#include "SamplingStrategy.h"
#include "Ray.h"
#include "Intersectable.h"
#include "Preprocessor.h"
#include "ViewCellsManager.h"
#include "AxisAlignedBox3.h"
#include "RssTree.h"
#include "Vector2.h"
#include "RndGauss.h"

namespace GtpVisibilityPreprocessor {


//HaltonSequence SamplingStrategy::sHalton;

HaltonSequence ObjectBasedDistribution::sHalton;
HaltonSequence MixtureDistribution::sHalton;
HaltonSequence GlobalLinesDistribution::sHalton;
HaltonSequence SpatialBoxBasedDistribution::sHalton;
HaltonSequence ObjectDirectionBasedDistribution::sHalton;
HaltonSequence DirectionBasedDistribution::sHalton;
HaltonSequence HwGlobalLinesDistribution::sHalton;


SamplingStrategy::SamplingStrategy(Preprocessor &preprocessor): 
mPreprocessor(preprocessor), 
mRatio(1.0f),  
mTotalRays(0), 
mTotalContribution(0.0f)
{  
}


SamplingStrategy::~SamplingStrategy() 
{
}

int
SamplingStrategy::GenerateSamples(const int number,
								  SimpleRayContainer &rays)
{
	SimpleRay ray;
	int samples = 0;
	int i = 0;
	const int maxTries = 20;
	// tmp changed matt. Q: should one rejected sample 
	// terminate the whole method?
	if (0)
	{
		for (; i < number; i++) {
			if (!GenerateSample(ray))
				return i;
			rays.push_back(ray);
		}
	}
	else
	{
		for (; i < number; i++) 
		{
			int j = 0;
			bool sampleGenerated = false;

			for (j = 0; !sampleGenerated && (j < maxTries); ++ j)
			{
				sampleGenerated = GenerateSample(ray);

				if (sampleGenerated)
				{		
					++ samples;
					rays.push_back(ray);
				}
			}
		}
	}
	
	return samples;
}


/*********************************************************************/
/*            Individual sampling strategies implementation          */
/*********************************************************************/


bool ObjectBasedDistribution::GenerateSample(SimpleRay &ray)
{
  Vector3 origin, direction; 
  
  float r[5];
  sHalton.GetNext(5, r);
  
  mPreprocessor.mViewCellsManager->GetViewPoint(origin,
												Vector3(r[2],r[3],r[4]));
  

  Vector3 point, normal;
  
  r[0] *= (float)mPreprocessor.mObjects.size() - 1;
  const int i = (int)r[0];
  
  Intersectable *object = mPreprocessor.mObjects[i];
  
  // take the remainder as a parameter over objects surface
  r[0] -= (float)i;
  
  object->GetRandomSurfacePoint(r[0], r[1], point, normal);
  
  direction = point - origin;
  
  const float c = Magnitude(direction);
  
  if (c <= Limits::Small) 
	return false;
  
  // $$ jb the pdf is yet not correct for all sampling methods!
  const float pdf = 1.0f;
  
  direction *= 1.0f / c;
  ray = SimpleRay(origin, direction, OBJECT_BASED_DISTRIBUTION, pdf);
  
  return true;
}


bool
ObjectDirectionBasedDistribution::GenerateSample(SimpleRay &ray)
{	
  Vector3 origin, direction; 


  float r[4];
  sHalton.GetNext(4, r);

  r[0] *= (float)mPreprocessor.mObjects.size() - 1;
  const int i = (int)r[0];
  
  Intersectable *object = mPreprocessor.mObjects[i];
  
  // take the remainder as a parameter over objects surface
  r[0] -= (float)i;

  Vector3 normal;

  object->GetRandomSurfacePoint(r[0], r[1], origin, normal);
  
  direction = Normalize(CosineRandomVector(r[2], r[3], normal));
  
  origin += 1e-2f*direction;
  
  // $$ jb the pdf is yet not correct for all sampling methods!
  const float pdf = 1.0f;
  
  ray = SimpleRay(origin, direction, OBJECT_DIRECTION_BASED_DISTRIBUTION, pdf);
  
  return true;
}


bool DirectionBasedDistribution::GenerateSample(SimpleRay &ray)
{	

  float r[5];
  sHalton.GetNext(5, r);

