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btSparseSDF.h

/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/

This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it freely,
subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
///btSparseSdf implementation by Nathanael Presson

#ifndef _14F9D17F_EAE8_4aba_B41C_292DB2AA70F3_
#define _14F9D17F_EAE8_4aba_B41C_292DB2AA70F3_

#include "BulletCollision/CollisionDispatch/btCollisionObject.h"
#include "BulletCollision/NarrowPhaseCollision/btGjkEpa2.h"

// Modified Paul Hsieh hash
template <const int DWORDLEN>
unsigned int HsiehHash(const void* pdata)
      {
      const unsigned short*   data=(const unsigned short*)pdata;
      unsigned                      hash=DWORDLEN<<2,tmp;
      for(int i=0;i<DWORDLEN;++i)
            {
            hash  +=    data[0];
            tmp         =     (data[1]<<11)^hash;
            hash  =     (hash<<16)^tmp;
            data  +=    2;
            hash  +=    hash>>11;
            }
      hash^=hash<<3;hash+=hash>>5;
      hash^=hash<<4;hash+=hash>>17;
      hash^=hash<<25;hash+=hash>>6;
      return(hash);
      }

template <const int CELLSIZE>
struct      btSparseSdf
      {
      //
      // Inner types
      //
      struct IntFrac
            {
            int                           b;
            int                           i;
            btScalar                f;
            };
      struct      Cell
            {
            btScalar                d[CELLSIZE+1][CELLSIZE+1][CELLSIZE+1];
            int                           c[3];
            int                           puid;
            unsigned                hash;
            btCollisionShape* pclient;
            Cell*                   next;
            };
      //
      // Fields
      //
      
      btAlignedObjectArray<Cell*>         cells;      
      btScalar                                  voxelsz;
      int                                             puid;
      int                                             ncells;
      int                                             nprobes;
      int                                             nqueries;   
      
