blender-archive/source/blender/freestyle/intern/stroke/Operators.cpp

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 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * along with this program; if not, write to the Free Software Foundation,
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/** \file blender/freestyle/intern/stroke/Operators.cpp
 *  \ingroup freestyle
 *  \brief Class gathering stroke creation algorithms
 *  \author Stephane Grabli
 *  \author Emmanuel Turquin
 *  \date 01/07/2003
 */

#include <algorithm>
#include <stdexcept>

#include "Operators.h"
#include "Canvas.h"
#include "Stroke.h"

#include "BKE_global.h"

LIB_STROKE_EXPORT Operators::I1DContainer Operators::_current_view_edges_set;
LIB_STROKE_EXPORT Operators::I1DContainer Operators::_current_chains_set;
LIB_STROKE_EXPORT Operators::I1DContainer *Operators::_current_set = NULL;
LIB_STROKE_EXPORT Operators::StrokesContainer Operators::_current_strokes_set;

int Operators::select(UnaryPredicate1D& pred)
{
	if (!_current_set)
		return 0;
	if (_current_set->empty())
		return 0;
	I1DContainer new_set;
	I1DContainer rejected;
	Functions1D::ChainingTimeStampF1D cts;
	Functions1D::TimeStampF1D ts;
	I1DContainer::iterator it = _current_set->begin();
	I1DContainer::iterator itbegin = it;
	while (it != _current_set->end()) {
		Interface1D *i1d = *it;
		cts(*i1d); // mark everyone's chaining time stamp anyway
		if (pred(*i1d) < 0) {
			new_set.clear();
			rejected.clear();
			return -1;
		}
		if (pred.result) {
			new_set.push_back(i1d);
			ts(*i1d);
		}
		else {
			rejected.push_back(i1d);
		}
		++it;
	}
	if ((*itbegin)->getExactTypeName() != "ViewEdge") {
		for (it = rejected.begin(); it != rejected.end(); ++it)
			delete *it;
	}
	rejected.clear();
	_current_set->clear();
	*_current_set = new_set;
	return 0;
}


int Operators::chain(ViewEdgeInternal::ViewEdgeIterator& it, UnaryPredicate1D& pred, UnaryFunction1D_void& modifier)
{
	if (_current_view_edges_set.empty())
		return 0;

	unsigned id = 0;
	ViewEdge *edge;
	I1DContainer new_chains_set;

	for (I1DContainer::iterator it_edge = _current_view_edges_set.begin();
	     it_edge != _current_view_edges_set.end();
	     ++it_edge)
	{
		if (pred(**it_edge) < 0)
			goto error;
		if (pred.result)
			continue;

		edge = dynamic_cast<ViewEdge*>(*it_edge);
		it.setBegin(edge);
		it.setCurrentEdge(edge);

		Chain *new_chain = new Chain(id);
		++id;
		while (TRUE) {
			new_chain->push_viewedge_back(*it, it.getOrientation());
			if (modifier(**it) < 0) {
				delete new_chain;
				goto error;
			}
			++it;
			if (it.isEnd())
				break;
			if (pred(**it) < 0) {
				delete new_chain;
				goto error;
			}
			if (pred.result)
				break;
		}
		new_chains_set.push_back(new_chain);
	}

	if (!new_chains_set.empty()) {
		for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
			_current_chains_set.push_back(*it);
		}
		new_chains_set.clear();
		_current_set = &_current_chains_set;
	}
	return 0;

error:
	for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
		delete (*it);
	}
	new_chains_set.clear();
	return -1;
}


int Operators::chain(ViewEdgeInternal::ViewEdgeIterator& it, UnaryPredicate1D& pred)
{
	if (_current_view_edges_set.empty())
		return 0;

	unsigned id = 0;
	Functions1D::IncrementChainingTimeStampF1D ts;
	Predicates1D::EqualToChainingTimeStampUP1D pred_ts(TimeStamp::instance()->getTimeStamp() + 1);
	ViewEdge *edge;
	I1DContainer new_chains_set;

	for (I1DContainer::iterator it_edge = _current_view_edges_set.begin();
	     it_edge != _current_view_edges_set.end();
	     ++it_edge)
	{
		if (pred(**it_edge) < 0)
			goto error;
		if (pred.result)
			continue;
		if (pred_ts(**it_edge) < 0)
			goto error;
		if (pred_ts.result)
			continue;

		edge = dynamic_cast<ViewEdge*>(*it_edge);
		it.setBegin(edge);
		it.setCurrentEdge(edge);