  Vector3 origin, direction; 
  mPreprocessor.mViewCellsManager->GetViewPoint(origin,
												Vector3(r[2],r[3],r[4])
												);
  
  direction = UniformRandomVector(r[0], r[1]);
  const float c = Magnitude(direction);
  
  if (c <= Limits::Small) 
	return false;
  
  const float pdf = 1.0f;
  
  direction *= 1.0f / c;
  ray = SimpleRay(origin, direction, DIRECTION_BASED_DISTRIBUTION, pdf);
  
  return true;
}


bool DirectionBoxBasedDistribution::GenerateSample(SimpleRay &ray)
{
	Vector3 origin, direction; 
	mPreprocessor.mViewCellsManager->GetViewPoint(origin);

	const float alpha = RandomValue(0.0f, 2.0f * (float)M_PI);
	const float beta = RandomValue((float)-M_PI * 0.5f, (float)M_PI * 0.5f);
	
	direction = VssRay::GetDirection(alpha, beta);
	
	const float c = Magnitude(direction);

	if (c <= Limits::Small) 
		return false;

	const float pdf = 1.0f;

	direction *= 1.0f / c;
	ray = SimpleRay(origin, direction, DIRECTION_BOX_BASED_DISTRIBUTION, pdf);

	return true;
}


bool SpatialBoxBasedDistribution::GenerateSample(SimpleRay &ray)
{
  Vector3 origin, direction; 

  float r[6];
  sHalton.GetNext(6, r);
  mPreprocessor.mViewCellsManager->GetViewPoint(origin, Vector3(r[0],r[1],r[2]));
  
  direction = mPreprocessor.mKdTree->GetBox().GetRandomPoint(Vector3(r[3],
																	 r[4],
																	 r[5])
																	 ) - origin;
  //cout << "z";
  const float c = Magnitude(direction);
  
  if (c <= Limits::Small) 
	return false;
  
  const float pdf = 1.0f;
  
  direction *= 1.0f / c;
  ray = SimpleRay(origin, direction, SPATIAL_BOX_BASED_DISTRIBUTION, pdf);
  
  return true;
}


bool ReverseObjectBasedDistribution::GenerateSample(SimpleRay &ray)
{
	Vector3 origin, direction; 

	mPreprocessor.mViewCellsManager->GetViewPoint(origin);

	Vector3 point;
	Vector3 normal;
	//cout << "y";
	const int i = (int)RandomValue(0, (float)mPreprocessor.mObjects.size() - 0.5f);

	Intersectable *object = mPreprocessor.mObjects[i];

	object->GetRandomSurfacePoint(point, normal);
	
	direction = origin - point;
	
	// $$ jb the pdf is yet not correct for all sampling methods!
	const float c = Magnitude(direction);
	
	if ((c <= Limits::Small) || (DotProd(direction, normal) < 0))
	{
		return false;
	}

	// $$ jb the pdf is yet not correct for all sampling methods!
	const float pdf = 1.0f;
	//cout << "p: " << point << " ";
	direction *= 1.0f / c;
	// a little offset
	point += direction * 0.001f;

	ray = SimpleRay(point, direction, REVERSE_OBJECT_BASED_DISTRIBUTION, pdf);
	
	return true;
}


bool ViewCellBorderBasedDistribution::GenerateSample(SimpleRay &ray)
{
	Vector3 origin, direction; 

	ViewCellContainer &viewCells = mPreprocessor.mViewCellsManager->GetViewCells();

	Vector3 point;
	Vector3 normal, normal2;
	
	const int vcIdx = (int)RandomValue(0, (float)viewCells.size() - 0.5f);
	const int objIdx = (int)RandomValue(0, (float)mPreprocessor.mObjects.size() - 0.5f);

	Intersectable *object = mPreprocessor.mObjects[objIdx];
	ViewCell *viewCell = viewCells[vcIdx];

