Plugin Structure

Plugins are stored in the plugins folder within the user folder. Each plugin should have a suffix called .pyp or .pype (for encrypted files). When C4D starts, it finds all files in this folder that end with .pyp or .pype and executes the plugin. A simple plugin possible thus looks like this:

def main():
    print "Hello World!"


Such a plugin isn’t very interesting, as it is only run when the program starts. Therefore we have the ability to register plugin hooks in various parts of the program.


All plugin hooks are built upon data classes derived from BaseData. These data classes contain a set of methods that are called by CINEMA 4D. An example from MessageData:

class SampleData(plugins.MessageData):

    def CoreMessage(self, id, bc):


To register the derived class with CINEMA 4D there is a specific Register*() function for each data class. Some of them take a new object of your data class or just the class so CINEMA 4D can create instances on it’s own:

plugins.RegisterCommandPlugin(id=PLUGIN_ID, str="TestBase-Plugin", info=0, dat=SampleData())

The registration functions for NodeData instead want a class name like this:

class SampleData(plugins.ObjectData):
    def GetVirtualObjects(self, op, hierarchyhelp):

plugins.RegisterObjectPlugin(id=PLUGIN_ID, str="TestNode-Plugin",
                            g=SampleData, description="", icon=None,


There are a few things to say about the lifetime of the data class instances, especially with convern to member variables. In those cases where a new object is passed to the registration function, as shown in the first example above, then this instance is kept for the whole C4D session. Since it’s constructor and destructor are called as usual, no special concern is necessary. The data classes where the name needs to be passed to the registration function have a 1:1 correspondence with a node in CINEMA 4D. Thus they are allocated and deleted by C4D along with the node. When this happens the constructor and the destructor are called as usual. However, CINEMA 4D additionally calls the NodeData.Init() methof after the constructor and NodeData.Free() before the destructor.

Directory Structure

While .pyp or .pype can be placed directly in the plugin directory, it is often better to group them into hierarchies. The standard layout for a plugin folder is like this:



The main file is myPlugin.pyp, which registers the hooks. The res directory contains plugin resources, which currently means dialogs, descriptions and strings.

For each description there is a res with the description and a .h file with enums for the constants used in the description. See Descriptions in CINEMA 4D. Each dialog is contained in its own .res file. The c4d_symbols.h file should contain enums for the constants used in the .res files.

Then there should be a directory named strings_xx for each language that the plugin supports, where xx is a two-letter language or country code according to the ISO 639 standard or the ISO 3361-1 standard. Currently there are C4D versions available for the following codes:

us - American English
de - German
fr - French
it - Italian
jp - Japanese

Each of the language directories should contain a .str file for every dialog and a c4d_strings.str for other resource strings. It is recommended that you first develop the plugin in one language, and then just copy the strings directory before translating. Finally you can of course have any other files you like in your folder, for example plugin icons or logos. These can be conveniently accessed using __file__:

dir, file = os.path.split(__file__)

Plugin Messages

PluginMessage(id, data)

Defining this function allows you to receive plugin messages. These can either be from CINEMA 4D or from other plugins via GePluginMessage().

  • id (int) –

    The message ID. Built-in ones are:

    C4DPL_STARTACTIVITY Sent to all plugins after all PluginStart() have been called.
    C4DPL_ENDACTIVITY Sent to all plugins before any PluginEnd() has been called. This allows you to close dialogs, end threads, delete temporary/undo buffers etc.
    C4DPL_RELOADPYTHONPLUGINS Sent when Python plugins are to be reloaded. See Python Plugins Reloading.
    C4DPL_COMMANDLINEARGS Sent to let plugins parse the command line arguments used when starting CINEMA 4D. Retrieve the arguments by calling sys.argv. See Command Line Arguments.
    C4DPL_BUILDMENU Called when the menus are built during startup. Use GetMenuResource() etc. to add your own menus here if necessary.
    C4DPL_ENDPROGRAM Sent when CINEMA 4D is about to close.
    C4DPL_PROGRAM_STARTED Sent when the application has been started.
  • data (any) – The message data.
Return type:



True if you consumed the message, otherwise False.

Command Line Arguments

To retrieve CINEMA 4D command line arguments at any time, implement PluginMessage() and filter the C4DPL_COMMANDLINEARGS message:

import c4d
import sys

def PluginMessage(id, data):
        print sys.argv #print arguments
        return True

    return False
  • Save this code in a .pyp file and place it in your plugins folder.
  • Start CINEMA 4D with some arguments like “CINEMA 4D.exe –hello”.
  • Open the console, it should contain the passed arguments.


Arguments which are handled by CINEMA 4D modules are removed from the list. For example, try starting CINEMA 4D with “CINEMA 4D.exe –hello -parallel”: open the console, parallel isn’t in the printed arguments list.

Python Plugins Reloading

The Python built-in reload() function reloads and recompiles the source of a .pyp file. Python modules which are imported by a .pyp file will not be reloaded again. Python first checks if the module is already imported, if yes this is skipped and just the reference is set.

You can use reload() to force the reload of a Python module when C4DPL_RELOADPYTHONPLUGINS message is received in PluginMessage(). This is also the place where you can close system resources (e.g. sockets, files) you opened before.

Table Of Contents