source: GTP/trunk/Lib/Vis/Preprocessing/src/GlRenderer.cpp @ 2002

#include "Mesh.h"
#include "glInterface.h"
#include "OcclusionQuery.h"
#include "GlRenderer.h"
#include "ViewCellsManager.h"
#include "SceneGraph.h"
#include "Pvs.h"
#include "Viewcell.h"
#include "Beam.h"
#include "KdTree.h"
#include "Environment.h"
#include "Triangle3.h"
#include "IntersectableWrapper.h"
#include "BvHierarchy.h"
#include "KdTree.h"

#ifdef USE_CG

#include <Cg/cg.h>
#include <Cg/cgGL.h>

#endif

namespace GtpVisibilityPreprocessor {


static bool arbQuerySupport = false;
static bool nvQuerySupport = false;

static GLuint frontDepthMap;
static GLuint backDepthMap;

const int depthMapSize = 512;

static void InitExtensions() 
{
        GLenum err = glewInit();

        if (GLEW_OK != err) 
        {
                // problem: glewInit failed, something is seriously wrong
                cerr << "Error: " << glewGetErrorString(err) << endl;
                exit(1);
        }

        if (GLEW_ARB_occlusion_query) 
                arbQuerySupport = true;
        
        if (GLEW_NV_occlusion_query) 
                nvQuerySupport = true;
        

        if  (!arbQuerySupport && !nvQuerySupport)
        {
                cout << "I require the GL_ARB_occlusion_query or the GL_NV_occlusion_query OpenGL extension to work.\n";
                exit(1);
        }
}


GlRenderer::GlRenderer(SceneGraph *sceneGraph,
                                           ViewCellsManager *viewCellsManager,
                                           KdTree *tree):
  Renderer(sceneGraph, viewCellsManager),
  mKdTree(tree)
{
  mSceneGraph->CollectObjects(&mObjects);

  //  mViewCellsManager->GetViewPoint(mViewPoint);

  viewCellsManager->GetViewPoint(mViewPoint);
        //mSceneGraph->GetBox().Center();
  mViewDirection = Vector3(0,0,1);

  //  mViewPoint = Vector3(991.7, 187.8, -271);
  //  mViewDirection = Vector3(0.9, 0, -0.4);

  //  timerId = startTimer(10);
  // debug coords for atlanta
  //  mViewPoint = Vector3(3473, 6.778, -1699);
  //  mViewDirection = Vector3(-0.2432, 0, 0.97);
  
  mFrame = 0;
  mWireFrame = false;
  Environment::GetSingleton()->GetBoolValue("Preprocessor.detectEmptyViewSpace",
                                                                                        mDetectEmptyViewSpace);
  mSnapErrorFrames = true;
  mSnapPrefix = "snap/";
  mUseForcedColors = false;
  mRenderBoxes = false;
  mUseGlLists = true;
  //mUseGlLists = false;

  Environment::GetSingleton()->GetIntValue("Preprocessor.pvsRenderErrorSamples", mPvsStatFrames);
  mPvsErrorBuffer.resize(mPvsStatFrames);
  ClearErrorBuffer();
  
}

GlRenderer::~GlRenderer()
{
  cerr<<"gl renderer destructor..\n";
 
  //CLEAR_CONTAINER(sQueries);
  CLEAR_CONTAINER(mOcclusionQueries);

  cerr<<"done."<<endl;
}


void
GlRenderer::RenderTriangle(TriangleIntersectable *object)
{
  Triangle3 &t = object->GetItem();
  
  glBegin(GL_TRIANGLES);
  Vector3 normal = t.GetNormal();
  glNormal3f(normal.x, normal.y, normal.z);
  glVertex3f(t.mVertices[0].x, t.mVertices[0].y, t.mVertices[0].z);
  glVertex3f(t.mVertices[1].x, t.mVertices[1].y, t.mVertices[1].z);
  glVertex3f(t.mVertices[2].x, t.mVertices[2].y, t.mVertices[2].z);
  glEnd();
}

void
GlRenderer::RenderIntersectable(Intersectable *object)
{
  if (object->Mailed())
        return;
  object->Mail();
  
  glPushAttrib(GL_CURRENT_BIT);
  if (mUseFalseColors)
        SetupFalseColor(object->mId);
  
  switch (object->Type()) {
  case Intersectable::MESH_INSTANCE:
        RenderMeshInstance((MeshInstance *)object);
        break;
  case Intersectable::VIEW_CELL:
        RenderViewCell(dynamic_cast<ViewCell *>(object));
        break;
  case Intersectable::TRANSFORMED_MESH_INSTANCE:
        RenderTransformedMeshInstance(dynamic_cast<TransformedMeshInstance *>(object));
        break;
  case Intersectable::TRIANGLE_INTERSECTABLE:
        RenderTriangle(dynamic_cast<TriangleIntersectable *>(object));
        break;
  case Intersectable::BVH_INTERSECTABLE: {

