All file formats are registered with a display name, a file extension and one or more image subtypes. Each format registration starts with a call to Renderer::AddOutputImageFormat, followed by one or more calls to Renderer::AddOutputImageFormatSubType. If the subtype call is omitted, the format is not registered.
The image subtypes indicate which render channel types the file format can support and what kind of image data format will be used to write out that channel type. For example, it is entirely possible to write out an object label channel as an RGB image, where each label is encoded as an RGB value.
For convenience, you can register supported file formats that have the same extension as file formats supported by Softimage-provided rendering engines, using the same display name and preferably with the same coverage of subtypes. This ensures a more uniform presentation to the user when switching engines and ensures that their already chosen output types remain, if not completely, at least mostly identical.
