Layers deliver a convenient way to manage and organize your scene while also providing a comprehensive live workflow. Basically, Layers are nested USD files with histories of their own. Added on top of this however is a live workflow allowing users to set each nested layer to be edited and viewed live. For example, lighting, content, and the environment can each exist on separate Layers (nested USDs). As things are edited within the Layers, deltas are stored allowing you to manipulate anything in the scene non-destructively. Additionally, those Layers can be set to live on an individual layer basis which will show updates in Realtime of other users working on either the layer directly or within the same root USD.

The effect of Layers (deltas, models and otherwise) are considered in a bottom-up fashion. The layer above takes the priority over the layer below on any alterations. You can move Layers up and down freely by dragging them, to give priority.

Layer Types

Layer Types consist of 3 types and are denoted by icons in the layer view. These types are Native, Reference, and Delta.

Layer Type	Layer Icon	Description
Native		Native denotes that the layer entity is local to the USD being edited. This means that the mesh, light etc. is embedded in the USD layer directly. For example, creating a mesh in a layer will create a native type within that layer for the mesh. The icon will resemble the type of asset it is.
Reference		Denotes that the file is un-editable directly as it is not native to the USD. Instead, it is a link to a resource existing elsewhere on your Nucleus. Any assets dragged in from the content browser will create a reference for the referenced mesh. An asset that is a reference will be overlaid with the reference icon.
Delta		Deltas are changes to a layer that get recorded when affecting any assets lower in the layer order then themselves. These changes do stack and are nondestructive. This means that changes on a preceding layer then altered further on a higher order layer will show the results of both changes. For example, if a lower layer moves an object and a higher layer changes the material, both the translation and the material change will be visible. An item that has received a change will be overlaid with the delta icon.

Layer Categories

Setting	Description
Import SubLayer	Import Any USD files as a SubLayer in the current USD file
Create SubLayer	Creates a new layer in the stage. When clicked will request a location for saving the layer. Once complete a new layer will be appended to the layer list
Delete SubLayer	Removes the current Layer
Contextual Search	Use to search for entities in the stage hierarchy
Local/Global Visibility	It is used in multiuser workflows. Many people can work in a file simultaneously, these Button allows you to hide or unhide Layer independently from what user can see. To change from Local and Global View, press the L or G buttons respectively. Global Visibility Hides and unhides the specified Layers from all users. In other hand, Local Visibility Hides or unhides that layers from the current computer/user.
Save Layers	Allows to save the layers in a single click. Although, if any changes made in the layer and has not yet been saved, then the icon will change colors to blue. If the icon color is grey, this indicates that the layer(s) are already saved
Live	The live controls are managed in the live column. Each layer can be set to live individually while the header icon allows the user to toggle all on, toggle all off, or all always on
Layer Options	This the option features for Layers. "Show Layer Contents" displays all the content generated within layers. On the other side, "Show Session Layer" displays of the Session Layer