	//cout << "vc: " << vcIdx << endl;
	//cout << "obj: " << objIdx << endl;

	object->GetRandomSurfacePoint(point, normal);
	viewCell->GetRandomEdgePoint(origin, normal2);

	direction = point - origin;

	// $$ jb the pdf is yet not correct for all sampling methods!
	const float c = Magnitude(direction);

	if ((c <= Limits::Small) /*|| (DotProd(direction, normal) < 0)*/)
	{
		return false;
	}

	// $$ jb the pdf is yet not correct for all sampling methods!
	const float pdf = 1.0f;
	//cout << "p: " << point << " ";
	direction *= 1.0f / c;
	ray = SimpleRay(origin, direction, VIEWCELL_BORDER_BASED_DISTRIBUTION, pdf);

	//cout << "ray: " << ray.mOrigin << " " << ray.mDirection << endl;

	return true;
}


#if 0
bool ObjectsInteriorDistribution::GenerateSample(SimpleRay &ray)
{
	Vector3 origin, direction; 

	// get random object
	const int i = RandomValue(0, mPreprocessor.mObjects.size() - 1);

	const Intersectable *obj = mPreprocessor.mObjects[i];

	// note: if we load the polygons as meshes, 
	// asymtotically every second sample is lost!
	origin = obj->GetBox().GetRandomPoint();

	// uniformly distributed direction
	direction = UniformRandomVector();

	const float c = Magnitude(direction);

	if (c <= Limits::Small) 
		return false;

	const float pdf = 1.0f;

	direction *= 1.0f / c;
	ray = SimpleRay(origin, direction, pdf);

	return true;
}

#endif


bool ReverseViewSpaceBorderBasedDistribution::GenerateSample(SimpleRay &ray)
{
	Vector3 origin, direction; 

	origin = mPreprocessor.mViewCellsManager->GetViewSpaceBox().GetRandomSurfacePoint();

	Vector3 point;
	Vector3 normal;
	//cout << "y";
	const int i = (int)RandomValue(0, (float)mPreprocessor.mObjects.size() - 0.5f);

	Intersectable *object = mPreprocessor.mObjects[i];

	object->GetRandomSurfacePoint(point, normal);
	
	direction = origin - point;
	
	// $$ jb the pdf is yet not correct for all sampling methods!
	const float c = Magnitude(direction);
	
	if ((c <= Limits::Small) || (DotProd(direction, normal) < 0))
	{
		return false;
	}

	// $$ jb the pdf is yet not correct for all sampling methods!
	const float pdf = 1.0f;
	//cout << "p: " << point << " ";
	direction *= 1.0f / c;
	// a little offset
	point += direction * 0.001f;

	ray = SimpleRay(point, direction, REVERSE_VIEWSPACE_BORDER_BASED_DISTRIBUTION, pdf);
	
	return true;
}


bool ViewSpaceBorderBasedDistribution::GenerateSample(SimpleRay &ray)
{
	Vector3 origin, direction; 

	origin = mPreprocessor.mViewCellsManager->GetViewSpaceBox().GetRandomSurfacePoint();

	Vector3 point;
	Vector3 normal;
	//cout << "w";
	const int i = (int)RandomValue(0, (float)mPreprocessor.mObjects.size() - 0.5f);

	Intersectable *object = mPreprocessor.mObjects[i];

	object->GetRandomSurfacePoint(point, normal);
	direction = point - origin;

	// $$ jb the pdf is yet not correct for all sampling methods!
	const float c = Magnitude(direction);

	if (c <= Limits::Small) 
		return false;

	// $$ jb the pdf is yet not correct for all sampling methods!
	const float pdf = 1.0f;
	
	direction *= 1.0f / c;

	// a little offset
	origin += direction * 0.001f;

	ray = SimpleRay(origin, direction, VIEWSPACE_BORDER_BASED_DISTRIBUTION, pdf);

	return true;
}


bool
GlobalLinesDistribution::GenerateSample(SimpleRay &ray) 
{
  Vector3 origin, termination, direction; 

  float radius = 0.5f*Magnitude(mPreprocessor.mViewCellsManager->GetViewSpaceBox().Size());
  Vector3 center = mPreprocessor.mViewCellsManager->GetViewSpaceBox().Center();

  const int tries = 1000;
  int i;
  for (i=0; i < tries; i++) {
	float r[4];
	sHalton.GetNext(4, r);
	
	origin = center + (radius*UniformRandomVector(r[0], r[1]));
	termination = center + (radius*UniformRandomVector(r[2], r[3]));
	
	direction = termination - origin;
	
