Houdini 20.5 Reference Windows

Edit Parameter Interface window

Creates, imports, or edits parameters on a node.

On this page

Overview

The controls in this window let you edit which parameters appear in the parameter editor for a node.

You can:

  • Import or promote parameters from another node, such as from a surface node up to its geometry container, to make controls more easily available.

  • Add rendering properties.

  • Add extra (“spare”) parameters to a node that can be used by expressions and/or scripts.

Note

This window lets you add/edit/remove parameters for a particular node. It does not affect all nodes of the same type. To edit the parameter interface of a digital asset, use the operator type properties window.

Open the window

  1. Select the node you want to edit in the network editor.

  2. In the parameter editor, click the Gear icon and choose Edit parameter interface.

    This window lets you create new parameters on a node, add rendering controls, and copy parameters from other nodes onto this one.

Import parameters from another node

  1. Open the Edit Parameter Interface window (see above).

  2. Click the From Existing Nodes tab on the left side. Use the tree control to select a parameter on a node, then drag it into the Existing parameters pane, or click the “move right” button.

    OR

    Select the other node in the network editor and drag the parameter directly from the parameter editor into the Existing parameters pane of the Edit Parameter Interface window.

  3. Use the options under Parameter Description on the right side of the window to customize the destination parameter’s appearance and behavior (this does not affect the source parameter on the other node).

When you import a parameter from another node, Houdini automatically edits the source parameter to be a parameter reference expression that looks up the value of the destination parameter. Once you import a parameter, you should only edit the destination parameter, not the source parameter (unless you delete the destination parameter to break the connection).

Render properties

See the section on render properties for information on rendering properties.

  1. Open the Edit Parameter Interface window (see above).

  2. Click the Render Properties tab on the left side. Use the tree control to select a property, then drag it into the Existing parameters pane, or click the “move right” button.

Spare parameters

Spare parameters let you store extra information on a node. You can add spare parameters to any node to provide extra storage for values and expressions. They are not used directly by the node, but you can reference them in other standard node parameters using expressions. Adding a spare parameter to a node only adds it to that node, not all the nodes of that operator type.

You can keyframe spare parameters, reference them, and add them to takes .

  1. Open the Edit Parameter Interface window (see above).

  2. Click the By type tab on the left side. Select the type of parameter you want to add, then drag it into the Existing parameters pane, or click the “move right” button.

  3. Use the options under Parameter Description on the right side of the window to customize the parameter’s appearance and behavior.

Parameter Description

The controls on this tab let you set up a menu of values the user can choose from for this parameter. You can also use the Callback script (on the Parameter sub-tab) to script actions based on the user’s menu choices.

Note

The menu editing interface is a holdover of very early Houdini UI. It can be a bit confusing.

Each menu item has a token and a label. The label is the human-readable label corresponding to the value that appears in the pop-up menu in the parameter editor.

  • In a String parameter, when the user selects an item, the parameter is set to the corresponding string token.

  • In an Integer parameter, by default when the user chooses an item, the parameter is set to the index of the item (for example, 0 for the first item, 1 for the second item, and so on). If you turn on Use Token as Value, the parameter will be set to the corresponding integer token instead.

  • Any menu item with the token _separator_ will be replaced with a menu separator.

If you know the items you want to appear in the menu ahead of time, you can define them using the Menu items table. If you want to dynamically compute the menu contents using a script, click Menu script instead.

Use menu

Converts the parameter UI from the default (for example, a text box for entering an integer or string) to a pop-up menu allowing the user to choose from the items configured below.

The pop-up menu to the right lets you choose the interface style for the menu:

Normal (Menu Only, Single Selection)

Display the parameter as a pop-up menu.

Normal Mini (Mini Menu Only, Single Selection)

Display the parameter as a “mini” pop-up menu. This style only shows a small button to open the menu, instead of showing the current value.

You can use this with Horizontally join to next parameter on the previous parameter to put a mini-popup menu after another parameter.

Control Next Parameter (Menu Only, Single Selection)

Display the parameter as a pop-up menu, and join it horizontally with the next parameter in the hierarchy.

Houdini uses this style for menus that modify the operation of the following parameter. (For example, in many LOPs nodes, each parameter has this type of menu preceding it, controlling how the parameter authors USD.)

Multiple menus of this type maintain a consistent indentation of the associated parameters. You may want to use icons and the Icon menu look on this menu to save space.

Replace (Field + Single Selection Menu)

This displays a regular field the user can manually edit, with a mini pop-up menu at the end from which they can choose items. Choosing an item replaces the contents of the field.