		Chain *new_chain = new Chain(id);
		++id;
		while (TRUE) {
			new_chain->push_viewedge_back(*it, it.getOrientation());
			ts(**it);
			++it;
			if (it.isEnd())
				break;
			if (pred(**it) < 0) {
				delete new_chain;
				goto error;
			}
			if (pred.result)
				break;
			if (pred_ts(**it) < 0) {
				delete new_chain;
				goto error;
			}
			if (pred_ts.result)
				break;
		}
		new_chains_set.push_back(new_chain);
	}

	if (!new_chains_set.empty()) {
		for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
			_current_chains_set.push_back(*it);
		}
		new_chains_set.clear();
		_current_set = &_current_chains_set;
	}
	return 0;

error:
	for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
		delete (*it);
	}
	new_chains_set.clear();
	return -1;
}


#if 0
void Operators::bidirectionalChain(ViewEdgeIterator& it, UnaryPredicate1D& pred, UnaryFunction1D_void& modifier)
{
	if (_current_view_edges_set.empty())
		return;

	unsigned id = 0;
	ViewEdge *edge;
	Chain *new_chain;

	for (I1DContainer::iterator it_edge = _current_view_edges_set.begin();
	     it_edge != _current_view_edges_set.end();
	     ++it_edge)
	{
		if (pred(**it_edge))
			continue;

		edge = dynamic_cast<ViewEdge*>(*it_edge);
		it.setBegin(edge);
		it.setCurrentEdge(edge);

		Chain *new_chain = new Chain(id);
		++id;
#if 0 // FIXME
		ViewEdgeIterator it_back(it);
		--it_back;
#endif
		do {
			new_chain->push_viewedge_back(*it, it.getOrientation());
			modifier(**it);
			++it;
		} while (!it.isEnd() && !pred(**it));
		it.setBegin(edge);
		it.setCurrentEdge(edge);
		--it;
		while (!it.isEnd() && !pred(**it)) {
			new_chain->push_viewedge_front(*it, it.getOrientation());
			modifier(**it);
			--it;
		}

		_current_chains_set.push_back(new_chain);
	}

	if (!_current_chains_set.empty())
		_current_set = &_current_chains_set;
}

void Operators::bidirectionalChain(ViewEdgeIterator& it, UnaryPredicate1D& pred)
{
	if (_current_view_edges_set.empty())
		return;

	unsigned id = 0;
	Functions1D::IncrementChainingTimeStampF1D ts;
	Predicates1D::EqualToChainingTimeStampUP1D pred_ts(TimeStamp::instance()->getTimeStamp() + 1);

	ViewEdge *edge;
	Chain *new_chain;

	for (I1DContainer::iterator it_edge = _current_view_edges_set.begin();
	     it_edge != _current_view_edges_set.end();
	     ++it_edge)
	{
		if (pred(**it_edge) || pred_ts(**it_edge))
			continue;

		edge = dynamic_cast<ViewEdge*>(*it_edge);
		it.setBegin(edge);
		it.setCurrentEdge(edge);

		Chain *new_chain = new Chain(id);
		++id;
#if 0  //FIXME
		ViewEdgeIterator it_back(it);
		--it_back;
#endif
		do {
			new_chain->push_viewedge_back(*it, it.getOrientation());
			ts(**it);
			++it;
		} while (!it.isEnd() && !pred(**it) && !pred_ts(**it));
		it.setBegin(edge);
		it.setCurrentEdge(edge);
		--it;
		while (!it.isEnd() && !pred(**it) && !pred_ts(**it)) {
			new_chain->push_viewedge_front(*it, it.getOrientation());
			ts(**it);
			--it;
		}

		_current_chains_set.push_back(new_chain);
	}

	if (!_current_chains_set.empty())
		_current_set = &_current_chains_set;
}
#endif

int Operators::bidirectionalChain(ChainingIterator& it, UnaryPredicate1D& pred)
{
	if (_current_view_edges_set.empty())
		return 0;

	unsigned id = 0;
	Functions1D::IncrementChainingTimeStampF1D ts;
	Predicates1D::EqualToChainingTimeStampUP1D pred_ts(TimeStamp::instance()->getTimeStamp() + 1);
	ViewEdge *edge;
	I1DContainer new_chains_set;

	for (I1DContainer::iterator it_edge = _current_view_edges_set.begin();
	     it_edge != _current_view_edges_set.end();
	     ++it_edge)
	{
		if (pred(**it_edge) < 0)
			goto error;
		if (pred.result)
			continue;
		if (pred_ts(**it_edge) < 0)
			goto error;
		if (pred_ts.result)
			continue;

		edge = dynamic_cast<ViewEdge*>(*it_edge);
		// re-init iterator
		it.setBegin(edge);
		it.setCurrentEdge(edge);
		it.setOrientation(true);
		if (it.init() < 0)
			goto error;