	
	// $$ jb the pdf is yet not correct for all sampling methods!
	const float c = Magnitude(direction);
	if (c <= Limits::Small) 
	  return false;
	
	direction *= 1.0f / c;

	// check if the ray intersects the view space box
	static Ray ray;
	ray.Init(origin, direction, Ray::LOCAL_RAY);	
	
	float tmin, tmax;
	if (mPreprocessor.mViewCellsManager->
		GetViewSpaceBox().ComputeMinMaxT(ray, &tmin, &tmax) && (tmin < tmax))
	  break;
  }
  
  if (i!=tries) {
	// $$ jb the pdf is yet not correct for all sampling methods!
	const float pdf = 1.0f;
	
	
	ray = SimpleRay(origin, direction, GLOBAL_LINES_DISTRIBUTION, pdf);
	ray.mType = Ray::GLOBAL_RAY;
	return true;
  }
  
  return false;
}


  // has to called before first usage
void
MixtureDistribution::Init()
{
  for (int i=0; i < mDistributions.size(); i++) {
	// small non-zero value
	mDistributions[i]->mRays = 1;
	mDistributions[i]->mGeneratedRays = 1;
	// unit contribution per ray
	if (1 || mDistributions[i]->mType != RSS_BASED_DISTRIBUTION)
	  mDistributions[i]->mContribution = 1.0f;
	else
	  mDistributions[i]->mContribution = 0.0f;
  }
  UpdateRatios();
}

void
MixtureDistribution::Reset()
{
  for (int i=0; i < mDistributions.size(); i++) {
	// small non-zero value
	mDistributions[i]->mTotalRays = 0;
	// unit contribution per ray
	mDistributions[i]->mTotalContribution = 0.0f;
  }
  UpdateRatios();
}

// Generate a new sample according to a mixture distribution
bool
MixtureDistribution::GenerateSample(SimpleRay &ray)
{
  float r;
  sHalton.GetNext(1, &r);
  int i;
  // pickup a distribution
  for (i=0; i < mDistributions.size()-1; i++)
	if (r < mDistributions[i]->mRatio)
	  break;

  bool result = mDistributions[i]->GenerateSample(ray);

  if (result)
	mDistributions[i]->mGeneratedRays++;
  
  return result;
}

  // add contributions of the sample to the strategies
void
MixtureDistribution::ComputeContributions(VssRayContainer &vssRays)
{
  int i;
  
  VssRayContainer::iterator it = vssRays.begin();

  for (i=0; i < mDistributions.size(); i++) {
	mDistributions[i]->mContribution = 0;
	mDistributions[i]->mRays = 0;
  }

  for(; it != vssRays.end(); ++it) {
	VssRay *ray = *it;
	for (i=0; i < mDistributions.size()-1; i++) {
	  if (mDistributions[i]->mType == ray->mDistribution)
		break;
	}
 
	float contribution =
	  mPreprocessor.mViewCellsManager->ComputeSampleContribution(*ray,
																 true,
																 false);

	mDistributions[i]->mContribution += contribution;
	mDistributions[i]->mRays ++;
	
	mDistributions[i]->mTotalContribution += contribution;
	mDistributions[i]->mTotalRays ++;
  }

  
  UpdateRatios();

}

void
MixtureDistribution::UpdateDistributions(VssRayContainer &vssRays)
{
  // now update the distributions with all the rays
  for (int i=0; i < mDistributions.size(); i++) {
	mDistributions[i]->Update(vssRays);
  }
}

