Introduction

This section guides the export of simulation data in the VTK (Visualization Toolkit) format, a widely recognized standard for 3D visualization in scientific computing. The exported files are compatible with visualization tools like ParaView (an open-source software), allowing for detailed analysis and rendering of complex datasets. Both the exported hydro cells and particle data can be opened together in ParaView. For certain functions, multi-threading is used (this feature is experimental). To utilize this, load Julia or your Jupyter Notebook with multiple threads, and the multi-threading will be applied automatically. Paraview can also be used remotely running on a server with MPI.

You can download the necessary files here: https://www.paraview.org.

using Mera

?export_vtk

search: export_vtk export exponent

Export hydro data to VTK format for visualization in tools like ParaView.

export data that is present in your database and can be processed by getvar() (done internally)
select scalar(s) and their unit(s)
select a vector and its unit (like velocity)
export data in log10
creates binary files with optional compression
supports multi-threading

-> generating per-level VTU files for scalar and optionally vector data and creates corresponding VTM multiblock container files to reference these VTU files.

export_vtk(
    dataobject::HydroDataType, outprefix::String;
    scalars::Vector{Symbol} = [:rho],
    scalars_unit::Vector{Symbol} = [:nH],
    scalars_log10::Bool=false,
    vector::Array{<:Any,1}=[missing, missing, missing],
    vector_unit::Symbol = :km_s,
    vector_name::String = "velocity",
    vector_log10::Bool=false,
    positions_unit::Symbol = :standard,
    lmin::Int = dataobject.lmin,
    lmax::Int = dataobject.lmax,
    chunk_size::Int = 50000,
    compress::Bool = true,
    interpolate_higher_levels::Bool = true,
    max_cells::Int = 100_000_000,
    verbose::Bool = true,
    myargs::ArgumentsType=ArgumentsType()
)

Arguments

Required:

dataobject::HydroDataType: The AMR data structure from MERA.jl containing variables like level, position, and physical quantities.
outprefix::String: The base path and prefix for output files (e.g., "output/data" will create files like "output/data_L0.vtu").

Predefined/Optional Keywords:

scalars: List of scalar variables to export (default is :rho); from the database or a predefined quantity (see field: info, function getvar(), dataobject.data)
scalars_unit: Sets the unit for the list of scalars (default is hydrogen number density in cm^-3).
scalars_log10: Apply log10 to the scalars (default false).
vector: List of vector component variables to export (default is missing); exports vector data as separate VTU files
vector_unit: Sets the unit for the vector components (default is km/s).
vector_name: The name of the vector field in the VTK file (default: "velocity").
vector_log10: Apply log10 to the vector components (default: false).
positions_unit: Sets the unit of the cell positions (default: code units); usefull in paraview to select regions
lmin: Minimum AMR level to process (default: simulations lmin); smaller levels are excluded in export
lmax: Maximum AMR level to process (default: simulations lmax); existing higher levels are interpolated down if interpolatehigherlevels is true, otherwise excluded from export
chunk_size::Int = 50000: Size of data chunks for processing (currently unused but reserved for future optimizations).
compress: If true (default), enable compression.
interpolate_higher_levels: If true, interpolate data from higher levels down to given lmax
max_cells: Maximum number of cells to export per level (caps output if exceeded, prioritizing denser regions), (default: 100000000)
verbose: If true (default), print detailed progress and diagnostic messages.

Export particle data to VTK format for visualization in tools like ParaView.

export data that is present in your database and can be processed by getvar() (done internally)
select scalar(s) and their unit(s)
select a vector and its unit (like velocity)
export data in log10
creates binary files with optional compression
supports multi-threading

-> generates VTU files; each particle is represented as a vertex point with associated scalar and vector data.

export_vtk(
    dataobject::PartDataType, outprefix::String;
    scalars::Vector{Symbol} = [:mass],
    scalars_unit::Vector{Symbol} = [:Msol],
    scalars_log10::Bool=false,
    vector::Array{<:Any,1}=[missing, missing, missing],
    vector_unit::Symbol = :km_s,
    vector_name::String = "velocity",
    vector_log10::Bool=false,
    positions_unit::Symbol = :standard,
    chunk_size::Int = 50000,
    compress::Bool = false,
    max_particles::Int = 100_000_000,
    verbose::Bool = true,
    myargs::ArgumentsType=ArgumentsType()
)

Arguments

Required:

**dataobject::PartDataType:*** needs to be of type "PartDataType"
outprefix: The base path and prefix for output file (e.g., "foldername/particles" will create "foldername/particles.vtu").

Predefined/Optional Keywords:

scalars: List of scalar variables to export (default is particle mass); from the database or a predefined quantity (see field: info, function getvar(), dataobject.data)
scalars_unit: Sets the unit for the list of scalars (default is Msun).
scalars_log10: Apply log10 to the scalars (default false).
vector: List of vector component variables to export (default is missing).
vector_unit: Sets the unit for the vector components (default is km/s).
vector_name: The name of the vector field in the VTK file (default: "velocity").
vector_log10: Apply log10 to the vector components (default: false).
positions_unit: Sets the unit of the particle positions (default: code units); usefull in paraview to select regions
chunk_size::Int = 50000: Size of data chunks for processing (reserved for future optimizations).
compress: If false (default), disable compression.
max_particles: Maximum number of particles to export (caps output if exceeded), (default: 100000000)
verbose: If true (default), print detailed progress and diagnostic messages.