UnrealEngineUWP/Engine/Plugins/Experimental/ProxyLODPlugin/Source/ThirdParty/DirectXMeshCode/DirectXMesh/DirectXMeshAdjacency.cpp

//-------------------------------------------------------------------------------------
// DirectXMeshAdjacency.cpp
//  
// DirectX Mesh Geometry Library - Adjacency computation
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
// PARTICULAR PURPOSE.
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// http://go.microsoft.com/fwlink/?LinkID=324981
//-------------------------------------------------------------------------------------

#include "DirectXMeshP.h"

using namespace DirectX;

namespace
{

//-------------------------------------------------------------------------------------
// Utilities
//-------------------------------------------------------------------------------------
struct vertexHashEntry
{
    XMFLOAT3            v;
    uint32_t            index;
    vertexHashEntry *   next;
};

struct edgeHashEntry
{
    uint32_t        v1;
    uint32_t        v2;
    uint32_t        vOther;
    uint32_t        face;
    edgeHashEntry * next;
};

// <algorithm> std::make_heap doesn't match D3DX10 so we use the same algorithm here
void MakeXHeap( _Out_writes_(nVerts) uint32_t *index, _In_reads_(nVerts) const XMFLOAT3* positions, size_t nVerts )
{
    for( uint32_t vert = 0; vert < nVerts; ++vert )
    {
        index[ vert ] = vert;
    }

    if(nVerts > 1)
    {
        // Create the heap
        uint32_t iulLim = uint32_t( nVerts );

        for( uint32_t vert = uint32_t( nVerts >> 1 ); --vert != -1; )
        {
            // Percolate down
            uint32_t iulI = vert;
            uint32_t iulJ = vert + vert + 1;
            uint32_t ulT = index[iulI];

            while(iulJ < iulLim)
            {
                uint32_t ulJ = index[iulJ];

                if(iulJ + 1 < iulLim)
                {
                    uint32_t ulJ1 = index[iulJ + 1];
                    if(positions[ulJ1].x <= positions[ulJ].x)
                    {
                        iulJ++;
                        ulJ = ulJ1;
                    }
                }

                if(positions[ulJ].x > positions[ulT].x)
                    break;

                index[iulI] = index[iulJ];
                iulI = iulJ;
                iulJ += iulJ + 1;
            }

            index[iulI] = ulT;
        }

        // Sort the heap
        while(--iulLim != -1)
        {
            uint32_t ulT = index[iulLim];
            index[iulLim] = index[0];

            // Percolate down
            uint32_t iulI = 0;
            uint32_t iulJ = 1;

            while(iulJ < iulLim)
            {
                uint32_t ulJ = index[iulJ];

                if(iulJ + 1 < iulLim)
                {
                    uint32_t ulJ1 = index[iulJ + 1];
                    if(positions[ulJ1].x <= positions[ulJ].x)
                    {
                        iulJ++;
                        ulJ = ulJ1;
                    }
                }

                if(positions[ulJ].x > positions[ulT].x)
                    break;

                index[iulI] = index[iulJ];
                iulI = iulJ;
                iulJ += iulJ + 1;
            }

            assert( iulI < nVerts );
            _Analysis_assume_( iulI < nVerts );
            index[iulI] = ulT;
        }
    }
}


//-------------------------------------------------------------------------------------
// PointRep computation
//-------------------------------------------------------------------------------------
template<class index_t>
HRESULT GeneratePointReps( _In_reads_(nFaces*3) const index_t* indices, size_t nFaces,
                           _In_reads_(nVerts) const XMFLOAT3* positions, size_t nVerts, 
                           float epsilon,
                           _Out_writes_(nVerts) uint32_t* pointRep )
{
    std::unique_ptr<uint32_t[]> temp( new (std::nothrow) uint32_t[ nVerts + nFaces * 3 ] );
    if ( !temp )
        return E_OUTOFMEMORY;

    uint32_t* vertexToCorner = temp.get();
    uint32_t* vertexCornerList = temp.get() + nVerts;

    memset( vertexToCorner, 0xff, sizeof(uint32_t) * nVerts );
    memset( vertexCornerList, 0xff, sizeof(uint32_t) * nFaces * 3 );