#define RAY_CAST_TIME 0.7f
#define VIEWCELL_CAST_TIME 0.3f

void
MixtureDistribution::UpdateRatios()
{
  // now compute importance (ratio) of all distributions
  float sum = 0.0f;
  int i;
  for (i=0; i < mDistributions.size(); i++) {
	cout<<i<<": c="<<mDistributions[i]->mContribution<<
	  " rays="<<mDistributions[i]->mRays<<endl;
	float importance = 0.0f;
	if (mDistributions[i]->mRays != 0) {
	  //importance = pow(mDistributions[i]->mContribution/mDistributions[i]->mRays, 2);
	  importance = mDistributions[i]->mContribution/
		(RAY_CAST_TIME*mDistributions[i]->mGeneratedRays +
		 VIEWCELL_CAST_TIME*mDistributions[i]->mRays);
	}
	mDistributions[i]->mRatio = importance;
	sum += importance;
  }

  if (sum == 0.0f)
	sum = Limits::Small;
  
  const float minratio = 0.01f;
  
  for (i=0; i < mDistributions.size(); i++) {
	mDistributions[i]->mRatio /= sum;
	if (mDistributions[i]->mRatio < minratio) 
	  mDistributions[i]->mRatio = minratio;
  }

  // recaluate the sum after clip
  sum = 0.0f;
  for (i=0; i < mDistributions.size(); i++)
	sum += mDistributions[i]->mRatio;

  for (i=0; i < mDistributions.size(); i++)
	mDistributions[i]->mRatio /= sum;
  
  for (i=1; i < mDistributions.size(); i++) {
	mDistributions[i]->mRatio = mDistributions[i-1]->mRatio + mDistributions[i]->mRatio;
  }
  
  cout<<"ratios: ";
  float last = 0.0f;
  for (i=0; i < mDistributions.size(); i++) {
	cout<<mDistributions[i]->mRatio-last<<" ";
	last = mDistributions[i]->mRatio;
  }
  cout<<endl;
}



bool
MixtureDistribution::Construct(char *str)
{
  char *curr = str;

  while (1) {
	char *e = strchr(curr,'+');
	if (e!=NULL) {
	  *e=0;
	}
	
	if (strcmp(curr, "rss")==0) {
	  mDistributions.push_back(new RssBasedDistribution(mPreprocessor));
	} else
	  if (strcmp(curr, "object")==0) {
		mDistributions.push_back(new ObjectBasedDistribution(mPreprocessor));
	  } else
		if (strcmp(curr, "spatial")==0) {
		  mDistributions.push_back(new SpatialBoxBasedDistribution(mPreprocessor));
		} else
		  if (strcmp(curr, "global")==0) {
			mDistributions.push_back(new GlobalLinesDistribution(mPreprocessor));
		  } else
			if (strcmp(curr, "direction")==0) {
			  mDistributions.push_back(new DirectionBasedDistribution(mPreprocessor));
			} else
			  if (strcmp(curr, "object_direction")==0) {
				mDistributions.push_back(new ObjectDirectionBasedDistribution(mPreprocessor));
			  } else
				if (strcmp(curr, "reverse_object")==0) {
				  mDistributions.push_back(new ReverseObjectBasedDistribution(mPreprocessor));
				} else
				  if (strcmp(curr, "reverse_viewspace_border")==0) {
					mDistributions.push_back(new ReverseViewSpaceBorderBasedDistribution(mPreprocessor));
				  } else
					if (strcmp(curr, "mutation")==0) {
					  mDistributions.push_back(new MutationBasedDistribution(mPreprocessor));
					} 
	
	
	if (e==NULL)
	  break;
	curr = e+1;
  }

  Init();
  return true;
}

int
MixtureDistribution::GenerateSamples(const int number,
									 SimpleRayContainer &rays)
{
  for (int i=0; i < mDistributions.size(); i++) 
	mDistributions[i]->mGeneratedRays = 0;

