; --j) order[j] = order[j-1]; order[j] = dxz;
              for(j = 6; j > 0 && dyz.dist < order[j-1].dist; --j) order[j] = order[j-1]; order[j] = dyz;
              loopi(8)
              {
                  int index = order[i].index^dir;
                  ivec o(index, co.x, co.y, co.z, csize);
                  cullpvs(children[index], o, csize);
              }
              if(!(p.flags & PVS_HIDE_BB)) return;
          }
          bvec edges = p.children ? bvec(0x80, 0x80, 0x80) : p.edges;
          if(edges.x==0xFF) return;
          shaftbb geom(co, size, edges);
          ivec diff = geom.max.toivec().sub(viewcellbb.min.toivec()).abs();
          cullorder order[3] = { cullorder(0, diff.x), cullorder(1, diff.y), cullorder(2, diff.z) };
          if(order[1].dist > order[0].dist) swap(order[0], order[1]);
          if(order[2].dist > order[1].dist) swap(order[1], order[2]);
          if(order[1].dist > order[0].dist) swap(order[0], order[1]);
          loopi(6)
          {
              int dim = order[i >= 3 ? i-3 : i].index, dc = (i >= 3) != (geom.max[dim] <= viewcellbb.min[dim]) ? 1 : 0, r = R[dim], c = C[dim];
              int ccenter = geom.min[c];
              if(geom.min[r]==geom.max[r] || geom.min[c]==geom.max[c]) continue;
              while(ccenter < geom.max[c])
              {
                  ivec rmin;
                  rmin[dim] = geom[dim + 3*dc] + (dc ? -1 : 0);
                  rmin[r] = geom.min[r];
                  rmin[c] = ccenter;
                  ivec rmax = rmin;
                  rmax[r] = geom.max[r] - 1;
                  int rcenter = (rmin[r] + rmax[r])/2;
                  resetlevels();
                  for(int minstep = -1, maxstep = 1; (minstep || maxstep) && rmax[r] - rmin[r] < maxpvsblocker;)
                  {
                      if(minstep) minstep = hasvoxel(rmin, r, 0);
                      if(maxstep) maxstep = hasvoxel(rmax, r, 1);
                      rmin[r] += minstep;
                      rmax[r] += maxstep;
                  }
                  rmin[r] = rcenter + (rmin[r] - rcenter)/2;
                  rmax[r] = rcenter + (rmax[r] - rcenter)/2;
                  if(rmin[r]>=geom.min[r] && rmax[r]<geom.max[r]) { rmin[r] = geom.min[r]; rmax[r] = geom.max[r] - 1; }
                  ivec cmin = rmin, cmax = rmin;
                  if(rmin[r]>=geom.min[r] && rmax[r]<geom.max[r])
                  {
                      cmin[c] = geom.min[c];
                      cmax[c] = geom.max[c]-1;
                  }
                  int cminstep = -1, cmaxstep = 1;
                  for(; (cminstep || cmaxstep) && cmax[c] - cmin[c] < maxpvsblocker;)
                  {
                      if(cminstep)
                      {
                          cmin[c] += cminstep; cminstep = INT_MIN;
                          cmin[r] = rmin[r];
                          resetlevels();
                          for(int rstep = 1; rstep && cmin[r] <= rmax[r];)
                          {
                              rstep = hasvoxel(cmin, r, 1, c, 0, &cminstep);
                              cmin[r] += rstep;
                          }
                          if(cmin[r] <= rmax[r]) cminstep = 0;
                      }
                      if(cmaxstep)
                      {
                          cmax[c] += cmaxstep; cmaxstep = INT_MAX;
                          cmax[r] = rmin[r];
                          resetlevels();
                          for(int rstep = 1; rstep && cmax[r] <= rmax[r];)
                          {
                              rstep = hasvoxel(cmax, r, 1, c, 1, &cmaxstep);
                              cmax[r] += rstep;
                          }
                          if(cmax[r] <= rmax[r]) cmaxstep = 0;
                      }
                  }
                  if(!cminstep) cmin[c]++;
                  if(!cmaxstep) cmax[c]--;
                  ivec emin = rmin, emax = rmax;
                  if(cmin[c]>=geom.min[c] && cmax[c]<geom.max[c])
                  {
                      if(emin[r]>geom.min[r]) emin[r] = geom.min[r];
                      if(emax[r]<geom.max[r]-1) emax[r] = geom.max[r]-1;
                  }
                  int rminstep = -1, rmaxstep = 1;
                  for(; (rminstep || rmaxstep) && emax[r] - emin[r] < maxpvsblocker;)
                  {
                      if(rminstep)
                      {
                          emin[r] += -1; rminstep = INT_MIN;
                          emin[c] = cmin[c];
                          resetlevels();
                          for(int cstep = 1; cstep && emin[c] <= cmax[c];)
                          {
                              cstep = hasvoxel(emin, c, 1, r, 0, &rminstep);
                              emin[c] += cstep;
                          }
                          if(emin[c] <= cmax[c]) rminstep = 0;
                      }
                      if(rmaxstep)
                      {
                          emax[r] += 1; rmaxstep = INT_MAX;
                          emax[c] = cmin[c];
                          resetlevels();
                          for(int cstep = 1; cstep && emax[c] <= cmax[c];)
                          {
                              cstep = hasvoxel(emax, c, 1, r, 1, &rmaxstep);
                              emax[c] += cstep;
                          }
                          if(emax[c] <= cmax[c]) rmaxstep = 0;
                      }
                  }
                  if(!rminstep) emin[r]++;
                  if(!rmaxstep) emax[r]--;
                  shaftbb bb;
                  bb.min[dim] = rmin[dim];
                  bb.max[dim] = rmin[dim]+1;
                  bb.min[r] = emin[r];
                  bb.max[r] = emax[r]+1;
                  bb.min[c] = cmin[c];
                  bb.max[c] = cmax[c]+1;
                  if(bb.min[dim] >= viewcellbb.max[dim] || bb.max[dim] <= viewcellbb.min[dim])
                  {
                      int ddir = bb.min[dim] >= viewcellbb.max[dim] ? 1 : -1,
                          dval = ddir>0 ? USHRT_MAX-1 : 0,
                          dlimit = maxpvsblocker,
                          numsides = 0;
                      loopj(4)
                      {
                          ivec dmax;
                          int odim = j < 2 ? c : r;
                          if(j&1)
                          {
                              if(bb.max[odim] >= viewcellbb.max[odim]) continue;
                              dmax[odim] = bb.max[odim]-1;
                          }
                          else
                          {
                              if(bb.min[odim] <= viewcellbb.min[odim]) continue;
                              dmax[odim] = bb.min[odim];
                          }
                          numsides++;
                          dmax[dim] = bb.min[dim];
                          int stepdim = j < 2 ? r : c, stepstart = bb.min[stepdim], stepend = bb.max[stepdim];
                          int dstep = ddir;
                          for(; dstep && ddir*(dmax[dim] - (int)bb.min[dim]) < dlimit;)
                          {
                              dmax[dim] += dstep; dstep = ddir > 0 ? INT_MAX : INT_MIN;
                              dmax[stepdim] = stepstart;
                              resetlevels();
                              for(int step = 1; step && dmax[stepdim] < stepend;)
                              {
                                  step = hasvoxel(dmax, stepdim, 1, dim, (ddir+1)/2, &dstep);
                                  dmax[stepdim] += step;
                              }
                              if(dmax[stepdim] < stepend) dstep = 0;
                          }
                          dlimit = min(dlimit, ddir*(dmax[dim] - (int)bb.min[dim]));
                          if(!dstep) dmax[dim] -= ddir;
                          if(ddir>0) dval = min(dval, dmax[dim]);
                          else dval = max(dval, dmax[dim]);
                      }
                      if(numsides>0)
                      {
                          if(ddir>0) bb.max[dim] = dval+1;
                          else bb.min[dim] = dval;
                      }
                      //printf("(%d,%d,%d) x %d,%d,%d, side %d, ccenter = %d, origin = (%d,%d,%d), size = %d\n", bb.min.x, bb.min.y, bb.min.z, bb.max.x-bb.min.x, bb.max.y-bb.min.y, bb.max.z-bb.min.z, i, ccenter, co.x, co.y, co.z, size);
                  }
                  bool dup = false;
                  loopvj(prevblockers)
                  {
                      if(prevblockers[j].contains(bb)) { dup = true; break; }
                  }
                  if(!dup)
                  {
                      shaft s(viewcellbb, bb);
                      shaftcullpvs(s, pvsnodes[0]);
                      prevblockers.add(bb);
                  }
                  if(bb.contains(geom)) return;
                  ccenter = cmax[c] + 1;
              }
          }
      }
  
