Grass and Vtk - Grass-wiki

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GRASS and VTK

From GRASS-Wiki

See also the GRASS and Paraview wiki page

Contents

1 Export for VTK

2 Workflows

3 vtkGRASSBridge

3.1 Using vtkGRASSBridge in Python

3.2 Import of VTK data into GRASS

4 Links

Export for VTK

Modules

r.out.vtk (http://grass.osgeo.org/grass64/manuals/r.out.vtk.html) - export raster data for VTK

r3.out.vtk (http://grass.osgeo.org/grass64/manuals/r3.out.vtk.html) - export 3D raster (voxel) data for

VTK

v.out.vtk (http://grass.osgeo.org/grass64/manuals/v.out.vtk.html) - export vector maps for VTK

r.colors.out_vtk addon script - export GRASS color rules for use with VTK

Workflows

Load 3D model data into GRASS with r3.in.ascii (http://grass.osgeo.org/grass64/manuals

/r3.in.ascii.html) . (see Help with 3D)

1.

Split 3D raster map into individual layers, and stack them all into one map. (see the r.stack addon

module)

2.

Run r.colors (http://grass.osgeo.org/grass64/manuals/r.colors.html) with the -e equalize histogram flag

to balance the colors nicely over the entire 3D dataset.

3.

Export the new color rules with r.colors.out_vtk.4.

Load in Paraview or similar, create a movie. (animated screenshot (http://stormy.msrc.sunysb.edu

/diecast/DieCAST_GoM_yr43_July16-30.gif) )

5.

vtkGRASSBridge

vtkGRASSBrige provides a VTK/C++ interface to most of the GRASS GIS raster and vector C library

functions. Its using an intuitive class structure to hide the complexity of the GRASS libraries.

ASS and VTK - GRASS-Wiki http://grasswiki.osgeo.org/wiki/GRASS_and_VTK

3 31/07/2013 22:08



Additionally, the vtkGRASSBridge provides access to GRASS C library functions for Python and Java,

using the VTK wrapper.

Reader to convert GRASS datasets (raster, vector) into VTK datasets are provided for raster and vector data.

All vtkImage- and vtkPolyDataAlgorithms can be used to process GRASS raster and vector data. vtkImages

can be directly written as GRASS raster maps into a GRASS location.

This library can be used to build comprehensive 3D visualisation of GRASS GIS data with Java, Python and

C++, as well as base for complex multithreaded image and vector filter to process GRASS GIS datasets i.e:

as backend for WPS server.

Using vtkGRASSBridge in Python

Here a small Python example to triangulate vector points from the North Carolina demo data set with the

VTK delaunay filter class:

# The purpose of this example is

# to read a grass vector map without topology information

# into the VTK poly data format and processing that map with vtkDelaunay2D.# The processed data is written as VTK XML file to the file system

# Init grass variables

init = vtkGRASSInit()

# Now build the pipeline

# read the vector map without creating topology

reader = vtkGRASSVectorPolyDataReader() # The reader does not need topology information

reader.SetVectorName("elev_lid792_randpts")

# Setup the delaunay triangulation

delaunay = vtkDelaunay2D()

delaunay.SetInputConnection(reader.GetOutputPort())

# write the data as XML with base64 encoding

writer = vtkXMLPolyDataWriter()

writer.SetFileName("/tmp/test.vtk")

writer.SetInputConnection(delaunay.GetOutputPort())

writer.Write()

Import of VTK data into GRASS

Implemented in the VTK-GRASS-Bridge:

http://code.google.com/p/vtk-grass-bridge/source/browse/trunk/IO/vtkGRASSRasterImageWriter.h

http://code.google.com/p/vtk-grass-bridge/source/browse/trunk/IO/vtkGRASSVectorPolyDataWriter.h

http://code.google.com/p/vtk-grass-bridge/source/browse/trunk/IO/vtkGRASSRaster3dImageWriter.h

Links

http://code.google.com/p/vtk-grass-bridge/

Retrieved from "http://grasswiki.osgeo.org/grass-wiki/index.php?title=GRASS_and_VTK&oldid=18968"

Categories: Development Linking to other languages VTK 3D Python

This page was last modified on 18 June 2013, at 17:37.

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Content is available under GNU Free Documentation License 1.2.


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Grass and Vtk - Grass-wiki

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