        BvhNode *node = dynamic_cast<BvhNode *>(object);
        
        if (mRenderBoxes)
          RenderBox(node->GetBoundingBox());
        else
          RenderBvhNode(node);
        break;
  }
  case Intersectable::KD_INTERSECTABLE: {
        KdNode *node = (dynamic_cast<KdIntersectable *>(object))->GetItem();
        
        if (mRenderBoxes)
          RenderBox(mKdTree->GetBox(node));
        else
          RenderKdNode(node);
        break;
  }
        
  default:
        cerr<<"Rendering this object not yet implemented\n";
        break;
  }

  glPopAttrib();
}

void
GlRenderer::RenderRays(const VssRayContainer &rays)
{
  VssRayContainer::const_iterator it = rays.begin(), it_end = rays.end();

  glBegin(GL_LINES);
  for (; it != it_end; ++it) {
        VssRay *ray = *it;
        float importance = log10(1e3*ray->mWeightedPvsContribution)/3.0f;
        //      cout<<"w="<<ray->mWeightedPvsContribution<<" r="<<ray->mWeightedPvsContribution;
        glColor3f(importance, importance, importance);
        glVertex3fv(&ray->mOrigin.x);
        glVertex3fv(&ray->mTermination.x);
  }
  glEnd();
}



void
GlRenderer::RenderViewCell(ViewCell *vc)
{
  if (vc->GetMesh()) {

        if (!mUseFalseColors) {
          if (vc->GetValid()) 
                glColor3f(0,1,0);
          else
                glColor3f(0,0,1);
        }
        
        RenderMesh(vc->GetMesh());
  } else {
        // render viewcells in the subtree
        if (!vc->IsLeaf()) {
          ViewCellInterior *vci = (ViewCellInterior *) vc;

          ViewCellContainer::iterator it = vci->mChildren.begin();
          for (; it != vci->mChildren.end(); ++it) {
                RenderViewCell(*it);
          }
        } else {
          //      cerr<<"Empty viewcell mesh\n";
        }
  }
}


void
GlRenderer::RenderMeshInstance(MeshInstance *mi)
{
  RenderMesh(mi->GetMesh());
}


void
GlRenderer::RenderTransformedMeshInstance(TransformedMeshInstance *mi)
{
        // apply world transform before rendering
        Matrix4x4 m;
        mi->GetWorldTransform(m);

        glPushMatrix();
/* cout << "\n";
        for (int i = 0; i < 4; ++ i)
                for (int j = 0; j < 4; ++ j)
                        cout << m.x[i][j] << " "; cout << "\n"*/

        glMultMatrixf((float *)m.x);

        /*GLfloat dummy[16];
        glGetFloatv(GL_MODELVIEW_MATRIX, dummy);
        for (int i = 0; i < 16; ++ i)
                cout << dummy[i] << " ";
        cout << endl;*/
        RenderMesh(mi->GetMesh());
        
        glPopMatrix();
}


void
GlRenderer::SetupFalseColor(const unsigned int id)
{
        // swap bits of the color
        glColor3ub(id&255, (id>>8)&255, (id>>16)&255);
}


unsigned int GlRenderer::GetId(const unsigned char r, 
                                                           const unsigned char g, 
                                                           const unsigned char b) const
{
        return r + (g << 8) + (b << 16);
}


void
GlRenderer::SetupMaterial(Material *m)
{
  if (m)
        glColor3fv(&(m->mDiffuseColor.r));
}


void
GlRenderer::RenderMesh(Mesh *mesh)
{
  int i = 0;

  if (!mUseFalseColors && !mUseForcedColors)
          SetupMaterial(mesh->mMaterial);
  
  for (i=0; i < mesh->mFaces.size(); i++) {
        if (mWireFrame)
          glBegin(GL_LINE_LOOP);
        else
          glBegin(GL_POLYGON);

        Face *face = mesh->mFaces[i];
        for (int j = 0; j < face->mVertexIndices.size(); j++) {
          glVertex3fv(&mesh->mVertices[face->mVertexIndices[j]].x);
        }
        glEnd();
  }
}
        
void
GlRenderer::InitGL()
{
  mSphere = (GLUquadric *)gluNewQuadric();
  
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();

  glFrontFace(GL_CCW);
  glCullFace(GL_BACK);
  glEnable(GL_CULL_FACE);
  glShadeModel(GL_FLAT);
  glDepthFunc( GL_LESS );
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_CULL_FACE);
  
  InitExtensions();

  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE );

  glEnable( GL_NORMALIZE );
  
  glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
  
  OcclusionQuery::GenQueries(mOcclusionQueries, 10);
}


void
GlRenderer::SetupProjection(const int w, const int h, const float angle)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(angle, 1.0, 0.1, 2.0*Magnitude(mSceneGraph->GetBox().Diagonal()));
  glMatrixMode(GL_MODELVIEW);
}



void
GlRenderer::SetupCamera()
{
  Vector3 target = mViewPoint + mViewDirection;

  Vector3 up(0,1,0);
  
  if (abs(DotProd(mViewDirection, up)) > 0.99f)
        up = Vector3(1, 0, 0);
  
  glLoadIdentity();
  gluLookAt(mViewPoint.x, mViewPoint.y, mViewPoint.z,
                        target.x, target.y, target.z,
                        up.x, up.y, up.z);
}

void
GlRenderer::_RenderScene()
{
  ObjectContainer::const_iterator oi = mObjects.begin();
  for (; oi != mObjects.end(); oi++)
        RenderIntersectable(*oi);
}

void
GlRenderer::_RenderSceneTriangles()
{
  glBegin(GL_TRIANGLES);