Toggle (Field + Multiple Selection Menu)

This setting is only useful for String parameters. If you choose it for an Integer parameter you will get the same UI as Replace (above).

This treats the parameter value as a space-separated list of keywords. It shows a regular text field the user can manually edit, with a mini pop-up menu at the end from which they can choose items. Choosing an item adds its token to the list (or removes it if it is already there).

Use Token as Value

In an Integer parameter, by default when the user chooses an item, the parameter is set to the index of the item (for example, 0 for the first item, 1 for the second item, and so on). If you turn this on, the parameter will be set to the corresponding integer token instead.

Menu items

Click this tab to define the items that will appear in the menu.

  • Select a row and use the fields under Token and Label to edit the row’s contents.

  • To add a new row, select the empty row at the end of the table.

  • Click the move up button to move a row higher in the table. Click the delete button to delete a row.

Menu script

When this tab is selected, Houdini will run this script to generate the menu contents. This lets you dynamically change the menu items depending on the current situation.

Below the script field is a Menu script language menu (you may need to scroll down to see it).

See Parameter Menu Scripts for more information on writing a menu script.

Tip

Houdini runs this script whenever the user opens the menu, and when the parameter is evaluated, so make it as simple and fast as possible.

Icon menus

To...Do this

Display icons in pop-up menus

You can use a special syntax in the Label part of the menu table to show an icon in a menu item:

![‹icon_name›] ‹Label›

For example:

![BUTTONS_plus] Add

Currently you can only specify native Houdini icons. (To see a gallery of available icons, open the internal help browser and go to /icons.)

You should add icons to all items or none. Currently, if only some items have icons, the indentation of the item labels is inconsistent.

Display the menu as an icon

You can customize a menu to appear only as the icon of the currently selected item (with a pop-up menu indicator). Clicking the icon shows the full menu with item labels.

  1. Add icons to the menu items (see above).

  2. In the parameter’s Parameter Description, on the Parameter tab, click Built-in Tags (below the tag table). In the pop-up dialog, select Standard Tags ▸ Parameter Look ▸ Icon Look (Menu), then click Accept.

  3. Click Apply in the type properties window to see the effect on the parameters. (Note that the parameter only appears in the header when it’s collapsed.)

Example

Create a sphere and add squash and stretch

  1. In this example, we’ll create a new “squash” parameter on a ball object by promoting a parameter from a node inside the ball’s geometry network.

  2. First, use the Sphere tool on the Create shelf to create a sphere. In the operation control toolbar (along the top of the viewer), set the sphere’s Primitive type to Polygon and the Frequency to 4.

  3. Select the sphere and use the Squash and Stretch tool on the Deform shelf to add squash and stretch to the sphere.

  4. The squash and stretch tool automatically dives into the sphere’s geometry container to show you its surface nodes: a sphere node that creates the sphere geometry, and a twist node set to squash and stretch.

  5. Select the twist node (probably called squashstretch1). In the parameter editor you can see that its Operation parameter is set to Squash & Stretch.

  6. Set the node’s Primary axis parameter to Y axis. Set the Pivot to 0 -1 0 to move the center of the squash and stretch to the bottom of the sphere (since the sphere is 1 unit in radius, moving the pivot down 1 along the Y axis puts it at the bottom of the sphere).

  7. Move the mouse over the Strength text box and press and hold . Drag left and right to squash and stretch the sphere.

    Note that negative values squash the sphere down, positive values stretch it up, and that the values need to be fairly small, so the slider beside Strength which goes from 0 to 360 is not very useful. You’ll want to type in values or use the ladder instead.

Promote the Strength parameter from the squash and stretch node

Now we’ll promote the Strength parameter from the squash and stretch node up to the geometry container so we can edit it at the Scene level.

  1. Click Back to return the Scene level.

  2. Click the ball’s object container to show its parameters in the parameter editor.

  3. In the parameter editor, click the Gear menu and choose Edit parameter interface.

  4. In the Edit Parameter Interface window, click From existing nodes on the left side.

  5. Use the tree control to find the squash and stretch node inside the ball. Open it up to show its parameters inside. Drag the strength parameter onto the Existing parameters tree, just above the Translate parameter.

  6. In the Parameter description section on the right side, set the Label option to Squash. This is the human-readable label that will appear in the parameter editor.

  7. In the Interface options subsection below, set the Range to -2, 2.

  8. Click Apply.

  9. Try using the new Squash parameter on the object.

Windows