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1、.(用外文写)外文出处：资料1： /CJFDTotal-GJDX200606003.htm 中文译文交互式三维显示器摘要本文介绍了一套对光场的自动立体交互式三维显示器，该显示器是由一个高速视频投影仪，覆盖着全息扩散器的旋转镜，及解码的电路FPGA组成的，能够同步显示360三维图形。其中，显示屏采用标准的可编程图形卡来显示，每秒能够显示超过5000次交互式三维图形，可视角度是360，分辨差是1.25度，每秒进行20次更新。本文同时也描述了三维显示器的投影几何和校准的过程。在此基础之上，我们创建一个了多中心的并且能够360投影显示器。在一些参数已知的情况下，我们能够显示所有角度和距离。同时，我们证
2、明了用交互式光栅图形跟踪系统可以衡量视点的高度和距离这一理论，由了这一理论，我们就运用投影技术来精确显示水平和垂直视差。最后，我们也讨论了视觉调试功能以及彩色图像显示。关键词三维立体显示，图形硬件，实时绘制，光场，基于图像的显示1. 简介 虽然现在有很多计算机能绘制图像，再用来三维显示，但许多三维图像本质上是用二维显示的。各种形式的三维显示构想与构建起码有100年(Lippman 1908年)的历史了。但是知道近年来，因为数字的获取、计算、和显示等功能的进步才使三维显示可能。在本文中，我们提供一个容易复制，低成本的三维显示系统。并辅以一个三维立体显示器的外形。我们的这个显示器是三维立体的，并不
3、需要特别是显示玻璃，与其他三维显示器一样，它也是全方向，多视角的，允许观察者站在任何地方观察。文中，我们发展和证明了投影几何与显示技术。此外，值得注意的是,如果以头部跟踪算法为研究对象，不管有多少观众,我们的显示器都可以对角度进行调整，以保证在任何角度观察的效果。纵观全局，我们展示显示的图形及实物，还有全方位的三维立体显示。我们的贡献包括:1.发明了一种简单的可再生的360水平视差光场显示器，包括低成本商品的图形和投影显示硬件。2.发明了一种新的软件/硬件体系结构,用标准的图像处理硬件，以千赫级的速度进行实时系统更新和高速视频投影。3.在光场显示技术中,用水平自动立体显示并用垂直头部跟踪算法，
4、为用户提供产生正确的垂直视差。4.显示多中心的新投影算法，把OpenGL图形投影到一个投影各向异性的表面。并适用于各个高度和距离。2.背景和相关工作通过调查最近丰富多样的三维显示技术,我们可以发现,我们这种显示属于多视点三维水平视差显示,这种显示器是把一个或多个投影仪连在一起并产生拥有独立视点的图像。在不同的视角，不同的观众将会根据自己所在的位置看到属于这个视点的图像。3.系统概述我们的三维显示系统包括由一个的全息各向异性扩散旋转镜，一个运动控制电机，高速视频投影机，和一个标准的PC。该DVI输出PC图形卡（NVIDIA GeForce8800）是对接口投影机使用的是基于FPGA的图像解码器。
5、旋转镜是倾斜的，倾角是45，这样有利于反摄从投影机的光线，允许尽可能多的观众能在任何地方观看显示的图像，同时，本节提供了系统组件的详细信息。其中包括:3.1高速投影机我们使用了修改以后的成品投影机，并使用新的DLP驱动卡自定义编程FPGA为基础的电路来实现高速视频投影。采用FPGA的每24位彩色框视频，但是我们并不是绘制一个彩色图像，而是显示每个位依次为单独的帧，即单一的色彩。因此，如果输入的数字视频信号为60Hz，那么，投影机显示60 24 =1440帧每秒。为了实现更快的速率，我们设置了180-240Hz刷新速率视频卡。这些视图被编码为24位的图像并发送到投影机。现在，Polaris Ro
6、ad公司可以提供一个完整的套件和组成的FPGA现在的DLP板。3.2旋转镜系统在体3D显示中，投影仪把图像投影到旋转镜上,并扩散到一个旋转的平面在所有方向。但这种显示器无法重新检视依赖效应。相比之下，我们的投影表面是各向异性扩散且粘结到一个全息面的镜子。全息扩散提供了对控制这个地区的宽度和高度。扩散器的特点是这样的，相对扩散X轴和Y轴之间约1:200。横向上，维持表面上大幅镜面视图之间的分辨差为1.25度。纵向上，因为镜面散射广泛，因此的影图像可从本质上讲可以到任何高度。图4显示了各向异性反射特性该反射镜系统。该镜面叶水平剖面近似于一个相邻的观点双线性插值;镜子增加了一些额外的模糊从而优化了显
7、示。全息的各向异性扩散器和镜子装配是安装在一个碳纤维面板和附加到铝飞轮，与水平方向呈45，飞轮同步旋转，并通过投影机显示图像。其中，两镜系统将在第8节描述。由于输出帧速率PC图形卡的相对恒定，所以只要稍作调整就可以了，我们使用主PC视频信号输出率来使系统同步。投影机的FPGA还决定了当前帧信号的编码率。这些控制信号接口直接连到Animatics SM3420D，其中包含的固件和运动控制参数产生一个稳定的速度为基础的控制回路，保证了电机转速停留在与投影机同步的信号。由于旋转到镜是每秒20个，视觉暂留时间就在镜子的中心创造了一个幻想浮动对象。3.3跟踪垂直视差 投影机和旋转镜产生一个横向视差，当视
8、点上下移动，或前进和后退时，并不会改变其正确的视图。但是，我们在第4节描述的投影算法必须把高度和距离计算在内才能正确的显示。如果要求了水平视差，我们就需要初始化距离和高度来达到所期望的高度和距离。外文原文Rendering for an Interactive 360 Light Field DisplayAbstractWe describe a set of rendering techniques for an autostereoscopic light field display able to present interactive 3D graphics to multiple
9、simultaneous viewers 360 degrees around the display. The display consists of a high-speed video projector, a spinning mirror covered by a holographic diffuser, and FPGA circuitry to decode specially rendered DVI video signals. The display uses a standard programmable graphics card to render over 5,0
10、00 images per second of interactive 3D graphics, projecting 360-degree views with 1.25 degree separation up to 20 updates per second. We describe the systems projection geometry and its calibration process, and we present a multiple-center-of-projection rendering technique for creating perspective-c
11、orrect images from arbitrary viewpoints around the display. Our projection technique allows correct vertical perspective and parallax to be rendered for any height and distance when these parameters are known, and we demonstrate this effect with interactive raster graphics using a tracking system to
