MotionTrackerObject Manual

Table of Contents

• About
• Access
• Allocation/Deallocation
• Parameters
• Access Data
• Further Reading

About

The MotionTrackerObject class represents a Cinema 4D motion tracker object. It provides read-only access to properties of the loaded video footage and the created 2D tracks.

MotionTrackerObject objects are an instance of Omotiontracker.

Access

A MotionTrackerObject object can be accessed like any other object.

  // This example accesses the Motion Tracker object
  // to print the used footage filename to the console.
 
  // check if an object is selected and if it is a Motion Tracker object
  BaseObject* const obj = doc->GetActiveObject();
  if (obj == nullptr || !obj->IsInstanceOf(Omotiontracker))
    return maxon::IllegalArgumentError(MAXON_SOURCE_LOCATION);
 
  const MotionTrackerObject* const moTrackObject = static_cast<MotionTrackerObject*>(obj);
 
  MtFootageData* footage = moTrackObject->GetFootageData();
  if (footage == nullptr)
    return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
 
  const Filename footageName = footage->GetFootageName();
  ApplicationOutput("Footage: " + footageName.GetString());
 
  // do not forget to free the copy
  MtFootageData::Free(footage);

Allocation/Deallocation

MotionTrackerObject objects are created with the usual tools:

• MotionTrackerObject::Alloc(): Creates a new MotionTrackerObject.
• MotionTrackerObject::Free(): Deletes the given MotionTrackerObject.

  // This example creates a new motion tracker object and adds it to the scene.
 
  MotionTrackerObject* const moTrackObj = MotionTrackerObject::Alloc();
  if (moTrackObj == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  moTrackObj->SetName("New Motion Tracker"_s);
 
  doc->InsertObject(moTrackObj, nullptr, nullptr);

Parameters

The standard object parameters of the Motion Tracker object can be accessed with C4DAtom::GetParameter() and C4DAtom::SetParameter(). The parameter IDs are defined in omotiontracker.h.

Additionally, footage information can be accessed with MotionTrackerObject::GetFootageData() (see below).

Access Data

Internal data of a MotionTrackerObject can be accessed by acquiring specialised data containers that store information on the footage and the 2D tracking data.

• MotionTrackerObject::Get2dTrackData(): Returns the MtFootageData object that stores information on the footage.
• MotionTrackerObject::GetFootageData(): Returns the Mt2dTrackData object that stores 2D track information.

See MtFootageData Manual and Mt2dTrackData / Mt2dTrack / MtData Manual.

  // This example accesses both footage data and track data
  // from the given MotionTrackerObject.
 
  // access MtFootageData
 
  MtFootageData* footage = moTrackObject->GetFootageData();
  if (footage == nullptr)
    return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
 
  const Int32 firstFrame = footage->GetFirstFrameNumber();
  const Int32 lastFrame  = footage->GetLastFrameNumber();
 
  const String firstFrameStr = String::IntToString(firstFrame);
  const String lastFrameStr  = String::IntToString(lastFrame);
  ApplicationOutput("Footage Range: " + firstFrameStr + " - " + lastFrameStr);
 
  // do not forget to free the copy
  MtFootageData::Free(footage);
 
  // access Mt2dTrackData
 
  Mt2dTrackData* trackData = moTrackObject->Get2dTrackData();
  if (trackData == nullptr)
    return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
 
  const Int32 trackCount = trackData->GetTrackCount();
  ApplicationOutput("Track Count: " + String::IntToString(trackCount));
 
  // do not forget to free the copy
  Mt2dTrackData::Free(trackData);

Further Reading

• Motion Tracker Overview
• MtFootageData Manual
• Mt2dTrackData / Mt2dTrack / MtData Manual