[vtkusers] Visualizing Sparse, Structured data in VTK

[David.Pont at ensisjv.com]

"Roland Gaboury" <rolandgaboury at gmail.com> wrote on 26/10/2007 05:58:07:

> Greetings.  I have a set of data which are organized into
> cylindrical geometry... radial spacing of points is constant.
> Angular spacing of radials is (mostly) constant.  Distance between
> layers is not necessarily constant, but it can be managed.
>
> The problem:  As the complexity of the model is increased
> (radially), the spacing between two radials increases until a
> threshold is reached, and a new intermediate radial is spawned from
> the two base radials... and this happens again as the radial
> threshold is crossed again. This is done to reduce the memory
> consumed by the model.
>
> The challenge:  I want to reconstruct these data as a 3D volume.  It
> has been suggested that the data obey a Structured Grid method, but
> a structured grid implies a data point for each and every point in
> the structured grid... which means filling in all the intermediate
> radial data points with some data, presumably interpolating, so that
> ALL radials are filled.  This defeats the purpose of having
> interpolated radials in the first place, and sucks up potentially a
> LOT more resources than we'd like to use... and thirdly it
> represents unnecessary processing that nobody really wants to do.
>
> Alternatively, we could compose an unstructured grid from the data,
> but by the time I read the data, all I have are arrays of X-Y-Z
> coords for each of the data points, plus the scalar data associated
> with each point (that's the storage format).  Can anyone suggest the
> most reasonable approach for reconstructing the volume from  these data?

>
> Roland Gaboury_______________________________________________
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Hi Roland,
   I have processed datasets very much like this (longitudinal series of
tree stem cross sections) and unstructured grid did it for me by creating
hexahedra (and 'wedges' if all radial strips meet at the 'midline'). But
you seem to be saying you dont have connectivity information? can you
access this when reading? it seems like it should be known...

  regards
     Dave P
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