Teatre nôh

The Noh Mask Effect: A Facial Expression Illusion
The full-face masks worn by skilled actors in Japanese Noh drama can induce a variety of perceived expressions with changes in head orientation. Rotation of the head out of the visual plane changes the two dimensional image characteristics of the mask which viewers may misinterpret as non-rigid changes due facial muscle action. The figure below shows the same Edo-period Noh mask, Magojiro, at three inclinations.

The lifelike changeability of Noh masks has been known in Japanese theatre for centuries. The earliest such Noh masks were carved in the Kamakura period (1192 - 1333). The effect is considered to be an important ingredient in the mysterious atmosphere of Noh drama.
Understanding the Noh Mask Effect
Examination of the the 3-D shape of the Noh mask suggests the origin of this effect. The shape of the Noh mask exaggerates certain features, particularly the depth of the contours of the mouth. The figure below shows that the 2-D projection of these contours varies greatly when the mask tilt is changed.

In the above figure, the 3-D shape of a Noh mask (Ko-omote) was obtained using a Cyberware laser range scanner. In figure 2A, the contour of the upper lip has been highlighted to draw attention to the effect of mouth inclination on its perceived shape. Other regions of the mask such as the eye contours and brow paints undergo changes in apparent shape as the mask is rotated forwards. In figure 2B, the 3D shapes of a Noh mask and a Japanese womens face are shown for comparison.

The Noh mask effect seems to be lessened by this regular, predictable motion.