EIC code displayed by LXR master/​tutorial-geometry-development-using-dd4hep/​episodes/​02-viewing-geometry.md	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

Warning, /tutorial-geometry-development-using-dd4hep/episodes/02-viewing-geometry.md is written in an unsupported language. File is not indexed.

 ---
 title: "Viewing the geometry"
 teaching: 10
 exercises: 10
 ---
 
 ::::::::::::::::::::::::::::::::::::::::::::: questions
 
 - How can we view the geometry?
 
 :::::::::::::::::::::::::::::::::::::::::::::
 
 ::::::::::::::::::::::::::::::::::::::::::::: objectives
 
 - Understand how to export the geometry with `dd_web_display`.
 - Know of multiple ways in which to open ROOT TGeo geometries.
 
 :::::::::::::::::::::::::::::::::::::::::::::
 
 ## Introduction
 
 Before we move to discussion of the detector plugins in the next part, let's discuss visualization on your local system.
 
 ## ROOT visualization
 
 The geometry included in `eic-shell` can be viewed with the ROOT geometry browser. However, we first need to export it from the built-in DD4hep format to the ROOT TGeo format, with a small utility program `dd_web_display`. To do this, we will need to ensure we are in a directory where we have write access, such as the directory `~/eic/`.
 
 ```bash
 $ cd ~/eic/
 $ dd_web_display --export $DETECTOR_PATH/$DETECTOR_CONFIG.xml
 ```
 
 ::::::::::::::::::::::::::::::::::::::::::::: callout
 
 Note: If you are not inside `eic-shell`, you may need to be connected to the internet as you run this command since a magnetic fieldmap will need to be downloaded.
 
 :::::::::::::::::::::::::::::::::::::::::::::
 
 The `dd_web_display` utility will create a ROOT file in the current directory that can be opened with the geometry viewer online at the [ANL geometry viewer](https://eic.phy.anl.gov/geoviewer/) or the [ROOT JSROOT viewer](https://root.cern/js/latest), or a local ROOT installation. VSCode also has a JSROOT extension which provides the same functionality as the browser.
 
 ::::::::::::::::::::::::::::::::::::::::::::: callout
 
 Note: The version of JSROOT on the [ANL geometry viewer](https://eic.phy.anl.gov/geoviewer/) is older than the [ROOT JSROOT viewer](https://root.cern/js/latest) version so some differences in the visualisation may be present.
 
 :::::::::::::::::::::::::::::::::::::::::::::
 
 The output file is by default named `detector_geometry.root` this can be changed if you want to look at several configurations using e.g.
 
 ```bash
 $ dd_web_display -o vertex_geometry.root --export $DETECTOR_PATH/epic_vertex_only.xml
 ```
 
 For local ROOT installations, the following commands may be helpful:
 
 ```c++
 TGeoManager::Import("detector_geometry.root");
 gGeoManager->GetTopVolume()->Draw("ogl")
 ```
 
 The geometry viewer has to make decisions on what to draw in order to keep the number of facets small enough. This means that detectors with a large number of repeated components may not be drawn, or other detectors may not be drawn when those detectors are drawn. For this reason, we also have the subsystem-specific entry points xml files. For visualization of specific subsystems, these files are recommended.
 
 Parameters describing how each component of the geometry should be vizualised are contained within the detector plugins and can be controlled through the xml description.
 
 ::::::::::::::::::::::::::::::::::::::::::::: challenge
 
 ## Exercise: view a subsystem
 
 - Export a different detector configuration from the default `epic.xml`, and export this to ROOT TGeo format.
 - Open the exported ROOT file in the geometry viewer at the [ANL geometry viewer](https://eic.phy.anl.gov/geoviewer/) or the [ROOT JSROOT viewer](https://root.cern/js/latest).
 
 ::::::::::::::: solution
 
 For example `dd_web_display -o vertex_geometry.root --export $DETECTOR_PATH/epic_vertex_only.xml`
 produces `vertex_geometry.root`; loading that file in either viewer shows only the vertex barrel,
 which renders faster and is easier to inspect than the full `epic.xml`.
 
 :::::::::::::::
 
 :::::::::::::::::::::::::::::::::::::::::::::
 
 ## Geant4 visualization
 
 **Warning: might not work for various reasons.** If you are used to the Geant4 geometry visualisation or want to visually inspect where a subset of your event sample this is still possible using npsim.
 
 ```bash
 npsim --runType qt --compactFile $DETECTOR_PATH/epic_vertex_only.xml --inputFiles root://dtn-eic.jlab.org//volatile/eic/EPIC/EVGEN/SIDIS/pythia6-eic/1.0.0/18x275/q2_0to1/pythia_ep_noradcor_18x275_q2_0.000000001_1.0_run9.ab.hepmc3.tree.root --macro macro/b0_vis.mac
 ```
 
 This particular example uses pythia6 min-bias events stored on the xrootd server at jlab. The visualization of particle tracks and the detector is controlled by the `macro/b0_vis.mac` file.
 
 ::::::::::::::::::::::::::::::::::::::::::::: callout
 
 Note: Geant4 does not try and limit its visualization of components so depending on your machine the full detector might struggle, please be patient. This performs much better outside of `eic-shell` but takes a long time to set up the environment.
 
 :::::::::::::::::::::::::::::::::::::::::::::
 
 ## Other visualisation you might want
 
 - ACTS Surfaces
 - Material Map
 - Event display
 
 These are avaliable in various forms but not covered in this tutorial.
 
 ::::::::::::::::::::::::::::::::::::::::::::: keypoints
 
 - The geometry, exported to the ROOT TGeo file, can be viewed with ROOT.
 
 :::::::::::::::::::::::::::::::::::::::::::::

This page was automatically generated by the 2.3.7 LXR engine. The LXR team