API

A Python package to interpolate data from a NetCFD file onto a VTU file.

netcdf2vtu provides a the Mapper class to read in a NetCFD input file, a destination VTU file and to set some specifics for data interpolation.

class netcdf2vtu.Mapper(nc_path, vtu_path, data_var_names, map_func_type, nc_crs, vtu_crs, nullvalue, **kwargs_nc)

Bases: object

A class for interpolating data from a NetCFD file on a VTU file.

Parameters:

  • nc_path (str) – The path to the NetCFD input file.

  • vtu_path (str) – The path to the destination VTU file.

  • data_var_names (list of str) – A list of variable names to read from the NetCFD file.

  • map_func_type (int) – The type of mapping function to use for interpolation.

  • nc_crs (str) – The coordinate reference system of the NetCFD file.

  • vtu_crs (str) – The coordinate reference system of the VTU file.

  • nullvalue (float) – The value to use for missing data points during interpolation.

  • kwargs_nc (dict) –

    Additional keyword arguments to pass to the NetCFD4 library when

    reading the NetCFD file.

get_nc_variables()

Returns a numpy.ndarray variable data of the NetCFD dataset.

interpolate()

Interpolates the data from the NetCFD file onto the VTU file. It creates a vtkPolyData instance from self.nc[“dataset”] and interpolates this on a copy of an instance of vtkUnstructuredGrid created from the input VTU file.

map(out_path, lat_name, lon_name, time_name=None)

A wrapper for simple interpolation.

read_nc_coords()

Reads the latitude, longitude, and time coordinates from the NetCFD dataset in self.nc[“dataset”].

read_nc_data()

Reads the data variables specified in self.nc[“data_names”] from the NetCFD dataset.

set_nc_coord_names(lat_name, lon_name, time_name=None)

Sets the names of the latitude, longitude, and time variables to be read from the dataset in self.nc[“dataset”].

set_nc_data_names(var_names)

Sets the names of the variables to be read from the NetCFD dataset in self.nc[“dataset”].

Parameters:

var_names (list of str) – A list of variable names to read from the NetCFD file.

write_out_vtu(path)

Writes the updated instance of vtkUnstructuredGrid to the specified path as VTU file.

Parameters:

path (str) – The path of the VTU file to be written.

write_vtp(path)

Writes the vtkPolyData instance created to the specified path as VTP file.

Parameters:

path (str) – The path of the VTP file to be written.

netcdf2vtu.create_vtp(lon_dat, lat_dat, nc_crs, vtu_crs)
Initializes a vtkPolyData object and sets its points and cells based

on input latitude and longitude coordinates.

The point coordinates are transformed to the specified destination coordinate reference system.

initialize src_poly as vtkPolyData set points and cells for src_poly (vtkPolyData object where NetCFD data goes into) cells are vertice cells based on points point coordinates are transformed

Parameters:

  • lon_dat (numpy.ndarray) – A numpy array of longitude coordinates.

  • lat_dat (numpy.ndarray) – A numpy array of latitude coordinates.

  • nc_crs (str) – The coordinate reference system of the input latitude and longitude coordinates.

  • vtu_crs (str) – The destination coordinate reference system to transform the point coordinates to.

Returns:

A vtkPolyData object with points and cells set based on input coordinates.

Return type:

vtk.vtkPolyData

netcdf2vtu.gaussian_kernel()

Gaussian filter of point cloud defined by radius around a point.

Returns:

The Gaussian filter interpolation kernel.

Return type:

vtk.vtkGaussianKernel

netcdf2vtu.get_nc_data(nc, data_var_names)

Extract variable data out of a netcdf4 dataset.

Parameters:

  • nc (netCDF4.Dataset) – The NetCFD dataset to extract data from.

  • data_var_names (list of str) – A list of variable names to extract from nc.

Returns:

A list of tuples, where each tuple contains a variable name and the corresponding data as a numpy array.

Return type:

list

netcdf2vtu.interpolate_vtp_data_on_vtu(vtp, vtu, map_func_type, nullvalue)

Maps the data of a vtkPolyData object onto a vtkUnstructuredGrid object using a specified interpolation algorithm.

Parameters:

  • vtp (vtk.vtkPolyData) – The object that contains the data to be interpolated.

  • vtu (vtk.vtkUnstructuredGrid) – The object that the data will be interpolated onto.

  • map_func_type (int) – The type of mapping function to use for interpolation.

  • nullvalue (float) – The value to use for missing data points during interpolation.

Returns:

An object with the interpolated data.

Return type:

vtk.vtkUnstructuredGrid

netcdf2vtu.nc_data_to_vtp(vtp, nc_data, time=None)

Adds extracted variable data from a NetCFD file to a vtkPolyData object.

Parameters:

  • vtp (vtk.vtkPolyData) – The vtkPolyData object to add the NetCFD data to.

  • nc_data (list) – A list of tuples, where each tuple contains a variable name and its corresponding data as a numpy array.

  • time (numpy.ndarray, optional) – An array of time values for the NetCFD data. If not provided, the time value will be set to “FALSE”.

netcdf2vtu.read_vtu(in_filepath)

Reads an OGS mesh file and returns it as a vtkUnstructuredGrid object.

Parameters:

in_filepath (str) – The path of the VTU file to read.

Returns:

The VTU file as a vtkUnstructuredGrid instance.

Return type:

vtk.vtkUnstructuredGrid

netcdf2vtu.set_map_function(map_func_type)

Returns the specified interpolation/mapping algorithm.

Parameters:

map_func_type (int) – The type of mapping function to use for interpolation. 1: voronoi_kernel 2: gaussian_kernel 3: shepard_kernel

Returns:

An object of the specified interpolation/mapping algorithm.

Return type:

vtk.vtkInterpolationKernel

netcdf2vtu.shepard_kernel()

Interpolation of a point cloud object defined by power function of the radius around a point.

Returns:

The Shepard interpolation kernel.

Return type:

vtk.vtkShepardKernel

netcdf2vtu.voronoi_kernel()

Preferred for categorical data. Takes value of the closest point.

Returns:

The voronoi interpolation kernel.

Return type:

vtk.vtkVoronoiKernel

netcdf2vtu.write_vtp(vtp, outputfile_name)

Writes a vtkPolyData object to a file.

Parameters:

  • vtp (vtk.vtkPolyData) – The vtkPolyData object to write to a file.

  • outputfile_name (str) – The path of the file to write the vtkPolyData object to.

netcdf2vtu.write_vtu(vtu, path)

Writes a vtkUnstructuredGrid object to a file.

Parameters:

  • vtp (vtk.vtkUnstructuredGrid) – The vtkUnstructuredGrid object to write to a file.

  • outputfile_name (str) – The path of the VTU file to be written.