[vtkusers] Infovis: Changing layout strategy parameters

[Eric E. Monson]

Hey Jeff,

When I call Modified() on the GraphLayout and update the pipeline it  
continues from where it was in the layout process, just with more  
iterations. If I also call Initialize() for the LayoutStrategy it  
resets to the initial temp and decay, but still starts with the  
current positions of the vertices, which is what I wanted -- thanks  
for getting me on the right track!

How does the LayoutStrategy (in these density grid based schemes)  
decide whether to start with random points or not? Will it detect  
whether the graph has non-zero coordinates assigned already, or is  
there some flag that can be set?

Thanks,
-Eric


On Dec 18, 2008, at 9:48 AM, Jeff Baumes wrote:

>> Why do the docs say "The strong recommendation is that you do not  
>> change
>> this parameter" for things like initial temperature and cool down  
>> rate on
>> layout strategies like Fast2D?
>
> You certainly may play around with these parameters. Those values were
> just found to be "good" in practice, where the layout is part of an
> interactive application and you want the layout to complete relatively
> quickly.
>
>> Instead of changing these parameters, is there a way to tell the  
>> layout
>> strategy to give the graph another "kick" from the current state  
>> (rather
>> than from the initial random layout) once it thinks the layout is  
>> complete?
>
> Try this: call Modified() on the vtkGraphLayout instance, then update
> the pipeline again. It should not start from scratch, but should
> instead start with the current positions of the graph.
>
> Jeff