  ObjectContainer::const_iterator oi = mObjects.begin();
  for (; oi != mObjects.end(); oi++) {
        
        if ((*oi)->Type() == Intersectable::TRIANGLE_INTERSECTABLE) {
          TriangleIntersectable *object = (TriangleIntersectable *)*oi;
          Triangle3 &t = object->GetItem();
          
          Vector3 normal = t.GetNormal();
          glNormal3f(normal.x, normal.y, normal.z);
          glVertex3f(t.mVertices[0].x, t.mVertices[0].y, t.mVertices[0].z);
          glVertex3f(t.mVertices[1].x, t.mVertices[1].y, t.mVertices[1].z);
          glVertex3f(t.mVertices[2].x, t.mVertices[2].y, t.mVertices[2].z);
          
        }
  }

  glEnd();
  
}

bool
GlRenderer::RenderScene()
{
  Intersectable::NewMail();
  static int glList = -1;
  if (mUseGlLists) {
        if (glList == -1) {
          glList = glGenLists(1);
          glNewList(glList, GL_COMPILE);
          _RenderSceneTriangles();
          glEndList();
        }
        
        glCallList(glList);
  } else
        _RenderSceneTriangles();
        
  
  return true;
}


void
GlRendererBuffer::EvalQueryWithItemBuffer(
                                                                                  //RenderCostSample &sample
                                                                           )
{
        // read back the texture
        glReadPixels(0, 0,
                                GetWidth(), GetHeight(),
                                GL_RGBA,
                                GL_UNSIGNED_BYTE,
                                mPixelBuffer);
                
                        
        unsigned int *p = mPixelBuffer;
                        
        for (int y = 0; y < GetHeight(); y++)
        {
                for (int x = 0; x < GetWidth(); x++, p++) 
                {
                        unsigned int id = (*p) & 0xFFFFFF;

                        if (id != 0xFFFFFF)
                                ++ mObjects[id]->mCounter;
                }
        }
}



/****************************************************************/
/*               GlRendererBuffer implementation                */
/****************************************************************/



GlRendererBuffer::GlRendererBuffer(SceneGraph *sceneGraph,
                                                                   ViewCellsManager *viewcells,
                                                                   KdTree *tree):
GlRenderer(sceneGraph, viewcells, tree)  
{
  
  mPixelBuffer = NULL;
  
  // implement width and height in subclasses
}


void
GlRendererBuffer::EvalQueryWithOcclusionQueries(
                                                                           //RenderCostSample &sample
                                                                           )
{
        glDepthFunc(GL_LEQUAL);
                
        glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
        glDepthMask(GL_FALSE);


        // simulate detectemptyviewspace using backface culling
        if (mDetectEmptyViewSpace) 
        {
                glEnable(GL_CULL_FACE);
                //cout << "culling" << endl;
        }
        else
        {
                //cout << "not culling" << endl;
                glDisable(GL_CULL_FACE);
        }

        
        //const int numQ = 1;
        const int numQ = (int)mOcclusionQueries.size();
        
        //glFinish();
#if 0
        //-- now issue queries for all objects
        for (int j = 0; j < (int)mObjects.size(); ++ j) 
        {
                mOcclusionQueries[j]->BeginQuery();
                RenderIntersectable(mObjects[j]);
                mOcclusionQueries[j]->EndQuery();

                unsigned int pixelCount;

                pixelCount = mOcclusionQueries[j]->GetQueryResult();
                mObjects[j]->mCounter += pixelCount;
        }
#else

        int q = 0;

        //-- now issue queries for all objects
        for (int j = 0; j < (int)mObjects.size(); j += q) 
        {       
                for (q = 0; ((j + q) < (int)mObjects.size()) && (q < numQ); ++ q) 
                {
                        //glFinish();
                        mOcclusionQueries[q]->BeginQuery();
                        
                        RenderIntersectable(mObjects[j + q]);
                
                        mOcclusionQueries[q]->EndQuery();
                        //glFinish();
                }
                //cout << "q: " << q << endl;
                // collect results of the queries
                for (int t = 0; t < q; ++ t) 
                {
                        unsigned int pixelCount;
                
                        //-- reenable other state
#if 0
                        bool available;

                        do 
                        {
                                available = mOcclusionQueries[t]->ResultAvailable();
                                
                                if (!available) cout << "W";
                        } 
                        while (!available);
#endif

                        pixelCount = mOcclusionQueries[t]->GetQueryResult();

                        //if (pixelCount > 0)
                        //      cout <<"o="<<j+q<<" q="<<mOcclusionQueries[q]->GetQueryId()<<" pc="<<pixelCount<<" ";
                        mObjects[j + t]->mCounter += pixelCount;
                }

                //j += q;
        }
#endif
        //glFinish();
        glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
        glDepthMask(GL_TRUE);
        
        glEnable(GL_CULL_FACE);
}


void
GlRenderer::RandomViewPoint()
{ 
  // do not use this function since it could return different viewpoints for
  // different executions of the algorithm

