Logo ROOT  
Reference Guide
 
Loading...
Searching...
No Matches
mandelbrot.C File Reference

Detailed Description

View in nbviewer Open in SWAN
Using TExec to handle keyboard events and TComplex to draw the Mandelbrot set.

Pressing the keys 'z' and 'u' will zoom and unzoom the picture near the mouse location, 'r' will reset to the default view.

Try it (in compiled mode!) with: root mandelbrot.C+

Details

when a mouse event occurs the myexec() function is called (by using AddExec). Depending on the pressed key, the mygenerate() function is called, with the proper arguments. Note the last_x and last_y variables that are used in myexec() to store the last pointer coordinates (px is not a pointer position in kKeyPress events).

#include <TStyle.h>
#include <TROOT.h>
#include <TH2.h>
#include <TComplex.h>
#include <TVirtualPad.h>
#include <TCanvas.h>
TH2F *last_histo = nullptr;
void mygenerate(double factor, double cen_x, double cen_y)
{
printf("Regenerating...\n");
// resize histo:
if(factor>0)
{
double dx=last_histo->GetXaxis()->GetXmax()-last_histo->GetXaxis()->GetXmin();
double dy=last_histo->GetYaxis()->GetXmax()-last_histo->GetYaxis()->GetXmin();
last_histo->SetBins(
last_histo->GetNbinsX(),
cen_x-factor*dx/2,
cen_x+factor*dx/2,
last_histo->GetNbinsY(),
cen_y-factor*dy/2,
cen_y+factor*dy/2
);
last_histo->Reset();
}
else
{
if(last_histo) delete last_histo;
// allocate first view...
last_histo = new TH2F("h2",
"Mandelbrot [move mouse and press z to zoom, u to unzoom, r to reset]",
200,-2,2,200,-2,2);
last_histo->SetStats(false);
}
const int max_iter=50;
for(int bx=1;bx<=last_histo->GetNbinsX();bx++)
for(int by=1;by<=last_histo->GetNbinsY();by++)
{
double x=last_histo->GetXaxis()->GetBinCenter(bx);
double y=last_histo->GetYaxis()->GetBinCenter(by);
TComplex point( x,y);
TComplex z=point;
int iter=0;
while (z.Rho()<2){
z=z*z+point;
last_histo->Fill(x,y);
iter++;
if(iter>max_iter) break;
}
}
last_histo->SetContour(99);
last_histo->Draw("colz");
gPad->Modified();
gPad->Update();
printf("Done.\n");
}
void myexec()
{
// get event information
int event = gPad->GetEvent();
int px = gPad->GetEventX();
int py = gPad->GetEventY();
// some magic to get the coordinates...
double xd = gPad->AbsPixeltoX(px);
double yd = gPad->AbsPixeltoY(py);
float x = gPad->PadtoX(xd);
float y = gPad->PadtoY(yd);
static float last_x;
static float last_y;
{
last_x=x;
last_y=y;
return;
}
const double Z=2.;
switch(px){
case 'z': // ZOOM
mygenerate(1./Z, last_x, last_y);
break;
case 'u': // UNZOOM
mygenerate(Z , last_x, last_y);
break;
case 'r': // RESET
mygenerate(-1 , last_x, last_y);
break;
};
}
void mandelbrot()
{
// cosmetics...
new TCanvas("canvas","View Mandelbrot set");
// this generates and draws the first view...
mygenerate(-1,0,0);
// add exec
gPad->AddExec("myexec","myexec()");
}
@ kKeyPress
Definition Buttons.h:20
constexpr Bool_t kTRUE
Definition RtypesCore.h:100
R__EXTERN TStyle * gStyle
Definition TStyle.h:433
#define gPad
virtual Double_t GetBinCenter(Int_t bin) const
Return center of bin.
Definition TAxis.cxx:478
Double_t GetXmax() const
Definition TAxis.h:140
Double_t GetXmin() const
Definition TAxis.h:139
The Canvas class.
Definition TCanvas.h:23
Double_t Rho() const
Definition TComplex.h:48
virtual Int_t GetNbinsY() const
Definition TH1.h:296
TAxis * GetXaxis()
Definition TH1.h:322
virtual Int_t GetNbinsX() const
Definition TH1.h:295
TAxis * GetYaxis()
Definition TH1.h:323
void Draw(Option_t *option="") override
Draw this histogram with options.
Definition TH1.cxx:3067
virtual void SetContour(Int_t nlevels, const Double_t *levels=nullptr)
Set the number and values of contour levels.
Definition TH1.cxx:8400
virtual void SetBins(Int_t nx, Double_t xmin, Double_t xmax)
Redefine x axis parameters.
Definition TH1.cxx:8684
virtual void SetStats(Bool_t stats=kTRUE)
Set statistics option on/off.
Definition TH1.cxx:8907
2-D histogram with a float per channel (see TH1 documentation)}
Definition TH2.h:258
void Reset(Option_t *option="") override
Reset this histogram: contents, errors, etc.
Definition TH2.cxx:3674
Int_t Fill(Double_t) override
Invalid Fill method.
Definition TH2.cxx:347
void SetPadGridX(Bool_t gridx)
Definition TStyle.h:359
void SetPadGridY(Bool_t gridy)
Definition TStyle.h:360
Double_t y[n]
Definition legend1.C:17
Double_t x[n]
Definition legend1.C:17
Author
Luigi Bardelli barde.nosp@m.lli@.nosp@m.fi.in.nosp@m.fn.i.nosp@m.t

Definition in file mandelbrot.C.