CERN Accelerating science


Advanced graphical user interface for particle simulation programs
Flair logo
Project Information with document generator
FLUKA Input editing in human readable way, with interpreted cards
Compiling of FLUKA executable
Classified Output of commands
Output files
Data File Processing
Geometry Plotting Dialog
USRBIN Plotting Dialog
USRBIN Gnuplot output
Photo realistic image with
USRBIN data as surface map
Fluence Plot
Residual Nuclei Dialog
Configuration Dialog
Interactive Graphical Geometry Editor
Geometry Editor interactive debugging
Advanced Layer mechanism: Images, 3D, Usrbin, biasing...
Advanced Layer mechanism: Technical drawing superposition on geometry
DICOM to voxel converter, with density corrections
DICOM to voxel converter, with density corrections
DICOM to voxel converter, with density corrections
DICOM to voxel converter, with density corrections
DICOM to voxel converter, with density corrections
DICOM 3D voxel representation of density > 1.2 g/cm3
DICOM 3D voxel representation of density
DICOM 3D voxel irradiation with 200 MeV proton beam
flair PET scanner geometry generator
3D view of LHC IR7 Long straight section (E.Skordis)
Topview of LHC IR7 (E.Skordis)
Geometry Editor: 3D view of LHC IR7 Dispersion Suppressor (E.Skordis)
Geometry Editor: 3D topview of LHC IR7 Dispersion Suppressor (E.Skordis)
Geometry Editor: Full LHC IR7 (E.Skordis)
Geometry Editor: Beam 2 at LHC interaction point LHC (E.Skordis)
ISOLDE new storage area
Table of isotopes
Sorted list of isotopes
Interactive Manual
Material Database
Full body CT
Full body CT cut with PET CT dose distribution
Full body CT inside PET scanner
BDC dump
Head CT with PET CT dose distribution
Head CT with PET CT dose distribution
Head CT with PET CT dose as source in PET scanner
Head CT with PET CT dose as source in PET scanner
Head CT with PET CT dose as source in PET scanner
Head CT with PET CT dose as source in PET scanner
IR7 geometry editing (E.Skordis)
IR7 geometry editing (E.Skordis)
3D view of the ATLAS Phase-II Upgrade Geometry (T.Manousos)
3D view of the ATLAS Run-2 Geometry with USRBIN layer superimposed (showing the Si1MeV fluences) (T.Manousos)
Beam loss monitor (C.Theis)
CHARM irradiation facility at CERN (C.Theis)
Screenshot of a target with irradiation samples (C.Theis)
Target assembly of the H4IRRAD facility
Energy deposition in a test target
LHC magnet cut open
Beam line of the PS Booster
ISOLDE target frontend
Volume rendering of a voxel phantom
PET simulation with a voxel phantom
Volume rendering of a voxel phantom
From Dec 2019, this site represents the OFFICIAL site for distributing flair v3, supported by the original author of the code.
Support to is discontinued.

Current Version

  • Latest version: 3.1-15.1
  • Released on: Fri 22-Oct-2021
  • Powered by python3, tkinter, gnuplot, pydicom


authors:  Vasilis Vlachoudis (lead author)
Christian Theis
Wioletta Kozlowska


  • modern and intuitive design
  • Input editor for error free inputs
  • Interactive geometry editor, photorealistic ray tracer and debugger
  • run and monitor the simulation
  • back-end for post-processing of results
  • I/O of other simulation formats (MCNPX,GDML,...)
  • Medical file importing, DICOM, RT-PLAN,DOSE,...
  • extended material library


/fleə(r)/  n [U,C] natural or instinctive ability to do something well, to select or recognize what is best, more useful, etc.

flair is an advanced user friendly interface for several Monte Carlo codes. Originally it was developed for FLUKA, where its unique features strongly contributed to the success of both codes FLUKA and flair. From version 3 the interface was separated from the functionality permitting an easy integration of other simulation packages.

The current line of development is to make flair a unique tool for performing calculations with the same input using FLUKA, Geant4, PENELOPE, and other simulations engines.

Presently is fully supporting the CERN FLUKA version and there is ongoing work to support:
  • Moira a Geant4 based application, permitting the user to run with Geant4 FLUKA equivalent inputs with the same geometry, materials, scoring,...
Other codes like MCNP, PHITS, PENELOPE could be added in the future.

Changelog *most* important changes

Version 3.1

Version 3.1 feature a lot of changes targeted mainly for medical applications:
  • DICOM handling improvements:
    • DICOM interface changed, simplified and enhanced in functionality
    • New DICOM editor to perform simple changes like anonymizing of DICOM files
    • Voxel generation can override the material on ROIs performing boolean operations like in the geometry
    • Enhanced RTViewer for cross checking calculations vs RTPLAN
    • RTPLAN processing to create the necessary beams for both Ion and PHOTON plan
    • Convert USRBIN to RTDOSE DICOM format
    • Automatic export to DVH both of RTDOSE and USRBIN's
  • Geometry Editor
    • FARM inclusion: Flair Advanced Render module (C.Theis) a high performance 3D renderer for generating high quality photorealistic 3D geometry plots directly in the geometry editor, comparable to the best 3D renders.
    • Planner tool: creation of RP intervention planning and dose estimation directly in the geometry editor, along a time spline path, assuming a point operator
    • Movie tool: creation of 3D movies with the use of a camera moving along a time-spline path
    • Advanced parenthesis expansion with online-optimization of unwanted zones Far more performant with the past and with the in-built fluka one.
    • Multiple orientation systems:
      • X-up
      • Y-up (default of flair)
      • Z-up
      • DICOM biped
      • DICOM quadruped
  • Input Editor - considerable speed up for undo/redo actions

Version 3

  1. WEBSITE Change, From December 1st 2019 the official web site of flair is
    Support to the is discontinued.
  2. Flair v3 is being completly restructured and based on python v3. Previous versions of flair (until v2.5) were based on Python v2. On January 1 2020, python v2 will no longer be supported by its creators and all major Linux distributions are already moving away from it.
  3. From v3 the master input file for flair is the ".flair" project file (no longer the ".inp"). i.e. the whole FLUKA input file is stored in the ".flair" file in an text human readable way.
  4. Input Editor is now based on a Text widget and no longer on the Canvas. This gives more flexibility to operate as a text-editor, with considerable improvement in performance. (i.e. a huge input file of 25000+ cards was taking almost 20s in the past to be displayed in the input editor, now on the same computer it takes less than 3s.)
  5. The geometry engine is restructured to allow its use as a geometry navigator for simulation programs, allowing the easy integration of the present FLUKA input geometries in Geant4.
  6. There are numerous improvements in the geometry engine for a better user experience, i.e. more logical error checks, 3D plots are enhanced with ambient occlusion for photorealistic shadows, and faster adaptive antialiasing and edge detection.
For a complete log of the new flair v3 features please look at the associated release notes.