  //  mViewCellsManager->GetViewPoint(mViewPoint);

  while (1) {
        Vector3 pVector = Vector3(halton.GetNumber(1),
                                                          halton.GetNumber(2),
                                                          halton.GetNumber(3));
        
        mViewPoint =  mViewCellsManager->GetViewSpaceBox().GetPoint(pVector);
        ViewCell *v = mViewCellsManager->GetViewCell(mViewPoint);
        if (v && v->GetValid())
          break;
        // generate a new vector
        halton.GenerateNext();
  }
  
  Vector3 dVector = Vector3(2*M_PI*halton.GetNumber(4),
                                                        M_PI*halton.GetNumber(5),
                                                        0.0f);
  
  mViewDirection = Normalize(Vector3(sin(dVector.x),
                                                                         //                                                                      cos(dVector.y),
                                                                         0.0f,
                                                                         cos(dVector.x)));
  halton.GenerateNext();
}


void
GlRenderer::RenderBox(const AxisAlignedBox3 &box)
{

  glBegin(GL_LINE_LOOP);
  glVertex3d(box.Min().x, box.Max().y, box.Min().z );
  glVertex3d(box.Max().x, box.Max().y, box.Min().z );
  glVertex3d(box.Max().x, box.Min().y, box.Min().z );
  glVertex3d(box.Min().x, box.Min().y, box.Min().z );
  glEnd();

  glBegin(GL_LINE_LOOP);
  glVertex3d(box.Min().x, box.Min().y, box.Max().z );
  glVertex3d(box.Max().x, box.Min().y, box.Max().z );
  glVertex3d(box.Max().x, box.Max().y, box.Max().z );
  glVertex3d(box.Min().x, box.Max().y, box.Max().z );
  glEnd();

  glBegin(GL_LINE_LOOP);
  glVertex3d(box.Max().x, box.Min().y, box.Min().z );
  glVertex3d(box.Max().x, box.Min().y, box.Max().z );
  glVertex3d(box.Max().x, box.Max().y, box.Max().z );
  glVertex3d(box.Max().x, box.Max().y, box.Min().z );
  glEnd();

  glBegin(GL_LINE_LOOP);
  glVertex3d(box.Min().x, box.Min().y, box.Min().z );
  glVertex3d(box.Min().x, box.Min().y, box.Max().z );
  glVertex3d(box.Min().x, box.Max().y, box.Max().z );
  glVertex3d(box.Min().x, box.Max().y, box.Min().z );
  glEnd();

  glBegin(GL_LINE_LOOP);
  glVertex3d(box.Min().x, box.Min().y, box.Min().z );
  glVertex3d(box.Max().x, box.Min().y, box.Min().z );
  glVertex3d(box.Max().x, box.Min().y, box.Max().z );
  glVertex3d(box.Min().x, box.Min().y, box.Max().z );
  glEnd();

  glBegin(GL_LINE_LOOP);
  glVertex3d(box.Min().x, box.Max().y, box.Min().z );
  glVertex3d(box.Max().x, box.Max().y, box.Min().z );
  glVertex3d(box.Max().x, box.Max().y, box.Max().z );
  glVertex3d(box.Min().x, box.Max().y, box.Max().z );

  glEnd();

}

void
GlRenderer::RenderBvhNode(BvhNode *node)
{
  if (node->IsLeaf()) {
        BvhLeaf *leaf = (BvhLeaf *) node;

#if 0
        if (leaf->mGlList == 0) {
          leaf->mGlList = glGenLists(1);
          if (leaf->mGlList != 0)
                glNewList(leaf->mGlList, GL_COMPILE);
          
          for (int i=0; i < leaf->mObjects.size(); i++)
                RenderIntersectable(leaf->mObjects[i]);
          
          if (leaf->mGlList != 0)
                glEndList();
        }
        
        if (leaf->mGlList != 0)
          glCallList(leaf->mGlList);
#else
        for (int i=0; i < leaf->mObjects.size(); i++)
          RenderIntersectable(leaf->mObjects[i]);
#endif
  } else {
        BvhInterior *in = (BvhInterior *)node;
        RenderBvhNode(in->GetBack());
        RenderBvhNode(in->GetFront());
  }

  //cout << "leaf obj " << i << endl;

}

void
GlRenderer::RenderKdNode(KdNode *node)
{
  if (node->IsLeaf()) {
        KdLeaf *leaf = (KdLeaf *) node;
        for (int i=0; i < leaf->mObjects.size(); i++) {
          RenderIntersectable(leaf->mObjects[i]);
        }
  } else {
        KdInterior *in = (KdInterior *)node;
        RenderKdNode(in->mBack);
        RenderKdNode(in->mFront);
  }
  
}







void
GlRendererBuffer::EvalRenderCostSample(RenderCostSample &sample,
                                                                           const bool useOcclusionQueries,
                                                                           const int threshold
                                                                           )
{
  // choose a random view point
  mViewCellsManager->GetViewPoint(mViewPoint);
  sample.mPosition = mViewPoint;
  //cout << "viewpoint: " << mViewPoint << endl;
  
  // take a render cost sample by rendering a cube
  Vector3 directions[6];
  
  directions[0] = Vector3(1,0,0);
  directions[1] = Vector3(0,1,0);
  directions[2] = Vector3(0,0,1);
  directions[3] = Vector3(-1,0,0);
  directions[4] = Vector3(0,-1,0);
  directions[5] = Vector3(0,0,-1);
  
  sample.mVisibleObjects = 0;
  
