OPC_SweepAndPrune.cpp

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/*
 *      OPCODE - Optimized Collision Detection
 *      Copyright (C) 2001 Pierre Terdiman
 *      Homepage: http://www.codercorner.com/Opcode.htm
 */




// Precompiled Header
#include "Stdafx.h"

using namespace Opcode;

inline_ void Sort(udword& id0, udword& id1)
{
        if(id0>id1)     Swap(id0, id1);
}

        class Opcode::SAP_Element
        {
                public:
                inline_                                 SAP_Element()                                                                                                           {}
                inline_                                 SAP_Element(udword id, SAP_Element* next) : mID(id), mNext(next)        {}
                inline_                                 ~SAP_Element()                                                                                                          {}

                                udword                  mID;
                                SAP_Element*    mNext;
        };

        class Opcode::SAP_Box
        {
                public:
                                SAP_EndPoint*   Min[3];
                                SAP_EndPoint*   Max[3];
        };

        class Opcode::SAP_EndPoint
        {
                public:
                                float                   Value;          // Min or Max value
                                SAP_EndPoint*   Previous;       // Previous EndPoint whose Value is smaller than ours (or null)
                                SAP_EndPoint*   Next;           // Next EndPoint whose Value is greater than ours (or null)
                                udword                  Data;           // Parent box ID *2 | MinMax flag

                inline_ void                    SetData(udword box_id, BOOL is_max)                     { Data = (box_id<<1)|is_max;    }
                inline_ BOOL                    IsMax()                                                         const   { return Data & 1;                              }
                inline_ udword                  GetBoxID()                                                      const   { return Data>>1;                               }

                inline_ void InsertAfter(SAP_EndPoint* element)
                {
                        if(this!=element && this!=element->Next)
                        {
                                // Remove
                                if(Previous)    Previous->Next = Next;
                                if(Next)                Next->Previous = Previous;

                                // Insert
                                Next = element->Next;
                                if(Next)        Next->Previous = this;

                                element->Next = this;
                                Previous = element;
                        }
                }

                inline_ void InsertBefore(SAP_EndPoint* element)
                {
                        if(this!=element && this!=element->Previous)
                        {
                                // Remove
                                if(Previous)    Previous->Next = Next;
                                if(Next)                Next->Previous = Previous;

                                // Insert
                                Previous = element->Previous;
                                element->Previous = this;

                                Next = element;
                                if(Previous)    Previous->Next = this;
                        }
                }
        };












SAP_PairData::SAP_PairData() :
        mNbElements             (0),
        mNbUsedElements (0),
        mElementPool    (null),
        mFirstFree              (null),
        mNbObjects              (0),
        mArray                  (null)
{
}



SAP_PairData::~SAP_PairData()
{
        Release();
}

void SAP_PairData::Release()
{
        mNbElements             = 0;
        mNbUsedElements = 0;
        mNbObjects              = 0;
        DELETEARRAY(mElementPool);
        DELETEARRAY(mArray);
}



bool SAP_PairData::Init(udword nb_objects)
{
        // Make sure everything has been released
        Release();
        if(!nb_objects) return false;

        mArray = new SAP_Element*[nb_objects];
        CHECKALLOC(mArray);
        ZeroMemory(mArray, nb_objects*sizeof(SAP_Element*));
        mNbObjects = nb_objects;

        return true;
}



inline_ void Remap(SAP_Element*& element, udword delta)
{
        if(element)     element = (SAP_Element*)(udword(element) + delta);
}



SAP_Element* SAP_PairData::GetFreeElem(udword id, SAP_Element* next, udword* remap)
{
        if(remap)       *remap = 0;

        SAP_Element* FreeElem;
        if(mFirstFree)
        {
                // Recycle
                FreeElem = mFirstFree;
                mFirstFree = mFirstFree->mNext; // First free = next free (or null)
        }
        else
        {
                if(mNbUsedElements==mNbElements)
                {
                        // Resize
                        mNbElements = mNbElements ? (mNbElements<<1) : 2;

                        SAP_Element* NewElems = new SAP_Element[mNbElements];

                        if(mNbUsedElements)     CopyMemory(NewElems, mElementPool, mNbUsedElements*sizeof(SAP_Element));

