Get Motive streaming with at least one rigid body. Make sure the Streaming settings are set up correctly, and the rigid body is active under the Assets pane.
You can install the OptiTrack - NatNet Streaming Client plugin by putting the plugin files into one of the following directories:
C:\Program Files\Epic Games\[Engine Version]\Engine\Plugins
Go to Edit → Plugins and enable the OptiTrack - LiveLink plugin as well as the Built-In LiveLink plugin in UE.
The LiveLink pane can be accessed from Window → Live Link from the toolbar in UE.
In the LiveLink pane under Source options, go to the OptiTrack Source menu and configure the proper connection settings and click Create. Please make sure to use matching network settings configured from the Streaming pane in Motive.
If your settings were correct, then the plugin will list out all of the detected rigid bodies, and they should have green dots next to them signifying that the asset has been created and is receiving data. If the dots are yellow, then either your take is paused, or there is some sort of connection error.
After you are connected to Motive through the Live Link plugin and have at least one rigid body tracking, then you can start animating an object in Unreal Engine as well.
The first step is to set up your object to track. To do this, right-click on a skeleton mesh object you would like to track in the content browser, choose → Create → Anim Blueprint. The mesh must be a skeleton mesh.
This will create an Animation Blueprint of the selected mesh. In the content browser, double-click the created animation blueprint to edit it.
In the blueprint, access the AnimGraph tab. There should be an output pose node in there already. Then right-click in the empty space and search for "Live Link" to find the "Live Link Pose" and add it to the graph.
On the Live Link Pose node, you should see the Live Link Subject Name property. Use the dropdown and select the name of a rigid body to use. Then, drag the pose output and connect it to the Output Pose.
Select the “Live Link Pose” node and select the “OptiTrackLiveLinkRetarget” option in the “Retarget Asset” property in the Details pane.
Compile and save the blueprint. Once the changes have been compiled, you should see the object animating according to the rigid body tracking in the mini 3D viewport.
Open the project settings and in the LiveLink section, for the Default Role Settings, set the Role to LiveLinkAnimationRole, and set the Setting Class to OptiTrackSubjectSettings.
Connect to Motive via LiveLink, each rigid body asset should already have their own translator:
Drag a camera or other actor object into your scene from the Place Actors pane.
Select the object you want to animate(in this case, a cube mesh), click the “Add Component” button on the details pane, and add LiveLinkController.
Under the LiveLinkPonentController, choose the asset name for the Subject Representation property. You can expand the setting by clicking the triangle next to it and choose LiveLinkTransformRole for the Role setting.
At this point the camera should be animating in the scene.