2927787
Real-time virtual object insertion
We present a system to insert virtual objects into real image sequences in real time. The system consists of offthe- shelf hardware (a camera connected to a Pentium PC) and software to (a) automatically select and track region features despite changes in illumination, (b) estimate threedimensional position and orientation of surface patches relative to an inertial reference frame despite individual pointfeatures appearing and disappearing, (c) insert a texturemapped virtual object into the scene so as to make it appear to be part of the scene and moving with it. This is all done in real time. The multi-thread C++ code, which is readily interfaced with a frame grabber as well as Matlab for development, will be made available to the public at the demonstration.
163013
A Variational Approach to Shape from Defocus
We address the problem of estimating the three-dimensional shape and radiance of a surface in space from images obtained with different focal settings. We pose the problem as an infinite-dimensional optimization and seek for the global shape of the surface by numerically solving a partial differential equation (PDE). Our method has the advantage of being global (so that regularization can be imposed explicitly), efficient (we use level set methods to solve the PDE), and geometrically correct (we do not assume a shift-invariant imaging model, and therefore are not restricted to equifocal surfaces).
121904888
Shedding light on stereoscopic segmentation
We propose a variational algorithm to jointly estimate the shape, albedo, and light configuration of a Lambertian scene from a collection of images taken from different vantage points. Our work can be thought of as extending classical multi-view stereo to cases where point correspondence cannot be established, or extending classical shape from shading to the case of multiple views with unknown light sources. We show that a first naive formalization of this problem yields algorithms that are numerically unstable, no matter how close the initialization is to the true geometry. We then propose a computational scheme to overcome this problem, resulting in provably stable algorithms that converge to (local) minima of the cost functional. Although we restrict our attention to Lambertian objects with uniform albedo, extensions of our framework are conceivable.
6346856
Real-Time Feature Tracking and Outlier Rejection with Changes in Illumination
We develop an efficient algorithm to track point features supported by image patches undergoing aflne deformations and changes in illumination. The algorithm is based on a combined model of geonietty and photometry that is used to track features as well as to detect outliers in a hypothesis testing framework. The algorithm runs in real time on a personal computer, and is available to the public.
9201508
Structure from Motion Causally Integrated Over Time
We describe an algorithm for reconstructing three-dimensional structure and motion causally, in real time from monocular sequences of images. We prove that the algorithm is minimal and stable, in the sense that the estimation error remains bounded with probability one throughout a sequence of arbitrary length. We discuss a scheme for handling occlusions (point features appearing and disappearing) and drift in the scale factor. These issues are crucial for the algorithm to operate in real time on real scenes. We describe in detail the implementation of the algorithm, which runs on a personal computer and has been made available to the community. We report the performance of our implementation on a few representative long sequences of real and synthetic images. The algorithm, which has been tested extensively over the course of the past few years, exhibits honest performance when the scene contains at least 20-40 points with high contrast, when the relative motion is "slow" compared to the sampling frequency of the frame grabber (30 Hz), and the lens aperture is "large enough" (typically more than 30/spl deg/ of visual field).
32436469
Special issue on scalable web services and architecture
With the rapid growth of the Internet, web services are becoming an increasingly important class of driving applications for scalable computer systems. Due to the popularity of many Internet applications, the load on Internet servers (web servers, proxy/caching servers, firewalls, etc.) is rapidly increasing. The next generation of Web services should support a very high rate of requests with varying needs imposing a big challenge for the networking infrastructure and the server environments. Since the network bandwidth increases faster than the server capacity, the server could be the next bottleneck of Web services. The efficient execution of Web applications will need to employ parallelism into the Application layer, and overall, into the Web server: (1) Intra-server parallelism, i.e. parallel execution of the web server tasks (e.g. a task or a thread for each HTTP request); (2) Inter-server parallelism, i.e. concurrent execution of different web servers. Cluster computing, a cost-effective technique to connect many small-scale computers to build a large-scale parallel computer, is the first step to build more powerful, interconnected, high performance computing systems. In particular, clusterbased distributed servers are being deployed by more and more popular web sites for scalable and highly available services. Major areas of research and development today include: caching and dynamic content delivering of scalable web servers to security solutions of computational grid. Topic areas covered include, scalability of distributed servers; web server traffic characterization; scheduling and load balancing on distributed servers; distributed server monitoring, fault tolerance, and management; caching, data replication, and concurrency control; security mechanism and policies for distributed servers. This special issue contains seven papers that deal with many of those issues. The purpose was to report both theoretical and practical solutions to some of the problems, and to identify new areas of research. In the first paper, A New Consistency Algorithm for Dynamic Documents in Content Distribution Networks, Fei develops a new strategy to maintain data consistency and integrity of dynamic documents in Content Distribution Networks (CDN). Compared to traditional propagation and invalidation approach to maintain the consistency of data at replicas with the original copy at the server, author proposed a hybrid approach that