I am making a model that is meant to be attached seamlessly onto an existing character model that contains its own shape keys. Because it is meant to attach seamlessly, I have to match the vertex normals of the verts that are in contact with the character. The custom normals work fine in basis key, but because the shape keys also move these verts, their normals do not line up in the other shape keys.
I am unable to adjust the custom normals in each individual shape key of my mesh. The data transfer modifier can pick up the vertex normal of the character mesh in its individual shape keys, but when applied to my own mesh it is applied across all shape keys. Is there a way to do this? If not, is a way to do it down the pipeline of Blender? Otherwise is there another software that can do this, customizing vertex normals differently for each shape key? Thanks.