Curve of growth analysis, applied to the Lyman series absorption ratios deduced in our previous paper, yields a measurement of the logarithmic slope of distribution of Lyman α clouds in column density N . The observed exponential distribution of the clouds’ equivalent widths W is then shown to require a broad distribution of velocity parameters b, extending up to 80 km s. We show how the expone...

We present a technique for approximating isotropic BRDFs and precomputed self-occlusion that enables accurate and efficient prefiltered environment map rendering. Our approach uses a nonlinear approximation of the BRDF as a weighted sum of isotropic Gaussian functions. Our representation requires a minimal amount of storage, can accurately represent BRDFs of arbitrary sharpness, and is above al...

Layer-bound, low-displacement normal faults, arranged into a broadly polygonal pattern, are common in many sedimentary basins. Despite having constrained their gross geometry, we have a relatively poor understanding of the processes controlling the nucleation and growth (i.e., the kinematics) of polygonal fault systems. In this study we use high-resolution 3-D seismic reflection and borehole da...

We introduce a novel fitting procedure that takes as input an arbitrary material, possibly anisotropic, and automatically converts it to a microfacet BRDF. Our algorithm is based on the property that the distribution of microfacets may be retrieved by solving an eigenvector problem that is built solely from backscattering samples. We show that the eigenvector associated to the largest eigenvalu...

We describe a system for rendering bubbles in natural environments using filtered environment maps. The system incorporates the optical properties of soap bubbles such as the interference patterns generated by the film. We describe a mathematical model to simulate the reflectance properties of the bubbles using a bidirectional reflectance field. This BRDF is used to filter an environment map ca...

This paper presents a novel method for photorealistic rendering of the bronchial lumen by directly deriving matched shading and texture parameters from video bronchoscope images. 2D/3D registration is used to match video bronchoscope images with 3D CT scan of the same patient, such that patient specific modelling and simulation with improved visual realism can be achieved. With the proposed met...

Manuscript received April 7, 2008. Q. Zhang and A. Zhou are with the Department of Computing and Electronic Systems, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, U.K. (e-mail: [email protected]; [email protected]). Y. Jin is with the Honda Research Institute Europe, 63073 Offenbach, Germany (e-mail: [email protected]). Color versions of one or more of the figures in this paper...

The purpose of this study was to evaluate the spatial changes of groundwater phosphate concentrations using geostatistical methods based on data from 10 groundwater wells. One of the conventional tools in decision making on the groundwater management is geostatistical method. To evaluate the spatial changes of phosphate concentrations in groundwater, the universal kriging method with cross-vali...