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 _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; 
        /* 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