This macro demonstrates how to use "glcol" option for TH3. 
  
void glvox1()
{
   
   const Double_t xMin = -1., xMax = 1., xStep = (xMax - xMin) / (nX - 1);
 
 
   const Double_t yMin = -1., yMax = 1., yStep = (yMax - yMin) / (nY - 1);
 
 
   const Double_t zMin = -1., zMax = 1., zStep = (zMax - zMin) / (nZ - 1);
 
 
   TH3F *hist = 
new TH3F(
"glvoxel", 
"glvoxel", 30, -1., 1., 30, -1., 1., 30, -1., 1.);
 
 
   
   for (
UInt_t i = 0; i < nZ; ++i) {
 
 
      for (
UInt_t j = 0; j < nY; ++j) {
 
 
         for (
UInt_t k = 0; k < nX; ++k) {
 
 
         }
      }
   }
 
 
}
R__EXTERN TStyle * gStyle
 
void Draw(Option_t *option="") override
Draw this histogram with options.
 
3-D histogram with a float per channel (see TH1 documentation)}
 
void SetBinContent(Int_t bin, Double_t content) override
Set bin content.
 
void SetCanvasPreferGL(Bool_t prefer=kTRUE)
 
- Author
 - Timur Pocheptsov 
 
Definition in file glvox1.C.