Re: Questions about Streamlines, FlowControl, and FlatField.resample()

• To: Olav Rybatzki <520024853634-0001@xxxxxxxxxxx>
• Subject: Re: Questions about Streamlines, FlowControl, and FlatField.resample()
• From: Bill Hibbard <billh@xxxxxxxxxxxxx>
• Date: Tue, 6 Jan 2004 15:49:35 -0600 (CST)

Hi Olav,

> You are right with your assumption for the analytic plane. The idea to
> override the resample method comes in mind while it would be easy to
> calculate the range values at the same time as calculating the point
> values on the plane. The time consuming task is always finding the
> involved  vertices, edges, and cells (tetrahedra, hexahedra, etc.). if i
> generate a grid in a pre-processing task and pass it into resample then
> the code has to make the search twice. Once by generating the grid and a
> second time during the resampling. the output will always a
> Irregular3DSet with manifold dimension = 2, that's right. But if i write
> it in a pre-processing task i would use the original data. I have to
> deal with structured multiblock grids and unstructured grids with any
> type of cell (tetrahedra, pyramid, prism, hexahedra, and a mixture of
> them). If i use the data from an Irregular3DSet this cells have first to
> be decomposed into tetrahedra that results in a large amount of cells.
> For hexahedra it is a factor between five and six (mostly = 6) for the
> cell number. Another reason is to present the user a grid view of the
> original data. Grid quality has a mayor impact on computing time and the
> accuracy of the result. I would like to do this work in a way that fits
> into VisAD, so that, if no law or contract restrict it, the code can go
> into VisAD under LGPL. At this point i have a little different question.
> Are there any Use Case diagrams available, to see the interaction
> between the diferent classes and methods, for VisAD? This would reduce
> the amount of time to find the right methods that has to be extended for
> my requirements.

We would welcome any new classes you want to add to
the system. You could define them in the visad package,
although I'd probably prefer them in a new package such
as visad.olav (or whatever you'd like to name it).

You could define another sunclass of Set for hexahedra
(rather than tetrahedra), probably a sub-class of
SampledSet (also the super-class of IrregularSet).

For the code to find a Set defined by the intersections
of an analytic plane with edges of hexahedra, that could
be in an instance method of your hexahedra class, or in
a static method. I don't see this code fitting in the
resample() method.

Cheers,
Bill

• References:
  • Re: Questions about Streamlines, FlowControl, and FlatField.resample()
    • From: Olav Rybatzki