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#!CSeaGreen #!N #!Rall609 Interactors and Control Panels #!N #!EC
#!N #!N Interactors are special two-part modules. To incorporate an interactor
into your visual program, you select the preferred type of interactor
from the Interactor category, place it on the VPE #!F-adobe-times-medium-i-normal--18* canvas
#!EF just like any other module, and connect it to the
appropriate input tab or tabs on other modules. The interactor module
that appears on the canvas is called a "stand-in." To use
the interactor interactively, you also place an instance of the interactor
in a Control Panel window. The interactor in the control panel
represents the actual manipulator used by the user exploring the data.
When a value is set by a user, it becomes the
new output of the interactor stand-in and is thereby fed to
the modules connected to the stand-in's output. Interactors have different appearances
depending on its type; numeric (integer or scalar) interactors can be
made to look like dials or sliders, while string interactors give
you a place to type in a string. List interactors let
you keep a list of items: there are lists of strings,
vectors, values, integers, and scalars. #!N #!N It is good "programming"
practice to set interactor minima, maxima, and increments to reasonable values.
For example, a Scale module will accept a value of 0.0,
but the effect will be to make the scaled object disappear!
That is usually not desirable; set the minimum permitted scale value
to be a positive value greater than 0.0 if you do
not want to confuse users of your visual program. #!N #!N
Some interactors can be used in a different mode than interactive:
these are called #!F-adobe-times-medium-i-normal--18* data-driven interactors #!EF . Scalar, Integer, and
Vector interactors, (and their respective List types) all have input tabs
of their own. By default, all the numeric interactors have arbitrary
ranges preset to -1,000,000 to +1,000,000. Clearly, these will rarely be
the appropriate ranges for your data. As part of good interactive
visual program design, you, the visual program author, would like to
restrict these ranges to the "correct" values for the input data
sets. But if you are building a visual program for use
by others, you won't know in advance the ranges of data
sets the user will import. If you build your visual program
such that the data Field (the output of Import, for example)
connects to the input tab on one of these interactors, the
correct maximum and minimum values will be automatically set the first
time the visual program is executed, and they will be updated
appropriately as the input data set changes. Thereafter, the user cannot
accidentally exceed the range of values by turning a dial or
sliding a slider too far in one direction or the other.
#!N #!N Data-driven interactors can be directly driven by Compute functions
that might in turn be connected to a Sequencer or other
data Fields or data components in a Field. As just a
simple example, a Sequencer could emit a series of integers from
0 to 360; a Compute can turn the integers into floating-point
angles in the range from 0.0 to 1.0 then make this
new number the first component of a 3-vector ("[a/360.0, 1.0, 1.0]");
then Convert can change this HSV vector into RGB. Connect the
output of Convert to a Vector Interactor and feed the interactor
output to Color. The result is that the Sequencer will make
the color of an object attached to this Color module pass
through the entire spectrum of hues; simultaneously, you can watch the
RGB values change on the Vector interactor in the Control Panel.
#!N #!N You can have as many Control Panels associated with
a visual program as you like. Furthermore, a handy feature is
that the same "stand-in" (the Interactor module that appears in the
visual program) can have multiple interactor instances associated with it. This
means you can have both simple Control Panels and elaborate Control
Panels with commonly needed interactors appearing in both. When you do
set things up like this, you will notice that the multiple
instances of the interactors will always maintain the same value: as
you change the value in one Control Panel(s), the associated interactor(s)
in the other Control Panel will stay in perfect agreement. #!N
#!N Control Panels can be named and accessed by name. This
allows you to set up hierarchies or even rings of Control
Panels. You might choose to make a simple panel with only
the most commonly used interactors, then create additional panels with less-used
interactors. The main panel can then be set up to access
the subpanels by name, using the Control Panel's #!F-adobe-times-bold-r-normal--18* Panels #!EF
menu. Select #!F-adobe-times-bold-r-normal--18* Open Control Panel by Name #!EF to see
the list of other Control Panels accessible by the current panel.
