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Virtual 3D perception in a fog projection installation

This paper presents a fog projection installation, entitled Dance in the Mist, that studies human visual experience and how depth perception is constructed. It resembles the Spinning Dancer - a famous bistable optical illusion published online a decade ago. A female dancer is perceived to be spinning clockwise or anti-clockwise by different observers, and some may even see the figure suddenly spins in the opposite direction. In the installation, an immaterial screen is created by a cloud of fog that is flowing continuously from a fog machine and rising up in the air. The dancer's silhouette is projected on the mist and appears to be suspending and spinning in mid-air. Based on the Mie scattering model, the animated image can be observed most clearly at the frontal position forward direction to incident radiation. As the image casts on a column of fog rather than a flat screen, the light rays are scattered at different depth positions in the fog. This gives rise to image thickness and depth that creates a virtual 3D effect. The translucent appearance of the image also contributes to the holographic depth sensation. Most importantly, the bistable property of the optical illusion preserves in the virtual 3D display. That is, observer would see the dancer appearing to be 3D and spinning in the space in either clockwise or anti-clockwise direction. This installation ingeniously and playfully exploits the interplay between illusion (lack of visual cues for depth) and augmented depth perception to create a new visual experience for audience.