btSparseSDF.h

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/*
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.
*/

#ifndef BT_SPARSE_SDF_H
#define BT_SPARSE_SDF_H

#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;
                const btCollisionShape* pclient;
                Cell*                           next;
        };
        //
        // Fields
        //

        btAlignedObjectArray<Cell*>             cells;  
        btScalar                                                voxelsz;
        int                                                             puid;
        int                                                             ncells;
        int                                                             m_clampCells;
        int                                                             nprobes;
        int                                                             nqueries;       

        //
        // Methods
        //

        //
        void                                    Initialize(int hashsize=2383, int clampCells = 256*1024)
        {
                //avoid a crash due to running out of memory, so clamp the maximum number of cells allocated
                //if this limit is reached, the SDF is reset (at the cost of some performance during the reset)
                m_clampCells = clampCells;
                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; 
                /* 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,
                const 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;
                        int sz = sizeof(Cell);
                        if (ncells>m_clampCells)
                        {
                                static int numResets=0;
                                numResets++;
//                              printf("numResets=%d\n",numResets);
                                Reset();
                        }

                        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,
                const btCollisionShape* shape)
        {
                btTransform     unit;
                unit.setIdentity();
                if(shape->isConvex())
                {
                        btGjkEpaSolver2::sResults       res;
                        const btConvexShape*                            csh=static_cast<const 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,const btCollisionShape* shape)
        {
                struct btS
                { 
                        int x,y,z;
                        void* p;
                };

                btS myset;

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

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


                return result;
        }
};


#endif //BT_SPARSE_SDF_H