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The convention used to store the user data can be found in different data types such as color, float, etc. For example:

  • Create a float Color type user data in C4D and call it 'TestFloatMy Color':

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  • Export the scene as an .ass file and open it in a text editor. We can see that the float 'TestFloat' is stored in the .ass file as follows:

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  • Create an Arnold Material and read the 'My Color' user data via a user_data_rgb shader.

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Only alphanumerical characters, dashes (-) and underscores (_) are allowed in the parameter name. Arnold converts all other characters (including spaces) to underscores. For instance in the above example 'My Color' becomes 'My_Color', which you have to set in the user_data shader. Also note that parameter names are case sensitive.

You can check the Arnold parameter name if you export the scene to an .ass file and look for the user parameter as follows:

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If display color of an object is enabled we will export the 'display_color' RGB as a user data.


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