The MetaHuman Video Live Link subject can be configured to enable head translation and reduce noise, among other things.
Basic Controls
| Option | Description |
|---|---|
Head Orientation | When enabled, the rotational orientation of the head is output. You may want to disable this option if the head is being tracked by other means (such as mocap) or if you wish to analyze the facial animation on a static head. The default value for this control can be set in the Project Preferences. |
Head Translation | When enabled, and a neutral frame has been captured, the translation of the head is output. The default value for this control can be set in the Project Preferences. |
Head Stabilization | Reduce noise in the head position and orientation. |
Image Rotation | Rotate the input video by 90, 180, or 270 degrees prior to processing. |
Focal Length | A read-only display of the calculated focal length in pixels. This is only available when head translation is enabled. |
The Create Neutrals button under the basic controls will capture a neutral for both head pose and normalizing neutral face as an alternative to doing this multiple times.
The Reload Subject button will reinitialize the Live Link subject with the current settings. This is useful in cases where the connection to the camera has been lost, such as the USB webcam has been unplugged.
The Remove Subject button will remove the subject from the Live Link Source.
Neutral Head Pose
Capturing a neutral pose sets a reference position and orientation that the head translation and angle will be measured relative to. This can be used to account for any offset between the actor and camera; for example, when a webcam is mounted on top of a monitor and looking downward at the actor.
While holding a neutral head pose, click the Capture Neutral button. The neutral pose must be held for a short period of time – a count down will show the time remaining.
Once captured, the Head Translation option in the Control section of the subject settings will be enabled.
The neutral head pose can be persisted by saving a Live Link preset.
Normalize Neutral Face to Control Rig Values
Calibration attempts to normalize the actor's neutral face to the control rig’s neutral values. It requires a neutral frame to be captured before having an effect on the animation values, and can be persisted by saving a Live Link preset.
Whilst holding a neutral facial expression, click the Capture Neutral button to begin calibrating the animation data for the current actor. The neutral expression should be held for a short period of time — a count down will show the time remaining.
Calibration is applied to the smoothed curves and therefore is dependent on the Smoothing Parameters.
Reduce Noise with Smoothing
Default Smoothing
The raw animation data can contain a degree of noise which can be reduced through the use of smoothing. The Smoothing section is preconfigured with a default set of smoothing parameters already applied, represented by the DefaultSmoothing asset.
The smoothing uses two different filter types:
Rolling Average
General smoothing which is good for reducing jitter and is set by incrementing a single value.
Rolling average isn't recommended on controls that start and stop abruptly or travel far over a few frames (such as eye direction).
The euro filter uses two parameters to smooth animation curves allowing for greater tuning.
Slope controls how much smoothing is applied at high speed.
Min cutoff affects how much noise is smoothed at low speed.
If high speed lag is a problem, increase Slope; if slow speed jitter is a problem, decrease Min cutoff.
There is a second HeavySmoothing preset, however it is recommended that smoothing should be edited to reflect the capture environment and device.
Custom Smoothing
Custom smoothing parameters can be applied by the creation of a new Data Asset in the Content Browser. This asset type is located within the Miscellaneous category when creating a new asset.
When prompted, pick the MetaHuman Realtime Smoothing class for the Data Asset instance.
Open the asset editor and expand the Parameters category. For each control, it is possible to specify the smoothing method (or filter) as either Rolling Average or One Euro and then tweak the parameters for each type.
Once you’re ready to apply your custom smoothing asset, select it within the Smoothing settings.
Reverting to Default Smoothing
In order to switch back to the DefaultSmoothing parameters, you will need to ensure that both Show Engine Content and Show Plugin Content are selected in your content browser settings.
