#ifndef _DifferenceSampling_H__
#define _DifferenceSampling_H__

#include "common.h"
//#include "ObjectPvs.h"

class SimpleRay;

namespace GtpVisibilityPreprocessor {


/** This sampling strategy utilizes the spatial filter to find 
	areas that are likely to be visible.

	First the filter is applied. The difference set of objects 
	(filtered pvs - unfiltered pvs) gives you the objects which 
	are not found visible yet but have a good probability that they 
	are in fact visible, based on the current 
	state of the sampling and the size of the filter. In fact the 
	difference set is a probably visible set.

	Algorithm overview:
	We apply the filter for n times, each time with a higher filter radius. 
	The difference set gives you the probable visible set. 
	Then we use a certain #random samples for sampling the view cell border + 
	the object border. We can use different filter sizes to estimate the probability 
	distribution. The objects shouldreceived samples 
	roughly according to their probability of becoming invisible.
*/	
class DifferenceSampling: public SamplingStrategy
{
public:
	DifferenceSampling(Preprocessor &preprocessor);
	/** Compute the difference set between filtered and unfiltered pvs.
	*/
	void ComputeDifferenceSet(ViewCell *vc, ObjectContainer &differenceSet);

private:

	virtual bool GenerateSample(SimpleRay &ray);

	//ObjectPvs mDifferencePvs;
	ObjectContainer mPvsDifference;

	ViewCell *mCurrentViewCell;
	int mNumSamples;
};


}

#endif