source: GTP/trunk/Lib/Vis/Preprocessing/src/SamplingStrategy.cpp @ 1888

#include "SamplingStrategy.h"
#include "Ray.h"
#include "Intersectable.h"
#include "Preprocessor.h"
#include "ViewCellsManager.h"
#include "AxisAlignedBox3.h"


namespace GtpVisibilityPreprocessor {


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];
  mHalton.GetNext(5, r);
  
  mPreprocessor.mViewCellsManager->GetViewPoint(origin,
                                                                                                Vector3(r[2],r[3],r[4]));
  

  Vector3 point, normal;
  
  r[0] *= 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];
  mHalton.GetNext(4, r);

  r[0] *= 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-2*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)
{       
        Vector3 origin, direction; 
        mPreprocessor.mViewCellsManager->GetViewPoint(origin);
         
        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, 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];
  mHalton.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];
        mHalton.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;
        // 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]->mRays = 1;
        // unit contribution per ray
        mDistributions[i]->mContribution = 1.0f;
  }
  UpdateRatios();
}

// Generate a new sample according to a mixture distribution
bool
MixtureDistribution::GenerateSample(SimpleRay &ray)
{
  float r;
  mHalton.GetNext(1, &r);

  // pickup a distribution
  for (int i=0; i < mDistributions.size(); i++)
        if (r < mDistributions[i]->mRatio)
          break;
  
  return mDistributions[i]->GenerateSample(ray);
}

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

  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->ComputeSampleContributions(vssRays, true, false);
        mDistributions[i]->mContribution += contribution;
        mDistributions[i]->mRays ++;
  }

  // now update the distributions with all the rays
  for (i=0; i < mDistributions.size(); i++)
        mDistributions[i]->Update(vssRays);
  
  
  UpdateRatios();
}

void
MixtureDistribution::UpdateRatios()
{
  // now compute importance (ratio) of all distributions
  float sum = 0.0f;
  int i;
  for (i=0; i < mDistributions.size(); i++) {
        float importance = mDistributions[i]->mContribution/mDistributions[i]->mRays;
        mDistributions[i]->mRatio = importance;
        sum += importance;
  }
  
  
  mDistributions[0]->mRatio /= sum;
  for (i=1; i < mDistributions.size(); i++) {
        float r = mDistributions[i]->mRatio / sum;
        mDistributions[i]->mRatio = mDistributions[i-1]->mRatio + r;
  }
  
  cout<<"ratios: ";
  for (i=0; i < mDistributions.size(); i++)
        cout<<mDistributions[i]->mRatio<<" ";
  cout<<endl;
}
}