Full simulation updates

docs/howto/full_simulation_tutorial.rst → docs/howto/full_simulation.rst

-Full simulation tutorial
-========================
+Full simulation
+===============
 
-Tutorials are available on a dedicated websites
+Tutorials
+---------
+
+Tutorials are available on a dedicated websites:
 
 Detector simulation
--------------------
+~~~~~~~~~~~~~~~~~~~
 
 - `Full simulation tutorials <https://eic.phy.anl.gov/tutorials/eic_tutorial/getting-started/quickstart>`_
 - `Quick start guide <https://eic.phy.anl.gov/tutorials/eic_tutorial/getting-started/quickstart>`_
@@ -15,6 +18,44 @@ Detector simulation
 `Perticipate in feedback! <https://docs.google.com/forms/d/e/1FAIpQLSclPBXv13pVtawt35XeaCDMOcmdo8fhKTapdmjFO_6gPTV-8w/viewform?usp=sf_link>`_
 
 Tracking
---------
+~~~~~~~~
 
 - `(in development) ACTS tracking repo <https://eicweb.phy.anl.gov/EIC/documentation/guide_to_tracking>`_
+
+
+
+Particle gun
+------------
+
+
+There are at least 2 ways of running a particle gun out of the box:
+
+- using npsim command line
+- using geant macro file and invoke gps
+
+
+Using npsim (wrapper around ddsim) command line: 
+
+.. code:: bash
+
+    # Assumed to run from the root of Athena detector repo
+    # no spread
+    npsim --compactFile=athena.xml --runType=run -G -N=2 --outputFile=test_gun.root --gun.position "0.0 0.0 1.0*cm" --gun.direction "1.0 0.0 1.0" --gun.energy 100*GeV --part.userParticleHandler='' 
+
+    # uniform spread inside an angle:
+    npsim --compactFile=athena.xml --random.seed 1 --enableGun --gun.energy 2*GeV --gun.thetaMin 0*deg --gun.thetaMax 90*deg --gun.distribution uniform --outputFile test.root
+
+
+
+Convert to GDML
+---------------
+
+There is a convert_to_gdml.py script in the detector repository 
+(https://eicweb.phy.anl.gov/EIC/detectors/athena/-/blob/master/scripts/convert_to_gdml.py). 
+That can be used to export ALL of ATHENA to gdml, but not individual detector systems. 
+
+This is actually [done](https://eicweb.phy.anl.gov/EIC/detectors/athena/-/blob/master/.gitlab-ci.yml#L168) on every commit
+and the results are saved as job artifacts. 
+
+`The latest athena.gdml from the master branch <https://eicweb.phy.anl.gov/api/v4/projects/473/jobs/artifacts/master/raw/geo/athena.gdml?job=report&item=default>`_
+

docs/howto/run_simulation.rst

+Run simulation
+==============
+
+This page provides information and tips about running the simulation, geometry visualization and 
+data processing. 
+

docs/howto/s3_file_storage.rst

@@ -39,7 +39,7 @@ One can utilize XRootD server to get access to files without credentials using:
     TFile* file = TFile::Open("root://sci-xrootd.jlab.org//osgpool/eic/ATHENA/" + fileName);
     // ...
 
-
+(!) Currently (July 2021) only RECO is on xrootd (since we only have a 2.5 TB limit there)
 
 Installation
 ------------