12、 measure the viewers height and distance. We further apply our projection technique to the display of photographed light fields with accurate horizontal and vertical parallax. We conclude with a discussion of the displays visual accommodation performance and discuss techniques for displaying color i
13、magery.Keywords: autostereocopic displays, graphics hardware, real-time rendering, light field, image-based rendering1.IntroductionWhile a great deal of computer generated imagery is modeled and rendered in 3D, the vast majority of this 3D imagery is shown on 2D displays. Various forms of 3D display
14、s have been contemplated and constructed for at least one hundred years Lippman 1908, but only recent advances in digital capture, computation, and display have made functional and practical 3D displays possible. We present an easily reproducible, low-cost 3D display system with a form factor that o
15、ffers a number of advantages for displaying three-dimensional objects in 3D. Our display is autostereoscopic, requiring no special viewing glasses, omnidirectional, allowing viewers to be situated anywhere around it, and multiview, producing a correct rendition of the light field with correct horizo
16、ntal parallax and vertical perspective for any viewpoint situated at a certain distance and height around the display. We develop and demonstrate the projection mathematics and rendering methods necessary to drive the display with real-time raster imagery or pre-recorded light fields so that they ex
17、hibit the correct cues of both horizontal and vertical parallax. Furthermore, if head tracking is employed to detect the height and distance of one or more viewers around the the display, our display allows the rendered perspective to be adjusted at run-time to allow one or more tracked users to pro
18、perly see objects from any 3D viewing position around the display. Our display uses primarily commodity graphics and display components and achieves real-time rendering with non-trivial scene complexity across its entire field of view. Our contributions include:1.An easily reproducible 360 horizonta
19、l-parallax light field display system that leverages low-cost commodity graphics and projection display hardware.2.A novel software/hardware architecture that enables real-time update of high-speed video projection at kilohertz rates using standard graphics hardware3.A light field display technique
20、that is horizontally multiview autostereoscopic and employs vertical head tracking to produce correct vertical parallax for tracked users.4.A novel projection algorithm for rendering multiple centers of projection OpenGL graphics onto an anisotropic projection surface with correct vertical perspecti
21、ve for any given viewerheight and distance.2.Background and Related WorkRecent surveys of the rich and varied field of three-dimensional display techniques can be found in Travis 1997; Favalora 2005; Dodgson2005. Our display belongs to an emerging class of horizontal-parallax multiview 3D displays t
22、hat combine one or more video projectors to generate view-dependent images on a non-stationary anisotropic screen. Viewers receive varying views of the scene depending on the position of their eyes with respect to the display.3.System OverviewOur 3D display system consists of a spinning mirror cover