      bool compresspvs(pvsnode &p, int size, int threshold)
      {
          if(!p.children) return true;
          if(p.flags&PVS_HIDE_BB) { p.children = 0; return true; }
          pvsnode *children = &pvsnodes[p.children];
          bool canreduce = true;
          loopi(8)
          {
              if(!compresspvs(children[i], size/2, threshold)) canreduce = false;
          }
          if(canreduce)
          {
              int hide = children[7].flags&PVS_HIDE_BB;
              loopi(7) if((children[i].flags&PVS_HIDE_BB)!=hide) canreduce = false;
              if(canreduce) 
              {
                  p.flags = (p.flags & ~PVS_HIDE_BB) | hide;
                  p.children = 0;
                  return true;
              }
          }
          if(size <= threshold)
          {
              p.children = 0;
              return true;
          }
          return false;
      }
      
      vector<uchar> outbuf;
  
      bool serializepvs(pvsnode &p, int storage = -1)
      {
          if(!p.children)
          {
              outbuf.add(0xFF);
              loopi(8) outbuf.add(p.flags&PVS_HIDE_BB ? 0xFF : 0);
              return true;
          }
          int index = outbuf.length();
          pvsnode *children = &pvsnodes[p.children];
          int i = 0;
          uchar leafvalues = 0;
          if(storage>=0)
          {
              for(; i < 8; i++)
              {   
                  pvsnode &child = children[i];
                  if(child.flags&PVS_HIDE_BB) leafvalues |= 1<<i;
                  else if(child.children) break;
              }
              if(i==8) { outbuf[storage] = leafvalues; return false; }
              // if offset won't fit, just mark the space as a visible to avoid problems
              int offset = (index - storage + 8)/9;
              if(offset>255) { outbuf[storage] = 0; return false; }
              outbuf[storage] = uchar(offset);
          }
          outbuf.add(0);
          loopj(8) outbuf.add(leafvalues&(1<<j) ? 0xFF : 0);
          uchar leafmask = (1<<i)-1;
          for(; i < 8; i++)
          {
              pvsnode &child = children[i];
              if(child.children) { if(!serializepvs(child, index+1+i)) leafmask |= 1<<i; }
              else { leafmask |= 1<<i; outbuf[index+1+i] = child.flags&PVS_HIDE_BB ? 0xFF : 0; }
          }
          outbuf[index] = leafmask;
          return true;
      }
  
      bool materialoccluded(pvsnode &p, const ivec &co, int size, const ivec &bbmin, const ivec &bbmax)
      {
          pvsnode *children = &pvsnodes[p.children];
          loopoctabox(co, size, bbmin, bbmax)
          {
              ivec o(i, co.x, co.y, co.z, size);
              if(children[i].flags & PVS_HIDE_BB) continue;
              if(!children[i].children || !materialoccluded(children[i], o, size/2, bbmin, bbmax)) return false;
          }
          return true;
      }
  
      bool materialoccluded(vector<materialsurface *> &matsurfs)
      {
          if(pvsnodes[0].flags & PVS_HIDE_BB) return true;
          if(!pvsnodes[0].children) return false;
          loopv(matsurfs)
          {
              materialsurface &m = *matsurfs[i];
              ivec bbmin(m.o), bbmax(m.o);
              int dim = dimension(m.orient);
              bbmin[dim] += dimcoord(m.orient) ? -2 : 2;
              bbmax[C[dim]] += m.csize;
              bbmax[R[dim]] += m.rsize;
              if(!materialoccluded(pvsnodes[0], vec(0, 0, 0), worldsize/2, bbmin, bbmax)) return false;
          }
          return true;
      }
  
