We consider the problem of task reweighting in fair-scheduled multiprocessor systems wherein each task's processor share is specified as a weight. Task reweighting can be used as a means for consuming (or making available) spare processing capacity. In this paper, we propose a multiprocessor reweighting scheme that can change a task's processor share with "minimal" error per share change.

Abstract We present a novel use of commodity graphics hardware that effectively combines a plane‐sweeping algorithm with view synthesis for real‐time, online 3D scene acquisition and view synthesis. Using real‐time imagery from a few calibrated cameras, our method can generate new images from nearby viewpoints, estimate a dense depth map from the current viewpoint, or create a textured triangular mesh. We can do each of these without any prior geometric information or requiring any user interaction, in real time and online. The heart of our method is to use programmable Pixel Shader technology to square intensity differences between reference image pixels, and then to choose final colors (or depths) that correspond to the minimum difference, i.e. the most consistent color. In this paper we describe the method, place it in the context of related work in computer graphics and computer vision, and present some results. ACM CSS: I.3.3 Computer Graphics—Bitmap and framebuffer operations, I.4.8 Image Processing and Computer Vision—Depth cues, Stereo

We present a novel use of commodity graphics hardware that effectively combines a plane-sweeping algorithm with view synthesis for real-time, on-line 3D scene acquisition and view synthesis. Using real-time imagery from a few calibrated cameras, our method can generate new images from nearby viewpoints, estimate a dense depth map from the current viewpoint, or create a textured triangular mesh. We can do this without prior geometric information or requiring any user interaction, in real time and on line. The heart of our method is using programmable pixel shader technology to square intensity differences between reference image pixels, and then to choose final colors (or depths) that correspond to the minimum difference, i.e. the most consistent color. In this paper we describe the method, place it in the context of related work in computer graphics and computer vision, and present results.

We present an extension to texture mapping that supports the representation of 3-D surface details and view motion parallax. The results are correct for viewpoints that are static or moving, far away or nearby. Our approach is very simple: a relief texture (texture extended with an orthogonal displacement per texel) is mapped onto a polygon using a two-step process: First, it is converted into an ordinary texture using a surprisingly simple 1-D forward transform. The resulting texture is then mapped onto the polygon using standard texture mapping. The 1-D warping functions work in texture coordinates to handle the parallax and visibility changes that result from the 3-D shape of the displacement surface. The subsequent texture-mapping operation handles the transformation from texture to screen coordinates.

We present a compact, image-based representation for threedimensional objects with complex shapes that can be rendered with correct perspective from arbitrary viewpoints using a listpriority algorithm. Objects are represented by six layered depth images sharing a single center of projection. They can be scaled, and freely translated and rotated, being used as primitives to construct more complex scenes. We also present a new listpriority algorithm for rendering such scenes and a back face culling strategy for a class of image-based objects. We demonstrate these concepts by constructing image-based representations from both synthetic and real objects, and rendering them at interactive rates on a PC. Due to their minimum storage requirements and rendering simplicity, image-based objects can find potential uses in games, virtual museum applications, and web catalogs. CR Categories and Subject Descriptors: I.3.3 [Computer Graphics]: Picture/Image Generation -- Display Algorithms; I.3.7 [...

Article LDI tree: a hierarchical representation for image-based rendering Share on Authors: Chun-Fa Chang University of North Carolina at Chapel Hill University of North Carolina at Chapel HillView Profile , Gary Bishop University of North Carolina at Chapel Hill University of North Carolina at Chapel HillView Profile , Anselmo Lastra University of North Carolina at Chapel Hill University of North Carolina at Chapel HillView Profile Authors Info & Claims SIGGRAPH '99: Proceedings of the 26th annual conference on Computer graphics and interactive techniquesJuly 1999 Pages 291–298https://doi.org/10.1145/311535.311571Online:01 July 1999Publication History 95citation1,161DownloadsMetricsTotal Citations95Total Downloads1,161Last 12 Months22Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Our HiBall Tracking System generates over 2000 head-pose estimates per second with less than one millisecond of latency, and less than 0.5 millimeters and 0.02 degrees of position and orientation noise, everywhere in a 4.5 by 8.5 meter room. The system is remarkably responsive and robust, enabling VR applications and experiments that previously would have been difficult or even impossible.

