Feature Input
The Feature Input node () is a special case of a User Input that also supports linking with any announced variable in the Model Builder. A feature input is matched against an announced variable by matching against a physical quantity that you have to set for both items. See Variable Declaration and Dependent Variable Declaration for information about how to set the physical quantity and the announce preference for variables. Similar to the Material Property, the feature input is a collection of two GUI components: one list with the matching variables plus a User defined option and one field for the user-defined value.
To add a Feature Input first add a feature node or property node (for example, a Generic Feature, Domain Condition, or Device Model Feature), then:
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From the contextual toolbar (in this example, Generic Feature, Domain Condition, or Device Model Feature), click the Feature Input () button.
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Right-click the feature node (in this example, Generic Feature, Domain Condition, or Device Model Feature) and select it from the Inputs submenu.
Declaration
The declaration of a feature input is similar to that of a material property, where you specify the name, description, symbol, physical quantity, and dimension; see Material Property for further details. An announced quantity has a certain dimension, but it is possible to use a smaller dimension for a feature input in a feature. You set this dimension with the Dimension list, which can only contain Scalar and Custom for a scalar feature input.
Options
In addition to the announced variables and User defined, you can add extra items to the list in the feature instance with Allowed Values child nodes. An alternative option is also entering them directly to the Extra list items table.
Select the Use as model input check box to use this feature input as a model input. The feature input name will start with minput_ and continue with the physical quantity field name. The feature input will then be placed in the model input section in the user interface and will be used as model input by the materials.
A feature input supports several levels of matching that you choose from the Feature input match type list. You can find a brief explanation of the matching options below:
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Always match. If there is any matching announced variable, always use the first one found.
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Synchronized. Match to a matching announced variable, if the provider to that variable fulfills the following conditions (see below for an example):
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It has a feature input of the quantity chosen in the Synchronized physical quantity list.
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That feature input chooses an announced variable from the provider owning the synchronized feature input.
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Always match within physics interface. If there is any matching announced variable by the current physics interface, use the first one found.
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Model input match. Also matches within the physics interface, but you can disable the matching through an interface setting.
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Never match. Never do any automatic matching. The default option is User defined, but you can always manually choose among the found announced variables.
For all the options except the Synchronized option, it is possible to set a regular expression in the Match tag filter combined text field and list. The predefined options here are None (the default), and all physical quantity field names. None is equivalent to an empty tag and should be unless it is necessary to limit matching in some sense. Use the regular expression if the input should accept several match tags; use, for example, the expression ^$|explicit to either match the default empty tag or an announced variable using the tag explicit. There are several resources on the Internet that explain the exact syntax of regular expressions.
Click the Select Physical Quantity as Tag button () to pick a physical quantity from the list in the Physical Quantity dialog box that appears. Click the Custom Tag button ()to use a custom tag that you type in for the announce tag. Click the Reset to None button () to reset the filter to None.
Use the Synchronized option in situations when the matching depends on another feature input in the provider (typically a physics feature) of an announced variable. For example, assume feature “A” has a feature input with the Never match option that picks up variables with the quantity electric potential. Feature “B” announces an electric potential without a tag and has a synchronized feature input that should pick up a current variable only from the feature that picks ups an electric potential from feature “B.” To make feature “A” a possible match, it has to announce a current variable with an Electric potential match tag. The synchronized feature input uses the Synchronized option but also needs the Electric potential option in the Synchronized physical quantity list. When the user selects the electric potential from a physics feature of type “B” in the input list of a physics feature of type “A”, the input (often hidden) in physics feature of type “B” automatically picks up (or auto-match) the electric current from physics feature “A”.
GUI Options
If you want the feature input to disappear when it is inactive, select the Hide user input in GUI when inactive check box. Select the Show no description check box to hide the text label containing the description above the GUI component of the input. Similarly, you can hide the symbol from the GUI by selecting the Show no symbol check box. Select the Show no user defined input check box to hide user-defined inputs.As a final option, it is possible to add a divider above the GUI component and any description text label. The divider is a horizontal line with an optional descriptive text. Select the Add divider above the feature input check box to add the divider. When selected, you can enter the divider text in the Text field.
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Designing the GUI Layout
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Materials in the COMSOL Multiphysics Reference Manual