      int wateroccluded, waterbytes;
  
      void calcpvs(const ivec &co, int size)
      {
          loopk(3)
          {
              viewcellbb.min[k] = co[k];
              viewcellbb.max[k] = co[k]+size;
          }
          memcpy(pvsnodes, origpvsnodes.getbuf(), origpvsnodes.length()*sizeof(pvsnode));
          prevblockers.clear();
          cullpvs(pvsnodes[0]);
  
          wateroccluded = 0;
          loopi(numwaterplanes)
          {
              if(waterplanes[i].height < 0)
              {
                  if(waterfalls.length() && materialoccluded(waterfalls)) wateroccluded |= 1<<i;
              }
              else if(waterplanes[i].matsurfs.length() && materialoccluded(waterplanes[i].matsurfs)) wateroccluded |= 1<<i;
          }
          waterbytes = 0;
          loopi(4) if(wateroccluded&(0xFF<<(i*8))) waterbytes = i+1;
  
          compresspvs(pvsnodes[0], worldsize, pvsleafsize);
          outbuf.setsize(0);
          serializepvs(pvsnodes[0]);
      }
  
      uchar *testviewcell(const ivec &co, int size, int *waterpvs = NULL, int *len = NULL)
      {
          calcpvs(co, size);
  
          uchar *buf = new uchar[outbuf.length()];
          memcpy(buf, outbuf.getbuf(), outbuf.length());
          if(waterpvs) *waterpvs = wateroccluded;
          if(len) *len = outbuf.length();
          return buf;
      }
  
      int genviewcell(const ivec &co, int size)
      {
          calcpvs(co, size);
  
          if(pvsmutex) SDL_LockMutex(pvsmutex);
          numviewcells++;
          pvsdata key(pvsbuf.length(), waterbytes + outbuf.length());
          loopi(waterbytes) pvsbuf.add((wateroccluded>>(i*8))&0xFF);
          pvsbuf.put(outbuf.getbuf(), outbuf.length());
          int *val = pvscompress.access(key);
          if(val) pvsbuf.setsize(key.offset);
          else
          {
              val = &pvscompress[key];
              *val = pvs.length();
              pvs.add(key);
          }
          if(pvsmutex) SDL_UnlockMutex(pvsmutex);
          return *val;
      }
  
      static int run(void *data)
      {
          pvsworker *w = (pvsworker *)data;
          SDL_LockMutex(viewcellmutex);
          while(viewcellrequests.length())
          {
              viewcellrequest req = viewcellrequests.pop();
              SDL_UnlockMutex(viewcellmutex);
              int result = w->genviewcell(req.o, req.size);
              SDL_LockMutex(viewcellmutex);
              *req.result = result;
          }
          SDL_UnlockMutex(viewcellmutex);
          return 0;
      }
  };
  
  struct viewcellnode
  {
      uchar leafmask;
      union viewcellchild
      {
          int pvs;
          viewcellnode *node;
      } children[8];
  
      viewcellnode() : leafmask(0xFF)
      {
          loopi(8) children[i].pvs = -1;
      }
      ~viewcellnode()
      {
          loopi(8) if(!(leafmask&(1<<i))) delete children[i].node;
      }
  };
  
  VARP(pvsthreads, 0, 0, 16);
  static vector<pvsworker *> pvsworkers;
  
  static volatile bool check_genpvs_progress = false;
  
  static Uint32 genpvs_timer(Uint32 interval, void *param)
  {
      check_genpvs_progress = true;
      return interval;
  }
  
  static int totalviewcells = 0;
  
  static void show_genpvs_progress(int unique = pvs.length(), int processed = numviewcells)
  {
      float bar1 = float(processed) / float(totalviewcells>0 ? totalviewcells : 1);
  
      defformatstring(text1)("%d%% - %d of %d view cells (%d unique)", int(bar1 * 100), processed, totalviewcells, unique);
  
      renderprogress(bar1, text1);
  
