.CAT4D File Extension
What is a CAT4D file?
Library created by Cinema 4D, a professional application that enables you to create 3D models and animations; contains only links to scenes, images, search results, presets, and other files.
In the "Content Browser" window, you will see a directory tree view of your different LIB4D and CAT4D files. You can create a new Catalog by selecting File → New Catalog..., naming it, and clicking OK. Once created, CAT4D files are typically located in the "browser" folder inside the "library" folder, which is located with the application in the "MAXON" folder.
To add items to a catalog you can drag and drop files into it. You can also right-click an object in the "Content Browser" and select Add to [catalogname].