This activity belongs to the GeoGebra book Voronoi Paintings.
If an image features a shape with a defined outline, it’s easy to isolate it from the rest by cutting out that outline. This way, we obtain a silhouette of the shape, as shown in Figure 4.
Figure 4: Silhouette of a figure
Notice that, if we consider on one side the silhouette of the laptop, on another the silhouette of the pipe, and on another the silhouette of the man, representing the three silhouettes would give us exactly the same black-on-white image shown in Figure 4. Likewise, if we added the silhouette of the log used as a seat, this silhouette would immediately integrate into the overall silhouette. In other words, only isolated silhouettes without a common border can be clearly distinguished. This characteristic has been widely used in shadow puppetry or in puzzle proposals, like the figures that can be created with tangram pieces (Figure 5).
Figure 5: Shadow puppetry and a figure (intended to be a cat) to build with the tangram
Figure 4: Silhouette of a figure
Figure 5: Shadow puppetry and a figure (intended to be a cat) to build with the tangram