		Chain *new_chain = new Chain(id);
		++id;
#if 0  // FIXME
		ViewEdgeIterator it_back(it);
		--it_back;
#endif
		while (TRUE) {
			new_chain->push_viewedge_back(*it, it.getOrientation());
			ts(**it);
			if (it.increment() < 0) {
				delete new_chain;
				goto error;
			}
			if (it.isEnd())
				break;
			if (pred(**it) < 0) {
				delete new_chain;
				goto error;
			}
			if (pred.result)
				break;
		}
		it.setBegin(edge);
		it.setCurrentEdge(edge);
		it.setOrientation(true);
		if (it.decrement() < 0) {
			delete new_chain;
			goto error;
		}
		while (!it.isEnd()) {
			if (pred(**it) < 0) {
				delete new_chain;
				goto error;
			}
			if (pred.result)
				break;
			new_chain->push_viewedge_front(*it, it.getOrientation());
			ts(**it);
			if (it.decrement() < 0) {
				delete new_chain;
				goto error;
			}
		}
		new_chains_set.push_back(new_chain);
	}

	if (!new_chains_set.empty()) {
		for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
			_current_chains_set.push_back(*it);
		}
		new_chains_set.clear();
		_current_set = &_current_chains_set;
	}
	return 0;

error:
	for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
		delete (*it);
	}
	new_chains_set.clear();
	return -1;
}

int Operators::bidirectionalChain(ChainingIterator& it)
{
	if (_current_view_edges_set.empty())
		return 0;

	unsigned id = 0;
	Functions1D::IncrementChainingTimeStampF1D ts;
	Predicates1D::EqualToChainingTimeStampUP1D pred_ts(TimeStamp::instance()->getTimeStamp() + 1);
	ViewEdge *edge;
	I1DContainer new_chains_set;

	for (I1DContainer::iterator it_edge = _current_view_edges_set.begin();
	     it_edge != _current_view_edges_set.end();
	     ++it_edge)
	{
		if (pred_ts(**it_edge) < 0)
			goto error;
		if (pred_ts.result)
			continue;

		edge = dynamic_cast<ViewEdge*>(*it_edge);
		// re-init iterator
		it.setBegin(edge);
		it.setCurrentEdge(edge);
		it.setOrientation(true);
		if (it.init() < 0)
			goto error;

		Chain *new_chain = new Chain(id);
		++id;
#if 0  // FIXME
		ViewEdgeIterator it_back(it);
		--it_back;
#endif
		do {
			new_chain->push_viewedge_back(*it, it.getOrientation());
			ts(**it);
			if (it.increment() < 0) { // FIXME
				delete new_chain;
				goto error;
			}
		} while (!it.isEnd());
		it.setBegin(edge);
		it.setCurrentEdge(edge);
		it.setOrientation(true);
		if (it.decrement() < 0) { // FIXME
			delete new_chain;
			goto error;
		}
		while (!it.isEnd()) {
			new_chain->push_viewedge_front(*it, it.getOrientation());
			ts(**it);
			if (it.decrement() < 0) { // FIXME
				delete new_chain;
				goto error;
			}
		}
		new_chains_set.push_back(new_chain);
	}

	if (!new_chains_set.empty()) {
		for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
			_current_chains_set.push_back(*it);
		}
		new_chains_set.clear();
		_current_set = &_current_chains_set;
	}
	return 0;

error:
	for (I1DContainer::iterator it = new_chains_set.begin(); it != new_chains_set.end(); ++it) {
		delete (*it);
	}
	new_chains_set.clear();
	return -1;
}

int Operators::sequentialSplit(UnaryPredicate0D& pred, float sampling)
{
	if (_current_chains_set.empty()) {
		cerr << "Warning: current set empty" << endl;
		return 0;
	}
	CurvePoint *point;
	Chain *new_curve;
	I1DContainer splitted_chains;
	Interface0DIterator first;
	Interface0DIterator end;
	Interface0DIterator last;
	Interface0DIterator it;
	I1DContainer::iterator cit = _current_chains_set.begin(), citend = _current_chains_set.end();
	for (; cit != citend; ++cit) {
		Id currentId = (*cit)->getId();
		new_curve = new Chain(currentId);
		first = (*cit)->pointsBegin(sampling);
		end = (*cit)->pointsEnd(sampling);
		last = end;
		--last;
		it = first;

		point = dynamic_cast<CurvePoint*>(&(*it));
		new_curve->push_vertex_back(point);
		++it;
		for (; it != end; ++it) {
			point = dynamic_cast<CurvePoint*>(&(*it));
			new_curve->push_vertex_back(point);
			if (pred(it) < 0) {
				delete new_curve;
				goto error;
			}
			if (pred.result && (it != last)) {
				splitted_chains.push_back(new_curve);
				currentId.setSecond(currentId.getSecond() + 1);
				new_curve = new Chain(currentId);
				new_curve->push_vertex_back(point);
			}
		}
		if (new_curve->nSegments() == 0) {
			delete new_curve;
			return 0;
		}

