The file extension C4D is used by the 3D software Cinema 4D. Maxon Cinema 4D is a 3D construction, animation and rendering program for professional use. The C4D format is the native format of Cinema 4D and includes data from 3D models, used textures and rendering settings.
C4D files are not downwardly compatible and can not be loaded in an older version. The opposite way is usually possible, although partially with restrictions. In addition, it has to be considered that C4D files saved with plugins require this plugin (usually the version number has to be the same) in order to be properly loaded. This is especially important if you want to exchange cross-platform data.
The C4D format is a proprietary format and can almost exclusively be read by Cinema 4D.
Most often resolving problems with opening C4D files is very simple. Just install an appropriate program that supports such files. All of the listed programs support C4D files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of C4D files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate C4D files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Cinema 4D applications is not on the list, select "Browse" option in order to manually locate the directory where Cinema 4D has been installed.
Sometimes problems with opening C4D files may not lie with the application itself, but can arise due to other causes, such as: