Assembly: RevitAPI (in RevitAPI.dll) Version: 18.104.22.168 (17.0.1090.0)
An instance of a class that implements this interface is passed in as a parameter of the CustomExporter constructor. The interface methods are then called at times of rendering entities that are currently visible in the view being rendered.
With this type of export context used to perform a custom export, Revit will traverse the model and output the model's geometry as if processing the Render command invoked via the UI. It means that only such elements that have actual geometry and are suitable to appear in a rendered view will be processed and output.