The Arnold tag (Arnold Parameters) is designed to assign special Arnold related settings to the supported native Cinema 4D objects such as Polygon object, Light, Hair, etc.

The tag adopts to the underlying object which means it dynamically displays the parameters defined by the type of the assigned object. If you add the tag to a polygon object, it will display parameters for the Arnold polymesh node. If you add the tag to an Omni Light object, it will display parameters of an Arnold point_light node, etc. If you don't see any parameters, it means that the object is not supported by C4DtoA directly.

Show Custom Parameters

Forces the tag to show parameters of a specific Arnold node. It is useful when no mapping exists between the assigned C4D object and an Arnold node.

For example, a Null object is not translated to an Arnold node, but it can be used to group C4D objects and easily assign the same parameters to all of the child objects. To do so, you have to add an Arnold tag to the Null, enable Show custom parameters and select an Arnold node from the drop-down. All objects under the Null will use the settings of the tag. Note that an object uses the first Arnold tag in its hierarchy, so if an object under the Null has its own tag it will override the Null. For example in an object tree like this:

Null           ---   Arnold tag 1 (polymesh)
  Sphere 1     ---
  Sphere 2     ---   Arnold tag 2 (polymesh)
    Sphere 3   ---
    Light      ---

Sphere 1 and Sphere 3 will use Arnold tag 1 while Sphere 2 will use Arnold tag 2. The Light object has no tags since it's not a polymesh.

You can add multiple Arnold Parameters tags to the Null object to define parameters of different Arnold node types.

Arnold Node Type

A list of all available nodes in Arnold. The selected node's parameters will be displayed on the interface in 'custom' mode.

User Options

This string field can be set to override any parameters of an Arnold node or define custom parameters. This allows you to, for example, access and set Arnold core parameters currently not exposed in the user interface.

You can query the list of parameters of an Arnold node by using kick. For instance, if you want to change a polymesh option, you can get the attribute names by running:

kick -info polymesh

List of 'kick -info polymesh' available through Kick

Always refer to the core Arnold nodes and not to the parameter name as exposed in C4DtoA. 

The format of the string is the same as found in an .ass file. If you want to set multiple Arnold parameters in a User Options string, you can use any whitespace (spaces, tabs, newlines e.g. \n). For example, this would set the smoothing and ray_bias parameters, and declare and set a user parameter named test:

smoothing off
ray_bias 0.01
declare test constant FLOAT
test 2
This is a powerful option and should be used with some care. The string is passed to the Arnold node directly, and it is up to the user to fully understand the parameters being set.

Export user ID

If enabled then the given id is exported to the Arnold node as an integer user parameter called user_id. Then the id can be read in a shader network via the user_data_int shader.

Export toon ID

Labels the shapes which belong together regarding edge detection of the toon shader. The Use toon ID option in the toon shader has to be turned on.

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