  // reset object counters
  ObjectContainer::const_iterator it, it_end = mObjects.end();
  
  for (it = mObjects.begin(); it != it_end; ++ it) 
        {
          (*it)->mCounter = 0;
        }

  ++ mFrame;
  
  //glCullFace(GL_FRONT);
  glCullFace(GL_BACK);
  glDisable(GL_CULL_FACE);
  
  
        // query all 6 directions for a full point sample
  for (int i = 0; i < 6; ++ i) 
        {
          mViewDirection = directions[i];
          SetupCamera();
          
          glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
          glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
          //glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);    glDepthMask(GL_TRUE);
          glDepthFunc(GL_LESS);
          
          mUseFalseColors = true;
          
          // the actual scene rendering fills the depth (for occlusion queries)
          // and the frame buffer (for item buffer)
          RenderScene();
          
          
          if (0) 
                {
                  char filename[256];
                  sprintf(filename, "snap/frame-%04d-%d.png", mFrame, i);
                  //              QImage im = toImage();
                  //              im.save(filename, "PNG");
                }
          
          // evaluate the sample
          if (useOcclusionQueries) 
                {
                  EvalQueryWithOcclusionQueries();
                }
          else 
                {
                  EvalQueryWithItemBuffer();
                }
        }  
  
  // now evaluate the statistics over that sample
  // currently only the number of visible objects is taken into account
  sample.Reset();
  
  for (it = mObjects.begin(); it != it_end; ++ it) 
        {
          Intersectable *obj = *it;
          if (obj->mCounter >= threshold) 
                {
                  ++ sample.mVisibleObjects;
                  sample.mVisiblePixels += obj->mCounter;
                }
        }
  
  //cout << "RS=" << sample.mVisibleObjects << " ";
}


GlRendererBuffer::~GlRendererBuffer()
{
#if 0
#ifdef USE_CG
        if (sCgFragmentProgram)
                cgDestroyProgram(sCgFragmentProgram);
        if (sCgContext)
                cgDestroyContext(sCgContext);
#endif
#endif
}


void
GlRendererBuffer::SampleRenderCost(const int numSamples,
                                                                   vector<RenderCostSample> &samples,
                                                                   const bool useOcclusionQueries,
                                                                   const int threshold
                                                                   )
{
  MakeCurrent();

  if (mPixelBuffer == NULL)
          mPixelBuffer = new unsigned int[GetWidth()*GetHeight()];
  
  // using 90 degree projection to capture 360 view with 6 samples
  SetupProjection(GetHeight(), GetHeight(), 90.0f);

  //samples.resize(numSamples);
  halton.Reset();
  
  // the number of queries queried in batch mode
  const int numQ = 500;

  //const int numQ = (int)mObjects.size();
  if (useOcclusionQueries)
  {
          cout << "\ngenerating " << numQ << " queries ... ";
          OcclusionQuery::GenQueries(mOcclusionQueries, numQ);
          cout << "finished" << endl;
  }

  // sampling queries 
  for (int i = 0; i < numSamples; ++ i)
  {
          cout << ".";
          EvalRenderCostSample(samples[i], useOcclusionQueries, threshold);
  }

  DoneCurrent();
}
  




void
GlRenderer::ClearErrorBuffer()
{
  for (int i=0; i < mPvsStatFrames; i++) {
        mPvsErrorBuffer[i].mError = 1.0f;
  }
  mPvsStat.maxError = 0.0f;
}


void
GlRendererBuffer::EvalPvsStat()
{

  MakeCurrent();

  GlRenderer::EvalPvsStat();
  
  DoneCurrent();
  
  //  mRenderingFinished.wakeAll();
}


void GlRendererBuffer::SampleBeamContributions(Intersectable *sourceObject,
                                                                                           Beam &beam,
                                                                                           const int desiredSamples,
                                                                                           BeamSampleStatistics &stat)
{
        // TODO: should be moved out of here (not to be done every time)
        // only back faces are interesting for the depth pass
        glShadeModel(GL_FLAT);
        glDisable(GL_LIGHTING);

        // needed to kill the fragments for the front buffer
        glEnable(GL_ALPHA_TEST);
        glAlphaFunc(GL_GREATER, 0);

        // assumes that the beam is constructed and contains kd-tree nodes
        // and viewcells which it intersects
  
  
        // Get the number of viewpoints to be sampled
        // Now it is a sqrt but in general a wiser decision could be made.
        // The less viewpoints the better for rendering performance, since less passes
        // over the beam is needed.
        // The viewpoints could actually be generated outside of the bounding box which
        // would distribute the 'efective viewpoints' of the object surface and thus
        // with a few viewpoints better sample the viewpoint space....

