Particles: Export Selected Variables to VTK

Simulation Overview & Load Particle Data

using Mera
# use compressed Mera file
path = "/Volumes/FASTStorage/Simulations/Mera-Tests/AV5CDhr/";
info = infodata(600, path)
particles = loaddata(600, path, :particles); # load full box

[Mera]: 2025-06-28T16:52:16.672

Use datatype: hydro
Code: RAMSES
output [600] summary:
mtime: 2024-09-08T15:29:04
ctime: 2024-09-10T11:23:16.230
=======================================================
simulation time: 891.71 [Myr]
boxlen: 48.0 [kpc]
ncpu: 5120
ndim: 3
-------------------------------------------------------
amr:           true
level(s): 6 - 13 --> cellsize(s): 750.0 [pc] - 5.86 [pc]
-------------------------------------------------------
hydro:         true
hydro-variables:  7  --> (:rho, :vx, :vy, :vz, :p, :var6, :var7)
hydro-descriptor: (:density, :velocity_x, :velocity_y, :velocity_z, :pressure, :scalar_00, :scalar_01)
γ: 1.6667
-------------------------------------------------------
gravity:       true
gravity-variables: (:epot, :ax, :ay, :az)
-------------------------------------------------------
particles:     true
- Nstars:   1.353087e+06 
particle-variables: 7  --> (:vx, :vy, :vz, :mass, :family, :tag, :birth)
particle-descriptor: (:position_x, :position_y, :position_z, :velocity_x, :velocity_y, :velocity_z, :mass, :identity, :levelp, :family, :tag, :birth_time)
-------------------------------------------------------
rt:            false
clumps:           false
-------------------------------------------------------
namelist-file: ("&COOLING_PARAMS", "&HYDRO_PARAMS", "&SF_PARAMS", "&AMR_PARAMS", "&BOUNDARY_PARAMS", "&OUTPUT_PARAMS", "&POISSON_PARAMS", "&INIT_PARAMS", "&RUN_PARAMS", "&FEEDBACK_PARAMS", "&REFINE_PARAMS")
-------------------------------------------------------
timer-file:       true
compilation-file: true
makefile:         true
patchfile:        true
=======================================================

[Mera]: 2025-06-28T16:52:22.750

Open Mera-file output_00600.jld2:

domain:
xmin::xmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
ymin::ymax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]
zmin::zmax: 0.0 :: 1.0  	==> 0.0 [kpc] :: 48.0 [kpc]

Memory used for data table :95.81350612640381 MB
-------------------------------------------------------

Export Scalars

Standard Export

# Export full box with all particles (here only stellar particles)

export_vtk(
    particles,                      # loaded data
    "output_part01/0600_galaxy";    # prefix for outputfiles; creates folder output_part01 (if not existing) 
    scalars=[:mass, :age],          # load mass data in Msun and particle age data in Myr
    scalars_unit=[:Msun, :Myr],
    scalars_log10=true,             # apply log10 on the scalars
    positions_unit=:kpc,            # particle positions in kpc (useful in Paraview for region selection)                   
);

[Mera]: 2025-06-28T16:54:51.056

Available Threads: 1
Total particles in dataset: 1353087
Extracting particle positions...
Extracting scalar data...
Writing particle VTU file...
  wrote 0600_galaxy.vtu (Size: 73.55 MB)
Memory cleaned

=== Export Summary ===
Particles exported: 1353087
Particle VTU file: 0600_galaxy.vtu
Available scalars: mass, age

readdir("output_part01")

1-element Vector{String}:
 "0600_galaxy.vtu"

# => in Paraview open the vtu file to load all level data

Export Maximum Number of Particles

# Export full box (here only stellar particles)
# -> limit the number of particles

export_vtk(
    particles,                      # loaded data
    "output_part03/0600_galaxy";    # prefix for outputfiles; creates folder output_part03 (if not existing) 
    scalars=[:age],                 # load age data in Myra
    scalars_unit=[:Myr],
    scalars_log10=true,             # apply log10 on the scalars
    positions_unit=:kpc,            # particle positions in kpc (useful in Paraview for region selection)

    max_particles=1_000             # (caps output if exceeded)
);

[Mera]: 2025-06-28T16:57:30.111

Available Threads: 1
Total particles in dataset: 1353087
Limiting export to 1000 particles (from 1353087)
Extracting particle positions...
Extracting scalar data...
Writing particle VTU file...
  wrote 0600_galaxy.vtu (Size: 0.05 MB)
Memory cleaned

=== Export Summary ===
Particles exported: 1000
Particle VTU file: 0600_galaxy.vtu
Available scalars: age

readdir("output_part03")

1-element Vector{String}:
 "0600_galaxy.vtu"

# => in Paraview open the vtu file to load all level data

Export Scalars and Vector

# Export full box with particles (here only stellar particles)

export_vtk(
    particles,                      # loaded data
    "output_part04/0600_galaxy";    # prefix for outputfiles; creates folder output_part04 (if not existing) 
    scalars=[:age],                 # load age data in Myr
    scalars_unit=[:Msun],
    scalars_log10=true,             # apply log10 on the scalars
    positions_unit=:kpc,            # particle positions in kpc (useful in Paraview for region selection)

    vector=[:vx, :vy, :vz],         # velocity components and its units
    vector_unit=:km_s,
    vector_name="velocity"          # vector name recognized by Paraview
);

[Mera]: 2025-06-28T16:58:14.003

Available Threads: 1
Created directory: output_part04
Total particles in dataset: 1353087
Extracting particle positions...
Extracting scalar data...
Extracting vector data...
Vector matrix dimensions: (3, 1353087) (should be 3×1353087)
Writing particle VTU file...
  wrote 0600_galaxy.vtu (Size: 94.2 MB)
Memory cleaned

=== Export Summary ===
Particles exported: 1353087
Particle VTU file: 0600_galaxy.vtu
Available scalars: age
Available vector: velocity

readdir("output_part04")

1-element Vector{String}:
 "0600_galaxy.vtu"

# => in Paraview open
# - the vtu file to load all particle scalar and vector data

Visualisation in Paraview

Visualize Particles in 3D

# Export full box with scalars and vector data

export_vtk(
    particles,                      # loaded data
    "output_part05/0600_galaxy";    # prefix for outputfiles; creates folder output05 (if not existing) 
    scalars=[:id, :age],            # load density data in cm^-3 
    scalars_unit=[:standard, :Myr],
    positions_unit=:kpc,            # particle positions in kpc (useful in Paraview for region selection)

    vector=[:vx, :vy, :vz],         # velocity components and its units
    vector_unit=:km_s,
    vector_name="velocity"          # vector name recognized by Paraview
);

[Mera]: 2025-06-28T17:02:48.237

Available Threads: 1
Created directory: output_part05
Total particles in dataset: 1353087
Extracting particle positions...
Extracting scalar data...
Extracting vector data...
Vector matrix dimensions: (3, 1353087) (should be 3×1353087)
Writing particle VTU file...
  wrote 0600_galaxy.vtu (Size: 104.52 MB)
Memory cleaned

=== Export Summary ===
Particles exported: 1353087
Particle VTU file: 0600_galaxy.vtu
Available scalars: id, age
Available vector: velocity

readdir("output_part05")

1-element Vector{String}:
 "0600_galaxy.vtu"

Load Data-File

Select age information

# => save state

Visualize Particles & Vectors

Select Glyphs, arrow orientation, number of sample points

# => save state