The Greyscale Vertex Attribute node does not work with native Nuke geometry. However, it will work with geometry contained in ORBXThe ORBX file format is the best way to transfer scene files from 3D Authoring software programs that use the Octane Plug-in such as Octane for Maya, Octane for Cinema 4D, or OctaneRender Standalone. This format is more efficient than FBX when working with Octane specific data as it provides a flexible, application independent format. ORBX is a container format that includes all animation data, models, textures etc. that is needed to transfer an Octane scene from one application to another. files. For more detailed information pertaining to working with the Greyscale Vertex Attribute node in ORBX files, please refer to the OctaneRender® Standalone documentation.