assimp/code/Common/SGSpatialSort.cpp

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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();
}
// ------------------------------------------------------------------------------------------------
// Destructor
SGSpatialSort::~SGSpatialSort() = default;
// ------------------------------------------------------------------------------------------------
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;
        }
    }
}