		splitted_chains.push_back(new_curve);
	}

	// Update the current set of chains:
	cit = _current_chains_set.begin();
	for (; cit != citend; ++cit) {
		delete (*cit);
	}
	_current_chains_set.clear();
#if 0
	_current_chains_set = splitted_chains;
#else
	for (cit = splitted_chains.begin(), citend = splitted_chains.end(); cit != citend; ++cit) {
		if ((*cit)->getLength2D() < M_EPSILON) {
			delete (*cit);
			continue;
		}
		_current_chains_set.push_back(*cit);
	}
#endif
	splitted_chains.clear();

	if (!_current_chains_set.empty())
		_current_set = &_current_chains_set;
	return 0;

error:
	cit = splitted_chains.begin();
	citend = splitted_chains.end();
	for (; cit != citend; ++cit) {
		delete (*cit);
	}
	splitted_chains.clear();
	return -1;
}

int Operators::sequentialSplit(UnaryPredicate0D& startingPred, UnaryPredicate0D& stoppingPred, float sampling)
{
	if (_current_chains_set.empty()) {
		cerr << "Warning: current set empty" << endl;
		return 0;
	}
	CurvePoint *point;
	Chain *new_curve;
	I1DContainer splitted_chains;
	Interface0DIterator first;
	Interface0DIterator end;
	Interface0DIterator last;
	Interface0DIterator itStart;
	Interface0DIterator itStop;
	I1DContainer::iterator cit = _current_chains_set.begin(), citend = _current_chains_set.end();
	for (; cit != citend; ++cit) {
		Id currentId = (*cit)->getId();
		first = (*cit)->pointsBegin(sampling);
		end = (*cit)->pointsEnd(sampling);
		last = end;
		--last;
		itStart = first;
		do {
			itStop = itStart;
			++itStop;

			new_curve = new Chain(currentId);
			currentId.setSecond(currentId.getSecond() + 1);

			point = dynamic_cast<CurvePoint*>(&(*itStart));
			new_curve->push_vertex_back(point);
			do {
				point = dynamic_cast<CurvePoint*>(&(*itStop));
				new_curve->push_vertex_back(point);
				++itStop;
				if (itStop == end)
					break;
				if (stoppingPred(itStop) < 0) {
					delete new_curve;
					goto error;
				}
			} while (!stoppingPred.result);
			if (itStop != end) {
				point = dynamic_cast<CurvePoint*>(&(*itStop));
				new_curve->push_vertex_back(point);
			}
			if (new_curve->nSegments() == 0) {
				delete new_curve;
			}
			else {
				splitted_chains.push_back(new_curve);
			}
			// find next start
			do {
				++itStart;
				if (itStart == end)
					break;
				if (startingPred(itStart) < 0)
					goto error;
			} while (!startingPred.result);
		} while ((itStart != end) && (itStart != last));
	}

	// Update the current set of chains:
	cit = _current_chains_set.begin();
	for (; cit != citend; ++cit) {
		delete (*cit);
	}
	_current_chains_set.clear();
#if 0
	_current_chains_set = splitted_chains;
#else
	for (cit = splitted_chains.begin(), citend = splitted_chains.end(); cit != citend; ++cit) {
		if ((*cit)->getLength2D() < M_EPSILON) {
			delete (*cit);
			continue;
		}
		_current_chains_set.push_back(*cit);
	}
#endif
	splitted_chains.clear();

	if (!_current_chains_set.empty())
		_current_set = &_current_chains_set;
	return 0;

error:
	cit = splitted_chains.begin();
	citend = splitted_chains.end();
	for (; cit != citend; ++cit) {
		delete (*cit);
	}
	splitted_chains.clear();
	return -1;
}

#include "CurveIterators.h"

// Internal function
static int __recursiveSplit(Chain *_curve, UnaryFunction0D<double>& func, UnaryPredicate1D& pred, float sampling,
                            Operators::I1DContainer& newChains, Operators::I1DContainer& splitted_chains)
{
	if (((_curve->nSegments() == 1) && (sampling == 0)) || (_curve->getLength2D() <= sampling)) {
		newChains.push_back(_curve);
		return 0;
	}

	CurveInternal::CurvePointIterator first  = _curve->curvePointsBegin(sampling);
	CurveInternal::CurvePointIterator second = first;
	++second;
	CurveInternal::CurvePointIterator end    = _curve->curvePointsEnd(sampling);
	CurveInternal::CurvePointIterator it     = second;
	CurveInternal::CurvePointIterator split  = second;
	Interface0DIterator it0d                 = it.castToInterface0DIterator();
	real _min                                = FLT_MAX; // func(it0d);
	++it;
	CurveInternal::CurvePointIterator next   = it;
	++next;

	bool bsplit = false;
	for (; ((it != end) && (next != end)); ++it, ++next) {
		it0d = it.castToInterface0DIterator();
		if (func(it0d) < 0)
			return -1;
		if (func.result < _min) {
			_min = func.result;
			split = it;
			bsplit = true;
		}
	}

	if (!bsplit) { // we didn't find any minimum
		newChains.push_back(_curve);
		return 0;
	}