  return SamplingStrategy::GenerateSamples(number, rays);
}

void
MutationBasedDistribution::Update(VssRayContainer &vssRays)
{
  //  for (int i=0; i < mRays.size(); i++)
  //	cout<<mRays[i].mSamples<<" ";
  //  cout<<endl;
  cerr<<"Muattion update..."<<endl;
  cerr<<"rays = "<<mRays.size()<<endl;
  if (mRays.size()) {
	cerr<<"Oversampling factors = "<<
	  GetEntry(0).mSamples<<" "<<
	  GetEntry(1).mSamples<<" "<<
	  GetEntry(2).mSamples<<" "<<
	  GetEntry(3).mSamples<<" "<<
	  GetEntry(4).mSamples<<" "<<
	  GetEntry(5).mSamples<<" ... "<<
	  GetEntry(mRays.size()-6).mSamples<<" "<<
	  GetEntry(mRays.size()-5).mSamples<<" "<<
	  GetEntry(mRays.size()-4).mSamples<<" "<<
	  GetEntry(mRays.size()-3).mSamples<<" "<<
	  GetEntry(mRays.size()-2).mSamples<<" "<<
	  GetEntry(mRays.size()-1).mSamples<<endl;
  }
  int contributingRays = 0;
  for (int i=0; i < vssRays.size(); i++) {
	if (vssRays[i]->mPvsContribution) {
	  contributingRays++;
	  if (mRays.size() < mMaxRays) {
		VssRay *newRay = new VssRay(*vssRays[i]);
		// add this ray
		newRay->Ref();
		mRays.push_back(RayEntry(newRay));
	  } else {
		// unref the old ray
		*mRays[mBufferStart].mRay = *vssRays[i];
		mRays[mBufferStart].mSamples = 0;
		//		mRays[mBufferStart] = RayEntry(newRay);
		mBufferStart++;
		if (mBufferStart >= mMaxRays)
		  mBufferStart = 0;
	  }
	}
  }
  
  float pContributingRays = contributingRays/(float)vssRays.size();
  float importance = 1.0f/(pContributingRays + 1e-5);
  // set this values for last contributingRays
  int index = mBufferStart - 1;
  
  for (int i=0; i < contributingRays; i++, index--) {
	if (index < 0)
	  index = mRays.size()-1;
	mRays[index].mImportance = importance;
  }

  
  // compute cdf
  mRays[0].mCdf = mRays[0].mImportance/(mRays[0].mSamples+1);
  for (int i=1; i < mRays.size(); i++) 
	mRays[i].mCdf = mRays[i-1].mCdf + mRays[i].mImportance/(mRays[i].mSamples+1);
  
  float scale = 1.0f/mRays[i-1].mCdf;
  for (i=0; i < mRays.size(); i++) {
	mRays[i].mCdf *= scale;
  }

  cout<<"Importance = "<<
	GetEntry(0).mImportance<<" "<<
	GetEntry(mRays.size()-1).mImportance<<endl;
  
  cerr<<"Mutation update done."<<endl;
}


Vector3
MutationBasedDistribution::ComputeOriginMutation(const VssRay &ray,
												 const Vector3 &U,
												 const Vector3 &V,
												 const Vector2 vr2,
												 const float radius
												 )
{
#if 0
  Vector3 v;
  if (d.DrivingAxis() == 0)
	v = Vector3(0, r[0]-0.5f, r[1]-0.5f);
  else
	if (d.DrivingAxis() == 1)
	  v = Vector3(r[0]-0.5f, 0, r[1]-0.5f);
	else
	  v = Vector3(r[0]-0.5f, r[1]-0.5f, 0);
  return v*(2*radius);
#endif
#if 0
  return (U*(r[0] - 0.5f) + V*(r[1] - 0.5f))*(2*radius);
#endif


  // Output random variable
  Vector2 gaussvec2; 
  
  // Here we apply transform to gaussian, so 2D bivariate
  // normal distribution
  //  float sigma = ComputeSigmaFromRadius(radius);
  float sigma = radius;
  GaussianOn2D(vr2,
			   sigma, // input
			   gaussvec2);  // output

	
    // Here we tranform the point correctly to 3D space using base
    // vectors of the 3D space defined by the direction
    Vector3 shift = gaussvec2.xx * U + gaussvec2.yy * V;
	
