See virtual worlds in the round

 作者:南湓洒     |      日期:2019-03-03 05:01:01
By Celeste Biever A GOLDFISH bowl in which 3D video images appear suspended in mid-air could help surgeons target tumours more precisely, air-traffic controllers prevent air accidents, and drug designers better understand the structures of promising molecules. “On a 2D screen, a protein molecule looks like tangled spaghetti. But when it appears in our machine, you begin to fully grasp its 3D structure,” says Gregg Favalora of Actuality Systems, which is behind the $40,000 display. As Favalora walks around his display, a 3D computer model of a protein molecule hovers inside its smoky white soccer-ball-sized sphere. At the click of a mouse, the molecule disappears and is replaced by images of two airliners on a collision course in simulated 3D airspace. Favalora is showing off his Massachusetts-based company’s new product, Perspecta 1.9. It’s the first 3D display that lets users view 3D moving images by walking all the way around it, view from on top or below, or zoom in and out in real time. It was unveiled last week at the Society for Information Display’s annual exhibition in Boston. A prototype version appeared in 2001 that could only show a low-resolution, static 3D image. Now, with the addition of dedicated graphics-processing hardware, the system is able to twist and turn images in real time at video rates. Several applications have already emerged. Two oil companies, three medical centres and the US air force have bought or loaned Perspectas and are using them respectively to visualise slices of the Earth’s crust from seismic data, human organs from MRI and CT scans, and squadrons of aircraft from radar data. This is a big step forward from rotating a 3D computer image on a flat screen, Favalora says. Nothing beats being able to walk all the way around the object, view it from the top and zoom in whenever you want, he claims. Medical physicist James Chu of the Rush University Medical Center in Chicago, Illinois, is using the Perspecta to ensure that when radiation beams are being used to destroy breast tumours, they do not injure healthy tissue en route. Until now, he has to build up a mental 3D image from a stack of 2D scans and choose what he thinks will be the least destructive path for a beam. The Perspecta system is made up of a circular white polymer screen 25 centimetres in diameter, mounted on a 1-metre-high black box so that people can walk around it. Like a giant spinning lollipop, the screen, encased in a transparent polycarbonate shell, turns at 15 revolutions per second, sweeping out a solid white sphere. To display the image, software inside the Perspecta chops a 3D model generated by the computer into 198 separate pieces, like slices of cake, which are then projected onto the screen in quick succession by a graphics accelerator that feeds image slices to an optical system mounted below the screen. The result looks to the viewer like a 3D image composed of 100 million “volume pixels” or “voxels”. The moving 3D aircraft and molecule in the demo system really do seem suspended in this strange white ball. But Chris Chinnock, from technology consultancy Insight Media in Norwalk, Connecticut,