IBM Visualization Data Explorer QuickStart Guide
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This section describes several ways of visualizing 2-dimensional
scalar and vector data.
Using the AutoColor tool to color 2-dimensional data is the simplest
visualization method available.
By default, AutoColor assigns blue to the smallest values and red to the
largest.
(If the data are vector, the colors are based on the magnitude
of the vectors).
- Open and execute visual program .../AutoColor2D.net.
The resulting image is a map of temperatures around the world: highest
near the equator and over continents; lowest near the poles and
in the oceans.
- To display the temperature values associated with each color,
connect the output tab of the ColorBar
icon in the VPE window to the open input tab on the
Collect icon.
- Reexecute the visual program.
The Color tool and the Colormap
Editor provide additional control of the
color map:
- Open and execute visual program .../Color2D.net.
- Open the Colormap Editor by double clicking on
the Colormap icon.
- Select Execute on Change in the
Execute pull-down menu.
Any change you now make in the Colormap Editor
appears immediately in the image.
For example, you can experiment with:
- moving control points (clicking on and dragging)
- adding control points (double clicking at the desired location)
- deleting control points (double clicking on individual points).
- Connect the output tab of the ColorBar icon in
the VPE window to the open input tab on the
Collect icon.
- Select Execute on Change in the
Execute pull-down menu.
The color bar from the Colormap Editor now also
appears in the image.
Again, a change made in the editor is immediately reflected in the
image.
For more information, see
AutoColor,
Color, and
ColorBar,
in IBM Visualization Data Explorer User's Reference.
Contour lines connect points of the same value in a 2-dimensional
data set.
The visual program in this example uses elevation data for the
southeastern United States.
- Open and execute visual program .../Isosurface2D.net.
The contour line that appears in the image has an isosurface value of
0 meters (sea level).
- Open the Isosurface configuration dialog box.
- In the value parameter field, change
"0.0" to "20" and click on OK.
The dialog box closes.
- Select Execute on Change in the
Execute pull-down menu and note
the change in the contour line.
- Reopen the Isosurface configuration dialog box and type "0
20" in the value parameter field.
- Click on OK.
The image now consists of two contour lines.
For more information, see Isosurface in IBM Visualization Data Explorer
User's Reference.
If your 2-dimensional data set consists of vectors, you can create
streamlines that trace the path of a massless particle in
a vector field.
- Open and execute visual program
.../Streamlines2D.net.
The image is a set of streamlines that follow a wind field over the
surface of the earth.
- Change the number of streamlines by changing the value of the
density parameter in the configuration dialog box
of the Sample tool.
- Reexecute the visual program.
Note: Streamlines can be generated in other ways as well.
For example:
- Pass a list of 2-dimensional positions to the
start parameter in the
Streamline
configuration dialog
box by either:
- inserting a VectorList interactor stand-in
(from Interactor in the categories palette)
into the visual program, and connecting it to the
start parameter tab of
Streamline or
- typing the start positions in the configuration dialog box for
Streamline.
- Use the Grid tool (from
Realization in the
categories palette) to create a
particular set of start
positions.
Any field that contains positions can be used as the starting point
for streamlines.
This sample visual program contains a Grid tool.
Connect it to the start parameter tab of Streamline.
It generates a 3 × 3 grid of points.
Modify it to create a 10 × 3 grid of starting points.
- Use the Probe tool (from
Special in the
categories palette) to select starting points in
the Image window.
This sample visual program contains a Probe tool.
(Compute is used to make the value of the probe point 2-dimensional.)
Connect the output of Compute to the start
input tab of Streamline, and then move the probe (i.e.,
enter cursor mode, using the View
Control dialog box).
See Grid, Probe, and Streamline in IBM Visualization Data Explorer User's
Reference.
You can "warp" the representation of 2-dimensional data with the
RubberSheet tool.
- Open and execute visual program
.../RubberSheet.net.
The image represents elevation above sea level in the southeastern
United States.
Regions of greatest elevation are colored red; regions of lowest
elevation, blue.
- Open the RubberSheet configuration dialog box.
- Change the value in the scale parameter field to
".002."
- Click on OK and reexecute the
visual program.
The contrast of variation is greatly increased.
For more information, see RubberSheet in IBM Visualization Data Explorer
User's Reference.
You can also add contour lines to a Rubbersheet image:
- Select Realization in the categories palette and
then
Isosurface in the tools palette.
- Place the icon to the right of RubberSheet.
- Connect the output of RubberSheet to the first
input tab of Isosurface (the only connection
that Data Explorer will allow you to make).
Make sure that you do not break the connection to
Shade.
- Open the Isosurface configuration dialog box.
- Change the number parameter value to "10"
and click on OK.
- Select Structuring in the categories palette
and Collect in the tools
palette.
- Place the Collect icon below
Isosurface.
- Connect the outputs of both Shade and
Isosurface to the inputs of
Collect (again, Data Explorer will
allow only valid connections).
- Disconnect Image from
Shade.
- Connect the output of Collect to the input of
Image.
- Reexecute the visual program.
The result is a set of colored contour lines combined with the
Rubbersheet image.
You can change the color of the contour lines:
- Select Transformation in the categories palette
and then Color in the tools palette.
- Place the Color icon to the right of
RubberSheet and
Collect.
- Open the Color configuration dialog box.
- Delete "(no color added)" in the color
parameter field and type in "black"
(the quotation marks are unnecessary and will be added
by Data Explorer).
- Click on OK.
- Move the output of Isosurface from
Collect to Color.
- Connect the output of Color to the input of
Collect.
- Reexecute the visual program.
See Color and Isosurface in IBM Visualization Data Explorer User's
Reference.
In this example, elevation data are represented both by color and by
glyphs (the black circles).
- Open and execute visual program
.../AutoGlyph2DScalar.net.
The elevation values range from higher (orange; larger circles) to lower
(blue; smaller circles).
The size of each glyph (circle) is proportional to the data value it
represents.
To display these values:
- Open the configuration dialog box for AutoGlyph.
- In the type parameter field, replace "(input
dependent)" with "text" and click on OK.
- Reexecute the program.
The actual data values that appear are called text glyphs.
See AutoGlyph in IBM Visualization Data Explorer User's Reference.
Glyphs can be used to represent vector as well as scalar data.
- Open and execute visual program
.../AutoGlyph2DVector.net.
Again, data values are represented by color and by glyphs (arrows).
In this example of wind velocity data, colors represent the magnitude
and arrows the direction.
(The black squares signify missing data or data omitted as invalid
by the Include module in the program.)
See AutoGlyph in IBM Visualization Data Explorer User's Reference.
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