	//	cout<<shift<<endl;
	return shift;
}

Vector3
MutationBasedDistribution::ComputeTerminationMutation(const VssRay &ray,
													  const Vector3 &U,
													  const Vector3 &V,
													  const Vector2 vr2,
													  const float radius
													  )
{
#if 0
  Vector3 v;
  // mutate the termination
  if (d.DrivingAxis() == 0)
	v = Vector3(0, r[2]-0.5f, r[3]-0.5f);
  else
	if (d.DrivingAxis() == 1)
	  v = Vector3(r[2]-0.5f, 0, r[3]-0.5f);
	else
	  v = Vector3(r[2]-0.5f, r[3]-0.5f, 0);
  
  //   Vector3 nv;
  
  //   if (Magnitude(v) > Limits::Small)
  // 	nv = Normalize(v);
  //   else
  // 	nv = v;
  
  //  v = nv*size + v*size;

  return v*(4.0f*radius);
#endif
#if 0
  return (U*(vr2.xx - 0.5f) + V*(vr2.yy - 0.5f))*(4.0f*radius);
#endif
  Vector2 gaussvec2; 
#if 1
  float sigma = radius;
  GaussianOn2D(vr2,
			   sigma, // input
			   gaussvec2);  // output
  Vector3 shift = gaussvec2.xx * U + gaussvec2.yy * V;
  //	cout<<shift<<endl;
  return shift;
#endif
#if 0
  // Here we estimate standard deviation (sigma) from radius
  float sigma = 1.1f*ComputeSigmaFromRadius(radius);
  Vector3 vr3(vr2.xx, vr2.yy, RandomValue(0,1));
  PolarGaussianOnDisk(vr3,
					  sigma,
					  radius, // input
					  gaussvec2); // output
  
  // Here we tranform the point correctly to 3D space using base
  // vectors of the 3D space defined by the direction
  Vector3 shift = gaussvec2.xx * U + gaussvec2.yy * V;
  
  //	cout<<shift<<endl;
  return shift;
#endif
}


bool
MutationBasedDistribution::GenerateSample(SimpleRay &sray)
{
  float rr[5];

  if (mRays.size() == 0) {
	// use direction based distribution
	Vector3 origin, direction;
	static HaltonSequence halton;
	
	halton.GetNext(5, rr);
	mPreprocessor.mViewCellsManager->GetViewPoint(origin,
												  Vector3(rr[0], rr[1], rr[2]));
	

	direction = UniformRandomVector(rr[3], rr[4]);
	
	const float pdf = 1.0f;
	sray = SimpleRay(origin, direction, MUTATION_BASED_DISTRIBUTION, pdf);

	return true;
  } 

  int index;
#if 1
  // get tail of the buffer
  index = (mLastIndex+1)%mRays.size();
  if (mRays[index].GetSamplingFactor() >
	  mRays[mLastIndex].GetSamplingFactor()) {
	// search back for index where this is valid
	index = (mLastIndex - 1 + mRays.size())%mRays.size();
	for (int i=0; i < mRays.size(); i++) {
	  
	  //	  if (mRays[index].mSamples > mRays[mLastIndex].mSamples)
	  //		break;
	  if (mRays[index].GetSamplingFactor() >
		  mRays[mLastIndex].GetSamplingFactor() )
		break;
	  index = (index - 1 + mRays.size())%mRays.size();
	}
	// go one step back
	index = (index+1)%mRays.size();
  }
#else
  static HaltonSequence iHalton;
  iHalton.GetNext(1, rr);
  //rr[0] = RandomValue(0,1);
  // use binary search to find index with this cdf
  int l=0, r=mRays.size()-1;
  while(l<r) {
	int i = (l+r)/2;
	if (rr[0] < mRays[i].mCdf )
	  r = i;
	else
	  l = i+1;
  }
  index = l;
  //  if (rr[0] >= mRays[r].mCdf)
  //	index = r;
  //  else
  //	index = l;
	
	
#endif
  //  cout<<index<<" "<<rr[0]<<" "<<mRays[index].mCdf<<" "<<mRays[(index+1)%mRays.size()].mCdf<<endl;
  
