[GRASS5] v.out.vtk and r3.out.vtk

Dear dev's and users,
i have implemented a new vector export module called "v.out.vtk". This module
exorts features (point,line,boundary,centroid,area) into the VTK ASCII polydata format.
If complete cat values are provided, they will attached as scalar data.
This modules creats only 3d output, if no elevation is available for the chosen feature,
zero will be the default.

Screenshot from Paraview showing the filed data with categories and the roads vector map (elev=0),
exported from the spearfish dataset with v.out.vtk:

http://www-pool.math.tu-berlin.de/~soeren/grass/modules/v.out.vtk-2dvect.jpg

The module is available at:

http://www-pool.math.tu-berlin.de/~soeren/grass/modules/v.out.vtk.tar.gz

r3.out.vtk:
I have also extended the r3.out.vtk module to support top and bottom surfaces:

http://www-pool.math.tu-berlin.de/~soeren/grass/modules/r3.out.vtk-elevation.jpg

The update is in cvs.

Now raster, raster3d and vector data can be exported into the VTK dataformat.
Some spearfish examples to show the combination of the export modules:

3D elevation with boundary and satellite image (r3.out.vtk and r.out.vtk exports)
http://www-pool.math.tu-berlin.de/~soeren/grass/modules/r.out.vtk-rgb-elevation.jpg

3D elevation output of r3.out.vtk and v.out.vtk (3d roads generated with v.drape)
http://www-pool.math.tu-berlin.de/~soeren/grass/modules/v.out.vtk-3dvect.jpg

To visualize the VTK data, Paraview "www.paraview.org" or MayaVi can be used.

Any suggestions are welcome!

Best regards
Soeren Gebbert