void ZOffset3D( TH3* h, float z0) {
//     This boosts the height for each bin of a histogram by a given constant value of z
   int nbinx = h->GetNbinsX();
   int nbiny = h->GetNbinsY();
   int nbinz = h->GetNbinsZ();
   for (int i=1; i<=nbinx; i++) {
      for (int j=1; j<=nbiny; j++) {
          for (int k=1; k<=nbinz; k++) {
            int h0=(h->GetBinContent(i,j,k));
            if (h0>0){h->SetBinContent(i,j,k,z0+h0);}
          }
      }
   }
    h->SetMinimum(0);
}


void NewPalette(int top, int z0,int MaxCol, int MinCol){
    Int_t palette[top]; int q0; int co;
    
    for (int qq=0;qq<top+1;qq++){
        q0=qq-z0;
        if (qq<z0){
            palette[qq]=MinCol;

        }
        if (qq>=z0){
    //         Set the rest of the values between MinCol and Max
            co= (MinCol+(MaxCol-MinCol)*q0*pow(top-z0,-1));            
            palette[qq]=co;
        }
    }
    gStyle->SetPalette(top,palette);

}



void Many3DHistograms(int Nc, int N){
// Nc is the number of planes I want, N is the ammount of bins on each axis per plane
    
    
    TCanvas * c16 = new TCanvas("c16","c16",600,400);
    gStyle->SetCanvasPreferGL(true);
    gStyle->SetOptStat(kFALSE);

    Float_t Xh[N+1],Yh[N+1],Zh[2*Nc];
    int cc2=0;
    int Z[Nc]; //The distances between histograms
    for (int cc=0;cc<Nc;cc++){
        Z[cc]=cc*10;
        Zh[cc2]=cc*10; Zh[cc2+1]=cc*10+1;
        cc2=cc2+2;
    }
    
    for (int ij=0;ij<N+1;ij++){
        Xh[ij]=ij; Yh[ij]=ij; 
    }
    
    TH3I * h = new TH3I("h","Filled", N,Xh, N,Yh, 2*Nc-1,Zh);//Represents the particles detected

    //     To make the straight line
    int x1=N*(gRandom->Rndm()); int y1=N*(gRandom->Rndm()); 
    int xL=N*(gRandom->Rndm()); int yL=N*(gRandom->Rndm()); 
    int z1=Z[0]-10; int zL=Z[Nc-1]+10;

    int XL0[2],YL0[2], ZL0[2];
    XL0[0]=x1;YL0[0]=y1;XL0[1]=xL;YL0[1]=yL;
    ZL0[0]=z1; ZL0[1]=zL;


    int Nin=2000;//Nin events

    for (int c=0;c<Nc;c++){
        int j=0; int k=0;
        int zc=Z[c]; 
        int xc; int yc; 
        
       for (int i=0; i<Nin; i++){
            xc=N*(gRandom->Rndm());
            yc=N*(gRandom->Rndm()); 
            h->Fill(xc,yc,zc);
        }   
        
    }

    ZOffset3D(h, 100); int T=h->GetMaximum();

    NewPalette(T, 100,19,12);  //greys, works great

    TPolyLine3D *g2 = new TPolyLine3D(2, XL0, YL0, ZL0);
    g2->SetLineColor(kRed); g2->SetLineWidth(3);    


    h->Draw("box2 fb");    
    g2->Draw("same");
    h->Draw("box2z fb same");    

    
}



int N=10; int Nc=3;
Many3DHistograms(Nc,N);