Re: glyphs and hyperstreamlines and VisAD?

• To: John Yao <johnyao@xxxxxxxxxxxxxxxxx>
• Subject: Re: glyphs and hyperstreamlines and VisAD?
• From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Date: Wed, 29 Aug 2001 09:18:05 -0500

Hi John,

> Is there a better way to generate shapes?  I saw a class named
> VisADGeometryArray, but I am not sure how to use the class.

In VisAD you'd create shapes using ScalarMaps of RealTypes to
Display.Shape. RealType values are quantized according to a 1-D
Set and used as indices into an array of shapes, represented as
VisADGeometryArrays (these are analogous to GeometryArray and its
subclasses in Java3D). VisADGeometryArrays may be VisADPointArray,
VisADLineArray, VisADLineStripArray, VisADTriangleArray,
VisADTriangleStripArray, VisADIndexedTriangleStripArray, or
VisADQuadArray8, for various types of geometry. You can control
the color and scale of shapes by mapping other RealTypes to
Display.RGB, Display.Red, etc, and Display.ShapeScale. There is
not yet a Display.ShapeAngle for controlling orientation, but we
are planning to create that and a Display.TextAngle.

There are examples of how to use shapes in Test46.java and
Test47.java in the visad/examples directory.

If you want color to vary over the shape, you can do it by
setting values into the colors array in VisADGeometryArray.

If you want color to be determined by the value of a variable
(i.e., a RealType) then you have to generate your shapes as
FlatFields rather than using ScalarMaps to Display.Shape. For
example, a surface in 3-D would be a FlatField whose domain
Set is a Gridded3DSet or Irregular3DSet with manifold
dimension = 2, and whose range RealTypes would be ScalarMap'ed
to color DisplayRealTypes (Display.RGB, Display.Red, etc).

> ... generate a shape, not to mention manipulating it.

You can combine shape with direct manipulation DataRenderers,
as in visad/rabin/Rain.java and visad/bom/TrackManipulation.java.
Note in the latter a VisADLineArray is constantly recomputed in
response to user manipulation and put into the display via a
call to ShapeControl.setShape().

If you use FlatFields to represent your shapes, then to manipulate
them the RealTuple tied to your DirectManipulationRenderer would
trigger a CellImpl that would recompute the domain Set and
FlatField and pass it to the setData() of a DataReference linked
to the display. Note there are some examples a bit like this in
visad/benjamin/Galaxy.java, notably 'CellImpl red_cursor_cell'.

Cheers,
Bill
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html

• References:
  • glyphs and hyperstreamlines and VisAD?
    • From: John Yao