There are a couple of ways that the silhouette maps can be generated. First, an editor could be used by an artist to generate the content. In fact, all of the silhouette maps shown in this talk were generated in this manner. This is surprisingly easy, since I was able to do them in a few hours with very limited artistic ability. The software could allow the artist to embed the silhouette points manually, or it might generate the silhouette maps directly from the vector representation. One might imagine, for example, a future plug-in to Adobe Illustrator that automatically generates a silhouette map texture of the desired resolution from the original artwork.
Another way they might be created is by applying edge-detection algorithms to an input image. These algorithms can isolate the edges of the image and store points along the curves into a silhouette map. This technique might be used for textures generated from photographs, for example.