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:

exchange.import_txt()
exchange.export_txt()
exchange.import_csv()
exchange.export_csv()

The following functions work with single or multiple surfaces:

exchange.import_obj()
exchange.export_obj()
exchange.export_stl()
exchange.export_off()
exchange.import_smesh()
exchange.export_smesh()

The following functions work with single or multiple volumes:

exchange.import_vmesh()
exchange.export_vmesh()

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

exchange.import_yaml()
exchange.export_yaml()
exchange.import_cfg()
exchange.export_cfg()
exchange.import_json()
exchange.export_json()

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

exchange.import_3dm()
exchange.export_3dm()

Function Reference

geomdl.exchange.export_3dm(obj, file_name, **kwargs)

Exports NURBS curves and surfaces to Rhinoceros/OpenNURBS .3dm files.

Deprecated since version 5.2.2: rw3dm Python module is replaced by json2on. It can be used to convert geomdl JSON format to .3dm files. Please refer to https://github.com/orbingol/rw3dm for more details.

Parameters:

obj (abstract.Curve, abstract.Surface, multi.CurveContainer, multi.SurfaceContainer) – curves/surfaces to be exported
file_name (str) – file name

geomdl.exchange.export_cfg(obj, file_name)

Exports curves and surfaces in libconfig format.

Note

Requires libconf package.

Parameters:

obj (abstract.SplineGeometry, multi.AbstractContainer) – input geometry
file_name (str) – name of the output file

Raises:

GeomdlException – an error occurred writing 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.export_json(obj, file_name)

Exports curves and surfaces in JSON format.

Parameters:

obj (abstract.SplineGeometry, multi.AbstractContainer) – input geometry
file_name (str) – name of the output file

Raises:

GeomdlException – an error occurred writing the file

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:

surface (abstract.Surface or multi.SurfaceContainer) – surface or surfaces to be saved
file_name (str) – name of the output file

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: 1
update_delta: use multi-surface evaluation delta for all surfaces. Default: True

Parameters:

surface (abstract.Surface or multi.SurfaceContainer) – surface or surfaces to be saved
file_name (str) – name of the output file

Raises:

GeomdlException – an error occurred writing 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:

surface (abstract.Surface or multi.SurfaceContainer) – surface(s) to be exported
file_name (str) – name of the output file

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: 1
update_delta: use multi-surface evaluation delta for all surfaces. Default: True

Parameters:

surface (abstract.Surface or multi.SurfaceContainer) – surface or surfaces to be saved
file_name (str) – name of the output file

Raises:

GeomdlException – an error occurred writing 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.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.export_yaml(obj, file_name)

Exports curves and surfaces in YAML format.

Note

Requires ruamel.yaml package.

Parameters:

obj (abstract.SplineGeometry, multi.AbstractContainer) – input geometry
file_name (str) – name of the output file

Raises:

GeomdlException – an error occurred writing the file

geomdl.exchange.import_3dm(file_name, **kwargs)

Imports curves and surfaces from Rhinoceros/OpenNURBS .3dm files.

Deprecated since version 5.2.2: rw3dm Python module is replaced by on2json. It can be used to convert .3dm files to geomdl JSON format. Please refer to https://github.com/orbingol/rw3dm for more details.

Parameters:: file_name (str) – input file name

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.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.

# 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.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.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.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.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:

# 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.

# 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.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.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

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:

obj (abstract.SplineGeometry, multi.AbstractContainer) – geometry object
file_name (str) – output file name

Raises:

GeomdlException – an error occurred writing the file