The widgets on the control panel allow you to control the value of the module parameters directly.

Widget Types

The widget types are listed on the Type option menu (see Figure 4-2) and described in detail in “Setting Module Parameters” in Chapter 2. All widgets must have a valid type selected, including those you place on a menu. The widget attributes are listed in the rest of the Widget Attributes pane.

Figure 4-2. Selecting a Widget Type

The properties of the selected widget are shown in the widget properties pane on the right. To display the widget properties, double-click on the widget in the preview control panel.

To select a widget from the Control Panel Editor:

1. Click on the name of the parameter in the “Parameters” pane.

2. Select a widget from the Widget Type option menu in the Widget Attributes pane (see Figure 4-2). The widget appears in the Preview window.

In Figure 4-2, for example, the parameter Color Variable is highlighted in the Parameters pane. The widget type selected for it on the Type menu is a slider, which is highlighted on the control panel. The slider properties are listed on the right.

Figure 4-3 shows a selection of widgets, as well as the control panel “decorations.” Decorations are vertical and horizontal lines, frames and labels, available from the Decorations menu (see Figure 4-4). You can size them and move them around in the same way as you manipulate widgets.

Figure 4-3. A Selection of Widgets

In general:

• dials are used for double precision parameters and sliders are used for long integer parameters. Text type-ins can be substituted for dials and sliders, with less functionality.

• Radio buttons and option menus can be interchanged.

• You can use text type-in slots where file browsers are used, although with more limited scope. File browsers are specifically for locating files, whereas you can use text type-in widgets for any parameter type.

• The scrolled list lets you make a selection from a list of items. Depending on how the list is defined, the user may be able to select only one, or several objects at a time.

Widget similarities are shown in Figure 4-1.

Table 4-1. Similar Widgets

Widget	Similar to
Dials	Sliders, Text type-in slots
Radio buttons	Option menus
Text type-in slots	File browsers

You can change the type of widget associated with any parameter by clicking on the parameter name and selecting a new widget type.

Widget Decorations

Use the Decorations menu to select frames and dividers for your control panel. Once you have selected a decoration, it is listed in the Parameters pane (see Figure 4-4).

Figure 4-4. The Decorations Menu

Editing a Scrolled List

Four selection modes are available for the scrolled list widget (see Figure 4-5). You can choose which mode suits the kind of parameter you have.

Figure 4-5. Scrolled List Properties

The options are:

Single Select		Only one item at a time can be selected from the list, but the module user need not select any.
Browse Select		The user must select one item from the list.
Multiple Select		Several adjacent items can be selected from the list at one time.
Extended Select		Several items, not necessarily adjacent, can be selected from the list at one time.

Click on the widget to activate it in both the Preview window and the Editor window. An active widget is enclosed by a “handlebox” of eight black squares (see Figure 4-6 ).

Figure 4-6. Widget Handlebox

The Widget Attributes pane in the Editor contains the absolute location of the active widget. The origin of the control panel is in the upper left corner. As you move the widget, the X and Y starting locations change. You can type values directly into these text slots if you wish.

To resize a widget, you can:

For really precise adjustments, use the Grid menu to activate the grid. You can size and position widgets exactly by snapping them to a grid.

The Grid menu contains a list of pixel resolutions that govern the location and size of widgets. You can select any one of these options. The default snaps to a grid size of 5 pixels.

When the “snap to grid” option is in effect, all subsequent widget moves and resizes occur only in multiples of the grid size. If you resize a widget in this mode, it becomes a factor of the grid's width or height, depending on the direction in which you resize it.

The Properties pane contains information specific to the widget, including the scalar type for dials and sliders and label information for option menus and radio buttons. A plain button has the port name as its label.

The primitive type is important for the proper operation of the module and should not be changed from its default value, which is what the underlying module is expecting. However, you can change it under special circumstances.

To change the widget primitive type, select an alternative from the Properties pane of the Control Panel Editor.