#!N #!N It is very important to create sensible labels for
the interactors in your Control Panels. Data Explorer will automatically assign
a name to a new interactor that reflects the name of
the module and input to which you have attached the interactor
stand-in in the visual program. However, this name tends to be
too generic, especially if you have several interactors connected to several
similar modules. For example, you connect a Scalar Interactor to the
"value" input of an Isosurface module. The interactor label in your
control panel will acquire the title #!F-adobe-times-bold-r-normal--18* Isosurface value #!EF .
But if you also place another Scalar connected to a different
Isosurface, you will end up with two interactors with identical names.
So it is incumbent upon you, the visual program author, to
change the names of your interactors to reflect their function in
your visual program. See #!Lbuico,dxall380 h Using Control Panels and Interactors #!EL and #!Linterac,dxall409 h Using Interactors #!EL for the instructions on
using Control Panels and Interactors. #!N #!N A very handy interactor
is the Selector. This interactor lets you construct a pop-up menu
containing one or more string items each associated with a value,
either a scalar (including integer scalar), vector or a string. Selector
has two outputs, the value and the string you have entered.
This allows you to present a menu that describes clearly what
choices the user has, and when the user picks an item,
Selector outputs both the value (through its left-hand output tab) and
the string choice (through the right-hand output tab). The right-hand output
can be attached to modules that accept string input. Remember Format?
You can use this technique to change a caption depending on
the user's current Selector choice. #!N #!N If you use integers
as the "values" in your Selector, the left-hand output will be
the currently selected integer. You can direct this numeric output of
Selector to any module that takes an integer; a common use
is to connect the integer output of Selector to a Switch
module. #!N #!N The Switch module (in the Structuring category) uses
a number to pick which of several inputs to pass to
its output. Suppose you have connected an Isosurface to the first
"input" (the second tab) of Switch and a ShowConnections to the
second "input" (third tab). You have also constructed a Selector menu
to offer the three choices: 0 = Both off; 1 =
Show Isosurface; and 2 = Show Connections. The left-hand output of
Selector is connected to the first tab (the "selector") of Switch.
Now when the user chooses item 1 on the menu in
the Selector interactor (located on a control panel, of course), the
number 1 is emitted and received by Switch. Switch then lets
the isosurface pass through. One more trick: you may want to
allow both the Isosurface and the ShowConnections images to appear at
the same time. Use a Collect module just before the Switch.
Attach the Isosurface output both to Switch input 1, and to
Collect; similarly, attach the ShowConnections output to Switch input 2 and
to the Collect. Now add a fourth choice to the Selector
menu: 3 = Show both. Attach the output of Collect to
"input" 3 of Switch, and you have provided this new capability
to the user. By the way, the value "0" will always
turn off all output from the Switch; you do not need
to provide a "0" valued choice if that is not appropriate;
in other words, if you always want Switch to pass at
least one item. #!N #!N The default settings for Selector are
0 = off, 1 = on. You may find this handy
as you begin to develop more complicated visual programs containing a
number of objects in the Image window. As you develop each
"subnet" (that is, a branch of the visual program that yields
a particular visual object), attach it to a Switch and add
an on-off Selector. Change the label of the Selector interactor in
the Control Panel to identify the object it controls. Run the
output of each Switch to a Collect (add inputs to Collect
as needed), then to Image. This way, you have a whole
panel of Switches, allowing you to turn off and on each
object in the scene. This will decrease the amount of time
you wait for all objects to be rendered if you know
that certain ones are OK but wish to test new ones
in the scene. This technique is easier than connecting and breaking
wires, too. #!N #!N #!N #!F-adobe-times-medium-i-normal--18* Next Topic #!EF #!N #!N
#!Lall610,dxall611 h Transmitters and Receivers #!EL #!N #!F-adobe-times-medium-i-normal--18* #!N
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