	// retrieves the current splitting id
	Id *newId = _curve->getSplittingId();
	if (newId == 0) {
		newId = new Id(_curve->getId());
		_curve->setSplittingId(newId);
	} 

	Chain *new_curve_a = new Chain(*newId);
	newId->setSecond(newId->getSecond() + 1);
	new_curve_a->setSplittingId(newId);
	Chain *new_curve_b = new Chain(*newId);
	newId->setSecond(newId->getSecond() + 1);
	new_curve_b->setSplittingId(newId);

	CurveInternal::CurvePointIterator vit = _curve->curveVerticesBegin(), vitend = _curve->curveVerticesEnd();
	CurveInternal::CurvePointIterator vnext = vit;
	++vnext;

	for (; (vit != vitend) && (vnext != vitend) && (vnext._CurvilinearLength < split._CurvilinearLength);
	     ++vit, ++vnext)
	{
		new_curve_a->push_vertex_back(&(*vit));
	}
	if ((vit == vitend) || (vnext == vitend)) {
		if (G.debug & G_DEBUG_FREESTYLE) {
			cout << "The split takes place in bad location" << endl;
		}
		newChains.push_back(_curve);
		delete new_curve_a;
		delete new_curve_b;
		return 0;
	}

	// build the two resulting chains
	new_curve_a->push_vertex_back(&(*vit));
	new_curve_a->push_vertex_back(&(*split));
	new_curve_b->push_vertex_back(&(*split));

	for (vit = vnext; vit != vitend; ++vit)
		new_curve_b->push_vertex_back(&(*vit));

	// let's check whether one or two of the two new curves satisfy the stopping condition or not.
	// (if one of them satisfies it, we don't split)
	if (pred(*new_curve_a) < 0 || (!pred.result && pred(*new_curve_b) < 0)) {
		delete new_curve_a;
		delete new_curve_b;
		return -1;
	}
	if (pred.result) {
		// we don't actually create these two chains
		newChains.push_back(_curve);
		delete new_curve_a;
		delete new_curve_b;
		return 0;
	}
	// here we know we'll split _curve:
	splitted_chains.push_back(_curve);

	__recursiveSplit(new_curve_a, func, pred, sampling, newChains, splitted_chains);
	__recursiveSplit(new_curve_b, func, pred, sampling, newChains, splitted_chains);
	return 0;
}

int Operators::recursiveSplit(UnaryFunction0D<double>& func, UnaryPredicate1D& pred, float sampling)
{
	if (_current_chains_set.empty()) {
		cerr << "Warning: current set empty" << endl;
		return 0;
	}

	Chain *currentChain = 0;
	I1DContainer splitted_chains;
	I1DContainer newChains;
	I1DContainer::iterator cit = _current_chains_set.begin(), citend = _current_chains_set.end();
	for (; cit != citend; ++cit) {
		currentChain = dynamic_cast<Chain*>(*cit);
		if (!currentChain)
			continue;
		// let's check the first one:
		if (pred(*currentChain) < 0)
			return -1;
		if (!pred.result) {
			__recursiveSplit(currentChain, func, pred, sampling, newChains, splitted_chains);
		}
		else {
			newChains.push_back(currentChain);
		}
	}
	// Update the current set of chains:
	if (!splitted_chains.empty()) {
		for (cit = splitted_chains.begin(), citend = splitted_chains.end(); cit != citend; ++cit) {
			delete (*cit);
		} 
		splitted_chains.clear();
	} 

	_current_chains_set.clear();
#if 0
	_current_chains_set = newChains;
#else
	for (cit = newChains.begin(), citend = newChains.end(); cit != citend; ++cit) {
		if ((*cit)->getLength2D() < M_EPSILON) {
			delete (*cit);
			continue;
		}
		_current_chains_set.push_back(*cit);
	}
#endif
	newChains.clear();

	if (!_current_chains_set.empty())
		_current_set = &_current_chains_set;
	return 0;
}


// recursive split with pred 0D
static int __recursiveSplit(Chain *_curve, UnaryFunction0D<double>& func, UnaryPredicate0D& pred0d,
                            UnaryPredicate1D& pred, float sampling,
                            Operators::I1DContainer& newChains, Operators::I1DContainer& splitted_chains)
{
	if (((_curve->nSegments() == 1) && (sampling == 0)) || (_curve->getLength2D() <= sampling)) {
		newChains.push_back(_curve);
		return 0;
	}