To set the value of a widget, you must first select it. To select a widget for editing, double-click on it in the Preview window with the left mouse or click on it in the Parameters pane.

To select all the widgets in the control panel at once, use “Select All” on the Edit menu of the Control Panel Editor. To de-select them, click on the background of the control panel.

You can change the value of dial and slider widgets by typing a new value into the upper text slot or moving the widget pointer. You can also set minimum and maximum values by typing them into the range text slots. You must press <Enter> for settings to take effect.

You can also change the number of options in the Properties pane for radio buttons and option menus. This might not have the desired effect, however, if you add labels beyond those expected in the module itself.

A good example of this is the Contour module. It has three sets of radio buttons that control contouring in the I, J, or K directions. Each radio button has two options: On or Off. If you add a third option, such as Half On, to one of these radio buttons, the module will not process it.

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Caution: You can seriously confuse the Map Editor if you switch a module widget type to one that is incompatible with what the module expects.

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To dismiss the Control Panel Editor click the OK button.

The Apply button saves the layout information without closing the Editor window.

The Cancel button dismisses the Editor without implementing your changes.

To display the Menu Bar Editor, select “Menu Bar” from the Edit menu on the Control Panel Editor.

The Menu Bar Editor appears (see Figure 4-7). You can create up to eight different menus, with up to 16 items on each menu, depending on the parameters you want to associate with a menu item.

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Note: It will help the users of your modules if you follow the conventions for menu placement; that is, File menu on the far left, then Edit menu, then your other menus.

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Figure 4-7. The Menu Bar Editor

Set up your menus by typing the name of each menu in the text slots in the Menu Bar Editor, for example, “File.” To save them, click on Apply.

You can set up menu “stubs” for parameters that currently do not exist and add the items to the menu at a later date if you wish.

To create the menu options for each item on the menu bar, click on the “Menu” push-button under the menu name. The Menu Editor is displayed (see Figure 4-8).

You can create entries for the current menu. For example, reader modules or groups that have reader functions will usually have “New” and “Open” entries in their File menus.

Figure 4-8. The Menu Editor

From the option menu next to the item name, you can set the action to be taken when the user selects this item from the menu bar of the completed module control panel.

The action items are:

If you choose “File selector,” a button appears in the next pane, allowing you to define the file selector parameter.

If you choose “Set param,” the button appears again, with a text slot for entering the name of the parameter.

If you choose “Script command,” or “System command,” a text slot appears for entering the name of the command.

You run the P-Func Editor from the module containing the parameter you want to control. Because a module input parameter must be connected to a module upstream before you can write a parameter function for it, the parameter is always in the module downstream in the relationship.

To display the P-Func Editor window:

The title bar of the P-Func Editor (see Figure 4-9) displays the name of the module for which you are creating the parameter function. The window also has these components:

The P-Func Editor provides a simple set of expressions for creating compound relationships among two or more input parameters in a module. You can use as many variables in the function as you have connections to the parameter, or any subset of them. For example, you can type A + 2*B, or A/B, or (A + B)/2 (the average of two inputs).

Table 4-2 lists the expressions accepted by Explorer.

The expressions are identical to the C language functions. For more information, refer to the C language manual pages for each function.

(long)A
(long)B

(string)A + (string)B 

(string)(long)(3.3 + 8.9)

 A + (string)B 

(double) (7+3)

min(sin(A * 3.14159/180.0)
cos(B*3.14159/180.0))

If sin(A) < 0 then this
If sin(A) > 0 then that
else the other

In the example below, a relationship is created between parameters from two different modules. The upstream module is IsosurfaceLat. It has a “Threshold” parameter (shown as a dial), which will be wired to the minimum and maximum level inputs of Contour, the downstream module (see Figure 4-11).

For example, in Figure 4-9, the input parameter is “Threshold” in the IsosurfaceLat module, and the connections are the “Min Level” and “Max Level” parameters from the Contour module, defined as A and B in the Variables box.

