assimp/code/SGSpatialSort.cpp

/*
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Open Asset Import Library (ASSIMP)
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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 <algorithm>
#include "SGSpatialSort.h"

#include "../include/aiAssert.h"

using namespace Assimp;


// ------------------------------------------------------------------------------------------------
SGSpatialSort::SGSpatialSort()
{
	// define the reference plane. We choose some arbitrary vector away from all basic axises 
	// 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()
{
	// nothing to do here, everything destructs automatically
}
// ------------------------------------------------------------------------------------------------
void SGSpatialSort::Add(const aiVector3D& vPosition, unsigned int index,
	unsigned int smoothingGroup)
{
	// store position by index and distance
	float distance = vPosition * mPlaneNormal;
	mPositions.push_back( Entry( 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) const
{
	float dist = pPosition * mPlaneNormal;
	float minDist = dist - pRadius, maxDist = dist + pRadius;

	// clear the array in this strange fashion because a simple clear() would also deallocate
	// the array which we want to avoid
	poResults.erase( poResults.begin(), poResults.end());

	// quick check for positions outside the range
	if( mPositions.size() == 0)
		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 aray

	float squareEpsilon = pRadius * pRadius;
	std::vector<Entry>::const_iterator it = mPositions.begin() + index;
	while( it->mDistance < maxDist)
	{
		if((it->mPosition - pPosition).SquareLength() < squareEpsilon &&
			(it->mSmoothGroups & pSG || 0 == it->mSmoothGroups || 0 == pSG))
		{
			poResults.push_back( it->mIndex);
		}
		++it;
		if( it == mPositions.end())
			break;
	}
}