Search TipsPrimitive Types and Primitive Attributes
Primitive Types
There are several different types of prims in the USD framework: Xforms, Scopes, Meshes, Materials, Shaders, Cameras, and Lights. In Nuke, these types come with a specific default behavior, but essentially these are just containers which you can set properties on.
| Type | Description | Example Nuke Nodes | Read more |
| Xform | An Xform prim is a container that you can put transformation data on. | GeoXform (USD native) | Creating Scope and Xform Prims |
| Scope | A Scope prim is a container that you can’t put transformation data on. | GeoScope (USD native) | Creating Scope and Xform Prims |
| Meshes | A Mesh prim is a geometric surface. | GeoCube, GeoCylinder, GeoSphere, GeoCard (USD native) | Creating Geometry Prims |
| Materials | A Material prim defines the appearance of a surface. | No USD native material prim nodes in Nuke - but materials can be assigned via GeoBindMaterial | Assigning Materials and Shaders |
| Shaders | A Shader prim is used for defining shading networks. |
No USD native shader nodes in Nuke - but shaders can be assigned via GeoBindMaterial The PreviewSurface node is a representation of the “USDPreviewSurface” shader which is meant to model a “modern” physically based surface with both specular and metalness workflows. |
Shading Geometry |
| Cameras | A Camera prim is a viewpoint onto the scene. |
Camera (Not USD native but can be converted to USD) GeoEditCamera (USD native) |
Working with Cameras in the New 3D System |
| Lights | A Light prim represents a light source in the scene. |
GeoDomeLight, GeoDiskLight, GeoDistantLight, GeoSphereLight (USD native) PointLight, SpotLight, DirectLight, EnvironmentLight (Not USD native but can be converted to USD) |
Light Your Scene |
Primitive Attributes
Primitive Attributes give you access to edit USD attributes in some of the New 3D System nodes in Nuke. You don't necessarily need to use these, but if you want some extra control, these knobs can be edited. On nodes such as GeoCard, you can find and expand the Primitive Attributes section in the Properties panel.
| Kind |
Kind lets you determine the selection category for this card, this can be used to refine your selection based on kinds in the 3D viewer selection controls. • Assembly: an important group model, often a published asset or reference to a published asset • Group: models that simply group other models. • Component: a “leaf model” that can contain no other models • Model: base class for all model kinds. “model” is considered an abstract type and should not be assigned as any prim’s kind. • Subcomponent: an identified, important “sub part” of a component model. |
| Purpose |
Purpose sets how your prims are displayed in the viewer allowing you to define the viewer render quality. • Default: Assigns the purpose based on the Layer settings, otherwise defaults to Render • Render: Assign to prims intended for final high-quality rendering. • Proxy: Assign to prims intended for lightweight proxy rendering. Guide: Assign to prims intended as markings, lines, arrows or interaction guides. |
| Visibility |
Visibility sets if your geometry and any descendants are displayed as hidden in the Viewer. • Inherited: When enabled the visibility of the selected prim is the same as the prim's parent. • Invisible: the selected prim and its descendants display as hidden in the viewport. |
| Mesh Attributes |
Under Mesh Attributes you also have the following controls: • Subdivision: sets how meshes are rendered in the viewer based on different subdivision models • Boundary: specifies where the boundary conditions needed for interpolation is defined • Double Sided: lets you shade both sides of your geo |
| Display |
Display concerns itself with how your card is displayed in your 3D viewer. • Display Color allows you to colour your geometry. • Display Opacity sets how transparent it is, but these are just for viewer display not rendering. |
Tip: Full descriptions of the controls can be found in each node’s Reference Guide page - see New 3D System Nodes.
In the Scene Graph
The Prim Type, Kind and Purpose that has been set also appears in the Scene Graph for easy reference, but they cannot be edited from the Scene Graph.
See more about the Scene Graph at New 3D Scenes in the Scene Graph.
