Projecting images onto water surfaces is the latest display technology to get a 3D makeover. With its ability to target light onto and between individual water droplets the AquaLux 3D can display text, video and other moving or still images on layers of falling water. In contrast to existing technologies for projecting images onto water surfaces, AquaLux 3D makes it possible to create 3D images by using multiple layers of precisely controlled water droplets.
Srinivasa Narasimhan, Associate Professor of Robotics, developed the display with Takeo Kanade, Professor of Computer Science and Robotics, and Peter Barnum, a Ph.D. student in robotics at Carnegie Mellon University’s Robotics Institute. To create a multi-dimensional display using water drops they needed to be able to target individual droplets and to direct light between them so that multiple layers could be illuminated.
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To accomplish this they developed a tightly coupled system that enabled them to generate rows of drops by using computer-controlled manifolds. By synchronizing the timing of drop generation between the rows, they ensured that drops in the front rows did not block the drops in the back rows. A camera tracks the positions of the drops, so a projector can independently target each row.
The system can generate drops at the rate of 60 per second, though a rate of 10 per second is sufficient for the human eye to perceive continuous resolution in each column; increasing the number of drops per second increases the brightness of the display. The Carnegie Mellon researchers have demonstrated the display with four linear layers of drops and a single projector, but Narasimhan said there is no limit to the number of layers and projectors that could be employed and that the drops could be arrayed in patterns other than linear rows.
"The beauty of water drops is that they refract most incident light, so they serve as excellent wide-angle lenses that can be among the brightest elements of an environment," said Narasimhan. "By carefully generating several layers of drops so that no two drops occupy the same line-of-sight from the projector, we can use each drop as a voxel that can be illuminated to create a 3-D image."
The researchers have used the water drops to display video images, text, a simulation of fish swimming in an aquarium, alternating sheets of solid colors and even a multi-dimensional version of the video game Tetris – all of which can be seen in the video below.
Narasimhan said that the technology could be used to create unique 3-D effects for theme parks, exhibitions and interactive games that don't require special eyeglasses to view by combining the droplets with clouds of mist.
"One unique aspect of AquaLux 3D is the potential for physical interaction," Narasimhan added. "People can touch the water drops and alter the appearance of images, which could lead to interactive experiences we can't begin to predict. We look forward to the day when creative people can fully explore the potential of this display."
The researchers will discuss AquaLux 3D on July 27 at SIGGRAPH, the 37th International Conference and Exhibition on Computer Graphics and Interactive Techniques, in Los Angeles.