TGraph2D SetPoint problems inside a non-for loop

ROOT
3

Try: [code]#include “TSystem.h”
#include “TCanvas.h”
#include “TPad.h”
#include “TRandom.h”
#include “TGraph2D.h”
#include “TPolyLine3D.h”

void trial(void) {
Int_t i, j;
Double_t x, y, z;

TCanvas *c1 = new TCanvas(“c1”);
c1 = c1; // get rid of the warning: unused variable ‘c1’

Int_t m = 100;
TGraph2D *g2 = ((TGraph2D *)0);

Int_t n = 10;
TPolyLine3D *l = ((TPolyLine3D *)0);

for (j = 0; j < 100; j++) {
// delete the “previous” TPolyLine3D
delete l; // delete “l” before deleting “g2”
// delete the “previous” TGraph2D
delete g2;

g2 = new TGraph2D(m);
g2->SetTitle("TGraph2D and TPolyLine3D");
for (i = 0; i < m; i++) {
  gRandom->Rannor(x, y);
  z = x*x + y*y;
  g2->SetPoint(i, x, y, z);
} // for (i ...

// c1->cd();
g2->Draw("surf4");
// gPad->Modified(); gPad->Update();
// gSystem->Sleep(100); // 100 ms delay

l = new TPolyLine3D(n);
for (i = 0; i < n; i++) {
  x = 2.0 * gRandom->Rndm();
  y = 2.0 * gRandom->Rndm();
  z = 2.0 * gRandom->Rndm();
  l->SetPoint(i, x, y, z);
} // for (i ...

// c1->cd();
l->Draw();
gPad->Modified(); gPad->Update();
gSystem->Sleep(100); // 100 ms delay

} // for (j …
} // void trial(void) …[/code]