[vtkusers] Interactive adjustment of data objects /CAD

[Nigel Nunn]

Hi Sebastien, 
 
> This is really blocking us... We wonder if using 
> VTK for a CAD application was a good idea... 
 
For a CAD application, let's say you have a model defined by 

 (1)  a set of vertices, and 
 (2)  the surfaces and volumes defined by the 
      connections between those vertices. 
 
Those vertices and connections ("geometry and topology") 
are the main data to be displayed and adjusted.  I treat 
the Vtk sources, filters and widgets as tools to help me 
display and adjust that "geometry and topology". 
 
> Are you saying that we could have a DataObject as 
> the initial object of a pipeline ? 
 
Yes!  Then you can slice it and dice it with all the tools 
Vtk offers for visualizing that data :-) and adjust it by 
catching and interpreting user-interactions.  On Win32/MFC,
we catch the usual messages (OnLButtonDown, OnMouseMove), 
and update the core data accordingly.  We mark THOSE data 
objects as "Modified()", then ask the mappers to "Update()". 
 
> That way, i would treat it like a source and all 
> modifications done to its content would not be lost 
> by any update calls to upstream objects.. (Since
> theres no such upstream objects !) 
 
Yep -- that data is ... "The Source" of "Your Model" 
 
Nigel 
 
 

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