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Science and Technology
科技
Computer-generated imagery
计算机图像生成技术
Fabricating fabric
虚拟面料
How to generate more realistic images of clothes
如何生成更逼真的衣物图像
FILMS like "Captain America", "Tron Legacy" and "The Curious Case of Benjamin Button" have shown that it is possible to use computer-generated imagery (CGI) to make actors look younger, older or wimpier than they actually are, in a surprisingly realistic manner.
电影《美国上尉》、《创战记》和《本杰明?巴顿奇事》表明计算机图像生成技术能以惊人的逼真手法使演员看上去比实际更年轻、老态或懦弱。
At least, it is possible if those altered actors are kept at a suitable distance from the viewer.
这种效果至少在那些被改造过的演员与观众保持合适距离时能够实现。
The difficulty of recreating the textures of both skin and fabric means the effect is less convincing when seen close up.
皮肤和面料纹理重建的困难在于它们被放大观看时，效果并不理想。
The reason is that, whereas it is possible to simulate realistically the forces which make virtual skin and fabric hang, bend, flap and stretch, recreating the subtle ways they reflect light has so far proved extremely tricky.
原因在于尽管计算机能够真实地模拟使虚拟皮肤及面料产生悬挂、弯曲、飘动和拉伸的外力，但迄今为止想要找到构建反射光的精妙方法仍是极为困难的事情。
The shimmer and sheen of both fabric and skin depend on the geometry of their internal structures—the exact arrangement of threads or protein fibres.
皮肤和面料的微光及光泽都取决于它们内部的几何结构——织线或蛋白纤维的精确排列。
This is hard to model accurately.
这种模型很难精确地建立。
Steve Marschner and his colleagues at Cornell University have, though, come up with a way to get round that problem.
不过康奈尔大学的史蒂夫?马施纳及其同事们发现了一个解决此问题的方法。
Instead of modelling, they are copying.
他们不是建立模型而是采用拷贝技术。
They are using computerised tomography (CT) to analyse the structures of fabrics at high resolution and then plugging the results into CGI.
他们利用电脑断层扫描术（简称CT）以高分辨率分析面料的结构，然后将结果输入到计算机影像生成系统。
That, allied to the laws of optics and some heavy-duty computer power, seems to do the trick.
结合光学定律和强大的计算机处理能力，这种方法似乎能够达到理想效果。
Computerised tomography is most familiar as a medical technique for examining people's insides.
"电脑断层扫描术"是最广为人知的医学技术，主要用于人体内部检查。
Like classical radiology it uses X-rays.
与传统放射学相同，它也使用X射线。
But because the image is constructed inside a computer using shots taken from many different directions, rather than being a single exposure recorded on photographic film, CT can capture fine detail and record soft tissues that are invisible to classical radiology.
但是因为计算机构建内部图像时采集的是多角度拍摄数据，而不是靠摄影胶片上的单一曝光影像，所以电脑断层扫描术能够捕捉细节并记录下传统放射学无法看到的软组织。
Dr Marschner and his colleagues used a benchtop version of CT, developed for looking at the structure of materials rather than at human bodies, for their experiment.
马施纳博士及其同事们采用了台式版本的CT进行实验，这种CT是被研制用来观察材料结构而非人体的。
Employing doses of X-rays many times stronger than those used to study people, they obtained high-resolution information about small pieces of fabric.
使用比人体研究高数倍的X射线剂量，他们获得了小块面料的高分辨率信息。
Computerised tomography allows the three-dimensional structure of the fibres in such scraps to be recorded, with all their kinks and imperfections.
"电脑断层扫描术"能够记录零碎面料的三维结构和所有的扭结和缺陷。
A number of small pieces can then be patched together into an entire garment inside a computer, in the same way that a handful of actors are turned into a CGI crowd.
然后计算机将大量细碎面料拼凑成一件完整的衣服，采用同样方法，可将少数演员转换成电脑合成人像。
But because the internal structure of each bit of the garment matches that of a real piece of cloth, the way light will play on it can be calculated far more realistically than if it were just a computer model of what the interior of cloth is thought to look like.
但是因为这件服装每片面料的内部结构都与真实布料匹配，因此与仅是看上去象布料的计算机衣服模型相比，光线在其上的表现效果能够更加逼真。
Demonstrating the results of their technique at the SIGGRAPH computer-graphics conference in Vancouver this week, Dr Marschner and his colleagues showed realistic renderings of felt, gaberdine, silk and velvet.
本周，马施纳博士及其同事们将他们的技术成果在温哥华举行的计算机图形会议上展示，并向人们演示了毛毡、华达呢、丝绸和天鹅绒的逼真效果图。
Moreover, their renderings remain realistic even when viewed close up.
此外，他们的效果图即使被放大观看依然很逼真。
Sadly, skin is still beyond them.
但可惜的是，他们仍然无法让皮肤实现这样的效果。
The high intensity of the X-rays involved would be too damaging for use on a living human being, and a corpse would probably not produce the right results.
因为高强度的X射线会对人体造成很大损伤，而采用尸体实验可能得不到正确的结果。
But once the rendering technique has been speeded up (at the moment it is still a bit slow and clunky), the swish of a virtual cloak or the doffing of a computerised hat should look far more realistic than it does now.
但是一旦绘图技术突飞猛进（目前技术仍有些缓慢和粗陋），虚拟斗篷的抖动或电脑生成帽子的脱落动作会比现在看上去更为逼真。
In the meantime, according to Dr Marschner's colleague Kavita Bala, the technology might have an application in online retailing.
同时，马施纳博士的同事卡维塔?巴拉表示这项技术可能会在网上零售业得到应用。
At the moment, people buying clothes over the internet have only standard photographs to help them choose their purchases.
目前，人们在网上购买衣物仅能通过浏览标准图片帮助选购。
Using CT-based computer graphics might, paradoxically, give a better idea of what the material an item of clothing is made from is really like than can be garnered from a boring, old photograph of the original.
相反，基于电脑断层扫描术的计算机图形技术可能提供了一个更好的办法，人们能够看到一件衣服所使用材料的真实质地，而无须将令人生厌，老旧的原物照片收集来观看。
