AliEVE

ALICE Event Visualization Environment

Matevž Tadel, CERN

CHEP-2006 M. Tadel: AliEVE- ALICE Event Visualization Environment 2

Overview

1. Introduction: EVE .vs. event-display two slides of problem statement

2. ALICE Pb—Pb event properties facts & pictures

3. Early exploratory period (Jan-Sep ‘05)

see what can be done; pictures & animation

4. Mature period usability & long-term maintainability; pictures

5. Conclusion

CHEP-2006 M. Tadel: AliEVE- ALICE Event Visualization Environment 3

EVE: definition / general requirements

Event Visualization Environment provides “visualization of” and “Graphical User Interface to”:

detector geometry event data

simulation records: kinematics, hits, digits raw data reconstructed objects: clusters, tracks, kinks, V0's, primary

vertex physics objects: b-tags, Z0, H-candidates, ...

reconstruction & analysis algorithms grid interface for visualization of remote-data calibration and alignment data simulation algorithms detector and machine status

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EVE: purpose

Experts: Visual debugging – of mostly everything Facilitate development of reconstruction and

analysis algorithms

Non-experts: Help users understand the detector, event

structure and reconstruction algorithms Presentations, demonstrations & outreach

activities

All can’t fit in the same box!EVE serves as a framework for construction

of Event Display programs.

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ALICE central Pb-Pb event properties

50-times the event-size of other LHC experiments. Large data size:

80 MB compressed raw-event 1.5 GB size of full simulation/reconstructionProblem for reading (speed) and keeping it in memory.

Large number of tracks, clusters, ... Kinematics: 60k primaries, 600k stored Hits: 150M (TPC); Clusters: 3.2M (TPC), 1.6M (TRD) Reconstructed tracks: 16k

That’s how this looks ...

60k primaries

150M TPC hits thinned down to ~6M (1/cm)

3.2M TPC clusters

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Exploratory period – VSD

VSD – Visualization Summary Data file repack ALICE data into canonic TTrees

global coordinates, flatten containers, summarize keep only data relevant for visualization

data reduced to ~20% use TTree selection mechanisms

general can type any formula can post-process matching entries

use tree-indices & tree-friends

VSD can be made independent of experiment software!

CHEP-2006 M. Tadel: AliEVE- ALICE Event Visualization Environment 10

Exploratory period – Gled

Gled provides object-collection management multi-threaded method execution auto-generated object-GUI general object browser direct access to OpenGL

We were able to try many different things many different combinations.

ALICE geometry(using ROOT’s TGeo classes)

Gled’s object browser

Kinematics & Hits

note track texturing

TPC digitsGL textures used for display

+hits, clusters

ITS digits

also: 2D prototype with GL GUI

Reconstructed & generated tracksselection: pTrec/pTgen in [0.99,1.01]

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Mid-term conclusions (Sep ‘05)

Visualization of complete Pb-Pb events is feasible with standard graphics hardware

ROOT’s trees can be used as an efficient and extensible selection mechanism

We have a flexible visualization engine high-resolution pictures outreach movies

We need to use ROOT’s native GUI & GL long term maintainability for ALICE accessibility to rewop users/developers

CHEP-2006 M. Tadel: AliEVE- ALICE Event Visualization Environment 18

Mature period – Guidelines

Many thanks to Rene for long discussions!

Drop requirements on VSD format, then:

1. Use CINT scripts for: steering of data extraction preparation of visualization objects creation of GUI elements

2. Provide application core: event management & navigation set of visualization atoms management of visualization / GUI elements execution environment for scripts

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Mature period – Benefits

1. Application core not experiment specific

2. Via scripts, users gain full flexibility1. edit them for specific selections, packing of output2. extend them to include user’s private data3. combine them togetherAllows fast development of specific display programs

3. Data can be visualized directly from ROOT1. trees and scripts can be packed together in a single

ROOT file containing several events2. independent of experiment software

laptops, unsupported platforms

use by universities, outreach

REVE browser/editor: editing geometry

ROOT standardGL viewer

note check-boxes and color-tags

Silicon Drift Detector digitscentral event

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Example script: silicon detector hits

void its_hits(const char *varexp = "fX:fY:fZ", const char *selection = "", Option_t *option = "goff"){ AliRunLoader* rl = AliReve::Event::AssertRunLoader(); rl->LoadHits("ITS");

TTree* ht = rl->GetTreeH("ITS", false); ht->Draw(varexp, selection, option);

ReveGui::GuiPointContainer* points = new ReveGui::GuiPointContainer("ITS Hits", ht);

points->SetMarkerColor((Color_t)2); points->SetMarkerStyle((Style_t)6);

gReveGui->AddRenderElement(points, Form("sel=\"%s\", N=%d", selection, points->GetN()));

gReveGui->DrawRenderElement(points);

}

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Conclusion

We have: a powerful prototyping toolkit

also for high resolution images and animations an extendible solution for users

also for stand-alone and external use still a lot of work to do

a major release planned for September