This paper presents the implementation and evaluation of a 50,000-pose-sample-per-second, 6-degree-of-freedom optical head tracking instrument with motion-to-pose latency of 28μs and dynamic precision of 1-2 arcminutes. The instrument uses high-intensity infrared emitters and two duo-lateral photodiode-based optical sensors to triangulate pose. This instrument serves two purposes: it is the first step towards the requisite head tracking component in sub- 100μs motion-to-photon latency optical see-through augmented reality (OST AR) head-mounted display (HMD) systems; and it enables new avenues of research into human visual perception - including measuring the thresholds for perceptible real-virtual displacement during head rotation and other human research requiring high-sample-rate motion tracking. The instrument's tracking volume is limited to about 120×120×250 but allows for the full range of natural head rotation and is sufficient for research involving seated users. We discuss how the instrument's tracking volume is scalable in multiple ways and some of the trade-offs involved therein. Finally, we introduce a novel laser-pointer-based measurement technique for assessing the instrument's tracking latency and repeatability. We show that the instrument's motion-to-pose latency is 28μs and that it is repeatable within 1-2 arcminutes at mean rotational velocities (yaw) in excess of 500°/sec.

For generalized augmented reality to be feasible, the augmenting elements must be visible in varied environments and under rapidly changing, high dynamic range lighting, from bright sunlight to deep shadows. We present a high dynamic range, optical see-through, augmented reality display that dynamically adjusts the brightness of the virtual imagery to match the current brightness of the real scene. Critical components include the spatial brightness sensor array and the positional brightness image intensity matcher. The color, scene-adaptive HDR display system is based on a high-rate (15 kHz) DMD projector using a high-speed RGB LED illuminator, each color with independent 16 bit intensity control for each binary DMD frame. The critical input to the intensity matching algorithm is the output of an array of high sensitivity light sensors. This paper discusses the implementation of the system and reports performance via still and video demonstrations under a variety of lighting conditions.

We describe an augmented reality, optical see-through display based on a DMD chip with an extremely fast (16 kHz) binary update rate. We combine the techniques of post-rendering 2-D offsets and just-in-time tracking updates with a novel modulation technique for turning binary pixels into perceived gray scale. These processing elements, implemented in an FPGA, are physically mounted along with the optical display elements in a head tracked rig through which users view synthetic imagery superimposed on their real environment. The combination of mechanical tracking at near-zero latency with reconfigurable display processing has given us a measured average of 80 µs of end-to-end latency (from head motion to change in photons from the display) and also a versatile test platform for extremely-low-latency display systems. We have used it to examine the trade-offs between image quality and cost (i.e. power and logical complexity) and have found that quality can be maintained with a fairly simple display modulation scheme.

We present initial results from a new image generation approach for low-latency displays such as those needed in head-worn AR devices. Avoiding the usual video interfaces, such as HDMI, we favor direct control of the internal display technology. We illustrate our new approach with a bench-top optical see-through AR proof-of-concept prototype that uses a Digital Light Processing (DLPTM) projector whose Digital Micromirror Device (DMD) imaging chip is directly controlled by a computer, similar to the way random access memory is controlled. We show that a perceptually-continuous-tone dynamic gray-scale image can be efficiently composed from a very rapid succession of binary (partial) images, each calculated from the continuous-tone image generated with the most recent tracking data. As the DMD projects only a binary image at any moment, it cannot instantly display this latest continuous-tone image, and conventional decomposition of a continuous-tone image into binary time-division-multiplexed values would induce just the latency we seek to avoid. Instead, our approach maintains an estimate of the image the user currently perceives, and at every opportunity allowed by the control circuitry, sets each binary DMD pixel to the value that will reduce the difference between that user-perceived image and the newly generated image from the latest tracking data. The resulting displayed binary image is “neither here nor there,” but always approaches the moving target that is the constantly changing desired image, even when that image changes every 50μs. We compare our experimental results with imagery from a conventional DLP projector with similar internal speed, and demonstrate that AR overlays on a moving object are more effective with this kind of low-latency display device than with displays of similar speed that use a conventional video interface.