	CurveInternal::CurvePointIterator first  = _curve->curvePointsBegin(sampling);
	CurveInternal::CurvePointIterator second = first;
	++second;
	CurveInternal::CurvePointIterator end      = _curve->curvePointsEnd(sampling);
	CurveInternal::CurvePointIterator it       = second;
	CurveInternal::CurvePointIterator split    = second;
	Interface0DIterator it0d                   = it.castToInterface0DIterator();
#if 0
	real _min                                  = func(it0d);
	++it;
#endif
	real _min                                  = FLT_MAX;
	++it;
	real mean                                  = 0.f;
	//soc unused - real variance                              = 0.0f;
	unsigned count                             = 0;
	CurveInternal::CurvePointIterator next     = it;
	++next;

	bool bsplit = false;
	for (; ((it != end) && (next != end)); ++it, ++next) {
		++count;
		it0d = it.castToInterface0DIterator();
		if (pred0d(it0d) < 0)
			return -1;
		if (!pred0d.result)
			continue;
		if (func(it0d) < 0)
			return -1;
		mean += func.result;
		if (func.result < _min) {
			_min = func.result;
			split = it;
			bsplit = true;
		}
	}
	mean /= (float)count;

	//if ((!bsplit) || (mean - _min > mean)) { // we didn't find any minimum
	if (!bsplit) { // we didn't find any minimum
		newChains.push_back(_curve);
		return 0;
	}

	// retrieves the current splitting id
	Id *newId = _curve->getSplittingId();
	if (newId == NULL) {
		newId = new Id(_curve->getId());
		_curve->setSplittingId(newId);
	}

	Chain *new_curve_a = new Chain(*newId);
	newId->setSecond(newId->getSecond() + 1);
	new_curve_a->setSplittingId(newId);
	Chain *new_curve_b = new Chain(*newId);
	newId->setSecond(newId->getSecond() + 1);
	new_curve_b->setSplittingId(newId);

	CurveInternal::CurvePointIterator vit = _curve->curveVerticesBegin(), vitend = _curve->curveVerticesEnd();
	CurveInternal::CurvePointIterator vnext = vit;
	++vnext;

	for (;
	     (vit != vitend) && (vnext != vitend) && (vnext._CurvilinearLength < split._CurvilinearLength);
	     ++vit, ++vnext)
	{
		new_curve_a->push_vertex_back(&(*vit));
	}
	if ((vit == vitend) || (vnext == vitend)) {
		if (G.debug & G_DEBUG_FREESTYLE) {
			cout << "The split takes place in bad location" << endl;
		}
		newChains.push_back(_curve);
		delete new_curve_a;
		delete new_curve_b;
		return 0;
	}

	// build the two resulting chains
	new_curve_a->push_vertex_back(&(*vit));
	new_curve_a->push_vertex_back(&(*split));
	new_curve_b->push_vertex_back(&(*split));

	for (vit = vnext; vit != vitend; ++vit)
		new_curve_b->push_vertex_back(&(*vit));

	// let's check whether one or two of the two new curves satisfy the stopping condition or not.
	// (if one of them satisfies it, we don't split)
	if (pred(*new_curve_a) < 0 || (!pred.result && pred(*new_curve_b) < 0)) {
		delete new_curve_a;
		delete new_curve_b;
		return -1;
	}
	if (pred.result) {
		// we don't actually create these two chains
		newChains.push_back(_curve);
		delete new_curve_a;
		delete new_curve_b;
		return 0;
	}
	// here we know we'll split _curve:
	splitted_chains.push_back(_curve);

	__recursiveSplit(new_curve_a, func, pred0d, pred, sampling, newChains, splitted_chains);
	__recursiveSplit(new_curve_b, func, pred0d, pred, sampling, newChains, splitted_chains);
	return 0;
}

int Operators::recursiveSplit(UnaryFunction0D<double>& func, UnaryPredicate0D& pred0d,  UnaryPredicate1D& pred,
                              float sampling)
{
	if (_current_chains_set.empty()) {
		cerr << "Warning: current set empty" << endl;
		return 0;
	}

	Chain *currentChain = 0;
	I1DContainer splitted_chains;
	I1DContainer newChains;
	I1DContainer::iterator cit = _current_chains_set.begin(), citend = _current_chains_set.end();
	for (; cit != citend; ++cit) {
		currentChain = dynamic_cast<Chain*>(*cit);
		if (!currentChain)
			continue;
		// let's check the first one:
		if (pred(*currentChain) < 0)
			return -1;
		if (!pred.result) {
			__recursiveSplit(currentChain, func, pred0d, pred, sampling, newChains, splitted_chains);
		}
		else {
			newChains.push_back(currentChain);
		}
	}
	// Update the current set of chains:
	if (!splitted_chains.empty()) {
		for (cit = splitted_chains.begin(), citend = splitted_chains.end(); cit != citend; ++cit) {
			delete (*cit);
		}
		splitted_chains.clear();
	}