    // build initial lists and validate indices
    for( size_t j = 0; j < (nFaces * 3); ++j )
    {
        index_t k = indices[ j ];
        if ( k == index_t(-1) )
            continue;

        if ( k >= nVerts )
            return E_UNEXPECTED;

        vertexCornerList[ j ] = vertexToCorner[ k ];
        vertexToCorner[ k ] = uint32_t( j );
    }

    if ( epsilon == 0.f )
    {
        size_t hashSize = nVerts / 3;

        std::unique_ptr<vertexHashEntry*[]> hashTable( new (std::nothrow) vertexHashEntry*[ hashSize ] );
        if ( !hashTable )
            return E_OUTOFMEMORY;

        memset( hashTable.get(), 0, sizeof(vertexHashEntry*) * hashSize );

        std::unique_ptr<vertexHashEntry[]> hashEntries( new (std::nothrow) vertexHashEntry[ nVerts ] );
        if ( !hashEntries )
            return E_OUTOFMEMORY;

        uint32_t freeEntry = 0;

        for( size_t vert = 0; vert < nVerts; ++vert )
        {
            uint32_t hashKey = ( *reinterpret_cast<const uint32_t*>( &positions[ vert ].x )
                                 + *reinterpret_cast<const uint32_t*>( &positions[ vert ].y )
                                 + *reinterpret_cast<const uint32_t*>( &positions[ vert ].z ) ) % hashSize;

            uint32_t found = UNUSED32;

            for( auto current = hashTable[ hashKey ]; current != 0; current = current->next )
            {
                if ( current->v.x == positions[ vert ].x
                     && current->v.y == positions[ vert ].y
                     && current->v.z == positions[ vert ].z )
                {
                    uint32_t head = vertexToCorner[ vert ];

                    bool ispresent = false;

                    while ( head != UNUSED32 )
                    {
                        uint32_t face = head / 3;
                        assert( face < nFaces );
                        _Analysis_assume_( face < nFaces );

                        assert( ( indices[ face*3 ] == vert ) || ( indices[ face*3 + 1 ] == vert ) || ( indices[ face*3 + 2 ] == vert ) );

                        if ( ( indices[ face*3 ] == current->index ) || ( indices[ face*3 + 1 ] == current->index ) || ( indices[ face*3 + 2 ] == current->index ) )
                        {
                            ispresent = true;
                            break;
                        }

                        head = vertexCornerList[ head ];
                    }

                    if ( !ispresent )
                    {
                        found = current->index;
                        break;
                    }
                }
            }

            if ( found != UNUSED32 )
            {
                pointRep[ vert ] = found;
            }
            else
            {
                assert( freeEntry < nVerts );
                _Analysis_assume_( freeEntry < nVerts );

                auto newEntry = &hashEntries[ freeEntry ];
                ++freeEntry;

                newEntry->v = positions[ vert ];
                newEntry->index = uint32_t( vert );
                newEntry->next = hashTable[ hashKey ];
                hashTable[ hashKey ] = newEntry;

                pointRep[ vert ] = uint32_t( vert );
            }
        }

        assert( freeEntry <= nVerts );

        return S_OK;
    }
    else
    {
        std::unique_ptr<uint32_t[]> xorder( new uint32_t[ nVerts ] );

        // order in descending order
        MakeXHeap( xorder.get(), positions, nVerts);

        memset( pointRep, 0xff, sizeof(uint32_t) * nVerts );

        XMVECTOR vepsilon = XMVectorReplicate( epsilon * epsilon );

        uint32_t head = 0;
        uint32_t tail = 0;

        while ( tail < nVerts )
        {
            // move head until just out of epsilon
            while ( ( head < nVerts )
                    && ( ( positions[ tail ].x - positions[ head ].x ) <= epsilon ) )
            {
                ++head;
            }

            // check new tail against all points up to the head
            uint32_t tailIndex = xorder[ tail ];
            assert( tailIndex < nVerts );
            _Analysis_assume_( tailIndex < nVerts );
            if ( pointRep[ tailIndex ] == UNUSED32 )
            {
                pointRep[ tailIndex ] = tailIndex;

