The Geometry Attribute Node is used to specify various parameters for a given object, such as the lights to use to light the attached objects, visibility to ray traced rays, and various RenderMan related attributes. Geometry attribute nodes are created and assigned inside the Shader Assignment Panel; refer to The Assignement Panel.
Figure 3.11: An empty Geometry Attribute Node
When a geometry attribute node is first created, it contains no attributes at all. It is an empty container where one can add just the relevant attributes. This avoids cluttering the UI and allows attribute inheritance. Attributes can be added and removed by using the Add / Remove Attributes button. ⟨Left-Click⟩ on this button brings up the Add / Remove Attributes Window, which is better suited for multiple attribute addition or removal (see The Add / Remove Attributes Window) ⟨Right-Click⟩ on the Add / Remove Attributes button offers the same functionality through popup menus, which are more convenient when only one attribute or attribute group needs to be added or removed.
Some of the attributes available in the ‘Geometry Attribute Node’ clash with the Maya Render Stats attributes. The attributes defined in a ‘Geometry Attribute Node’ attached to an object will override the related Maya Render Stat attribute. Refer to Section 5.4.1 [Maya Render Stats and Geometry Attribute Nodes], page 128 for more details.
Reference Geometry
If the Maya primitive has an attached reference geometry then 3Delight For Maya can output it along with the rendered object. Reference geometry can be accessed in the shaders using the Pref and NRef variables.
Output Pref
When this attribute is on, the geometry passed to 3delight will also contain reference geometry that represents geometry before any deformation has been applied to it. This geometry is accessible to any shader that declares the varying point Pref parameter. This attribute is off by default.
Output Nref
If checked, geometry passed to 3delight will also contain reference normals; those are normals before any deformation has been applied. These non deformed normals are accessible to shaders that declare the varying normal Nref parameter. This attribute is off by default.
User Attributes
Each Geometry Attribute Node can define as many arbitrary user attributes as needed. For each geometry attribute node, 3Delight for Maya will look for attributes whose name begin with "user ". This prefix is removed from the name and the attribute is output to RIB as a user attribute, along with its value. For instance, a ‘color float3’ attribute named ‘user_colorMultiplier’ will produce a Attribute "colorMultiplier". The supported attribute types are: string, bool, long, long2, long3, float, float2, float3 (color or non-color), double, double2, double3.