How do I learn "event display"?

ROOT
1

Hi,

I am a very beginner of ROOT.I joined a project in high energy physics.My work is to learn “detector simulation”.Now I have learned GDML language to describe the detector geometry(In fact,I wonder whether it is strong).

The teacher told me that the event data is stored in root file.So I am eager to know how to display the particle,the cluster or the track events using ROOT, how to define them by myself and how to show the event data together with detector.I cannot find the course about these questions above in the Internet.

So I want your advice sincerely.Would you give me directions or tell me what I should do or what document I should read and learn from now on？

2

Hi everybody,

I also got this via a private message two days back, here’s my reply. Apparently it was insufficient :wink:

Cheers,
Matevz

On 04/23/13 20:27, phpbb@root.cern.ch wrote:

Hello,sir.I am sorry for disturbing you.

Don’t worry, all is good … your English is fine

I am a perplexed beginner from China(My English is not very

good,sorry).I joined a project in high energy physics.My work is to learn
“detector simulation”.Now I learned GDML language to describe the detector
geometry(In fact,I wonder whether it is strong).

It’s used quite frequently … and these days it should be easy to transform it to TGeo geometry used by ROOT.

The teacher tell me that the event data is stored in root file.So now my

largest problem is how to display the track ,the particle or the cluster
event using ROOT and how to define them by myself and how to show the event
data together with detector.What makes me uneasy is I cannot find the
information about the questions above in the Internet.

Wow, you got a complicated task Visualization seems easy but at the end, as you see, you must handle and show all kinds of data. Take a look at examples in $ROOTSYS/tutorials/eve/ and run them, in particular:
geom_cms.C (and other geom_*)
alice_vsd.C
alice_esd.C
but do look at others, too.

Some documentation about eve is here:
root.cern.ch/root/htmldoc/GRAF3D_EVE_Index.html

So I want your advice sincerely.Would you give me directions or tell me

what I should do or what document I should read and learn from now on.

My advice is to take it one step at a time and learn about both your data and visualization tools. So, you can start with geometry, then do clusters and tracks at the end. I can help you a little but I’m quite busy these days.

Out of curiosity, what experiment are you working for?

Best,
Matevz

3

Hi，

I am grateful that you replied me in such patience. :smiley: The project is called LHAASO(Large High Altitude Air Shower Observatory).I have tried to run the files,some can run smoothly,but some can not.The error is such as “…Function alice_vsd() is not defined in current scope /home/cnscott/root/tutorials/eve/alice_vsd.C:29:” :confused:

Cheers,
Suo

4

Hi Suo,

Strange, it seems to work OK here with latest 5.34:

cd $ROOTSYS/tutorials/eve/ root.exe alice_vsd.C
There is logic in this macro to automatically compile it using aclic (it needs proper dictionaries for GUI callbacks to work) so I you run it as:

.L alice_vsd.C alice_vsd()
it might be that what you describe happens … let me try :slight_smile: ah yes, I get:

root [0] .L alice_vsd.C root [1] alice_vsd() Error: alice_vsd() declared but not defined (tmpfile):1: *** Interpreter error recovered ***
but this works OK, too:

root [0] .L alice_vsd.C+ Info in <TUnixSystem::ACLiC>: creating shared library /home/matevz/root-dev/5.34-patches/tutorials/eve/./alice_vsd_C.so root [1] alice_vsd()

Interesting about LHAASO … I didn’t know about it until now, thanks!

Cheers,
Matevz