With the real-time beta feature, you can live-stream your motion from the RADiCAL Studio in to a scene in Unreal Engine 4. To do this, you need a Professional Studio account (or monthly LiveLink access). See our pricing page for more information.

For indies and students we have special pricing for LiveLink access, get in touch here.

 

Live Link Setup

After starting the Live Link stream from Radical Studio, open the UE4 editor and go to Window -> Live Link. Go to Source -> Message Bus Source -> select the RadLiveLink source. There will be a random alphanumeric string appended to the name, to differentiate between multiple Live Link sources on the network (e.g. other instances of Radical Studio). You can now close this window.

 

Live Link Preview

The Live Link data can be previewed inside the Skeleton, Skeletal Mesh, Blueprint or Animation Blueprint windows for a given skeletal asset. On the right side, go to Preview Scene Settings, under Animation, change the Preview Controller to Live Link Preview Controller. Then, change the Live Link Subject Name to RadicalPose. For Retarget Asset, select the corresponding blueprint Remap Asset file for that skeleton. For example, for the Radical skeleton, choose the RadToRadRemap asset. For the Epic skeleton, choose the BP_RadToEpicRemap asset.

 

Remap Assets

In order to use skeletons other than the Radical skeleton, we need to remap the Radical skeleton’s bone names to their counterparts on other skeletons. For example, if you open the BP_RadToEpicRemap asset and go to the GetRemappedBoneName function, you can see a big switch statement that performs the remapping. For Mixamo, the skeleton bone names match the RADiCAL skeleton bone names, so this step is unnecessary.

 

Rotation conversions

To account for some of the differences between the Radical Studio coordinate frame and Unreal, we have flipped the incoming LiveLink data’s rotation and position axes. You can inspect the conversions at the RadicalLiveLinkRemapAssetBase class and its child classes. We expect that other skeletons will require different rotation adjustments, including swapping axes. We exposed three overridable methods to implement the root bone position, root bone rotation, and non-root bone rotation conversions. Please note that the AI output in Radical Studio uses the hip bone as a root, so position data should be mapped to the hips (or pelvis) in the target skeleton.

 

Real-time Remapping/Retargeting

To remap the LiveLink data (which matches RADiCAL 3.1 skeleton structure) to other skeletons, modifications to the bone rotations may be required. The incoming LiveLink data contains rotation offsets from the RADiCAL’s base T-pose, and hip position. For the Epic skeleton, we tweaked the arm rotations in the AnimBP, as the Epic skeleton uses an A pose by default. For the Mixamo skeleton, there are more complex differences, such as an inverted rotation for the the LeftUpLeg bone’s Y axis (among others).

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An Unreal sample scene is available for download here.

Credit for instructions to Xuelong Mu.