                XMVECTOR outer = XMLoadFloat3( &positions[ tailIndex ] );

                for( size_t current = tail + 1; current < head; ++current )
                {
                    uint32_t curIndex = xorder[ current ];
                    assert( curIndex < nVerts );
                    _Analysis_assume_( curIndex < nVerts );

                    // if the point is already assigned, ignore it
                    if ( pointRep[ curIndex ] == UNUSED32 )
                    {
                        XMVECTOR inner = XMLoadFloat3( &positions[ curIndex ] );

                        XMVECTOR diff = XMVector3LengthSq( inner - outer );
             
                        if ( XMVector2Less( diff, vepsilon ) )
                        {
                            uint32_t headvc = vertexToCorner[ tailIndex ];

                            bool ispresent = false;

                            while ( headvc != UNUSED32 )
                            {
                                uint32_t face = headvc / 3;
                                assert( face < nFaces );
                                _Analysis_assume_( face < nFaces );

                                assert( ( indices[ face*3 ] == tailIndex ) || ( indices[ face*3 + 1 ] == tailIndex ) || ( indices[ face*3 + 2 ] == tailIndex ) );

                                if ( ( indices[ face*3 ] == curIndex ) || ( indices[ face*3 + 1 ] == curIndex ) || ( indices[ face*3 + 2 ] == curIndex ) )
                                {
                                    ispresent = true;
                                    break;
                                }

                                headvc = vertexCornerList[ headvc ];
                            }

                            if ( !ispresent )
                            {
                                pointRep[ curIndex ] = tailIndex;
                            }
                        }
                    }
                }
            }

            ++tail;
        }

        return S_OK;
    }
}


//-------------------------------------------------------------------------------------
// Convert PointRep to Adjacency
//-------------------------------------------------------------------------------------
template<class index_t>
HRESULT _ConvertPointRepsToAdjacency( _In_reads_(nFaces*3) const index_t* indices, size_t nFaces,
                                      _In_reads_(nVerts) const XMFLOAT3* positions, size_t nVerts, 
                                      _In_reads_(nVerts) const uint32_t* pointRep,
                                      _Out_writes_(nFaces*3) uint32_t* adjacency )
{
    size_t hashSize = nVerts / 3;

    std::unique_ptr<edgeHashEntry*[]> hashTable( new (std::nothrow) edgeHashEntry*[ hashSize ] );
    if ( !hashTable )
        return E_OUTOFMEMORY;

    memset( hashTable.get(), 0, sizeof(edgeHashEntry*) * hashSize );

    std::unique_ptr<edgeHashEntry[]> hashEntries( new (std::nothrow) edgeHashEntry[ 3 * nFaces ] );
    if ( !hashEntries )
        return E_OUTOFMEMORY;

    uint32_t freeEntry = 0;

    // add face edges to hash table and validate indices
    for( size_t face = 0; face < nFaces; ++face )
    {
        index_t i0 = indices[ face*3 ];
        index_t i1 = indices[ face*3 + 1 ];
        index_t i2 = indices[ face*3 + 2 ];

        if ( i0 == index_t(-1)
             || i1 == index_t(-1)
             || i2 == index_t(-1) )
            continue;

        if ( i0 >= nVerts
             || i1 >= nVerts
             || i2 >= nVerts )
            return E_UNEXPECTED;

        uint32_t v1 = pointRep[ i0 ];
        uint32_t v2 = pointRep[ i1 ];
        uint32_t v3 = pointRep[ i2 ];