      if(interceptkey(SDLK_ESCAPE)) genpvs_canceled = true;
      check_genpvs_progress = false;
  }
  
  static shaftbb pvsbounds;
  
  static void calcpvsbounds()
  {
      loopk(3) pvsbounds.min[k] = USHRT_MAX;
      loopk(3) pvsbounds.max[k] = 0;
      extern vector<vtxarray *> valist;
      loopv(valist)
      {
          vtxarray *va = valist[i];
          loopk(3)
          {
              if(va->geommin[k]>va->geommax[k]) continue;
              pvsbounds.min[k] = min(pvsbounds.min[k], (ushort)va->geommin[k]);
              pvsbounds.max[k] = max(pvsbounds.max[k], (ushort)va->geommax[k]);
          }
      }
  }
  
  static inline bool isallclip(cube *c)
  {
      loopi(8)
      {
          cube &h = c[i];
          if(h.children ? !isallclip(h.children) : (!isentirelysolid(h) && (h.material&MATF_CLIP)!=MAT_CLIP))
              return false;
      }
      return true;
  }
     
  static int countviewcells(cube *c, const ivec &co, int size, int threshold)
  {
      int count = 0;
      loopi(8)
      {
          ivec o(i, co.x, co.y, co.z, size);
          if(pvsbounds.outside(o, size)) continue;
          cube &h = c[i];
          if(h.children)
          {
              if(size>threshold)
              {
                  count += countviewcells(h.children, o, size>>1, threshold);
                  continue;
              }
              if(isallclip(h.children)) continue;
          }
          else if(isentirelysolid(h) || (h.material&MATF_CLIP)==MAT_CLIP) continue;
          count++;
      }
      return count;
  }
  
  static void genviewcells(viewcellnode &p, cube *c, const ivec &co, int size, int threshold)
  {
      if(genpvs_canceled) return;
      loopi(8)
      {
          ivec o(i, co.x, co.y, co.z, size);
          if(pvsbounds.outside(o, size)) continue;
          cube &h = c[i];
          if(h.children)
          {
              if(size>threshold)
              {
                  p.leafmask &= ~(1<<i);
                  p.children[i].node = new viewcellnode;
                  genviewcells(*p.children[i].node, h.children, o, size>>1, threshold);
                  continue;
              }
              if(isallclip(h.children)) continue;
          }
          else if(isentirelysolid(h) || (h.material&MATF_CLIP)==MAT_CLIP) continue;
          if(pvsworkers.length())
          {
              if(genpvs_canceled) return;
              p.children[i].pvs = pvsworkers[0]->genviewcell(o, size);
              if(check_genpvs_progress) show_genpvs_progress();
          }
          else
          {
              viewcellrequest &req = viewcellrequests.add();
              req.result = &p.children[i].pvs;
              req.o = o;
              req.size = size;
          }
      }
  }
  
  static viewcellnode *viewcells = NULL;
  static int lockedwaterplanes[MAXWATERPVS];
  static uchar *curpvs = NULL, *lockedpvs = NULL;
  static int curwaterpvs = 0, lockedwaterpvs = 0;
  
  static inline pvsdata *lookupviewcell(const vec &p)
  {
      uint x = uint(floor(p.x)), y = uint(floor(p.y)), z = uint(floor(p.z));
      if(!viewcells || (x|y|z)>=uint(worldsize)) return NULL;
      viewcellnode *vc = viewcells;
      for(int scale = worldscale-1; scale>=0; scale--)
      {
          int i = octastep(x, y, z, scale);
          if(vc->leafmask&(1<<i))
          {
              return vc->children[i].pvs>=0 ? &pvs[vc->children[i].pvs] : NULL;
          }
          vc = vc->children[i].node;
      }
      return NULL;
  }
  
  static void lockpvs_(bool lock)
  {
      if(lockedpvs) DELETEA(lockedpvs);
      if(!lock) return;
      pvsdata *d = lookupviewcell(camera1->o);
      if(!d) return;
      int wbytes = d->len%9, len = d->len - wbytes;
      lockedpvs = new uchar[len];
      memcpy(lockedpvs, &pvsbuf[d->offset + wbytes], len);
      lockedwaterpvs = 0;
      loopi(wbytes) lockedwaterpvs |= pvsbuf[d->offset + i] << (i*8);
      loopi(MAXWATERPVS) lockedwaterplanes[i] = waterplanes[i].height;
      conoutf("locked view cell at %.1f, %.1f, %.1f", camera1->o.x, camera1->o.y, camera1->o.z);
  }
  
