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 and the Face Recognition models and place them into the dlib
directory.
Precompiled Dlib for windows can be found here.