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Natali M.,University of Bergen | Klausen T.G.,University of Bergen | Patel D.,University of Bergen | Patel D.,Christian Michelsen Research
Computers and Geosciences | Year: 2014

We propose a method for sketching and visualizing geological models by sequentially defining stratigraphic layers, where each layer represents a unique erosion or deposition event. Evolution of rivers and deltas is important for geologists when interpreting the stratigraphy of the subsurface, in particular for hydrocarbon exploration. We illustratively visualize mountains, basins, lakes, rivers and deltas, and how they change the morphology of a terrain during their evolution. We present a compact representation of the model and a novel rendering algorithm that allows us to obtain an interactive and illustrative layer-cake visualization. A user study has been performed to evaluate our method. © 2014 Elsevier Ltd. Source


You J.,Christian Michelsen Research
2013 IEEE China Summit and International Conference on Signal and Information Processing, ChinaSIP 2013 - Proceedings | Year: 2013

User experience plays a crucial role in emerging multimedia services. Traditional Quality of Service (QoS) criteria have been demonstrated to be not adequately accurate to measure and manage the user viewing experience when consuming multimedia content. Recently Quality of Experience (QoE), a quality criterion purely driven by subjective cognition, has been defined to evaluate the overall acceptability of a service. As a perceptual concept, QoE is influenced by internal and external factors. In order to effectively manage visual QoE for multimedia services, visual attention, an integral mechanism of the human perceptual system, should be integrated into QoE definition, assessment, and improvement. This paper systematically presents visual QoE management methodologies driven by attention mechanism. © 2013 IEEE. Source


Bruvik E.M.,University of Bergen | Hjertaker B.T.,University of Bergen | Hjertaker B.T.,The Michelsen Center for Industrial Measurement Science and Technology | Hallanger A.,Christian Michelsen Research
Flow Measurement and Instrumentation | Year: 2010

Gamma-ray tomography is a technique well suited to visualize gas void fraction distribution in two-phase flows. The liquid phase considered in this paper is a homogeneous mixture of oil and water. Gamma-ray tomography will be used to qualitatively visualize the distribution of gas in the flow, and also to provide more quantitative average void fraction measurements. The subject treatment is practical and experimental with a primary focus on multiphase sampling. Experimental results for total average void fraction are compared to the drift-flux model for two-phase flow by comparing measurements with the calculated slip. © 2009 Elsevier Ltd. Source


Sandve T.H.,University of Bergen | Berre I.,University of Bergen | Berre I.,Christian Michelsen Research | Nordbotten J.M.,University of Bergen | Nordbotten J.M.,Princeton University
Journal of Computational Physics | Year: 2012

We consider a control volume discretization with a multi-point flux approximation to model Discrete Fracture-Matrix systems for anisotropic and fractured porous media in two and three spatial dimensions. Inspired by a recently introduced approach based on a two-point flux approximation, we explicitly account for the fractures by representing them as hybrid cells between the matrix cells. As well as simplifying the grid generation, our hybrid approach excludes small cells in the intersection of the fractures and hence avoids severe time-step restrictions associated with small cells. Excluding the small cells also reduces the condition number of the discretization matrix. For examples involving realistic anisotropy ratios in the permeability, numerical results show significant improvement compared to existing methods based on two-point flux approximations. We also investigate the hybrid method by studying the convergence rates for different apertures and fracture/matrix permeability ratios. Finally, the effect of removing the cells in the intersections of the fractures are studied. Together, these examples demonstrate the efficiency, flexibility and robustness of our new approach. © 2012 Elsevier Inc. Source


Solteszova V.,University of Bergen | Patel D.,Christian Michelsen Research | Bruckner S.,Simon Fraser University | Viola I.,University of Bergen
Computer Graphics Forum | Year: 2010

In this paper, we present a novel technique which simulates directional light scattering for more realistic interactive visualization of volume data. Our method extends the recent directional occlusion shading model by enabling light source positioning with practically no performance penalty. Light transport is approximated using a tilted cone-shaped function which leaves elliptic footprints in the opacity buffer during slice-based volume rendering. We perform an incremental blurring operation on the opacity buffer for each slice in front-to-back order. This buffer is then used to define the degree of occlusion for the subsequent slice. Our method is capable of generating high-quality soft shadowing effects, allows interactive modification of all illumination and rendering parameters, and requires no pre-computation. © 2010 The Eurographics Association and Blackwell Publishing Ltd. Source

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