In image-based rendering, images acquired from a scene are used to represent the scene itself.A number of reference images are required to fully represent even the simplest scene.This leads to a number of problems during image acquisition and subsequent reconstruction.We present the multiple-center-of-projection image, a single image acquired from multiple locations, which solves many of the problems of working with multiple range images.This work develops and discusses multiple-center-ofprojection images, and explains their advantages over conventional range images for image-based rendering.The contributions include greater flexibility during image acquisition and improved image reconstruction due to greater connectivity information.We discuss the acquisition and rendering of multiple-center-of-projection datasets, and the associated sampling issues.We also discuss the unique epipolar and correspondence properties of this class of image.

A pair of rendered images and tbek Z-buffers contain almost all of the information necessary tore-render from nearby viewpoints.For the small changes in viewpoint that occur in a fraction of a second, this information is sufficient for high quafity re-rendering with cost independent of scene complexity.Re-rendenng from previously computed views allows an order-of-magnitude increase in apparent frame rate over that provided by conventional rendering alone.It can also compensate for system latency in local or remote display.We use McMillan and Bishop's image warping algorithm to re-render, allowing us to compensate for viewpoint translation as well as rotation.We avoid occlusion-related artifacts by warping two different reference images and compositing the results, This paper explains the basic design of our system and provides details of our reconstruction and multi-image compositing afgoritbms.We present our method for selecting reference image locations and the heuristic we use for any portions of the scene which happen to be occluded in both reference images.We also discuss properties of our technique which make it suitable for real-time implementation, and briefly describe our simpler rerd-time remote dkplay system.

We present a promising new mathematical method for tracking a user's pose (position and orientation) for interactive computer graphics.The method, which is applicable to a wide variety of both commercial and experimental systems, improves accuracy by properly assimilating sequential observations, filtering sensor measurements, and by concurrently autocalibrating source and sensor devices.It facilitates user motion prediction, multisensor data fusion, and higher report rates with lower latency than previous methods.Tracking systems determine the user's pose by measuring signals from low-level hardware sensors.For reasons of physics and economics, most systems make multiple sequential measurements which are then combined to produce a single tracker report.For example, commercial magnetic trackers using the SPASYN ( Space Synchro ) system sequentially measure three magnetic vectors and then combine them mathematically to produce a report of the sensor pose.Our new approach produces tracker reports as each new lowlevel sensor measurement is made rather than waiting to form a complete collection of observations.Because single observations under-constrain the mathematical solution, we refer to our approach as single-constraint-at-a-time or SCAAT tracking.The key is that the single observations provide some information about the user's state, and thus can be used to incrementally improve a previous estimate.We recursively apply this principle, incorporating new sensor data as soon as it is measured.With this approach we are able to generate estimates more frequently, with less latency, and with improved accuracy.We present results from both an actual implementation, and from extensive simulations.

Latency or lag in an interactive graphics system is the delay between user input and displayed output. We have found latency and the apparent bobbing and swimming of objects that it produces to be a serious problem for head-mounted display (HMD) and augmented reality applications. At UNC, we have been investigating a number of ways to reduce latency; we present two of these. Slats is an experimental rendering system for our Pixel-Planes 5 graphics machine guaranteeing a constant single NTSC field of latency. This guaranteed response is especially important for predictive tracking. Just-in-time pixels is an attempt to compensate for rendering latency by rendering the pixels in a scanned display based on their position in the scan.

The use of prediction to eliminate or reduce the effects of system delays in Head-Mounted Display systems has been the subject of several recent papers.A variety of methods have been proposed but almost all the analysis has been empirical, making comparisons of results difficult and providing little direction to the designer of new systems.In this paper, we characterize the performance of two classes of head-motion predictors by analyzing them in the frequency domain.The first predictor is a polynomial extrapolation and the other is based on the Kalman filter.Our analysis shows that even with perfect, noise-free inputs, the error in predicted position grows rapidly with increasing prediction intervals and input signal frequencies.Given the spectra of the original head motion, this analysis estimates the spectra of the predicted motion, quantifying a predictor's performance on different systems and applications.Acceleration sensors are shown to be more useful to a predictor than velocity sensors.The methods described will enable designers to determine maximum acceptable system delay based on maximum tolerable error and the characteristics of user motions in the application.