        // filter out degenerate triangles
        if ( v1 == v2 || v1 == v3 || v2 == v3 )
            continue;

        for( uint32_t point = 0; point < 3; ++point )
        {
            uint32_t va = pointRep[ indices[ face * 3 + point ] ];
            uint32_t vb = pointRep[ indices[ face * 3 + ( ( point + 1 ) % 3 ) ] ];
            uint32_t vOther = pointRep[ indices[ face * 3 + ( ( point + 2) % 3 ) ] ];

            uint32_t hashKey = va % hashSize;

            assert( freeEntry < (3 * nFaces) );
            _Analysis_assume_( freeEntry < (3 * nFaces) );

            auto newEntry = &hashEntries[ freeEntry ];
            ++freeEntry;

            newEntry->v1 = va;
            newEntry->v2 = vb;
            newEntry->vOther = vOther;
            newEntry->face = uint32_t( face );
            newEntry->next = hashTable[ hashKey ];
            hashTable[ hashKey ] = newEntry;
        }
    }

    assert( freeEntry <= ( 3 * nFaces ) );

    memset( adjacency, 0xff, sizeof(uint32_t) * nFaces * 3 );

    for( size_t face = 0; face < nFaces; ++face )
    {
        index_t i0 = indices[ face*3 ];
        index_t i1 = indices[ face*3 + 1 ];
        index_t i2 = indices[ face*3 + 2 ];

        // filter out unused triangles
        if ( i0 == index_t(-1)
             || i1 == index_t(-1)
             || i2 == index_t(-1) )
            continue;

        assert( i0 < nVerts );
        assert( i1 < nVerts );
        assert( i2 < nVerts );

        _Analysis_assume_( i0 < nVerts );
        _Analysis_assume_( i1 < nVerts );
        _Analysis_assume_( i2 < nVerts );

        uint32_t v1 = pointRep[ i0 ];
        uint32_t v2 = pointRep[ i1 ];
        uint32_t v3 = pointRep[ i2 ];

        // filter out degenerate triangles
        if ( v1 == v2 || v1 == v3 || v2 == v3 )
            continue;

        for( uint32_t point = 0; point < 3; ++point )
        {
            if ( adjacency[ face * 3 + point ] != UNUSED32 )
                continue;

            // see if edge already entered, if not then enter it
            uint32_t va = pointRep[ indices[ face * 3 + ( ( point + 1 ) % 3 ) ] ];
            uint32_t vb = pointRep[ indices[ face * 3 + point ] ];
            uint32_t vOther = pointRep[ indices[ face * 3 + ( ( point + 2) % 3 ) ] ];

            uint32_t hashKey = va % hashSize;

            edgeHashEntry* current = hashTable[ hashKey ];
            edgeHashEntry* prev = nullptr;

            uint32_t foundFace = UNUSED32;

            while( current != 0 )
            {
                if ( ( current->v2 == vb ) && ( current->v1 == va ) )
                {
                    foundFace = current->face;
                    break;
                }

                prev = current;
                current = current->next;
            }

            edgeHashEntry* found = current;
            edgeHashEntry* foundPrev = prev;

            float bestDiff = -2.f;

            // Scan for additional matches
            if ( current != 0 )
            {
                prev = current;
                current = current->next;

                // find 'better' match
                while ( current != 0 )
                {
                    if ( ( current->v2 == vb ) && ( current->v1 == va ) )
                    {
                        XMVECTOR pB1 = XMLoadFloat3( &positions[ vb ] );
                        XMVECTOR pB2 = XMLoadFloat3( &positions[ va ] );
                        XMVECTOR pB3 = XMLoadFloat3( &positions[ vOther ] );

                        XMVECTOR v12 = pB1 - pB2;
                        XMVECTOR v13 = pB1 - pB3;

                        XMVECTOR bnormal = XMVector3Normalize( XMVector3Cross( v12, v13 ) );

                        if ( bestDiff == -2.f )
                        {
                            XMVECTOR pA1 = XMLoadFloat3( &positions[ found->v1 ] );
                            XMVECTOR pA2 = XMLoadFloat3( &positions[ found->v2 ] );
                            XMVECTOR pA3 = XMLoadFloat3( &positions[ found->vOther ] );

                            v12 = pA1 - pA2;
                            v13 = pA1 - pA3;

                            XMVECTOR anormal = XMVector3Normalize( XMVector3Cross( v12, v13 ) );

                            bestDiff = XMVectorGetX( XMVector3Dot( anormal, bnormal ) );
                        }

                        XMVECTOR pA1 = XMLoadFloat3( &positions[ current->v1 ] );
                        XMVECTOR pA2 = XMLoadFloat3( &positions[ current->v2 ] );
                        XMVECTOR pA3 = XMLoadFloat3( &positions[ current->vOther ] );

