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/** @file Implementation of the helper class to quickly find

vertices close to a given position. Special implementation for

the 3ds loader handling smooth groups correctly  */

#include <assimp/SGSpatialSort.h>

using namespace Assimp;

// ------------------------------------------------------------------------------------------------

SGSpatialSort::SGSpatialSort() {

    // define the reference plane. We choose some arbitrary vector away from all basic axes

    // in the hope that no model spreads all its vertices along this plane.

    mPlaneNormal.Set( 0.8523f, 0.34321f, 0.5736f);

    mPlaneNormal.Normalize();

}

// ------------------------------------------------------------------------------------------------

void SGSpatialSort::Add(const aiVector3D& vPosition, unsigned int index,

    unsigned int smoothingGroup)

{

    // store position by index and distance

    float distance = vPosition * mPlaneNormal;

    mPositions.emplace_back( index, vPosition,

        distance, smoothingGroup);

}

// ------------------------------------------------------------------------------------------------

void SGSpatialSort::Prepare()

{

    // now sort the array ascending by distance.

    std::sort( this->mPositions.begin(), this->mPositions.end());

}

// ------------------------------------------------------------------------------------------------

// Returns an iterator for all positions close to the given position.

void SGSpatialSort::FindPositions( const aiVector3D& pPosition,

    uint32_t pSG,

    float pRadius,

    std::vector<unsigned int>& poResults,

    bool exactMatch /*= false*/) const

{

    float dist = pPosition * mPlaneNormal;

    float minDist = dist - pRadius, maxDist = dist + pRadius;

    // clear the array

    poResults.clear();

    // quick check for positions outside the range

    if( mPositions.empty() )

        return;

    if( maxDist < mPositions.front().mDistance)

        return;

    if( minDist > mPositions.back().mDistance)

        return;

    // do a binary search for the minimal distance to start the iteration there

    unsigned int index = (unsigned int)mPositions.size() / 2;

    unsigned int binaryStepSize = (unsigned int)mPositions.size() / 4;

    while( binaryStepSize > 1)

    {

        if( mPositions[index].mDistance < minDist)

            index += binaryStepSize;

        else

            index -= binaryStepSize;

        binaryStepSize /= 2;

    }

    // depending on the direction of the last step we need to single step a bit back or forth

    // to find the actual beginning element of the range

    while( index > 0 && mPositions[index].mDistance > minDist)

        index--;

    while( index < (mPositions.size() - 1) && mPositions[index].mDistance < minDist)

        index++;

    // Mow start iterating from there until the first position lays outside of the distance range.

    // Add all positions inside the distance range within the given radius to the result array

    float squareEpsilon = pRadius * pRadius;

    std::vector<Entry>::const_iterator it  = mPositions.begin() + index;

    std::vector<Entry>::const_iterator end = mPositions.end();

    if (exactMatch)

    {

        while( it->mDistance < maxDist)

        {

            if((it->mPosition - pPosition).SquareLength() < squareEpsilon && it->mSmoothGroups == pSG)

            {

                poResults.push_back( it->mIndex);

            }

            ++it;

            if( end == it )break;

        }

    }

    else

    {

        // if the given smoothing group is 0, we'll return all surrounding vertices

        if (!pSG)

        {

            while( it->mDistance < maxDist)

            {

                if((it->mPosition - pPosition).SquareLength() < squareEpsilon)

                    poResults.push_back( it->mIndex);

                ++it;

                if( end == it)break;

            }

        }

        else while( it->mDistance < maxDist)

        {

            if((it->mPosition - pPosition).SquareLength() < squareEpsilon &&

                (it->mSmoothGroups & pSG || !it->mSmoothGroups))

            {

                poResults.push_back( it->mIndex);

            }

            ++it;

            if( end == it)break;

        }

    }

}