23、ed by an anisotropic holographic diffuser, a motion-control motor, a highspeed video projector, and a standard PC. The DVI output of the PC graphics card (an nVIDIA GeForce 8800) is interfaced to the projector using an FPGA-based image decoder. As seen in Figure 2, the spinning mirror is tilted at 4
24、5 to reflect rays of light from the projector to all possible viewing positions around the device, allowing many people to view the display simultaneously. The remainder of this section provides details of the system components. 3.1 High-Speed Projector We achieve high-speed video projection by modi
25、fying an off-the-shelf projector to use a new DLP drive card with custom programmed FPGA-based circuitry. The FPGA decodes a standard DVI signal from the graphics card. Instead of rendering a color image, the FPGA takes each 24-bit color frame of video and displays each bit sequentially as separate
26、frames (Figure 3). Thus, if the incoming digital video signal is 60Hz, the projector displays 6024 = 1,440 frames per second. To achieve even faster rates, we set the video card refresh to rates of 180-240Hz. At200Hz, the projector displays 4,800 binary frames per second. We continuously render new
27、horizontal views of the subject (288 images per rotation). These views are encoded into 24-bit images and sent to the projector. A complete kit consisting of the FPGA and DLP boards is now available from Polaris Road, Inc.3.2 Spinning Mirror System Previous volumetric displays projected images onto
28、a spinning diffuse plane which scattered light in all directions. Such displays could not recreate view-dependent effects such as occlusion. In contrast, our projection surface is an anisotropic holographic diffuser bonded onto a first surface mirror. The mirrored surface reflects each projector pix
29、el to a narrow range of viewpoints. The holographic diffuser provides control over the width and height of this region. The characteristics of the diffuser are such that the relative diffusion between x and y is approximately 1:200. Horizontally, the surface is sharply specular to maintain a 1.25 de
30、gree separation between views. Vertically, the mirror scatters widely so the projected image can be viewed from essentially any height. Figure 4 shows the anisotropic reflectance characteristics of the mirror system. The horizontal profile of the specular lobe approximates a bilinear interpolation b
31、etween adjacent viewpoints; the motion of the mirror adds some additional blur which improves reproduction of halftoned imagery at the expense of angular resolution.The anisotropic holographic diffuser and mirror assembly are mounted on a carbon fiber panel and attached to an aluminum flywheel at 45
32、. The flywheel spins synchronously relative to the images displayed by the projector. A two-mirror system (which is more balanced) for reflecting multi-color imagery is described in Section 8.3.3 Tracking for Vertical Parallax The projector and spinning mirror yield a horizontal-parallax-only displa
33、y; the image perspective does not change correctly as the viewpoint moves up and down, or forward and backward. However, the projection algorithms we describe in Section 4 take into account the height and distance of the viewer to render the scene with correct perspective. If just horizontal parallax is required, a good course of action is to initialize this height and distance to the expected typical viewing height and distance.: