Import and Export Data

This module allows users to export/import NURBS shapes in common CAD exchange formats. The functions starting with import_ are used for generating B-spline and NURBS objects from the input files. The functions starting with export_ are used for saving B-spline and NURBS objects as files.

The following functions import/export control points or export evaluated points:

The following functions work with single or multiple surfaces:

The following functions work with single or multiple volumes:

The following functions can be used to import/export rational or non-rational spline geometries:

The following functions work with single or multiple curves and surfaces:

Function Reference

geomdl.exchange.import_txt(file_name, two_dimensional=False, **kwargs)

Reads control points from a text file and generates a 1-dimensional list of control points.

The following code examples illustrate importing different types of text files for curves and surfaces:

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# Import curve control points from a text file
curve_ctrlpts = exchange.import_txt(file_name="control_points.txt")

# Import surface control points from a text file (1-dimensional file)
surf_ctrlpts = exchange.import_txt(file_name="control_points.txt")

# Import surface control points from a text file (2-dimensional file)
surf_ctrlpts, size_u, size_v = exchange.import_txt(file_name="control_points.txt", two_dimensional=True)

If argument jinja2=True is set, then the input file is processed as a Jinja2 template. You can also use the following convenience template functions which correspond to the given mathematical equations:

  • sqrt(x): \sqrt{x}
  • cubert(x): \sqrt[3]{x}
  • pow(x, y): x^{y}

You may set the file delimiters using the keyword arguments separator and col_separator, respectively. separator is the delimiter between the coordinates of the control points. It could be comma 1, 2, 3 or space 1 2 3 or something else. col_separator is the delimiter between the control points and is only valid when two_dimensional is True. Assuming that separator is set to space, then col_operator could be semi-colon 1 2 3; 4 5 6 or pipe 1 2 3| 4 5 6 or comma 1 2 3, 4 5 6 or something else.

The defaults for separator and col_separator are comma (,) and semi-colon (;), respectively.

The following code examples illustrate the usage of the keyword arguments discussed above.

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# Import curve control points from a text file delimited with space
curve_ctrlpts = exchange.import_txt(file_name="control_points.txt", separator=" ")

# Import surface control points from a text file (2-dimensional file) w/ space and comma delimiters
surf_ctrlpts, size_u, size_v = exchange.import_txt(file_name="control_points.txt", two_dimensional=True,
                                                   separator=" ", col_separator=",")

Please note that this function does not check whether the user set delimiters to the same value or not.

Parameters:
  • file_name (str) – file name of the text file
  • two_dimensional (bool) – type of the text file
Returns:

list of control points, if two_dimensional, then also returns size in u- and v-directions
Return type:

list
Raises:

GeomdlException – an error occurred reading the file
geomdl.exchange.export_txt(obj, file_name, two_dimensional=False, **kwargs)

Exports control points as a text file.

For curves the output is always a list of control points. For surfaces, it is possible to generate a 2-dimensional control point output file using two_dimensional.

Please see exchange.import_txt() for detailed description of the keyword arguments.

Parameters:
  • obj (abstract.SplineGeometry) – a spline geometry object
  • file_name (str) – file name of the text file to be saved
  • two_dimensional (bool) – type of the text file (only works for Surface objects)
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_csv(file_name, **kwargs)

Reads control points from a CSV file and generates a 1-dimensional list of control points.

It is possible to use a different value separator via separator keyword argument. The following code segment illustrates the usage of separator keyword argument.

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# By default, import_csv uses 'comma' as the value separator
ctrlpts = exchange.import_csv("control_points.csv")

# Alternatively, it is possible to import a file containing tab-separated values
ctrlpts = exchange.import_csv("control_points.csv", separator="\t")

The only difference of this function from exchange.import_txt() is skipping the first line of the input file which generally contains the column headings.

Parameters:file_name (str) – file name of the text file
Returns:list of control points
Return type:list
Raises:GeomdlException – an error occurred reading the file
geomdl.exchange.export_csv(obj, file_name, point_type='evalpts', **kwargs)

Exports control points or evaluated points as a CSV file.

Parameters:
  • obj (abstract.SplineGeometry) – a spline geometry object
  • file_name (str) – output file name
  • point_type (str) – ctrlpts for control points or evalpts for evaluated points
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_cfg(file_name, **kwargs)

Imports curves and surfaces from files in libconfig format.

Note

Requires libconf package.

Use jinja2=True to activate Jinja2 template processing. Please refer to the documentation for details.

Parameters:file_name (str) – name of the input file
Returns:a list of rational spline geometries
Return type:list
Raises:GeomdlException – an error occurred writing the file
geomdl.exchange.export_cfg(obj, file_name)

Exports curves and surfaces in libconfig format.

Note

Requires libconf package.

Libconfig format is also used by the geomdl command-line application as a way to input shape data from the command line.

Parameters:
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_yaml(file_name, **kwargs)

Imports curves and surfaces from files in YAML format.

Note

Requires ruamel.yaml package.

