Re: Horizontal slices of 3D data

• To: "P. Tewson" <ptewson@xxxxxxxxxxxxxxxx>
• Subject: Re: Horizontal slices of 3D data
• From: "From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>" <billh@xxxxxxxxxxxxx>
• Date: Tue, 16 Oct 2001 15:03:01 -0500 (CDT)

> Thanks for your help -- moving to the gridded set works great, except for
> a couple of things.
> 
> Trying to resample the FlatField over the newly created domain (to change
> the z-axis value of the horizontal slice) creates the following exception:
> 
> visad.SetException: Gridded3DSet.valueToGrid: ManifoldDimension must be 3
>         at visad.Gridded3DSet.valueToGrid(Gridded3DSet.java:686)
>         at visad.GriddedSet.valueToInterp(GriddedSet.java:319)
>         at visad.FlatField.resample(FlatField.java:3350)
>         at sennev.SEView1b.setCDLevel(sennev/SEView1b.java:205)

This Exception indicates that the domain Set of your
FlatField has domain dimension less than 3 (e.g., 2).
Your original volume data should be a FlatField whose
domain dimension = 3, and your Set argument to this
FlatField's resample() method should have manifold
dimension = 2. The resample method should return a
FlatField whose domain Set has manifold dimension = 2.

> This is not a severe problem as I am able to simply recreate the flatfield
> without any memory or performance problems.
> 
> The second issue is that using the gridded 3D set creates a grid of points
> to make up the horizonal slice, whereas we are intending a 'solid',
> continuous surface that is also transparent (using the Display.Alpha
> scalar map). I can make the surface appear continuous by increasing the
> point size until the entire plane is filled, although zooming in to the
> display still makes the gaps between points apparent, but the alphaMap
> seems to have no effect of making the surface transparent with the 3D set,
> which worked previously using the 2D set mapped to a value on the Z-Axis.

This is strange, and may be because of something about
your MathType and ScalarMaps. If you have a FlatField
whose domain Set is a Gridded3DSet with manifold dimension
= 2 (the result of the resample() call above), then with
proper ScalarMaps your display should be a 'solid' surface,
possibly transparent.

>  |    ____________
>  |   /            /
>  |  /            / <--- transparent, solid
>  | /  .         /
>  |/__:_________/
>  |  /
>  | /
>  |/
>  /_____________

Cheers, Bill

• Follow-Ups:
  • Re: Horizontal slices of 3D data
    • From: P. Tewson

• References:
  • Re: Horizontal slices of 3D data
    • From: P. Tewson