USD lighting

Create a USD light

To create a USD light, right-click a prim, go to Add New Prim > All Registered > Lighting, and select the light you want from the list. After the light is created, you can edit its properties in the Command Panel.

Light Link Collection

The Light Link Collection widget lets you specify which objects are affected by a USD light. You can either use the Include/Exclude tab to provide a list of prims to be included or excluded from illumination, or provide a path expression in the Expression tab to specify which objects are illuminated.

Specify Collection using prim paths

Include/Exclude Objects: Click to add one or more objects to the Include or Exclude list.
Include: List of objects to be included in the collection for illumination. The Include all option is on by default. If no object is specified in the Include or Exclude panel, the light illuminates all the objects. It's automatically turned off when an object is added into the Include panel.
Exclude: List of objects to be excluded from the collection for illumination.
Search bar: Searches for an object in the Include or Exclude panels.
More menu: Click to view more options. See More options for light link collection.

In the Include/Exclude tab, you can specify which objects are illuminated by the light.

To include or exclude one or more objects in the collection, click the plus icon , choose Include/Exclude Objects, and select the objects from the pop-up window. Use the search bar in the pop-up window to quickly filter objects.
- Click the Pin Stack icon to pin the rollouts for the light, select the objects from the USD Explorer, click the plus icon , then choose Add Selection to Include/Exclude.
When rendering in Arnold, the light only illuminates included objects and does not affect the excluded ones.
To update a prim path in the Include or Exclude panel, double-click on the path to edit it, and press Enter or click elsewhere to save the change. Type-ahead suggestions are available upon double-clicking on a path for quick selection.
To remove objects from the Include or Exclude list, select them and click the delete icon .
To select one or more included or excluded objects in the viewport, choose them from the Include or Exclude list, and click the select icon .
You can drag and drop one or more objects between the Include and Exclude panels.

Specify Collection using path expression

Expression tab: Lets you write a path expression for specifying which objects to illuminate.
More menu: Click to view more options. See More options for light link collection.

To specify which objects are illuminated using a path expression, type the expression in the Expression panel. If Include All is on, typing an expression automatically turns it off.

Some of the commonly used functions include:

* : Matches zero or more characters (not path or property separators). For example, /shape* can match /shape, /shapes and /shape123, but not /shape/sphere.
? : Matches any single character (not a path or property separator). For example, /shape? can match /shape1 and /shape2.
// : Matches any prim with the specified name in any path hierarchy. For example, /shape//sphere can match /shape/sphere and /shape/group1/subgroup2/sphere.

Note:

When both the Include/Exclude tab and Expression tab are in use, a warning icon appears and the expressions will be ignored. The default tab will be the one that contains data. When both tabs have data, the default one will be Include/Exclude.