Creating and Viewing geometries

//
//This macro generates two canvases.
// The  first Canvas  has 2 views of the ATLAS detector.
// The  second Canvas  has 2 views of the NA49 detector.
//
gROOT.Reset(c1)
TCanvas c1(c1,"The ATLAS canvas",700,780)
c1.MoveOpaque
//
// Inside the ATLAS canvas, we create 2 pads for 2 different ATLAS views
//
TPad oute(oute,"Outer Detector",0.02,0.02,0.46,0.80,18)
TPad gaas(cryo,"Ga Arsenite Detector",0.52,0.02,0.46,0.80,18)
oute.Draw
gaas.Draw
TPaveLabel atlastitle(0.1,0.86,0.9,0.98,"Two views of the ATLAS detector")
atlastitle.SetFillColor(28)
atlastitle.Draw
//
// Connect ROOT file with the ATLAS detector geometry.
// see TGeometry for explanations how this file was produced
TFile atgeom(atlas.root)
//
//
// ATLAS is a barrel detector. Let's make an exploded view
atlas.cd    //Set current geometry
atlas.SetBomb(2)
//
// Set colors
FMUC2.SetLineColor(5)
RPCB1.SetLineColor(3)
RPTI1.SetLineColor(4)
RPT12.SetLineColor(4)
RPT23.SetLineColor(3)
RPT34.SetLineColor(3)
oute.cd     //Set current pad
OUTE1.Draw
c1.Update
GAAS1.SetVisibility(0)
GDSI2.SetVisibility
GDSI2.SetLineColor(5)
GSUP1.SetLineColor(2)
gaas.cd
GAAS1.Draw
c1.Update
//
// Repeat similar operation for the NA49 detector.
//
TCanvas c2(c2,"The NA49 canvas",700,780)
c2.MoveOpaque
TPad all(all,"A Global view of NA49",0.02,0.02,0.46,0.80,18)
TPad tof(tof,"One Time Of Flight element",0.52,0.02,0.46,0.80,18)
all.Draw
tof.Draw
TPaveLabel na49title(0.1,0.86,0.9,0.98,"Two views of the NA49 detector")
na49title.SetFillColor(28)
na49title.Draw
//
TFile nageom(na49.root)
na49.SetBomb(1.2)
na49.cd    //Set current geometry
all.cd     //Set current pad
na49.Draw
c2.Update
tof.cd
TOFR1.Draw
c2.Update
// To have a better and dynamic view of any of these pads,
// you can click with the middle button of your mouse to select it.
// Then select "View with x3d" in the VIEW menu of the Canvas.
// Once in x3d, you are in wireframe mode by default.
// You can switch to:
//   - Hidden Line mode by typing E
//   - Solid mode by typing R
//   - Wireframe mode by typing W
//   - Stereo mode by clicking S (and you need special glasses)
//   - To leave x3d type Q