        //TODO: comment in
        //int viewPointSamples = sqrt((float)desiredSamples);
        int viewPointSamples = max(desiredSamples / (GetWidth() * GetHeight()), 1);
        
        // the number of direction samples per pass is given by the number of viewpoints
        int directionalSamples = desiredSamples / viewPointSamples;
        
        Debug << "directional samples: " << directionalSamples << endl;
        for (int i = 0; i < viewPointSamples; ++ i) 
        {
                Vector3 viewPoint = beam.mBox.GetRandomPoint();
                
                // perhaps the viewpoint should be shifted back a little bit so that it always lies
                // inside the source object
                // 'ideally' the viewpoints would be distributed on the soureObject surface, but this
        // would require more complicated sampling (perhaps hierarchical rejection sampling of
                // the object surface is an option here - only the mesh faces which are inside the box
                // are considered as candidates) 
                
                SampleViewpointContributions(sourceObject,
                                                                         viewPoint,
                                                                         beam,
                                                                         directionalSamples,
                                                                         stat);
        }


        // note:
        // this routine would be called only if the number of desired samples is sufficiently
        // large - for other rss tree cells the cpu based sampling is perhaps more efficient
        // distributing the work between cpu and gpu would also allow us to place more sophisticated
        // sample distributions (silhouette ones) using the cpu and the jittered once on the GPU
        // in order that thios scheme is working well the gpu render buffer should run in a separate
        // thread than the cpu sampler, which would not be such a big problem....

        // disable alpha test again
        glDisable(GL_ALPHA_TEST);
}



void GlRendererBuffer::SampleViewpointContributions(Intersectable *sourceObject,
                                                                                                        const Vector3 viewPoint,
                                                                                                        Beam &beam,
                                                                                                        const int samples,
                                                    BeamSampleStatistics &stat)
{
    // 1. setup the view port to match the desired samples
        glViewport(0, 0, samples, samples);

        // 2. setup the projection matrix and view matrix to match the viewpoint + beam.mDirBox
        SetupProjectionForViewPoint(viewPoint, beam, sourceObject);


        // 3. reset z-buffer to 0 and render the source object for the beam
        //    with glCullFace(Enabled) and glFrontFace(GL_CW)
        //    save result to the front depth map
        //    the front depth map holds ray origins


        // front depth buffer must be initialised to 0
        float clearDepth;
        
        glGetFloatv(GL_DEPTH_CLEAR_VALUE, &clearDepth);
        glClearDepth(0.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);


        // glFrontFace(GL_CCW);
        glEnable(GL_CULL_FACE);
        glCullFace(GL_FRONT);
        glColorMask(0, 0, 0, 0);
        

        // stencil is increased where the source object is located
        glEnable(GL_STENCIL_TEST);      
        glStencilFunc(GL_ALWAYS, 0x1, 0x1);
        glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);


#if 0
        static int glSourceObjList = -1;         
        if (glSourceObjList != -1) 
        {
                glSourceObjList = glGenLists(1);
                glNewList(glSourceObjList, GL_COMPILE);

                RenderIntersectable(sourceObject);
        
                glEndList();
        }
        glCallList(glSourceObjList);

#else
        RenderIntersectable(sourceObject);

#endif  

         // copy contents of the front depth buffer into depth texture
        glBindTexture(GL_TEXTURE_2D, frontDepthMap);    
        glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, depthMapSize, depthMapSize);

        // reset clear function
        glClearDepth(clearDepth);
        
        
        // 4. set up the termination depth buffer (= standard depth buffer)
        //    only rays which have non-zero entry in the origin buffer are valid since
        //    they realy start on the object surface (this is tagged by setting a
        //    stencil buffer bit at step 3).
        
        glStencilFunc(GL_EQUAL, 0x1, 0x1);
        glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glDepthMask(1);

        glEnable(GL_DEPTH_TEST);
                
        glEnable(GL_CULL_FACE);
        glCullFace(GL_BACK);

        // setup front depth buffer
        glEnable(GL_TEXTURE_2D);
        
#if 0
#ifdef USE_CG
        // bind pixel shader implementing the front depth buffer functionality
        cgGLBindProgram(sCgFragmentProgram);
        cgGLEnableProfile(sCgFragmentProfile);
#endif
#endif
        // 5. render all objects inside the beam 
        //    we can use id based false color to read them back for gaining the pvs

        glColorMask(1, 1, 1, 1);

        
        // if objects not stored in beam => extract objects
        if (beam.mFlags & !Beam::STORE_OBJECTS)
        {
                vector<KdNode *>::const_iterator it, it_end = beam.mKdNodes.end();

                Intersectable::NewMail();
                for (it = beam.mKdNodes.begin(); it != it_end; ++ it)
                {
                        mKdTree->CollectObjects(*it, beam.mObjects);
                }
        }


        //    (objects can be compiled to a gl list now so that subsequent rendering for
        //    this beam is fast - the same hold for step 3)
        //    Afterwards we have two depth buffers defining the ray origin and termination
        

#if 0
        static int glObjList = -1; 
        if (glObjList != -1) 
        {
                glObjList = glGenLists(1);
                glNewList(glObjList, GL_COMPILE);
        
                ObjectContainer::const_iterator it, it_end = beam.mObjects.end();
                for (it = beam.mObjects.begin(); it != it_end; ++ it)
                {
                        // render all objects except the source object
                        if (*it != sourceObject)
                                RenderIntersectable(*it);
                }
                
                glEndList();
        }

        glCallList(glObjList);
#else
        ObjectContainer::const_iterator it, it_end = beam.mObjects.end();
        for (it = beam.mObjects.begin(); it != it_end; ++ it)
        {       
                // render all objects except the source object
                if (*it != sourceObject)
                        RenderIntersectable(*it);
        }
#endif
        
