We present a fully-automated method for real-time and marker-free 3D human motion capture. The system computes the 3D shape of the person filmed from a synchronized camera set. We obtain a robust and real-time system by using both a fast 3D shape analysis and a skin segmentation algorithm for human tracking. A skeleton-based approach facilitates the shape analysis. We are able to track fast and complex human motion in very difficult cases, like self-occlusion. Results on long video sequences with rapid and complex movements, demonstrate our approach robustness.

Hair is a major feature of digital characters. Unfortunately, it has a complex geometry which challenges standard modeling tools. Some dedicated techniques exist, but creating a realistic hairstyle still takes hours. Complementary to user-driven methods, we here propose an image-based approach to capture the geometry of hair.The novelty of this work is that we draw information from the scattering properties of the hair that are normally considered a hindrance. To do so, we analyze image sequences from a fixed camera with a moving light source. We first introduce a novel method to compute the image orientation of the hairs from their anisotropic behavior. This method is proven to subsume and extend existing work while improving accuracy. This image orientation is then raised into a 3D orientation by analyzing the light reflected by the hair fibers. This part relies on minimal assumptions that have been proven correct in previous work.Finally, we show how to use several such image sequences to reconstruct the complete hair geometry of a real person. Results are shown to illustrate the fidelity of the captured geometry to the original hair. This technique paves the way for a new approach to digital hair generation.

Application-level networking is a promising software organization for improving performance and functionality for important network services. The Xok/ExOS exokernel system includes application-level support for standard network services, while at the same time allowing application writers to specialize networking services. This paper describes how Xok/ExOS's kernel mechanisms and library operating system organization achieve this flexibility, and retrospectively shares our experiences and lessons learned (both positive and negative). It also describes how we used this flexibility to build and specialize three network data services: the Cheetah HTTP server, the webswamp Web benchmarking tool, and an application-level TCP forwarder. Overall measurements show large performance improvements relative to similar services built on conventional interfaces, in each case reaching the maximum possible end-to-end performance for the experimental platform. For example, Cheetah provides factor of 2--4 increases in throughput compared to highly tuned socket-based implementations and factor of 3--8 increases compared to conventional systems. Webswamp can offer loads that are two to eight times heavier. The TCP forwarder provides 50--300% higher throughput while also providing end-to-end TCP semantics that cannot be achieved with POSIX sockets. With more detailed measurements and profiling, these overall performance improvements are also broken down and attributed to the specific specializations described, providing server writers with insights into where to focus their optimization efforts.

The distribution of digital video content over computer networks has become commonplace. Unfortunately, most digital video encoding standards do not degrade gracefully in the face of packet losses, which often occur in a bursty fashion. We propose an new video encoding system that scales well with respect to the network's performance and degrades gracefully under packet loss. Our encoder sends packets that consist of a small random subset of pixels distributed throughout a video frame. The receiver places samples in their proper location (through a previously agreed ordering), and applies a reconstruction algorithm on the received samples to produce an image. Each of the packets is independent, and does not depend on the successful transmission of any other packets. Additionally, each packet contains information that is distributed over the entire image. We also apply spatial and temporal optimization to achieve better compression.

The exokernel operating system architecture safely gives untrusted software efficient control over hardware and software resources by separating management from protection. This paper describes an exokernel system that allows specialized applications to achieve high performance without sacrificing the performance of unmod-ified UNIX programs. It evaluates the exokernel architecture by measuring end-to-end application performance on Xok, an exo-kernel for Intel x86-based computers, and by comparing Xok’s performance to the performance of two widely-used 4.4BSD UNIX systems (FreeBSD and OpenBSD). The results show that common unmodified UNIX applications can enjoy the benefits of exoker-nels: applications either perform comparably on Xok/ExOS and the BSD UNIXes, or perform significantly better. In addition, the results show that customized applications can benefit substantially from control over their resources (e.g., a factor of eight for a Web server). This paper also describes insights about the exokernel ap-proach gained through building three different exokernel systems, and presents novel approaches to resource multiplexing. 1