How to stick Grease Pencil animation to your models

tutorial

Your file will have two scenes: a 2D scene and a 3D scene

In the 2D scene, create a Grease Pencil object and a camera to look at it.

  • Put them in a collection to make it more organized

Draw your character's eye poses or mouth shapes

It can be a fully animated sequence with lip sync, or a bunch of poses you'll switch between using the armature later.

Render out from this scene to a texture folder

  • set Film -> transparent to get your cels on a transparent background

Make your model in your 3D scene

Texture your model

Make a plane, texture it with the rendered GP animation

  • image texture sequence w/ alpha channel

Add a Shrinkwrap modifier to the plane

  • set it to Project on the head of the model

Rig your model

When building the rig, make bones for the eye and mouth animation

Drive the frame offset of the texture with the bones

You may have to constrain the eye/mouth planes to the bones to keep them aligned with the model

References

Blender

(Tutorials > How to stick Grease Pencil animation to your models)