Complex origami models normally require thin, strong paper or tissue foil for successful folding; these lightweight materials allow for more layers before the model becomes impractically thick. Modern origami has broken free from the traditional linear construction techniques of the past, and models are now frequently wet-folded or constructed from materials other than paper and foil. With popularity, a new generation of origami creators has experimented with crinkling techniques and smooth-flowing designs used in creating realistic masks, animals, and other traditional artistic themes.