                        // Remap everything
                        {
                                udword Delta = udword(NewElems) - udword(mElementPool);

                                for(udword i=0;i<mNbUsedElements;i++)   Remap(NewElems[i].mNext, Delta);
                                for(udword i=0;i<mNbObjects;i++)                Remap(mArray[i], Delta);

                                Remap(mFirstFree, Delta);
                                Remap(next, Delta);

                                if(remap)       *remap = Delta;
                        }

                        DELETEARRAY(mElementPool);
                        mElementPool = NewElems;
                }

                FreeElem = &mElementPool[mNbUsedElements++];
        }

        FreeElem->mID = id;
        FreeElem->mNext = next;

        return FreeElem;
}



inline_ void SAP_PairData::FreeElem(SAP_Element* elem)
{
        elem->mNext = mFirstFree;       // Next free
        mFirstFree = elem;
}

// Add a pair to the set.
void SAP_PairData::AddPair(udword id1, udword id2)
{
        // Order the ids
        Sort(id1, id2);

        ASSERT(id1<mNbObjects);
        if(id1>=mNbObjects)     return;

        // Select the right list from "mArray".
        SAP_Element* Current = mArray[id1];

        if(!Current)
        {
                // Empty slot => create new element
                mArray[id1] = GetFreeElem(id2, null);
        }
        else if(Current->mID>id2)
        {
                // The list is not empty but all elements are greater than id2 => insert id2 in the front.
                mArray[id1]     = GetFreeElem(id2, mArray[id1]);
        }
        else
        {
                // Else find the correct location in the sorted list (ascending order) and insert id2 there.
                while(Current->mNext)
                {
                        if(Current->mNext->mID > id2)   break;

                        Current = Current->mNext;
                }

                if(Current->mID==id2)   return; // The pair already exists
                
//              Current->mNext = GetFreeElem(id2, Current->mNext);
                udword Delta;
                SAP_Element* E = GetFreeElem(id2, Current->mNext, &Delta);
                if(Delta)       Remap(Current, Delta);
                Current->mNext = E;
        }
}

// Delete a pair from the set.
void SAP_PairData::RemovePair(udword id1, udword id2)
{
        // Order the ids.
        Sort(id1, id2);

        // Exit if the pair doesn't exist in the set
        if(id1>=mNbObjects)     return;

        // Otherwise, select the correct list.
        SAP_Element* Current = mArray[id1];

        // If this list is empty, the pair doesn't exist.
        if(!Current) return;

        // Otherwise, if id2 is the first element, delete it.
        if(Current->mID==id2)
        {
                mArray[id1] = Current->mNext;
                FreeElem(Current);
        }
        else
        {
                // If id2 is not the first element, start traversing the sorted list.
                while(Current->mNext)
                {
                        // If we have moved too far away without hitting id2, then the pair doesn't exist
                        if(Current->mNext->mID > id2)   return;

                        // Otherwise, delete id2.
                        if(Current->mNext->mID == id2)
                        {
                                SAP_Element* Temp = Current->mNext;
                                Current->mNext = Temp->mNext;
                                FreeElem(Temp);
                                return;
                        }
                        Current = Current->mNext;
                }
        }
}

void SAP_PairData::DumpPairs(Pairs& pairs) const
{
        // ### Ugly and slow
        for(udword i=0;i<mNbObjects;i++)
        {
                SAP_Element* Current = mArray[i];
                while(Current)
                {
                        ASSERT(Current->mID<mNbObjects);

                        pairs.AddPair(i, Current->mID);
                        Current = Current->mNext;
                }
        }
}

void SAP_PairData::DumpPairs(PairCallback callback, void* user_data) const
{
        if(!callback)   return;

        // ### Ugly and slow
        for(udword i=0;i<mNbObjects;i++)
        {
                SAP_Element* Current = mArray[i];
                while(Current)
                {
                        ASSERT(Current->mID<mNbObjects);

                        if(!(callback)(i, Current->mID, user_data))     return;
                        Current = Current->mNext;
                }
        }
}






























