This is a general-purpose property, consisting of a string. This string field can be set to override any parameter of an Arnold core node. This allows you to, for example, access and set Arnold core parameters currently not exposed in the user interface. The property can be applied to poly-meshes, hair, and lights. For example, if sharper renders are important, you could set texture_max_sharpen to 1.5. Another example would be to set options.gpu_sparse_textures to 0 to disable sparse textures. You can query the list of parameters an Arnold core node has by using a kick. For instance, you can get the attribute names of a polymesh node by using: Always refer to the core Arnold nodes (see the bottom of page), and not to the parameter's name as exposed in the Arnold plugin. If you want to set multiple Arnold parameters in a user_options string, you can use any whitespace (spaces, tabs, newlines e.g., \n) that you would use in an actual ASS file. kick -info polymesh