[vtkusers] Graph visualization features in VTK

[Jeff Baumes]

On Wed, Jan 26, 2011 at 5:33 AM, Steffen Oeltze <
stoeltze at isg.cs.uni-magdeburg.de> wrote:

>  Hi,
>
>
>     DearAll,
>>>
>>> I plan to evaluate VTK for graph visualization and I wonder whether it
>>> provides the features listed below.
>>> For some features, I already found information online.
>>>
>>
>>
>>> - modifying the edge thickness/width according to some edge weight (???)
>>>
>>
>>  Not currently possible. To stress certain edges I normally use a color
>> map for edges that changes their opacity based on the weight.
>>
>>   Using the opacity is also a good idea. However, I just discovered the
>> vtkGraphToPolyData class which should provide access to the edge geometry.
>> Maybe, by using, e.g., vtkRibbonFilter, I will be able to change the edge
>> width? I wonder how this would influence the edge picking in the view.
>>
>
>  Absolutely. If you want to use the lower-level filters like
> vtkGraphToPolyData, all sorts of other opportunities open up. Ribbons or
> tubes could be used to change the width based on a metric. But you are
> correct that then you don't get picking for free like you do in
> vtkGraphLayoutView. As long as you have a cell or point data array that
> indicates which edge the geometry came from, you should be able to use the
> picker classes in VTK without too much trouble.
>
>
> I toyed around a bit with the above mentioned ribbons and tubes. However, I
> was wondering if there is a more simple method to replace lines as edges by
> my own 2D primitive. For example, would it be possible to derive my own
> class from the class that draws the graph and then, overwrite the method
> that does the actual painting? So far, I was not able to find the class that
> does the line drawing in the graph but I discovered a promising example:
> http://vtk.org/gitweb?p=VTK.git;a=blob;f=Examples/Charts/Cxx/vtkGraphItem.cxx(Paint()-function). Any thoughts on that are very welcome.
>

Yes, this is the way to go for totally customized 2D rendering. Feel free to
use that as a starting point. Longer term, we may want a new general-purpose
graph view that uses this newer 2D rendering engine. This is the engine that
powers all the new charting classes.

Jeff

-- 
Jeff Baumes, Ph.D.
Technical Lead, Kitware Inc.
(518) 881-4932
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