The value of “Threshold” as defined in the Parameter Function box is (A+B)* 0.5. When the modules fire, the P-Func Editor calculates the new value of the input parameter.

The parameter function is applied only when you change the value of the output parameter in the function (“Threshold” in the previous example). It is not applied if you change Contour's “Min Level” or “Max Level” parameters, for example. The change must be in the upstream parameter.

This example shows how to link parameters from different modules, and then define the relationships between them. Launch the map named simple, consisting of ReadLat connected to IsosurfaceLat connected to Render.

To make a parameter connection (see Figure 4-11):

To create a parameter function:

Close the P-Func Editor and save the modified map under a new name.

Now when you move the dial on IsosurfaceLat, Contour fires as well. Set the number of levels in Contour to 2 or 3 and see what happens. The image should resemble that in Figure 4-13.

Figure 4-13. Simple Example with a Parameter Function

The values of the contour lines, therefore, are always 30% to 80% higher than the isosurface threshold.

If you click on the Check button, the P-func Editor tests the function you have entered to make sure that it is valid and prints a message in the Message pane. The Editor window stays open. For example, the second expression in the Parameter Function pane in Figure 4-14 has been entered incorrectly.

Figure 4-14. Messages in the P-Func Editor

This is a summary of the steps you take to create a parameter function in the P-Func Editor:

Saving the Parameter Functions

Use the four buttons at the bottom of the Editor to save or reject modifications to the input parameter. The buttons function as follows:

OK		Accepts the changes you have made, implements them, and closes the Editor window.
Apply		Accepts the changes you have made, implements them, and keeps the Editor window open.
Check		Checks the validity of the function and sends a message to the Message pane.
Cancel		Closes the Editor window without accepting or implementing any changes on the screen. Example 4-2. Creating a Complex Function

This example illustrates how to create a more complex parameter function by establishing a relationship between three parameters. The parameters are Contour's Min Level and Max Level and IsosurfaceLat's Threshold.

First, create a map by launching a GenLat module, a Contour module, an IsosurfaceLat module, and a Render module and wiring them together as shown in Figure 4-15.

Figure 4-15. A Parameter Function Using Two Variables

To create an object in Render like the one in Figure 4-15, open GenLat's full-scale control panel and set these widgets as follows:

• Coord Type: curv torus

• Coord Representation: curvilinear

• Function: sines

You want the threshold value of the isosurface to lie directly in the midrange of the contour levels generated by the Contour module. To do this, you connect two output ports from Contour to an input port on IsosurfaceLat, and set up a relationship between the two output parameters and the input parameter.

To make these connections:

1. Connect Contour's “Min Level” output parameter into IsosurfaceLat's “Threshold” input parameter.

2. Connect Contour's “Max Level” output parameter into IsosurfaceLat's “Threshold” input parameter.

3. Bring up the P-Func Editor from IsosurfaceLat. The parameter of interest on IsosurfaceLat, “Threshold,” is highlighted in the Input Parameters pane.

   The Connections box has two listings, Contour.Max Level and Contour.Min Level. The Variables box shows their aliases, A and B.

4. In the Parameter Function box, type in the expression:

   (A + B) / 2

   This averages the two inputs that are fanned into “Threshold.”

5. Click on the Apply button to establish the relationship.

6. Set Contour's Min Level dial to 100 and the Max Level dial to 200. Set the number of contour levels to 4 or 5.

From now on, when you turn Contour's Min and Max Level dials, the Map Editor sends these values to Explorer's parameter interpreter. It evaluates the expression and feeds the result to IsosurfaceLat's “Threshold” parameter.

You can see the calculated value reflected in the position of IsosurfaceLat's “Threshold” slider. There are now contour levels outside the isosurface.

You can change the transparency of the isosurface in Render so that you can see the contour values inside the surface as well. For more information, see “Visualizing Data” in Chapter 3, “Using Modules.”