        // 6. Use occlusion queries for all viewcell meshes associated with the beam ->
        //     a fragment passes if the corresponding stencil fragment is set and its depth is
        //     between origin and termination buffer

        // create new queries if necessary
        OcclusionQuery::GenQueries(mOcclusionQueries, (int)beam.mViewCells.size());

        // check whether any backfacing polygon would pass the depth test?
        // matt: should check both back /front facing because of dual depth buffer
        // and danger of cutting the near plane with front facing polys.
        
        glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
        glDepthMask(GL_FALSE);
        glDisable(GL_CULL_FACE);

  
        ViewCellContainer::const_iterator vit, vit_end = beam.mViewCells.end();

        int queryIdx = 0;

        for (vit = beam.mViewCells.begin(); vit != vit_end; ++ vit)
        {
                mOcclusionQueries[queryIdx ++]->BeginQuery();

                RenderIntersectable(*vit);
                
                mOcclusionQueries[queryIdx]->EndQuery();

                ++ queryIdx;
        }

        // at this point, if possible, go and do some other computation

        // 7. The number of visible pixels is the number of sample rays which see the source
        //    object from the corresponding viewcell -> remember these values for later update
        //   of the viewcell pvs - or update immediately?

        queryIdx = 0;

        for (vit = beam.mViewCells.begin(); vit != vit_end; ++ vit)
        {
                // fetch queries
                unsigned int pixelCount = mOcclusionQueries[queryIdx ++]->GetQueryResult();

                if (pixelCount)
                        Debug << "view cell " << (*vit)->GetId() << " visible pixels: " << pixelCount << endl;
        }
        

        // 8. Copmpute rendering statistics
        // In general it is not neccessary to remember to extract all the rays cast. I hope it
        // would be sufficient to gain only the intergral statistics about the new contributions
        // and so the rss tree would actually store no new rays (only the initial ones)
        // the subdivision of the tree would only be driven by the statistics (the glrender could
        // evaluate the contribution entropy for example)
        // However might be an option to extract/store only those the rays which made a contribution
        // (new viewcell has been discovered) or relative contribution greater than a threshold ... 

        ObjectContainer pvsObj;
        stat.pvsSize = ComputePvs(beam.mObjects, pvsObj);
        
        // to gain ray source and termination
        // copy contents of ray termination buffer into depth texture
        // and compare with ray source buffer
#if 0
        VssRayContainer rays;

        glBindTexture(GL_TEXTURE_2D, backDepthMap);     
        glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, depthMapSize, depthMapSize);

        ComputeRays(Intersectable *sourceObj, rays);

#endif

        ////////
        //-- cleanup

        // reset gl state
        glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
        glDepthMask(GL_TRUE);
        glEnable(GL_CULL_FACE);
        glDisable(GL_STENCIL_TEST);

#if 0
#ifdef USE_CG
        cgGLDisableProfile(sCgFragmentProfile);
#endif
#endif

        glDisable(GL_TEXTURE_2D);

        // remove objects from beam
        if (beam.mFlags & !Beam::STORE_OBJECTS)
                beam.mObjects.clear();
}


void GlRendererBuffer::SetupProjectionForViewPoint(const Vector3 &viewPoint, 
                                                                                                   const Beam &beam, 
                                                                                                   Intersectable *sourceObject)
{
        float left, right, bottom, top, znear, zfar;

        beam.ComputePerspectiveFrustum(left, right, bottom, top, znear, zfar,
                                                                   mSceneGraph->GetBox());

        //Debug << left << " " << right << " " << bottom << " " << top << " " << znear << " " << zfar << endl;
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glFrustum(left, right, bottom, top, znear, zfar);
        //glFrustum(-1, 1, -1, 1, 1, 20000);

    const Vector3 center = viewPoint + beam.GetMainDirection() * (zfar - znear) * 0.3f;
        const Vector3 up = 
                Normalize(CrossProd(beam.mPlanes[0].mNormal, beam.mPlanes[4].mNormal));

#ifdef GTP_DEBUG
        Debug << "view point: " << viewPoint << endl;
        Debug << "eye: " << center << endl;
        Debug << "up: " << up << endl;
#endif

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        gluLookAt(viewPoint.x, viewPoint.y, viewPoint.z, 
                          center.x, center.y, center.z,                   
                          up.x, up.y, up.z);
}               

  
void GlRendererBuffer::InitGL()
{
        MakeCurrent(); 
        GlRenderer::InitGL();

        // initialise dual depth buffer textures
        glGenTextures(1, &frontDepthMap);
        glBindTexture(GL_TEXTURE_2D, frontDepthMap);
        
        glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, depthMapSize, 
                                 depthMapSize, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, NULL);

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

        glGenTextures(1, &backDepthMap);
        glBindTexture(GL_TEXTURE_2D, backDepthMap);
        
        glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, depthMapSize, 
                                 depthMapSize, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, NULL);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