Personal mobile computing devices share many of the same properties of nodes in a sensor network. They are both sensor-rich, power-limited, and wirelessly connected. Indeed, a number of researchers have described sensor networks composed of collections of mobile devices. Sensor networks may be naively characterized as instrumentation of a fixed space or structure. Mobile devices are appliances in the service of an individual. Imagining the potential of these technologies in combination is a matter of proposing applications. However, combined applications must abide by the tight energy and bandwidth constraints imposed on sensor networks. A conventional mobile device risks becoming the bull in a china shop if it requires service from surrounding sensor networks. This talk examines both the potential and limitations of combined applications.

Image-based rendering is perceived as a new technique, as yet unsupported by hardware. In fact, IBR has been an integral part of computer graphics for some time. However it is not as well supported as one might wish in conventional graphics hardware and software libraries. This overview highlights some of the hardware and software issues of IBR, surveys current practice, and proposes guidelines for designing a unified IBR platform.

No abstract available.

No abstract available.

This paper describes an implementation of Cook's "shade trees" in which shaders are described as networks of modules, building blocks, whose connections can be defined interactively.The high level interface to the shaders is a graphical editor which permits users to construct complex shaders by connecting shading elements in a network, in effect a graphical shading language. A low level interface to the shaders is also provided. In the low level interface, shading elements are programmed in a standard programming language and compiled into modules which can linked either at run time or compile time.Each link in the shading network represents a subroutine call. In essence, execution of the network is analogous to the execution of an interpreted language.

No abstract available.

We illustrate two enhancements to procedural geometric models which allow autonomous procedures to jointly satisfy mutual constraints. One of the techniques adds communications paths between procedures which may affect one another. Conflicts are resolved by modifying communicating procedures as they execute.The second technique is a generalization of widely used subdivision procedures. The termination test of typical subdivision methods is replaced with a "transition" test. The subdivision procedure is augmented with a "script" in the form of a state transition table which controls the procedures' response to external events as well as to the normal termination conditions.In the examples we show how effective these techniques are building complex geometric models with very sparse input.

This algorithm draws lines on a gray-scale raster display by dragging a “brush” along the path of the line. The style of the line is determined by the properties of the brush. An anti-aliasing calculation is performed once for the brush itself and thereafter only a trivial additional operation is needed for each pixel through which the brush is dragged to yield an anti-aliased line.

A set of utility programs for 3D shaded display that make up a testbed for creating raster scan display systems is described.The principal feature of this system is a flexible scan conversion processor that can simultaneously manage several different object types.Communications between the scan conversion routine and processes which follow it in the display pipeline can be routed through a structure called a span buffer which retains some of the highresolution, three-dimensional data of the object description and at the same time has the characteristics of a run length encoded image.It was found that the testbed software has the flexibility for a variety of experimental applications, and that the building block approach reduces the amount of programming effort required for new applications.

We describe a set of utility routines for 3-D shaded display which allow us to create raster scan display systems for various experimental and production applications. The principal feature of this system is a flexible scan conversion processor that can simultaneously manage several different object types.

Hierarchical representations of 3-dimensional objects are both time and space efficient. They typically consist of trees whose branches represent bounding volumes and whose terminal nodes represent primitive object elements (usually polygons). This paper describes a method whereby the object space is represented entirely by a hierarchical data structure consisting of bounding volumes, with no other form of representation. This homogencity allows the visible surface rendering to be performed simply and efficiently.

To accurately render a scene, global illumination information that affects the intensity of each pixel of the image must be known at the time the intensity is calculated. In a simplified form, this information is stored in a tree of “rays” extending from the viewer to the first surface encountered and from there to other surfaces and to the light sources. The visible surface algorithm creates this tree for each pixel of the display and passes it to the shader. The shader then traverses the tree to determine the intensity of the light received by the viewer. Consideration of all of these factors allows the shader to accurately simulate true reflection, shadows, and refraction as well as the effects simulated by conventional shaders. Anti-aliasing is included as an integral part of the visibility calculations. Surfaces displayed include curved as well as polygonal surfaces.

The conventional procedure for generating shaded images of curved surfaces is to approximate each surface element by a mosaic of polygons and to then apply one of several established polygon display algorithms. The method described here produces an excellent approximation of bi-cubic parametric surfaces in scan line order. Each surface patch is described in terms of edge curves which are intersected by successive scanning planes to form endpoints of scan line segments. Visibility is calculated for each segment by a hybrid priority/zbuffer scheme. Shading is computed using Phong's illumination model with interpolated surface normal values. CR Categories: 8.2.