  VssRay *ray = mRays[index].mRay;
  mRays[index].mSamples++;
  mLastIndex = index;

  mRays[index].mHalton.GetNext(4, rr);

  // mutate the origin
  Vector3 d = ray->GetDir();


  AxisAlignedBox3 box = ray->mTerminationObject->GetBox();
  float objectRadius = 0.5f*Magnitude(box.Diagonal());
  //  cout<<objectRadius<<endl;
  if (objectRadius < Limits::Small)
	return false;
  
  // Compute right handed coordinate system from direction
  Vector3 U, V;
  Vector3 nd = Normalize(d);
  nd.RightHandedBase(U, V);

  Vector3 origin = ray->mOrigin;
  Vector3 termination = ray->mTermination; //box.Center(); //ray->mTermination; //box.Center();

  float radiusExtension = 1.0f;
  //  + mRays[index].mSamples/50.0f;
  
  //  origin += ComputeOriginMutation(*ray, U, V, Vector2(r[0], r[1]), 0.5f*mOriginMutationSize*radiusExtension);
  origin += ComputeOriginMutation(*ray, U, V,
								  Vector2(rr[0], rr[1]),
								  objectRadius*radiusExtension);
  termination += ComputeTerminationMutation(*ray, U, V,
											Vector2(rr[2], rr[3]),
											objectRadius*radiusExtension);
  
  Vector3 direction = termination - origin;
  
  if (Magnitude(direction) < Limits::Small)
	return false;
  
  // shift the origin a little bit
  origin += direction*0.5f;
  
  direction.Normalize();
  
  // $$ jb the pdf is yet not correct for all sampling methods!
  const float pdf = 1.0f;
  
  sray = SimpleRay(origin, direction, MUTATION_BASED_DISTRIBUTION, pdf);
  return true;
}

MutationBasedDistribution::MutationBasedDistribution(Preprocessor &preprocessor
													 ) :
  SamplingStrategy(preprocessor)
{
  mType = MUTATION_BASED_DISTRIBUTION;
  mBufferStart = 0;
  mMaxRays = 500000;
  mRays.reserve(mMaxRays);
  mOriginMutationSize = 10.0f;
  mLastIndex = 0;
  //  mOriginMutationSize = Magnitude(preprocessor.mViewCellsManager->
  //								  GetViewSpaceBox().Diagonal())*1e-3;
  
}


bool HwGlobalLinesDistribution::GenerateSample(SimpleRay &ray) 
{
	Vector3 origin, termination, direction; 

	float radius = 0.5f * 
		Magnitude(mPreprocessor.mViewCellsManager->GetViewSpaceBox().Size());

	Vector3 center = mPreprocessor.mViewCellsManager->GetViewSpaceBox().Center();

	const int tries = 1000;
	int i;
	for (i=0; i < tries; i++) 
	{
		float r[2];
		sHalton.GetNext(2, r);

		origin = center + (radius * UniformRandomVector(r[0], r[1]));
		termination = center;
		
		if (0)
		{
			// add a small offset to provide some more randomness in the sampling
			Vector3 offset(Random(radius * 1e-3f), 
						   Random(radius * 1e-3f), 
						   Random(radius * 1e-3f));
			termination += offset;
		}

		direction = termination - origin;

		// $$ jb the pdf is yet not correct for all sampling methods!
		const float c = Magnitude(direction);

		if (c <= Limits::Small) 
			return false;

		direction *= 1.0f / c;

		// check if the ray intersects the view space box
		static Ray ray;
		ray.Init(origin, direction, Ray::LOCAL_RAY);	

		float tmin, tmax;
		if (mPreprocessor.mViewCellsManager->
			GetViewSpaceBox().ComputeMinMaxT(ray, &tmin, &tmax) && (tmin < tmax))
			break;
	}

	if (i != tries) 
	{
		// $$ jb the pdf is yet not correct for all sampling methods!
		const float pdf = 1.0f;

		ray = SimpleRay(origin, direction, HW_GLOBAL_LINES_DISTRIBUTION, pdf);
		ray.mType = Ray::GLOBAL_RAY;
		return true;
	}

	return false;
}


}