#if 0
#ifdef USE_CG

        // cg initialization
        cgSetErrorCallback(handleCgError);
        sCgContext = cgCreateContext();
        
        if (cgGLIsProfileSupported(CG_PROFILE_ARBFP1))
                sCgFragmentProfile = CG_PROFILE_ARBFP1;
        else 
        {
          // try FP30
          if (cgGLIsProfileSupported(CG_PROFILE_FP30))
            sCgFragmentProfile = CG_PROFILE_FP30;
          else 
          {
                  Debug << "Neither arbfp1 or fp30 fragment profiles supported on this system" << endl;
                  exit(1);
          }
  }

 sCgFragmentProgram = cgCreateProgramFromFile(sCgContext,
                                                                                           CG_SOURCE, "../src/dual_depth.cg",
                                                                                           sCgFragmentProfile,
                                                                                           NULL, 
                                                                                           NULL);

  if (!cgIsProgramCompiled(sCgFragmentProgram))
          cgCompileProgram(sCgFragmentProgram);

  cgGLLoadProgram(sCgFragmentProgram);
  cgGLBindProgram(sCgFragmentProgram);

  Debug << "---- PROGRAM BEGIN ----\n" <<
          cgGetProgramString(sCgFragmentProgram, CG_COMPILED_PROGRAM) << "---- PROGRAM END ----\n";

#endif

#endif
  DoneCurrent();
}


void GlRendererBuffer::ComputeRays(Intersectable *sourceObj, VssRayContainer &rays)
{
        for (int i = 0; i < depthMapSize * depthMapSize; ++ i)
        {
                //todo glGetTexImage()
        }
}


void
GlRenderer::EvalPvsStat()
{

  mPvsStat.Reset();
  halton.Reset();

  SetupProjection(GetWidth(), GetHeight());

  cout<<"mPvsStatFrames="<<mPvsStatFrames<<endl;
  
  for (int i=0; i < mPvsStatFrames; i++) {
        float err;
        // set frame id for saving the error buffer
        mFrame = i;
        RandomViewPoint();

        if (mPvsErrorBuffer[i].mError == 1.0f) {
          // check if the view point is valid
          if (!ValidViewPoint())
                mPvsErrorBuffer[i].mError = -1.0f;

          // manualy corrected view point
          if (mFrame == 5105)
                mPvsErrorBuffer[i].mError = -1.0f;
        }
        
        
        // atlanta problematic frames: 325 525 691 1543
#if 0
        if (mFrame != 325 &&
                mFrame != 525 &&
                mFrame != 691 &&
                mFrame != 1543)
          mPvsErrorBuffer[i] = -1;
        else {
          Debug<<"frame ="<<mFrame<<" vp="<<mViewPoint<<" vd="<<mViewDirection<<endl;
        }
#endif
        
        if (mPvsErrorBuffer[i].mError > 0.0f) {
          int pvsSize;
          
          float error = GetPixelError(pvsSize);
          mPvsErrorBuffer[i].mError = error;
          mPvsErrorBuffer[i].mPvsSize = pvsSize;

          //      emit UpdatePvsErrorItem(i,
          //                                                      mPvsErrorBuffer[i]);
          cout<<"("<<i<<","<<mPvsErrorBuffer[i].mError<<")";
          //      swapBuffers();
        }
        
        err = mPvsErrorBuffer[i].mError;
        
        if (err >= 0.0f) {
          if (err > mPvsStat.maxError)
                mPvsStat.maxError = err;
          mPvsStat.sumError += err;
          mPvsStat.sumPvsSize += mPvsErrorBuffer[i].mPvsSize;
          
          if (err == 0.0f)
                mPvsStat.errorFreeFrames++;
          mPvsStat.frames++;
        }
  }
  
  glFinish();
  cout<<endl<<flush;
}

bool
GlRenderer::ValidViewPoint()
{
  if (!mDetectEmptyViewSpace)
        return true;

  OcclusionQuery *query = mOcclusionQueries[0];

  // now check whether any backfacing polygon would pass the depth test
  SetupCamera();
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glEnable( GL_CULL_FACE );
  glCullFace(GL_BACK);
  
  //  cout<<"VV1 ";
  RenderScene();
  
  glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
  glDepthMask(GL_FALSE);
  glDisable( GL_CULL_FACE );
  
  query->BeginQuery();
  
  //  cout<<"VV2 ";
  RenderScene();
  //  cout<<"VV3 ";
  
  query->EndQuery();
  
  // at this point, if possible, go and do some other computation
  glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
  glDepthMask(GL_TRUE);
  glEnable( GL_CULL_FACE );

  //  int wait = 0;
  //  while (!query.ResultAvailable()) {
  //    wait++;
  //  }
  
  // reenable other state
  unsigned int pixelCount = query->GetQueryResult();
  //  cout<<"VV4 ";
  
  if (pixelCount > 0)
        return false; // backfacing polygon found -> not a valid viewspace sample

  return true;
}

float
GlRenderer::GetPixelError(int &pvsSize)
{
  return -1.0f;
}

void
GlRenderer::RenderViewPoint()
{
  mWireFrame = true;
  glPushMatrix();
  glTranslatef(mViewPoint.x, mViewPoint.y, mViewPoint.z);
  glScalef(5.0f,5.0f,5.0f);
  glPushAttrib(GL_CURRENT_BIT);
  glColor3f(1.0f, 0.0f, 0.0f);
  gluSphere((::GLUquadric *)mSphere,
                        1e-3*Magnitude(mViewCellsManager->GetViewSpaceBox().Size()), 6, 6);
  glPopAttrib();
  glPopMatrix();
  mWireFrame = false;
}




}