This extension uses DLib or InsightFace to calculate the Euclidean and Cosine distance between two faces.
The best way to evaluate generated faces is to first send a batch of 3 reference images to the node and compare them to a forth reference (all actual pictures of the person). That will give you a baseline number that you can use to compare to generated images.
You need to install either InsightFace or Dlib (or both).
For DLIB download Shape Predictor, Face Predictor 5 landmarks, Face Predictor 81 landmarks and the Face Recognition models and place them into the dlib
directory.
Precompiled Dlib for Windows can be found here.