SweepAndPrune::SweepAndPrune()
{
}



SweepAndPrune::~SweepAndPrune()
{
}

void SweepAndPrune::GetPairs(Pairs& pairs) const
{
        mPairs.DumpPairs(pairs);
}

void SweepAndPrune::GetPairs(PairCallback callback, void* user_data) const
{
        mPairs.DumpPairs(callback, user_data);
}

bool SweepAndPrune::Init(udword nb_objects, const AABB** boxes)
{
        // 1) Create sorted lists
        mNbObjects = nb_objects;

        mBoxes = new SAP_Box[nb_objects];
//      for(udword i=0;i<nb_objects;i++)        mBoxes[i].Box = *boxes[i];

        float* Data = new float[nb_objects*2];

        for(udword Axis=0;Axis<3;Axis++)
        {
                mList[Axis] = new SAP_EndPoint[nb_objects*2];

                for(udword i=0;i<nb_objects;i++)
                {
                        Data[i*2+0] = boxes[i]->GetMin(Axis);
                        Data[i*2+1] = boxes[i]->GetMax(Axis);
                }
                RadixSort RS;
                const udword* Sorted = RS.Sort(Data, nb_objects*2).GetRanks();

                SAP_EndPoint* PreviousEndPoint = null;

                for(udword i=0;i<nb_objects*2;i++)
                {
                        udword SortedIndex      = *Sorted++;
                        float SortedCoord       = Data[SortedIndex];
                        udword BoxIndex         = SortedIndex>>1;

                        ASSERT(BoxIndex<nb_objects);

                        SAP_EndPoint* CurrentEndPoint = &mList[Axis][SortedIndex];
                        CurrentEndPoint->Value          = SortedCoord;
//                      CurrentEndPoint->IsMax          = SortedIndex&1;                // ### could be implicit ?
//                      CurrentEndPoint->ID                     = BoxIndex;                             // ### could be implicit ?
                        CurrentEndPoint->SetData(BoxIndex, SortedIndex&1);      // ### could be implicit ?
                        CurrentEndPoint->Previous       = PreviousEndPoint;
                        CurrentEndPoint->Next           = null;
                        if(PreviousEndPoint)    PreviousEndPoint->Next = CurrentEndPoint;

                        if(CurrentEndPoint->IsMax())    mBoxes[BoxIndex].Max[Axis] = CurrentEndPoint;
                        else                                                    mBoxes[BoxIndex].Min[Axis] = CurrentEndPoint;

                        PreviousEndPoint = CurrentEndPoint;
                }
        }

        DELETEARRAY(Data);

        CheckListsIntegrity();

        // 2) Quickly find starting pairs

        mPairs.Init(nb_objects);

        {
                Pairs P;
                CompleteBoxPruning(nb_objects, boxes, P, Axes(AXES_XZY));
                for(udword i=0;i<P.GetNbPairs();i++)
                {
                        const Pair* PP = P.GetPair(i);

                        udword id0 = PP->id0;
                        udword id1 = PP->id1;

                        if(id0!=id1 && boxes[id0]->Intersect(*boxes[id1]))
                        {
                                mPairs.AddPair(id0, id1);
                        }
                        else ASSERT(0);
                }
        }

        return true;
}

bool SweepAndPrune::CheckListsIntegrity()
{
        for(udword Axis=0;Axis<3;Axis++)
        {
                // Find list head
                SAP_EndPoint* Current = mList[Axis];
                while(Current->Previous)        Current = Current->Previous;

                udword Nb = 0;

                SAP_EndPoint* Previous = null;
                while(Current)
                {
                        Nb++;

                        if(Previous)
                        {
                                ASSERT(Previous->Value <= Current->Value);
                                if(Previous->Value > Current->Value)    return false;
                        }

                        ASSERT(Current->Previous==Previous);
                        if(Current->Previous!=Previous) return false;

                        Previous = Current;
                        Current = Current->Next;
                }

                ASSERT(Nb==mNbObjects*2);
        }
        return true;
}

inline_ BOOL Intersect(const AABB& a, const SAP_Box& b)
{
        if(b.Max[0]->Value < a.GetMin(0) || a.GetMax(0) < b.Min[0]->Value
        || b.Max[1]->Value < a.GetMin(1) || a.GetMax(1) < b.Min[1]->Value
        || b.Max[2]->Value < a.GetMin(2) || a.GetMax(2) < b.Min[2]->Value)      return FALSE;

        return TRUE;
}



bool SweepAndPrune::UpdateObject(udword i, const AABB& box)
{
        for(udword Axis=0;Axis<3;Axis++)
        {
//              udword Base = (udword)&mList[Axis][0];

