GDML rendering example (ODD)

In this example we demonstrate how to render detector geometries from a GDML file in Geant4. The example uses the OpenDataDetector model and renders a number of logical volumes to a PNG image. The rendering is done using the GLMakie backend of the Makie.jl graphics library.

Loading the necessary Julia modules

• Geant4 and Geant4.SystemOfUnits for the Geant4 interface and units
• GLMakie for the OpenGL-based rendering backend of Makie

using Geant4
using Geant4.SystemOfUnits
using GLMakie

Set the number of rotation steps for polyhedra to get smoother meshes

HepPolyhedron!SetNumberOfRotationSteps(64)
set_theme!(backgroundcolor = :black)

Create the detector geometry from a GDML file

The function G4JLDetectorGDML reads a GDML file and creates the corresponding Geant4 geometry. The validate_schema=false option is used to skip GDML schema validation for faster loading.

detname = "OpenDataDetector"
detector = G4JLDetectorGDML("$(@__DIR__)/$(detname).gdml"; validate_schema=false);

G4GDML: Reading '/home/runner/work/Geant4.jl/Geant4.jl/docs/src/examples/OpenDataDetector.gdml'...
G4GDML: Reading definitions...
G4GDML: Reading materials...
G4GDML: Reading solids...
G4GDML: Reading structure...
G4GDML: Reading setup...
G4GDML: Reading '/home/runner/work/Geant4.jl/Geant4.jl/docs/src/examples/OpenDataDetector.gdml' done!
Stripping off GDML names of materials, solids and volumes ...

Get the logical volumes to render

odd     = GetVolume("world_volume")[]
lstrips = GetVolume("LongStrips")[]
pixels  = GetVolume("Pixels")[]

Geant4.G4LogicalVolumeDereferenced(Ptr{Nothing}(0x000000008d81ac90))

Create and render scenes

• You can adjust the maxlevel keyword argument in the draw! function to control the level of detail in the rendering.
• The clip keyword argument can be used to apply clipping planes to the geometry for better visibility of internal structures. In this example, we use clip=:xy to clip along the X=0 and Y=0 planes. Other possible values are :x, :y, :z for single-plane, :xz, :yz, :xyz clipping for double and triple planes, and :none for no clipping.
• Lighting options and camera position can be adjusted. See the Lighting and Camera3D documentation of Makie.

for lv in (odd, lstrips, pixels)
  lvname = GetName(lv) |> String
  println("Drawing logical volume: $lvname")
  fig = Figure(size=(1080, 800))
  ax = LScene(fig[1, 1]; show_axis=false, scenekw=(;
      lights=[ PointLight(RGBf(1, 1, 1), Vec3f(1, 1, 0)),
               DirectionalLight(RGBf(1, 1, 1), Vec3f(1, 1, 1) ),
               AmbientLight(RGBf(.5, .5, .5)),
             ]))
  Camera3D(ax.scene, upvector=Vec3f(0, 1, 0), eyeposition=Vec3f(8m, 8m, 2m), lookat=Vec3f(0, 0, 0))
  draw!(ax, lv; maxlevel=7, clip=:xy);
  #display(fig)
  save("$(detname)_$(lvname).png", fig)
end

Drawing logical volume: world_volume
Collecting LV meshes with clip=xy...
 68.430650 seconds (434.60 M allocations: 20.038 GiB, 29.61% gc time, 7.64% compilation time)
Drawning 172553 meshes with total of 50547542 points in 9 steps.
 78.200712 seconds (269.98 M allocations: 210.439 GiB, 37.00% gc time, 3.34% compilation time)
Drawing logical volume: LongStrips
Collecting LV meshes with clip=xy...
 12.179505 seconds (88.67 M allocations: 4.246 GiB, 34.92% gc time)
Drawning 48779 meshes with total of 10514826 points in 6 steps.
 16.567431 seconds (62.77 M allocations: 44.417 GiB, 42.66% gc time)
Drawing logical volume: Pixels
Collecting LV meshes with clip=xy...
  3.781422 seconds (23.58 M allocations: 1.206 GiB, 10.82% gc time)
Drawning 16103 meshes with total of 3000736 points in 6 steps.
  9.654941 seconds (19.56 M allocations: 12.670 GiB, 73.06% gc time)

Show the resulting images

CMS detector rendering

Tracker (long strips) rendering

Pixels rendering

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