[vtk-developers] Geocoordinate System Filter, 2D Text Manager, 2D Text Preformance, and Buffered Hardware Picking

Andrew Maclean andrew.amaclean at gmail.com
Tue Dec 18 18:39:13 EST 2007

It may be a good idea but will involve a lot of work.

Are you using Moldensky transforms or Readfern for Lat/Long to UTM? Also for
ECEF (Earth-centered fixed Cartesian coordinates) to Lat/Long you may like
to look at K.M.Borkowski's work. He found a closed form solution. Also UTM
to Lat/Long needs to handle the exceptions near Norway and and to handle
coordinates near the edges of the grid.

You will most likley need to also do inverse and forward transforms using
Vincenty's equations.

Remember to be applicable inVTK iit needs to be world wide and there are
meny coordinate systems out there. So you will need the classes to be

You will also need to specify the accuracy of the transforms.


On Dec 19, 2007 8:18 AM, Philip Schuchardt <ohc at vt.edu> wrote:

> Hello,
> I would like to thank you all for all your hard work.  I love the well
> thought
> out vtk pipeline.
> I'm developing CaveWhere(www.cavewhere.org) and I'm currently using vtk
> and
> wxWidgets to model underground cave systems.  I have also modified and
> developed some useful filter and fixes to vtk.  I would like to contribute
> to
> the vtk project.  I'm just wonding, if your interested in:
> -- Geocoordinate System Filter --
> I work with many geographical coordinate systems (UTM, Stateplane, Lat
> Long,
> etc.).  I currently working on a filter that takes polydata and transforms
> the data to match current geographic projection(ie. world coordinates).
>  All
> geocoordinate filters work together to scale and offset all the data
> around
> the origin.  Scaling and offsetting the data around the origin, reduces
> Z-Buffer persion errors.  Filter's properties will modified by a
> GeocoordinateProperty*. GeocoordinateProperty allow multiple filters to
> share
> the same geographical coordinate system.  I believe this class would be
> useful for anyone doing geo-spatial visualizations.
> -- 2D Text Manager --
> I've written a class that managers 3D anchored, 2D text actors.  It keeps
> multiple text actors from overlapping each other.  It also support
> Z-buffer
> checking, which keeps "hidden" 2D text actors from showing.
> I've also had performance issues while displaying 100's of 2D text actors,
> at
> once.  I think it's a openGL pipeline issue.  Does vtk/ftgl use display
> lists
> for 2D text actors?  If it doesn't, I think display lists would greatly
> improved 2D text actors rendering performance.
> -- Buffered Hardware Picking --
> Also, I've noticed that vtk doesn't support buffered hardware picking.
> In vtkOpenGLCamera.cxx
> vtkgluPickMatrix(ren->GetPickX(), ren->GetPickY(), 1, 1, lowerLeft, size);
> 1,1 - States that the buffer is 1 pixel by 1 pixel.  This small buffer
> makes
> it very difficult to select lines or points.  In my project I have
> extended
> the vtkOpenGLCamera to support buffer greater then 1 by 1 pixels.
> If you like one or more of the ideas please email me back.  I will
> definitely,
> work on getting my code up VTK specifications.
> Thanks,
> Philip Schuchardt
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Andrew J. P. Maclean
Centre for Autonomous Systems
The Rose Street Building J04
The University of Sydney  2006  NSW
Ph: +61 2 9351 3283
Fax: +61 2 9351 7474
URL: http://www.acfr.usyd.edu.au/
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