                        v12 = pA1 - pA2;
                        v13 = pA1 - pA3;

                        XMVECTOR anormal = XMVector3Normalize( XMVector3Cross( v12, v13 ) );

                        float diff = XMVectorGetX( XMVector3Dot( anormal, bnormal ) );

                        // if face normals are closer, use new match
                        if ( diff > bestDiff )
                        {
                            found = current;
                            foundPrev = prev;
                            foundFace = current->face;
                            bestDiff = diff;
                        }
                    }

                    prev = current;
                    current = current->next;
                }
            }

            if ( foundFace != UNUSED32 )
            {
                assert( found != 0 );

                // remove found face from hash table
                if ( foundPrev != 0 )
                {
                    foundPrev->next = found->next;
                }
                else
                {
                    hashTable[ hashKey ] = found->next;
                }

                assert( adjacency[ face * 3 + point ] == UNUSED32 );
                adjacency[ face * 3 + point ] = foundFace;

                // Check for other edge
                uint32_t hashKey2 = vb % hashSize;

                current = hashTable[ hashKey2 ];
                prev = nullptr;

                while( current != 0 )
                {
                    if ( ( current->face == uint32_t( face ) ) && ( current->v2 == va ) && ( current->v1 == vb ) )
                    {
                        // trim edge from hash table
                        if ( prev != 0 )
                        {
                            prev->next = current->next;
                        }
                        else
                        {
                            hashTable[ hashKey2 ] = current->next;
                        }
                        break;
                    }

                    prev = current;
                    current = current->next;
                }

                // mark neighbor to point back
                bool linked = false;

                for( uint32_t point2 = 0; point2 < point; ++point2 )
                {
                    if ( foundFace == adjacency[ face * 3 + point2 ] )
                    {
                        linked = true;
                        adjacency[ face * 3 + point ] = UNUSED32;
                        break;
                    }
                }

                if ( !linked )
                {
                    uint32_t point2 = 0;
                    for( ; point2 < 3; ++point2 )
                    {
                        index_t k = indices[ foundFace * 3 + point2 ];
                        if ( k == index_t(-1) )
                            continue;

                        assert( k < nVerts );
                        _Analysis_assume_( k < nVerts );

                        if ( pointRep[ k ] == va )
                            break;
                    }

                    if ( point2 < 3 )
                    {
#ifndef NDEBUG
                        uint32_t testPoint = indices[ foundFace * 3 + ( ( point2 + 1 ) % 3 ) ];
                        testPoint = pointRep[ testPoint ];
                        assert( testPoint == vb );
#endif
                        assert( adjacency[ foundFace * 3 + point2 ] == UNUSED32 );

                        // update neighbor to point back to this face match edge
                        adjacency[ foundFace * 3 + point2 ] = uint32_t( face );
                    }
                }
            }
        }
    }

    return S_OK;
}

};

namespace DirectX
{

//=====================================================================================
// Entry-points
//=====================================================================================

//-------------------------------------------------------------------------------------
_Use_decl_annotations_
HRESULT GenerateAdjacencyAndPointReps( const uint16_t* indices, size_t nFaces,
                                       const XMFLOAT3* positions, size_t nVerts,
                                       float epsilon,
                                       uint32_t* pointRep, uint32_t* adjacency )
{
    if ( !indices || !nFaces || !positions || !nVerts  )
        return E_INVALIDARG;

    if ( !pointRep && !adjacency )
        return E_INVALIDARG;

    if ( nVerts >= UINT16_MAX )
        return E_INVALIDARG;

    if ( ( uint64_t(nFaces) * 3 ) >= UINT32_MAX )
        return HRESULT_FROM_WIN32( ERROR_ARITHMETIC_OVERFLOW );

    std::unique_ptr<uint32_t[]> temp;
    if ( !pointRep )
    {
        temp.reset( new (std::nothrow) uint32_t[ nVerts ] );
        if ( !temp )
            return E_OUTOFMEMORY;

        pointRep = temp.get();
    }

    HRESULT hr = GeneratePointReps<uint16_t>( indices, nFaces, positions, nVerts, epsilon, pointRep );
    if ( FAILED(hr) )
        return hr;

    if ( !adjacency )
        return S_OK;

    return _ConvertPointRepsToAdjacency<uint16_t>( indices, nFaces, positions, nVerts, pointRep, adjacency );
}

