Abstract This paper presents a technique to recover geometry from time‐lapse sequences of outdoor scenes. We build upon photometric stereo techniques to recover approximate shadowing, shading and normal components allowing us to alter the material and normals of the scene. Previous work in analyzing such images has faced two fundamental difficulties: 1. the illumination in outdoor images consists of time‐varying sunlight and skylight, and 2. the motion of the sun is restricted to a near‐planar arc through the sky, making surface normal recovery unstable. We develop methods to estimate the reflection component due to skylight illumination. We also show that sunlight directions are usually non‐planar, thus making surface normal recovery possible. This allows us to estimate approximate surface normals for outdoor scenes using a single day of data. We demonstrate the use of these surface normals for a number of image editing applications including reflectance, lighting, and normal editing.

Reconstruction plates (deformable metal plates) are widely used in reduction and internal fixation surgeries for bone fractures at sites with irregular or individually different anatomical morphology. Traditional surgical procedures require intra-operative manual implant templating, which often leads to prolonged operations with unnecessary damage or hemorrhage. In this paper, we present a novel approach that uses computer graphics and augmented reality (AR) techniques to assist preoperative implant templating, substantially improving these surgical procedures. We exploit the symmetry of the human body to virtually reconstruct the broken skeletal structure using intact contralateral bones. Then 3D models of virtual implants are generated along a drawn path and rendered in an AR environment, to guide preoperative implant templating, thus reducing surgical invasiveness and operation duration. A successful clinical application is presented to demonstrate the effectiveness of our method.

We present a new method for modeling real-world surface reflectance, described with non-parametric spatially-varying bidirectional reflectance distribution functions(SVBRDF). Our method seeks to achieve high reconstruction accuracy, compactness and "editability" of representation meanwhile speeding up both the SVBRDF capturing and modeling processes. For a planar surface, we 1) design a fast capturing device to acquire reflectance samples at dense surface locations; 2) propose a Laplacian-based angular interpolation scheme for a 2D slice of BRDF at a given surface location, and then a Kernel Nyström method for SVBRDF data matrix reconstruction; 3) propose a practical algorithm to extract linear-independent basis BRDFs, and to calculate blending weights through projecting reconstructed reflectance onto these bases. Results demonstrate that our approach models real-world reflectance with both high accuracy and high visual fidelity for real-time virtual environment rendering.

In cluster-based sensor networks, part of the sensor nodes can be switched into a sleep state in order to conserve energy if their neighbors can provide the same or almost the same sensing coverage. However, as the number of nodes in the sleep state increases, coverage for the cluster is degraded. It is crucial to maintain high coverage of clusters in order to preserve performance. In this paper, we propose a coverage- aware sleep scheduling (CS) algorithm to improve the coverage of each cluster. Compared with two previous schemes: the randomized scheduling (RS) scheme and the distance-based scheduling (DS) scheme, the CS algorithm maintains higher coverage, while guaranteeing the same lifetime for the cluster. The CS algorithm thus improves the overall performance of the cluster-based sensor networks.

The connected dominating set (CDS) has been extensively used for routing and broadcast in mobile ad hoc networks. While existing CDS protocols are successful in constructing CDS of competitive size with localized information, they either lack the mechanism to properly handle nodal mobility or require lengthy period of time to recover when CDS becomes corrupted. In this paper, a novel protocol, namely Multi-Initiator Connected Dominating Set protocol (MI-CDS), is proposed that constructs and maintains CDS of competitive size efficiently without introducing much communication overhead. The simulation results demonstrate that MI-CDS permits CDS to be available for the highest percentage of time in the mobile network scenario compared with the other CDS protocols.