Fill TPolyLine object by using colZ

ROOT
1

Dear Rooters,

I would like to create an array of TPolyLine objects which will reflect a detector geometry. Then I want to fill in (or paint) each cell to look like what a TH2 will look like with colZ option. Do you have suggestions how to do that?

Thanks,

2

You will need to access the color palette like THistPainter::PaintColorLevels does it.
root.cern.ch/root/html/src/THist … html#YSSJU

3

Probably the simplest solution is to
-create a TH2F empty
-set min and max
-draw it with colz
-draw your polylines with a color code corresponding to the min/max of the TH2F

Rene

4

Hi,

Thanks for your suggestions. I tried the following lines for filling individual TPolyLine objects:

    float zmin = hist->GetMinimum();
    float zmax = hist->GetMaximum();
    int ndiv     = TMath::(gStyle->GetNumberContours());
    int ncolors  = gStyle->GetNumberOfColors();
   {//loop over i and j
            int binx = hist->GetXaxis()->FindBin(i);
            int biny = hist->GetYaxis()->FindBin(j);
            int bin = hist->GetBin(binx,biny,0);
            float cont = hist->GetBinContent(bin);            
            int q = int((cont/zmax*ncolors)+0.5);
            if( cont > 0)plineW[j][i]->SetFillColor( gStyle->GetColorPalette(q-1));
            if( cont == 0)plineW[j][i]->SetFillColor(0);
    }

It seems working but the color coding on original TH2F and poly lines are different. How can I make the same color scheme? Could you comment on this?

Thanks.

5

Where do you set the hist min/max?
The min/max must correspond to what you set in your polylines.

Rene

6

Hi Brun,

The hist has its min/max set in a different program. I’m accessing to this histogram, and then getting its min and max. In the code I pasted before the max, along with bin content, is used to calculate color number.

Could you explain it little bit more if I’m not answering your question?

Thanks

7

So I assume that for each polyline you have a Z value (like with option COL).
If you want the same behavior as the COL option you should mimic what is done in the function: THistPainter::PaintColorLevels(). something like:

       Double_t scale = ndivz/dz;

       [...]

        color = Int_t(0.01+(z-zmin)*scale);

        [...]

         Int_t theColor = Int_t((color+0.99)*Float_t(ncolors)/Float_t(ndivz));
         if (theColor > ncolors-1) theColor = ncolors-1;
         YourPolygon->SetFillColor(gStyle->GetColorPalette(theColor));