  VARF(lockpvs, 0, 0, 1, lockpvs_(lockpvs!=0));
  
  VARN(pvs, usepvs, 0, 1, 1);
  VARN(waterpvs, usewaterpvs, 0, 1, 1);
  
  void setviewcell(const vec &p)
  {
      if(!usepvs) curpvs = NULL;
      else if(lockedpvs) 
      {
          curpvs = lockedpvs;
          curwaterpvs = lockedwaterpvs;
      }
      else
      {
          pvsdata *d = lookupviewcell(p);
          curpvs = d ? &pvsbuf[d->offset] : NULL;
          curwaterpvs = 0;
          if(d)
          {
              loopi(d->len%9) curwaterpvs |= *curpvs++ << (i*8);
          }
      }
      if(!usepvs || !usewaterpvs) curwaterpvs = 0;
  }
  
  void clearpvs()
  {
      DELETEP(viewcells);
      pvs.setsize(0);
      pvsbuf.setsize(0);
      curpvs = NULL;
      numwaterplanes = 0;
      lockpvs = 0;
      lockpvs_(false);
  }
  
  COMMAND(clearpvs, "");
  
  static void findwaterplanes()
  {
      extern vector<vtxarray *> valist;
      loopi(MAXWATERPVS)
      {
          waterplanes[i].height = -1;
          waterplanes[i].matsurfs.setsize(0);
      }
      waterfalls.setsize(0);
      numwaterplanes = 0;
      loopv(valist)
      {
          vtxarray *va = valist[i];
          loopj(va->matsurfs)
          {
              materialsurface &m = va->matbuf[j];
              if((m.material&MATF_VOLUME)!=MAT_WATER || m.orient==O_BOTTOM) { j += m.skip; continue; }
              if(m.orient!=O_TOP)
              {
                  waterfalls.add(&m);
                  continue;
              }
              loopk(numwaterplanes) if(waterplanes[k].height == m.o.z)
              {
                  waterplanes[k].matsurfs.add(&m);
                  goto nextmatsurf;
              }
              if(numwaterplanes < MAXWATERPVS)
              {
                  waterplanes[numwaterplanes].height = m.o.z;
                  waterplanes[numwaterplanes].matsurfs.add(&m);
                  numwaterplanes++;
              }
          nextmatsurf:;
          }
      }
      if(waterfalls.length() > 0 && numwaterplanes < MAXWATERPVS) numwaterplanes++;
  }
  
  void testpvs(int *vcsize)
  {
      lockpvs_(false);
  
      uint oldnumwaterplanes = numwaterplanes;
      int oldwaterplanes[MAXWATERPVS];
      loopi(numwaterplanes) oldwaterplanes[i] = waterplanes[i].height;
  
      findwaterplanes();
  
      pvsnode &root = origpvsnodes.add();
      memset(root.edges.v, 0xFF, 3);
      root.flags = 0;
      root.children = 0;
      genpvsnodes(worldroot);
  
      genpvs_canceled = false;
      check_genpvs_progress = false;
  
      int size = *vcsize>0 ? *vcsize : 32;
      for(int mask = 1; mask < size; mask <<= 1) size &= ~mask;
  
      ivec o = camera1->o;
      o.mask(~(size-1));
      pvsworker w;
      int len;
      lockedpvs = w.testviewcell(o, size, &lockedwaterpvs, &len);
      loopi(MAXWATERPVS) lockedwaterplanes[i] = waterplanes[i].height;
      lockpvs = 1;
      conoutf("generated test view cell of size %d at %.1f, %.1f, %.1f (%d B)", size, camera1->o.x, camera1->o.y, camera1->o.z, len);
  
      origpvsnodes.setsize(0);
      numwaterplanes = oldnumwaterplanes;
      loopi(numwaterplanes) waterplanes[i].height = oldwaterplanes[i];
  }
  
