Prosopagnosia (sometimes known as face blindness) is a disorder of face perception where the ability to recognize faces is impaired, while the ability to recognize other objects may be relatively intact. Few successful therapies have so far been developed for affected people, although individuals often learn to use "piecemeal" or "feature by feature" recognition strategies. This may involve secondary clues such as clothing, hair color, body shape, and voice. Because the face seems to function as an important identifying feature in memory, it can also be difficult for people with this condition to keep track of information about people, and socialize normally with others (via).
The difficulty of face-blind people could hardly be explained and understood by people around because we are taking face recognition so for granted and seldom think of how faces are specifically optimized in our memory system. The analogy of the stones were used by Cecilia Burman on her website on prosopagnosia and I found it a relatively effective approach of making this explanation short.
The clouds are generated by several different features on peoples faces and are overlaying on their faces to obscure them The optimized mechanism for face-recognition in our brain would not be activated since most of the facial features are turned off by the noises (clouds). However since the clouds are generated from an abstraction of facial features so ideally I could still create a unique cloud mask for each person. In this way, we could probably experience the difficulty of face blindness and, however, could also experience the "piecemeal" or "feature by feature" recognition strategy by observing the shape, texture and other features of the clouds.