                // Update min
                {
                        SAP_EndPoint* const CurrentMin = mBoxes[i].Min[Axis];
                        ASSERT(!CurrentMin->IsMax());

                        const float Limit = box.GetMin(Axis);
                        if(Limit == CurrentMin->Value)
                        {
                        }
                        else if(Limit < CurrentMin->Value)
                        {
                                CurrentMin->Value = Limit;

                                // Min is moving left:
                                SAP_EndPoint* NewPos = CurrentMin;
                                ASSERT(NewPos);

                                SAP_EndPoint* tmp;
                                while((tmp = NewPos->Previous) && tmp->Value > Limit)
                                {
                                        NewPos = tmp;

                                        if(NewPos->IsMax())
                                        {
                                                // Our min passed a max => start overlap
                                                //udword SortedIndex = (udword(CurrentMin) - Base)/sizeof(NS_EndPoint);
                                                const udword id0 = CurrentMin->GetBoxID();
                                                const udword id1 = NewPos->GetBoxID();

                                                if(id0!=id1 && Intersect(box, mBoxes[id1]))     mPairs.AddPair(id0, id1);
                                        }
                                }

                                CurrentMin->InsertBefore(NewPos);
                        }
                        else// if(Limit > CurrentMin->Value)
                        {
                                CurrentMin->Value = Limit;

                                // Min is moving right:
                                SAP_EndPoint* NewPos = CurrentMin;
                                ASSERT(NewPos);

                                SAP_EndPoint* tmp;
                                while((tmp = NewPos->Next) && tmp->Value < Limit)
                                {
                                        NewPos = tmp;

                                        if(NewPos->IsMax())
                                        {
                                                // Our min passed a max => stop overlap
                                                const udword id0 = CurrentMin->GetBoxID();
                                                const udword id1 = NewPos->GetBoxID();

                                                if(id0!=id1)    mPairs.RemovePair(id0, id1);
                                        }
                                }

                                CurrentMin->InsertAfter(NewPos);
                        }
                }

                // Update max
                {
                        SAP_EndPoint* const CurrentMax = mBoxes[i].Max[Axis];
                        ASSERT(CurrentMax->IsMax());

                        const float Limit = box.GetMax(Axis);
                        if(Limit == CurrentMax->Value)
                        {
                        }
                        else if(Limit > CurrentMax->Value)
                        {
                                CurrentMax->Value = Limit;

                                // Max is moving right:
                                SAP_EndPoint* NewPos = CurrentMax;
                                ASSERT(NewPos);

                                SAP_EndPoint* tmp;
                                while((tmp = NewPos->Next) && tmp->Value < Limit)
                                {
                                        NewPos = tmp;

                                        if(!NewPos->IsMax())
                                        {
                                                // Our max passed a min => start overlap
                                                const udword id0 = CurrentMax->GetBoxID();
                                                const udword id1 = NewPos->GetBoxID();

                                                if(id0!=id1 && Intersect(box, mBoxes[id1]))     mPairs.AddPair(id0, id1);
                                        }
                                }

                                CurrentMax->InsertAfter(NewPos);
                        }
                        else// if(Limit < CurrentMax->Value)
                        {
                                CurrentMax->Value = Limit;

                                // Max is moving left:
                                SAP_EndPoint* NewPos = CurrentMax;
                                ASSERT(NewPos);

                                SAP_EndPoint* tmp;
                                while((tmp = NewPos->Previous) && tmp->Value > Limit)
                                {
                                        NewPos = tmp;

                                        if(!NewPos->IsMax())
                                        {
                                                // Our max passed a min => stop overlap
                                                const udword id0 = CurrentMax->GetBoxID();
                                                const udword id1 = NewPos->GetBoxID();

                                                if(id0!=id1)    mPairs.RemovePair(id0, id1);
                                        }
                                }

                                CurrentMax->InsertBefore(NewPos);
                        }
                }
        }

        return true;
}