  COMMAND(testpvs, "i");
  
  void genpvs(int *viewcellsize)
  {
      if(worldsize > 1<<15)
      {
          conoutf(CON_ERROR, "map is too large for PVS");
          return;
      }
  
      renderbackground("generating PVS (esc to abort)");
      genpvs_canceled = false;
      Uint32 start = SDL_GetTicks();
  
      renderprogress(0, "finding view cells");
  
      clearpvs();
      calcpvsbounds();
      findwaterplanes();
  
      pvsnode &root = origpvsnodes.add();
      memset(root.edges.v, 0xFF, 3);
      root.flags = 0;
      root.children = 0;
      genpvsnodes(worldroot);
  
      totalviewcells = countviewcells(worldroot, ivec(0, 0, 0), worldsize>>1, *viewcellsize>0 ? *viewcellsize : 32);
      numviewcells = 0;
      genpvs_canceled = false;
      check_genpvs_progress = false;
      SDL_TimerID timer = NULL;
      int numthreads = pvsthreads > 0 ? pvsthreads : numcpus;
      if(numthreads<=1) 
      {
          pvsworkers.add(new pvsworker);
          timer = SDL_AddTimer(500, genpvs_timer, NULL);
      }
      viewcells = new viewcellnode;
      genviewcells(*viewcells, worldroot, ivec(0, 0, 0), worldsize>>1, *viewcellsize>0 ? *viewcellsize : 32);
      if(numthreads<=1)
      {
          SDL_RemoveTimer(timer);
      }
      else
      {
          renderprogress(0, "creating threads");
          if(!pvsmutex) pvsmutex = SDL_CreateMutex();
          if(!viewcellmutex) viewcellmutex = SDL_CreateMutex();
          loopi(numthreads)
          {
              pvsworker *w = pvsworkers.add(new pvsworker);
              w->thread = SDL_CreateThread(pvsworker::run, w);
          }
          show_genpvs_progress(0, 0);
          while(!genpvs_canceled)
          {
              SDL_Delay(500);
              SDL_LockMutex(viewcellmutex);
              int unique = pvs.length(), processed = numviewcells, remaining = viewcellrequests.length();
              SDL_UnlockMutex(viewcellmutex);
              show_genpvs_progress(unique, processed);
              if(!remaining) break;
          }        
          SDL_LockMutex(viewcellmutex);
          viewcellrequests.setsize(0);
          SDL_UnlockMutex(viewcellmutex);
          loopv(pvsworkers) SDL_WaitThread(pvsworkers[i]->thread, NULL);
      }
      pvsworkers.deletecontents();
  
      origpvsnodes.setsize(0);
      pvscompress.clear();
  
      Uint32 end = SDL_GetTicks();
      if(genpvs_canceled) 
      {
          clearpvs();
          conoutf("genpvs aborted");
      }
      else conoutf("generated %d unique view cells totaling %.1f kB and averaging %d B (%.1f seconds)", 
              pvs.length(), pvsbuf.length()/1024.0f, pvsbuf.length()/max(pvs.length(), 1), (end - start) / 1000.0f);
  }
  
  COMMAND(genpvs, "i");
  
  void pvsstats()
  {
      conoutf("%d unique view cells totaling %.1f kB and averaging %d B",          
          pvs.length(), pvsbuf.length()/1024.0f, pvsbuf.length()/max(pvs.length(), 1));
  }
  