Article Free Access Share on Plenoptic modeling: an image-based rendering system Authors: Leonard McMillan Department of Computer Science, University of North Carolina at Chapel Hill, CB 3175 Sitterson Hall, Chapel Hill, NC Department of Computer Science, University of North Carolina at Chapel Hill, CB 3175 Sitterson Hall, Chapel Hill, NCView Profile , Gary Bishop Department of Computer Science, University of North Carolina at Chapel Hill, CB 3175 Sitterson Hall, Chapel Hill, NC Department of Computer Science, University of North Carolina at Chapel Hill, CB 3175 Sitterson Hall, Chapel Hill, NCView Profile Authors Info & Claims SIGGRAPH '95: Proceedings of the 22nd annual conference on Computer graphics and interactive techniquesSeptember 1995 Pages 39–46https://doi.org/10.1145/218380.218398Published:15 September 1995Publication History 651citation5,126DownloadsMetricsTotal Citations651Total Downloads5,126Last 12 Months352Last 6 weeks50 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

In Augmented Reality, see-through HMDs superimpose virtual 3D objects on the real world. This technology has the potential to enhance a user's perception and interaction with the real world. However, many Augmented Reality applications will not be accepted until we can accurately register virtual objects with their real counterparts. In previous systems, such registration was achieved only from a limited range of viewpoints, when the user kept his head still. This paper offers improved registration in two areas. First, our system demonstrates accurate static registration across a wide variety of viewing angles and positions. An optoelectronic tracker provides the required range and accuracy. Three calibration steps determine the viewing parameters. Second, dynamic errors that occur when the user moves his head are reduced by predicting future head locations. Inertial sensors mounted on the HMD aid head-motion prediction. Accurate determination of prediction distances requires low-overhead operating systems and eliminating unpredictable sources of latency. On average, prediction with inertial sensors produces errors 2-3 times lower than prediction without inertial sensors and 5-10 times lower than using no prediction at all. Future steps that may further improve registration are outlined.

The use of double-buffered displays, in which the previous image is displayed until the next image is complete, can impair the interactivity of systems that require tight coupling between the human user and the computer. We are experimenting with an alternate rendering strategy that computes each pixel based on the most recent input (i.e., view and object positions) and immediately updates the pixel on the display. We avoid the image tearing normally associated with single-buffered displays by randomizing the order in which pixels are updated. The resulting image sequences give the impression of moving continuously, with a rough approximation of motion blur, rather than jerking between discrete positions.

A geographical information system (GIS) has proved to be a valuable tool in the Direct/Delayed Response Project—a comprehensive examination of the future, long-term chemical response of surface waters to acidic deposition. The role of the GIS within the project includes aggregation, analysis and display of various forms, scales and projections of environmental data related to acidic deposition. The GIS is particularly valuable for effectively communicating key scientific findings and results of regional, national and international importance to a diverse audience.

The authors consider an object is undergoing rotational motions, with orientation known at given times, and wish to interpolate the orientation between those times. If the orientations are represented as unit quaternions, this is equivalent to interpolating among a sequence of points on the three-sphere in four-space. They present an algorithm for doing this smoothly. If the object possesses rotational symmetry, then its orientation is given by its axis, and can be represented as a point on the unit sphere in three-space. The problem of interpolating on the sphere is of interest in its own right, and has other applications. The authors have implemented an algorithm for this, and present graphical results.>

Computer image generation systems often represent curved surfaces as a mesh of planar polygons that are shaded to restore a smooth appearance. Phong shading is a well known algorithm for producing a realistic shading but it has not been used by real-time systems because of the 3 additions, 1 division, and 1 square-root required per pixel for its evaluation. We describe a new formulation for Phong shading that reduces the amount of computation per pixel to only 2 additions for simple Lambertian reflection and 5 additions and 1 memory reference for Phong's complete reflection model. We also show how to extend our method to compute the specular component with the eye at a finite distance from the scene rather than at infinity as is usually assumed. The method can be implemented in hardware for real-time applications or in software to speed image generation for almost any system.