_Use_decl_annotations_
HRESULT GenerateAdjacencyAndPointReps( const uint32_t* indices, size_t nFaces,
                                       const XMFLOAT3* positions, size_t nVerts,
                                       float epsilon,
                                       uint32_t* pointRep, uint32_t* adjacency )
{
    if ( !indices || !nFaces || !positions || !nVerts  )
        return E_INVALIDARG;

    if ( !pointRep && !adjacency )
        return E_INVALIDARG;

    if ( nVerts >= UINT32_MAX )
        return E_INVALIDARG;

    if ( ( uint64_t(nFaces) * 3 ) >= UINT32_MAX )
        return HRESULT_FROM_WIN32( ERROR_ARITHMETIC_OVERFLOW );
    
    std::unique_ptr<uint32_t[]> temp;
    if ( !pointRep )
    {
        temp.reset( new (std::nothrow) uint32_t[ nVerts ] );
        if ( !temp )
            return E_OUTOFMEMORY;

        pointRep = temp.get();
    }

    HRESULT hr = GeneratePointReps<uint32_t>( indices, nFaces, positions, nVerts, epsilon, pointRep );
    if ( FAILED(hr) )
        return hr;

    if ( !adjacency )
        return S_OK;

    return _ConvertPointRepsToAdjacency<uint32_t>( indices, nFaces, positions, nVerts, pointRep, adjacency );
}


//-------------------------------------------------------------------------------------
_Use_decl_annotations_
HRESULT ConvertPointRepsToAdjacency( const uint16_t* indices, size_t nFaces,
                                     const XMFLOAT3* positions, size_t nVerts, 
                                     const uint32_t* pointRep,
                                     uint32_t* adjacency )
{
    if ( !indices || !nFaces || !positions || !nVerts || !adjacency )
        return E_INVALIDARG;

    if ( nVerts >= UINT16_MAX )
        return E_INVALIDARG;

    if ( ( uint64_t(nFaces) * 3 ) >= UINT32_MAX )
        return HRESULT_FROM_WIN32( ERROR_ARITHMETIC_OVERFLOW );

    std::unique_ptr<uint32_t[]> temp;
    if ( !pointRep )
    {
        temp.reset( new (std::nothrow) uint32_t[ nVerts ] );
        if ( !temp )
            return E_OUTOFMEMORY;

        for( size_t j = 0; j < nVerts; ++j )
        {
            temp[ j ] = uint32_t( j );
        }

        pointRep = temp.get();
    }

    return _ConvertPointRepsToAdjacency<uint16_t>( indices, nFaces, positions, nVerts, pointRep, adjacency );
}

_Use_decl_annotations_
HRESULT ConvertPointRepsToAdjacency( const uint32_t* indices, size_t nFaces,
                                     const XMFLOAT3* positions, size_t nVerts, 
                                     const uint32_t* pointRep,
                                     uint32_t* adjacency )
{
    if ( !indices || !nFaces || !positions || !nVerts || !adjacency )
        return E_INVALIDARG;

    if ( nVerts >= UINT32_MAX )
        return E_INVALIDARG;

    if ( ( uint64_t(nFaces) * 3 ) >= UINT32_MAX )
        return HRESULT_FROM_WIN32( ERROR_ARITHMETIC_OVERFLOW );

    std::unique_ptr<uint32_t[]> temp;
    if ( !pointRep )
    {
        temp.reset( new (std::nothrow) uint32_t[ nVerts ] );
        if ( !temp )
            return E_OUTOFMEMORY;

        for( size_t j = 0; j < nVerts; ++j )
        {
            temp[ j ] = uint32_t( j );
        }

        pointRep = temp.get();
    }

    return _ConvertPointRepsToAdjacency<uint32_t>( indices, nFaces, positions, nVerts, pointRep, adjacency );
}

} // namespace