  COMMAND(pvsstats, "");
  
  static inline bool pvsoccluded(uchar *buf, const ivec &co, int size, const ivec &bbmin, const ivec &bbmax)
  {
      uchar leafmask = buf[0];
      loopoctabox(co, size, bbmin, bbmax)
      {
          ivec o(i, co.x, co.y, co.z, size);
          if(leafmask&(1<<i))
          {
              uchar leafvalues = buf[1+i];
              if(!leafvalues || (leafvalues!=0xFF && octaboxoverlap(o, size>>1, bbmin, bbmax)&~leafvalues))
                  return false;
          }
          else if(!pvsoccluded(buf+9*buf[1+i], o, size>>1, bbmin, bbmax)) return false;
      }
      return true;
  }
  
  static inline bool pvsoccluded(uchar *buf, const ivec &bbmin, const ivec &bbmax)
  {
      int diff = (bbmin.x^bbmax.x) | (bbmin.y^bbmax.y) | (bbmin.z^bbmax.z);
      if(diff&~((1<<worldscale)-1)) return false;
      int scale = worldscale-1;
      while(!(diff&(1<<scale)))
      {
          int i = octastep(bbmin.x, bbmin.y, bbmin.z, scale);
          scale--;
          uchar leafmask = buf[0];
          if(leafmask&(1<<i))
          {
              uchar leafvalues = buf[1+i];
              return leafvalues && (leafvalues==0xFF || !(octaboxoverlap(ivec(bbmin).mask(~((2<<scale)-1)), 1<<scale, bbmin, bbmax)&~leafvalues));
          }
          buf += 9*buf[1+i];
      }
      return pvsoccluded(buf, ivec(bbmin).mask(~((2<<scale)-1)), 1<<scale, bbmin, bbmax);
  }
  
  bool pvsoccluded(const ivec &bbmin, const ivec &bbmax)
  {
      return curpvs!=NULL && pvsoccluded(curpvs, bbmin, bbmax);
  }
  
  bool pvsoccludedsphere(const vec &center, float radius)
  {
      if(curpvs==NULL) return false;
      ivec bbmin = vec(center).sub(radius), bbmax = vec(center).add(radius+1);
      return pvsoccluded(curpvs, bbmin, bbmax);
  }
  
  bool waterpvsoccluded(int height)
  {
      if(!curwaterpvs) return false;
      if(lockedpvs)
      {
          loopi(MAXWATERPVS) if(lockedwaterplanes[i]==height) return (curwaterpvs&(1<<i))!=0;
      }
      else
      {
          loopi(numwaterplanes) if(waterplanes[i].height==height) return (curwaterpvs&(1<<i))!=0;
      }
      return false;
  }
  
  void saveviewcells(stream *f, viewcellnode &p)
  {
      f->putchar(p.leafmask);
      loopi(8)
      {
          if(p.leafmask&(1<<i)) f->putlil<int>(p.children[i].pvs);
          else saveviewcells(f, *p.children[i].node);
      }
  }
  
  void savepvs(stream *f)
  {
      uint totallen = pvsbuf.length() | (numwaterplanes>0 ? 0x80000000U : 0);
      f->putlil<uint>(totallen);
      if(numwaterplanes>0)
      {
          f->putlil<uint>(numwaterplanes);
          loopi(numwaterplanes)
          {
              f->putlil<int>(waterplanes[i].height);
              if(waterplanes[i].height < 0) break;
          }
      }
      loopv(pvs) f->putlil<ushort>(pvs[i].len);
      f->write(pvsbuf.getbuf(), pvsbuf.length());
      saveviewcells(f, *viewcells);
  }
  
  viewcellnode *loadviewcells(stream *f)
  {
      viewcellnode *p = new viewcellnode;
      p->leafmask = f->getchar();
      loopi(8)
      {
          if(p->leafmask&(1<<i)) p->children[i].pvs = f->getlil<int>();
          else p->children[i].node = loadviewcells(f);
      }
      return p;
  }
  
  void loadpvs(stream *f, int numpvs)
  {
      uint totallen = f->getlil<uint>();
      if(totallen & 0x80000000U)
      {
          totallen &= ~0x80000000U;
          numwaterplanes = f->getlil<uint>();
          loopi(numwaterplanes) waterplanes[i].height = f->getlil<int>();
      }
      int offset = 0;
      loopi(numpvs)
      {
          ushort len = f->getlil<ushort>();
          pvs.add(pvsdata(offset, len));
          offset += len;
      }
      f->read(pvsbuf.reserve(totallen).buf, totallen);
      pvsbuf.advance(totallen);
      viewcells = loadviewcells(f);
  }
  
  int getnumviewcells() { return pvs.length(); }
  
  