Thread Utility Manual


The Cinema 4D classic API provides various functions to handle threads and thread related tasks.

For MAXON API threading utilities see Threads Manual.

Utility Functions

Various tasks should only be performed from the main thread. For example any GUI interaction or any change of the currently active BaseDocument must only happen from the main thread. To make sure that such code is only executed in the main thread the following functions can be used:

  • GeIsMainThread(): Returns true if the code is running in the context of the main thread.
  • GeIsMainThreadAndNoDrawThread(): Returns true if the code is running in the context of the main thread and if the main thread does not execute any viewport drawing.
// This example shows how a context less function can check
// if it is allowed to edit the active document.
static maxon::Result<void> SetActiveDocumentTime(const Float time)
// check if the function is called
// from within the main thread
if (doc == nullptr)
return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
return maxon::OK;

Running Systems

CheckIsRunning() does not check if the current code is running within the context of the checked task. See IdentifyThread() above.
// This example checks if the external render thread is running.
// If so it should stop.
// check if the external renderer ("Picture Viewer") is running

Get Threads

These functions are used to obtain certain threads:

// This example will execute the while loop until the "Esc" key is pressed.
BaseThread* const escThread = GeGetEscTestThread();
if (escThread == nullptr)
return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
// execute the loop until the escThread signals to stop
while (!escThread->TestBreak())

Further Reading