// Display a 3D histogram using GL (box option).
//Author: Timur Pocheptsov
void glh3c()
{
  gStyle->SetCanvasPreferGL(kTRUE);
  

  TGLTH3Composition * comp = new TGLTH3Composition;
  TH3F * h1 = new TH3F("h1", "h1", 10, -1., 1., 10, -1., 1., 10, -1., 1.);
  h1->FillRandom("gaus");
  h1->SetFillColor(kRed);
  TH3F * h2 = new TH3F("h2", "h2", 10, -1., 1., 10, -1., 1., 10, -1., 1.);
  h2->FillRandom("landau");
  h2->SetFillColor(kGreen);
  TH3F * h3 = new TH3F("h3", "h3", 10, -1., 1., 10, -1., 1., 10, -1., 1.);
  h3->FillRandom("gaus");
  h3->SetFillColor(kBlue);
  
  comp->AddTH3(h1);
  comp->AddTH3(h2, TGLTH3Composition::kSphere);
  comp->AddTH3(h3);

  comp->Draw();

  TPaveLabel *title = new TPaveLabel(0.04, 0.86, 0.96, 0.98,
                                     "TH3 composition.");
  title->SetFillColor(32);
  title->Draw();
}