	_current_chains_set.clear();
#if 0
	_current_chains_set = newChains;
#else
	for (cit = newChains.begin(), citend = newChains.end(); cit != citend; ++cit) {
		if ((*cit)->getLength2D() < M_EPSILON) {
			delete (*cit);
			continue;
		}
		_current_chains_set.push_back(*cit);
	}
#endif
	newChains.clear();

	if (!_current_chains_set.empty())
		_current_set = &_current_chains_set;
	return 0;
}

// Internal class
class PredicateWrapper
{
public:
	inline PredicateWrapper(BinaryPredicate1D& pred)
	{
		_pred = &pred;
	}

	inline bool operator()(Interface1D *i1, Interface1D *i2)
	{
		if ((*_pred)(*i1, *i2) < 0)
			throw std::runtime_error("comparison failed");
		return _pred->result;
	}

private:
	BinaryPredicate1D *_pred;
};

int Operators::sort(BinaryPredicate1D& pred)
{
	if (!_current_set)
		return 0;
	PredicateWrapper wrapper(pred);
	try {
		std::sort(_current_set->begin(), _current_set->end(), wrapper);
	}
	catch (std::runtime_error &e) {
		cerr << "Warning: Operator.sort(): " << e.what() << endl;
		return -1;
	}
	return 0;
}

static Stroke *createStroke(Interface1D& inter)
{
	Stroke *stroke = new Stroke;
	stroke->setId(inter.getId());

	float currentCurvilignAbscissa = 0.0f;

	Interface0DIterator it = inter.verticesBegin(), itend = inter.verticesEnd();
	Interface0DIterator itfirst = it;

	Vec2r current(it->getPoint2D());
	Vec2r previous = current;
	SVertex *sv;
	CurvePoint *cp;
	StrokeVertex *stroke_vertex = NULL;  
	bool hasSingularity = false;

	do {
		cp = dynamic_cast<CurvePoint*>(&(*it));
		if (!cp) {
			sv = dynamic_cast<SVertex*>(&(*it));
			if (!sv) {
				cerr << "Warning: unexpected Vertex type" << endl;
				continue;
			}
			stroke_vertex = new StrokeVertex(sv);
		}
		else {
			stroke_vertex = new StrokeVertex(cp);
		}
		current = stroke_vertex->getPoint2D();
		Vec2r vec_tmp(current - previous);
		real dist = vec_tmp.norm();
		if (dist < 1.0e-6)
			hasSingularity = true;
		currentCurvilignAbscissa += dist;
		stroke_vertex->setCurvilinearAbscissa(currentCurvilignAbscissa);
		stroke->push_back(stroke_vertex);
		previous = current;
		++it;
	} while ((it != itend) && (it != itfirst));

	if (it == itfirst) {
		// Add last vertex:
		cp = dynamic_cast<CurvePoint*>(&(*it));
		if (!cp) {
			sv = dynamic_cast<SVertex*>(&(*it));
			if (!sv)
				cerr << "Warning: unexpected Vertex type" << endl;
			else
				stroke_vertex = new StrokeVertex(sv);
		}
		else {
			stroke_vertex = new StrokeVertex(cp);
		}
		current = stroke_vertex->getPoint2D();
		Vec2r vec_tmp(current - previous);
		real dist = vec_tmp.norm();
		if (dist < 1.0e-6)
			hasSingularity = true;
		currentCurvilignAbscissa += dist;
		stroke_vertex->setCurvilinearAbscissa(currentCurvilignAbscissa);
		stroke->push_back(stroke_vertex);
	}
	// Discard the stroke if the number of stroke vertices is less than two
	if (stroke->strokeVerticesSize() < 2) {
		delete stroke;
		return NULL;
	}
	stroke->setLength(currentCurvilignAbscissa);
	if (hasSingularity) {
		// Try to address singular points such that the distance between two subsequent vertices
		// are smaller than epsilon.
		Interface0DIterator v = stroke->verticesBegin();
		Interface0DIterator vnext = v;
		++vnext;
		Vec2r next((*v).getPoint2D());
		while (!vnext.isEnd()) {
			current = next;
			next = (*vnext).getPoint2D();
			if ((next - current).norm() < 1.0e-6) {
				Interface0DIterator vprevious = v;
				if (!vprevious.isBegin())
					--vprevious;

				// collect a set of overlapping vertices
				std::vector<Interface0D *> overlapping_vertices;
				overlapping_vertices.push_back(&(*v));
				do {
					overlapping_vertices.push_back(&(*vnext));
					current = next;
					++v;
					++vnext;
					if (vnext.isEnd())
						break;
					next = (*vnext).getPoint2D();
				} while ((next - current).norm() < 1.0e-6);

