Metahuman facemesh morph target preview not working?

Hi, I’ve imported the metahuman character into my UE4 project without any problem and found the facemesh created separately. So I opened the facemesh to preview its morph targets, but after adjusting some morph target values in the preview panel, no vertex moved in the mesh. Any clue for this? BTW the facial animation imported played without any problem.

Most of the facial movement is done with bones, morph targets are only used at LOD0, and for subtle correctives on top of the bone movement, so you may not see a large effect when manually applying the morph targets on the neutral pose.

All I need is using the script to control metahuman character facial expression, so can I still change the morph target values to achieve this purpose?

You would animate the face by driving input parameters of RigLogic node in the ControlRig. This is how Sequencer drives facial animation, for example. There is a ‘face board’ included to make this easier. There is more info in these videos:

I forgot to mention that I also need to control the facial rig at run time for customizing character facial expression. All the above videos are for editor only.