Use jinja2=True to activate Jinja2 template processing. Please refer to the documentation for details.

Parameters:file_name (str) – name of the input file
Returns:a list of rational spline geometries
Return type:list
Raises:GeomdlException – an error occurred reading the file
geomdl.exchange.export_yaml(obj, file_name)

Exports curves and surfaces in YAML format.

Note

Requires ruamel.yaml package.

YAML format is also used by the geomdl command-line application as a way to input shape data from the command line.

Parameters:
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_json(file_name, **kwargs)

Imports curves and surfaces from files in JSON format.

Use jinja2=True to activate Jinja2 template processing. Please refer to the documentation for details.

Parameters:file_name (str) – name of the input file
Returns:a list of rational spline geometries
Return type:list
Raises:GeomdlException – an error occurred reading the file
geomdl.exchange.export_json(obj, file_name)

Exports curves and surfaces in JSON format.

JSON format is also used by the geomdl command-line application as a way to input shape data from the command line.

Parameters:
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_obj(file_name, **kwargs)

Reads .obj files and generates faces.

Keyword Arguments:
  • callback: reference to the function that processes the faces for customized output

The structure of the callback function is shown below:

def my_callback_function(face_list):
    # "face_list" will be a list of elements.Face class instances
    # The function should return a list
    return list()
Parameters:file_name (str) – file name
Returns:output of the callback function (default is a list of faces)
Return type:list
geomdl.exchange.export_obj(surface, file_name, **kwargs)

Exports surface(s) as a .obj file.

Keyword Arguments:
  • vertex_spacing: size of the triangle edge in terms of surface points sampled. Default: 2
  • vertex_normals: if True, then computes vertex normals. Default: False
  • parametric_vertices: if True, then adds parameter space vertices. Default: False
  • update_delta: use multi-surface evaluation delta for all surfaces. Default: True
Parameters:
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.export_stl(surface, file_name, **kwargs)

Exports surface(s) as a .stl file in plain text or binary format.

Keyword Arguments:
  • binary: flag to generate a binary STL file. Default: True
  • vertex_spacing: size of the triangle edge in terms of points sampled on the surface. Default: 2
  • update_delta: use multi-surface evaluation delta for all surfaces. Default: True
Parameters:
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.export_off(surface, file_name, **kwargs)

Exports surface(s) as a .off file.

Keyword Arguments:
  • vertex_spacing: size of the triangle edge in terms of points sampled on the surface. Default: 2
  • update_delta: use multi-surface evaluation delta for all surfaces. Default: True
Parameters:
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_smesh(file)

Generates NURBS surface(s) from surface mesh (smesh) file(s).

smesh files are some text files which contain a set of NURBS surfaces. Each file in the set corresponds to one NURBS surface. Most of the time, you receive multiple smesh files corresponding to an complete object composed of several NURBS surfaces. The files have the extensions of txt or dat and they are named as

  • smesh.X.Y.txt
  • smesh.X.dat

where X and Y correspond to some integer value which defines the set the surface belongs to and part number of the surface inside the complete object.

Parameters:file (str) – path to a directory containing mesh files or a single mesh file
Returns:list of NURBS surfaces
Return type:list
Raises:GeomdlException – an error occurred reading the file
geomdl.exchange.export_smesh(surface, file_name, **kwargs)

Exports surface(s) as surface mesh (smesh) files.

Please see import_smesh() for details on the file format.

Parameters:
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_vmesh(file)

Imports NURBS volume(s) from volume mesh (vmesh) file(s).

Parameters:file (str) – path to a directory containing mesh files or a single mesh file
Returns:list of NURBS volumes
Return type:list
Raises:GeomdlException – an error occurred reading the file
geomdl.exchange.export_vmesh(volume, file_name, **kwargs)

Exports volume(s) as volume mesh (vmesh) files.

Parameters:
  • volume (abstract.Volume) – volume(s) to be exported
  • file_name (str) – name of the output file
Raises:

GeomdlException – an error occurred writing the file
geomdl.exchange.import_3dm(file_name, **kwargs)

Imports Rhinoceros/OpenNURBS .3dm file format.

Note

Requires rw3dm module: https://github.com/orbingol/rw3dm

Parameters:file_name (str) – input file name
geomdl.exchange.export_3dm(obj, file_name, **kwargs)

Exports NURBS curves and surfaces in Rhinoceros/OpenNURBS .3dm format.

Note

Requires rw3dm module: https://github.com/orbingol/rw3dm

Parameters:

VTK Support

The following functions export control points and evaluated points as VTK files (in legacy format).

geomdl.exchange_vtk.export_polydata(obj, file_name, **kwargs)

Exports control points or evaluated points in VTK Polydata format.

Please see the following document for details: http://www.vtk.org/VTK/img/file-formats.pdf

Keyword Arguments:
  • point_type: ctrlpts for control points or evalpts for evaluated points
  • tessellate: tessellates the points (works only for surfaces)
Parameters:
Raises:

GeomdlException – an error occurred writing the file