				Vec2r target;
				bool reverse;
				if (!vnext.isEnd()) {
					target = (*vnext).getPoint2D();
					reverse = false;
				}
				else if (!vprevious.isBegin()) {
					target = (*vprevious).getPoint2D();
					reverse = true;
				}
				else {
					// Discard the stroke because all stroke vertices are overlapping
					delete stroke;
					return NULL;
				}
				current = overlapping_vertices.front()->getPoint2D();
				Vec2r dir(target - current);
				real dist = dir.norm();
				real len = 1.0e-3; // default offset length
				int nvert = overlapping_vertices.size();
				if (dist < len * nvert) {
					len = dist / nvert;
				}
				dir.normalize();
				Vec2r offset(dir * len);
				// add the offset to the overlapping vertices
				StrokeVertex *sv;
				std::vector<Interface0D *>::iterator it = overlapping_vertices.begin();
				if (!reverse) {
					for (int n = 1; n < nvert; n++) {
						sv = dynamic_cast<StrokeVertex*>(*it);
						sv->setPoint(sv->getPoint() + offset * n);
						++it;
					}
				}
				else {
					int last = nvert - 1;
					for (int n = 0; n < last; n++) {
						sv = dynamic_cast<StrokeVertex*>(*it);
						sv->setPoint(sv->getPoint() + offset * (last - n));
						++it;
					}
				}

				if (vnext.isEnd())
					break;
			}
			++v;
			++vnext;
		}
	}
	{
		// Check if the stroke no longer contains singular points
		Interface0DIterator v = stroke->verticesBegin();
		Interface0DIterator vnext = v;
		++vnext;
		Vec2r next((*v).getPoint2D());
		bool warning = false;
		while (!vnext.isEnd()) {
			current = next;
			next = (*vnext).getPoint2D();
			if ((next - current).norm() < 1.0e-6) {
				warning = true;
				break;
			}
			++v;
			++vnext;
		}
		if (warning && G.debug & G_DEBUG_FREESTYLE) {
			printf("Warning: stroke contains singular points.\n");
		}
	}
	return stroke;
}


inline int applyShading(Stroke& stroke, vector<StrokeShader*>& shaders)
{
	for (vector<StrokeShader*>::iterator it = shaders.begin(); it != shaders.end(); ++it) {
		if ((*it)->shade(stroke) < 0) {
			return -1;
		}
	}
	return 0;
}


int Operators::create(UnaryPredicate1D& pred, vector<StrokeShader*> shaders)
{
	//Canvas* canvas = Canvas::getInstance();
	if (!_current_set) {
		cerr << "Warning: current set empty" << endl;
		return 0;
	}
	StrokesContainer new_strokes_set;
	for (Operators::I1DContainer::iterator it = _current_set->begin(); it != _current_set->end(); ++it) {
		if (pred(**it) < 0)
			goto error;
		if (!pred.result)
			continue;

		Stroke *stroke = createStroke(**it);
		if (stroke) {
			if (applyShading(*stroke, shaders) < 0) {
				delete stroke;
				goto error;
			}
			//canvas->RenderStroke(stroke);
			new_strokes_set.push_back(stroke);
		}
	}

	for (StrokesContainer::iterator it = new_strokes_set.begin(); it != new_strokes_set.end(); ++it) {
		_current_strokes_set.push_back(*it);
	}
	new_strokes_set.clear();
	return 0;

error:
	for (StrokesContainer::iterator it = new_strokes_set.begin(); it != new_strokes_set.end(); ++it) {
		delete (*it);
	}
	new_strokes_set.clear();
	return -1;
}

void Operators::reset()
{
	ViewMap *vm = ViewMap::getInstance();
	if (!vm) {
		cerr << "Error: no ViewMap computed yet" << endl;
		return;
	}
	_current_view_edges_set.clear();
	for (I1DContainer::iterator it = _current_chains_set.begin(); it != _current_chains_set.end(); ++it)
		delete *it;
	_current_chains_set.clear();
#if 0
	_current_view_edges_set.insert(_current_view_edges_set.begin(),
	vm->ViewEdges().begin(),
	vm->ViewEdges().end());
#else
	ViewMap::viewedges_container& vedges = vm->ViewEdges();
	ViewMap::viewedges_container::iterator ve = vedges.begin(), veend = vedges.end();
	for (; ve != veend; ++ve) {
		if ((*ve)->getLength2D() < M_EPSILON)
			continue;
		_current_view_edges_set.push_back(*ve);
	}
#endif
	_current_set = &_current_view_edges_set;
	_current_strokes_set.clear();
}