v.out.vtk(1)

NAME
v.out.vtk - Convert a GRASS binary vector map to VTK ASCII output

KEYWORDS
vector

SYNOPSIS
v.out.vtk
v.out.vtk help
v.out.vtk [-c] input=name [output=string] [type=string[,string,...]] [dp=integer] [layer=integer]

  Flags:

-c  Correct the coordinates to fit the VTK-OpenGL precision

  Parameters:

input=name
    Name of input vector map

output=string
    Path to resulting VTK file.

type=string[,string,...]
    Type Options: point,kernel,centroid,line,boundary,area,face Default: point,kernel,centroid,line,boundary,area,face

dp=integer
    Number of significant digits (floating point only)

layer=integer
    Layer number Default: 1

DESCRIPTION
v.out.vtk converts a GRASS vector map in binary format to the VTK ASCII output.

If the output parameter is not given, the output will be send to stdout.

NOTES
The following vector types can be exported together in one VTK ascii file:

        point

        line

        centroid

        boundary

        area

        face
Category data (cat) for the selected vector type and layer will be written as scalar data with name "cat_{vectorname}". If no cat exists, the value will set to -1 as normal cat's are always positive. If a vector has more categories in one layer, only the first category will be exported.
3d vectors are supported by default. The created VTK data always includes x, y and z coordinates (z = 0 if not a 3d vector map). Note that you can easily convert your 2d vectors into 3d vectors with v.drape.
Because of the 32bit limits of OpenGL which is used by VTK, visualisation errors may occure if the grass region contains coordinates greater than 1.000.000 and vector coordinates with 0.01 - 0.001 meters precisison. For this reason, the flag "-c" was added. The coordinates are transformed to smaller coordinates (by decreasing the coordinates with the region center).
If the "-c" flag is used and the data should be visualised together with other data exported via *.out.vtk modules, be sure the "-c" flag was also set in these modules. But this will only work with data from the SAME location (The reference point for the coordinates transformation is based on the default region).
The GRASS vector data is converted into the polydata format of VTK:

        vtk Vertices -- representing points and centroids

        vtk lines -- representing lines and boundaries

        vtk polygons -- representing areas and faces

The VTK file can be visualized with VTK Toolkit, Paraview and MayaVi.

  Attention
If areas or faces are exported, the data have to be triangulated within Paraview or MayaVi.

EXAMPLE
Spearfish example:

Export the soils with cats in layer 1:
v.out.vtk input=soils type=area layer=1 output=/tmp/soils.vtk
Export the streams with cats in layer 1:
v.out.vtk input=streams type=line layer=1 output=/tmp/streams.vtk
Write the archsite vtk output to stdout with cats in layer 1:
v.out.vtk input=archsites type=point layer=1

SEE ALSO
v.out.ascii
r.out.vtk
r3.out.vtk

AUTHOR
Soeren Gebbert

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