      //
      // Methods
      //
      
      //
      void                          Initialize(int hashsize=2383)
            {
            cells.resize(hashsize,0);
            Reset();          
            }
      //
      void                          Reset()
            {
            for(int i=0,ni=cells.size();i<ni;++i)
                  {
                  Cell* pc=cells[i];
                  cells[i]=0;
                  while(pc)
                        {
                        Cell* pn=pc->next;
                        delete pc;
                        pc=pn;
                        }
                  }
            voxelsz           =0.25;
            puid        =0;
            ncells            =0;
            nprobes           =1;
            nqueries    =1;
            }
      //
      void                          GarbageCollect(int lifetime=256)
            {
            const int life=puid-lifetime;
            for(int i=0;i<cells.size();++i)
                  {
                  Cell*&      root=cells[i];
                  Cell* pp=0;
                  Cell* pc=root;
                  while(pc)
                        {
                        Cell* pn=pc->next;
                        if(pc->puid<life)
                              {
                              if(pp) pp->next=pn; else root=pn;
                              delete pc;pc=pp;--ncells;
                              }
                        pp=pc;pc=pn;
                        }
                  }
            //printf("GC[%d]: %d cells, PpQ: %f\r\n",puid,ncells,nprobes/(btScalar)nqueries);
            nqueries=1;
            nprobes=1;
            ++puid;     /* TODO: Reset puid's when int range limit is reached */ 
                        /* else setup a priority list...                                  */ 
            }
      //
      int                                 RemoveReferences(btCollisionShape* pcs)
            {
            int   refcount=0;
            for(int i=0;i<cells.size();++i)
                  {
                  Cell*&      root=cells[i];
                  Cell* pp=0;
                  Cell* pc=root;
                  while(pc)
                        {
                        Cell* pn=pc->next;
                        if(pc->pclient==pcs)
                              {
                              if(pp) pp->next=pn; else root=pn;
                              delete pc;pc=pp;++refcount;
                              }
                        pp=pc;pc=pn;
                        }
                  }
            return(refcount);
            }
      //
      btScalar                      Evaluate(   const btVector3& x,
                                                            btCollisionShape* shape,
                                                            btVector3& normal,
                                                            btScalar margin)
            {
            /* Lookup cell                */ 
            const btVector3   scx=x/voxelsz;
            const IntFrac     ix=Decompose(scx.x());
            const IntFrac     iy=Decompose(scx.y());
            const IntFrac     iz=Decompose(scx.z());
            const unsigned    h=Hash(ix.b,iy.b,iz.b,shape);
            Cell*&                  root=cells[static_cast<int>(h%cells.size())];
            Cell*             c=root;
            ++nqueries;
            while(c)
                  {
                  ++nprobes;
                  if(   (c->hash==h)      &&
                        (c->c[0]==ix.b)   &&
                        (c->c[1]==iy.b)   &&
                        (c->c[2]==iz.b)   &&
                        (c->pclient==shape))
                        { break; }
                        else
                        { c=c->next; }
                  }
            if(!c)
                  {
                  ++nprobes;        
                  ++ncells;
                  c=new Cell();
                  c->next=root;root=c;
                  c->pclient=shape;
                  c->hash=h;
                  c->c[0]=ix.b;c->c[1]=iy.b;c->c[2]=iz.b;
                  BuildCell(*c);
                  }
            c->puid=puid;
            /* Extract infos        */ 
            const int         o[]={ ix.i,iy.i,iz.i};
            const btScalar    d[]={ c->d[o[0]+0][o[1]+0][o[2]+0],
                                                c->d[o[0]+1][o[1]+0][o[2]+0],
                                                c->d[o[0]+1][o[1]+1][o[2]+0],
                                                c->d[o[0]+0][o[1]+1][o[2]+0],
                                                c->d[o[0]+0][o[1]+0][o[2]+1],
                                                c->d[o[0]+1][o[1]+0][o[2]+1],
                                                c->d[o[0]+1][o[1]+1][o[2]+1],
                                                c->d[o[0]+0][o[1]+1][o[2]+1]};
            /* Normal   */ 
            #if 1
            const btScalar    gx[]={      d[1]-d[0],d[2]-d[3],
                                                d[5]-d[4],d[6]-d[7]};
            const btScalar    gy[]={      d[3]-d[0],d[2]-d[1],
                                                d[7]-d[4],d[6]-d[5]};
            const btScalar    gz[]={      d[4]-d[0],d[5]-d[1],
                                                d[7]-d[3],d[6]-d[2]};
            normal.setX(Lerp( Lerp(gx[0],gx[1],iy.f),
                                          Lerp(gx[2],gx[3],iy.f),iz.f));
            normal.setY(Lerp( Lerp(gy[0],gy[1],ix.f),
                                          Lerp(gy[2],gy[3],ix.f),iz.f));
            normal.setZ(Lerp( Lerp(gz[0],gz[1],ix.f),
                                          Lerp(gz[2],gz[3],ix.f),iy.f));
            normal            =     normal.normalized();
            #else
            normal            =     btVector3(d[1]-d[0],d[3]-d[0],d[4]-d[0]).normalized();
            #endif
            /* Distance */ 
            const btScalar    d0=Lerp(Lerp(d[0],d[1],ix.f),
                                                Lerp(d[3],d[2],ix.f),iy.f);
            const btScalar    d1=Lerp(Lerp(d[4],d[5],ix.f),
                                                Lerp(d[7],d[6],ix.f),iy.f);
            return(Lerp(d0,d1,iz.f)-margin);
            }
      //
      void                          BuildCell(Cell& c)
            {
            const btVector3   org=btVector3(    (btScalar)c.c[0],
                                                            (btScalar)c.c[1],
                                                            (btScalar)c.c[2]) *
                                                            CELLSIZE*voxelsz;
            for(int k=0;k<=CELLSIZE;++k)
                  {
                  const btScalar    z=voxelsz*k+org.z();
                  for(int j=0;j<=CELLSIZE;++j)
                        {
                        const btScalar    y=voxelsz*j+org.y();
                        for(int i=0;i<=CELLSIZE;++i)
                              {
                              const btScalar    x=voxelsz*i+org.x();
                              c.d[i][j][k]=DistanceToShape( btVector3(x,y,z),
                                                                              c.pclient);
                              }
                        }
                  }
            }
      //
      static inline btScalar  DistanceToShape(const btVector3& x,
                                                                  btCollisionShape* shape)
            {
            btTransform unit;
            unit.setIdentity();
            if(shape->isConvex())
                  {
                  btGjkEpaSolver2::sResults     res;
                  btConvexShape*                      csh=static_cast<btConvexShape*>(shape);
                  return(btGjkEpaSolver2::SignedDistance(x,0,csh,unit,res));
                  }
            return(0);
            }
      //
      static inline IntFrac   Decompose(btScalar x)
            {
            /* That one need a lot of improvements... */
            /* Remove test, faster floor...                       */ 
            IntFrac                 r;
            x/=CELLSIZE;
            const int         o=x<0?(int)(-x+1):0;
            x+=o;r.b=(int)x;
            const btScalar    k=(x-r.b)*CELLSIZE;
            r.i=(int)k;r.f=k-r.i;r.b-=o;
            return(r);
            }
      //
      static inline btScalar  Lerp(btScalar a,btScalar b,btScalar t)
            {
            return(a+(b-a)*t);
            }

      

      //
      static inline unsigned int    Hash(int x,int y,int z,btCollisionShape* shape)
            {
            struct btS
            { 
                  int x,y,z;
                  void* p;
            };

            btS myset;
            
            myset.x=x;myset.y=y;myset.z=z;myset.p=shape;
            const void* ptr = &myset;

            unsigned int result = HsiehHash<sizeof(btS)/4> (ptr);
            

            return result;
            }
};
      

#endif

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