i'm still very new to Unreal Engine's control rig but thought this doodle may be helpful for learning. there may be better ways to implement.
here is an example of driving 4 blendshapes (the blendshapes were created in Blender and exported to fbx so they could be imported into Unreal Engine):
here is a picture of the control rig graph for a simpler example driving 2 blendshapes. similar logic can be used by copying and pasting these nodes and changing up the blendshape names and driving transformation channel to get it to work for 4 blendshapes.
here is a picture of the control rig graph that has the various nodes used to drive 2 blendshapes.
basically starting left to right:
on far left is the animator control that will be used to drive the blendshapes.
next it uses a 'Greater' node to decide if the controls transform z channel is positive or negative. here the z axis of the control will be used to drive 2 blendshapes. if the z translate axis is positive it uses its value after clamping it to a number between 0 and 1 to drive the first blendshape which is set in the 'set curve value' node. if the control's z is negative it first multiplies its value by -1 to get a positive number then it also eventually clamps its value and sends it to the second blendshape 'set curve value' node. (some of the float multiplies was to tweak the sensitivity of how much the animator control moves is enough to turn on blendshapes).
Hope this is helpful.
Happy Sketching!
also i highly recommend checking out JC's YouTube channel for learning about control rig.
inspired by,
JC's '3D Education with JC' YouTube channel's 'Build a control rig from scratch' video
