> For the complete documentation index, see [llms.txt](https://docs.optitrack.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.optitrack.com/v1.1/developer-tools/motive-api/class-cttapilistener.md).

# Class: cTTAPIListener

When using the Motive API, you can attach or detach cTTAPIListener class to a project by using the following functions.

* TT\_AttachListener
* TT\_DetachListener

### Member Functions

#### TTAPIFrameAvailable

TTAPIFrameAvailable callback is called when a new synchronized group of camera frames has been delivered to the TTAPI and is ready for processing. You can use this notification to then call TT\_Update() without having to poll blindly for new data.

#### InitialPointCloud

InitialPointCloud is called when the initial point cloud is calculated from the connected cameras. During this callback 3D markers can be added (up to MaxMarkers) or removed by modifying the Markers list as well as the MarkerCount variable. After this callback the marker list is passed onto the rigid body solver.

### Declaration: cTTAPIListener

{% code overflow="wrap" %}

```
class TTAPI cTTAPIListener
{
public:
    cTTAPIListener();
    virtual ~cTTAPIListener();

    //== TTAPIFrameAvailable callback is called when a new synchronized group of camera frames has been delivered
    //== to the TTAPI and is ready for processing.  You can use this notification to then call TT_Update() without
    //== having to poll blindly for new data.

    virtual void TTAPIFrameAvailable();

    //== InitialPointCloud is called when the initial point cloud is calculated from the connected cameras. During
    //== this callback 3D markers can be added (up to MaxMarkers) or removed by modifying the Markers list as well
    //== as the MarkerCount variable.  After this callback the marker list is passed onto the rigid body solver.

    virtual void InitialPointCloud(Core::cMarker* markers, int &markerCount, int maxMarkers);
};
```

{% endcode %}


---

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