# Live Link Content: Active Puck Static Meshes ## Overview OptiTrack's plugin for Unreal Engine includes an array of content options. the 5.3 plugin includes the following new content: * ActivePuckMesh * CinePuckMesh * MotiveAvatarMesh * MotiveSkeletalMesh * MotiveSkeleton This page covers the Active Puck and CinePuck static meshes, using the Active Puck as the example.

The Active Puck Mesh provides a couple of different use cases: 1. Data validation. Tracking an active puck in the physical volume using the OptiTrack Live Link display provides a point of reference that allows you to validate rotation, placements, and even the scale of your volume. 2. Lens calibration device. Because the static mesh is the same scale as a real puck, its markers can be used for calibration purposes. Please see the section [Create a Lens Calibration Device](#create-a-lens-calibration-device), below, for more details. {% hint style="info" %} We used the standard *InCameraVFX* template in Unreal Engine for our sample project. The template includes all the necessary macros and assets needed for virtual production. This template is located under *Film / Video & Live Events* in the Unreal Project Browser. {% endhint %} ## Add a Puck to an Unreal Engine Project This section walks the user through adding the puck static mesh to a project and aligning it with the puck streaming from Motive. ### Show Plugin Content * From the Content Browser window, click the

button. * Check the boxes for *Show Engine Content* and *Show Plugin Content*.

* The Content Browser’s Navigation pane will now show the Engine Content, where the Plugins folder resides. * Open the OptiTrack—Live Link Content folder.

OptiTrack's Live Link Content for Unreal Engine.

* Open the *ActivePuckMesh* folder. If using a CinePuck, open the *CinePuckMesh* folder . ### Create Labeled Markers The Live Link asset automatically aligns with its source in Motive. The *Markers* settings display a visual map of the marker locations. This map is helpful for confirming the alignment of a static mesh to a streamed asset. * In the Live Link pane, select *OptiTrack*. * In the *Markers* section of the OptiTrack Properties pane, set *Create Labeled Markers* to true. {% hint style="info" %} To open the Live Link pane, select *Virtual Production → Live Link* from the *Window* menu. {% endhint %}

Live Link Pane in Unreal Engine: Create Labeled Markers.

### Create Blueprint Class * Right click in the Content Browser to open the menu. * Under *Create Basic Asset*, select *Blueprint Class*.

Create Blueprint Class from Content Browser menu in UE.

* Select Actor as the Parent Class. * Double-click the name to give it a more meaningful name. In our example, we renamed the component *BP\_CalibratorPuck.* We will use this puck later to create a [Lens Calibration Device](#create-a-lens-calibration-device).

Unreal Engine: Pick Parent Class for a new blueprint.

### Add the Static Mesh * Open the newly created Blueprint linked to the puck streaming from Motive. * This will open a new tab. Click the

*Add* button in the top left of the Component pane and select *Static Mesh* from the list of options.

* Double-click the newly created static mesh in the list of components to rename it. In our example, we called it *ActivePuck*. * Select the static mesh in the Components pane to display its properties in the Details pane. * Click the Static Mesh property (set to None by default) to select the asset to use. * Select *SM\_ActivePuck\_Opti* for the Active Puck, or *SM\_CinePuck\_Opti* if using a CinePuck.

Details for a Static Mesh component in UE.

The Active Puck static mesh will now appear in the scene. ## Create a Lens Calibration Device An Active Puck can serve as a lens calibration device in Unreal Engine by aligning calibration points to the markers at each of the four corners. For accuracy and precision, use the *Top* view in the UE Viewport.

### Add Calibration Points * Select the Active Puck in the Viewport and click the

Add button on the Components tab. * Search for and select *Calibration Point* from the list of options.

Top down view of the Active Puck Static Mesh in Unreal Engine.

* Click to rename the Calibration point. We recommend using names that match the point's location, such as top left, bottom right, etc. * Drag the newly created point to align it with the center of the corner marker.

Adding a Calibration Point to the Active Puck Static Mesh in UE.

* Use **Ctrl + D** to *Duplicate* the point to make the next one. * Rename the second point and drag it to the appropriate location, aligning it with the previously placed point on either the X or Y axis. * Repeat these last two steps until each of the four corners has a Calibration Point at its center. * Select the ActivePuck in the list of components. The four calibration points should be nested underneath. * Click the *Compile* button on the main toolbar, then *Save* and Close the tab for the Blueprint.

Compile changes to the Static Mesh in UE.

### Link the Static Mesh to the Live Link Asset * In the project, click and drag the Blueprint created in the prior steps into the project. * In the Outliner pane, drag the Blueprint under *OptiTrackLiveLinkDisplay.* * In the Transform Section of the Details pane, click the

button to the right of the Location settings to reset all location values to zero.

* Click the

Add button in the Details pane. Search for and select *Live Link Controller*. * Under Subject Representation, click and select *ActivePuck* from the list of available assets (below, left). * This will link the static mesh to the puck. The Labeled Markers setting shows the device properly aligned (below, right). {% hint style="info" %} Use the translate tool to reorient the static mesh if the OptiTrack brand and the status lights on the mesh do not align with those on the physical puck. {% endhint %} * Having confirmed the alignment is correct, you can turn off the [Labeled Marker](#create-labeled-markers) display. The Live Link display settings can also be closed. * The puck is now available as a tracked calibrator tool that can be used in conjunction with a lens file in Unreal Engine for lens calibration.

Select a Subject Representation for the
*LiveLinkComponentController* in UE.

A fully aligned Active Puck Static Mesh in UE.

### Create a Lens File * Right click in the Content Browser in the folder where you'd like to save the lens file. * Search for and select Lens File from the list of Content types and give the file an appropriate name, such as *35mm\_Lens*. * Open the Lens File.

* Click *Lens Distortion* on the *Calibration Steps* tab. * In the *Lens Distortion Algo* setting on the right, select *Lens Distortion Points Method*. * The *Calibrator* setting will default to the calibrator puck. * Select the current calibrator point in the camera viewport to complete the alignment.