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Consistent Scene Illumination using a Chromatic Flash
(The Eurographics Association, 2009) Kim, Min H.; Kautz, Jan; Oliver Deussen and Peter Hall
Flash photography is commonly used in low-light conditions to prevent noise and blurring artifacts. However, flash photography commonly leads to a mismatch between scene illumination and flash illumination, due to the bluish light that flashes emit. Not only does this change the atmosphere of the original scene illumination, it also makes it difficult to perform white balancing because of the illumination differences. Professional photographers sometimes apply colored gel filters to the flashes in order to match the color temperature. While effective, this is impractical for the casual photographer. We propose a simple but powerful method to automatically match the correlated color temperature of the auxiliary flash light with that of scene illuminations allowing for well-lit photographs while maintaining the atmosphere of the scene. Our technique consists of two main components. We first estimate the correlated color temperature of the scene, e.g., during image preview. We then adjust the color temperature of the flash to the scene's correlated color temperature, which we achieve by placing a small trichromatic LCD in front of the flash. We demonstrate the effectiveness of this approach with a variety of examples.
Wind projection basis for real-time animation of trees
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Diener, Julien; Rodriguez, Mathieu; Baboud, Lionel; Reveret, Lionel
This paper presents a real-time method to animate complex scenes of thousands of trees under a user-controllable wind load. Firstly, modal analysis is applied to extract the main modes of deformation from the mechanical model of a 3D tree. The novelty of our contribution is to precompute a new basis of the modal stress of the tree under wind load. At runtime, this basis allows to replace the modal projection of the external forces by a direct mapping for any directional wind. We show that this approach can be efficiently implemented on graphics hardware. This modal animation can be simulated at low computation cost even for large scenes containing thousands of trees.
Interactive Modeling of Virtual Ecosystems
(The Eurographics Association, 2009) Benes, Bedrich; Andrysco, Nathan; Stava, Ondrej; Eric Galin and Jens Schneider
We present a novel technique for interactive, intuitive, and efficient modeling of virtual plants and plant ecosystems. Our approach is biologically-based, but shades the user from overwhelming input parameters by simplifying them to intuitive controls. Users are able to create scenes that are populated by virtual plants. Plants communicate actively with the environment and attempt to generate an optimal spatial distribution that dynamically adapts to neighboring plants, to user defined obstacles, light, and gravity. We demonstrate simulations of ecosystems composed of up to 140 trees that are computed in less than two minutes. Various phenomena previously available for non-realtime procedural approaches are created interactively, such as plants competing for space, topiary, plant lighting, virtual forests, etc. Results are aimed at architectural modeling, the entertainment industry, and everywhere that quick and fast creation of believable biological plant models is necessary.
A Dynamic Caching System for Rendering an Animated Crowd in Real-Time
(The Eurographics Association, 2009) Lister, Wayne; Laycock, Robert G.; Day, Andrew M.; P. Alliez and M. Magnor
We present a method to accelerate the rendering of large crowds of animated characters. Recent trends have seen matrix-palette skinning become the prevalent approach due to its low memory overhead and fully dynamic geometry. However, the performance of skeletal animation remains modest in comparison to static rendering since neither temporal nor intra-frame coherency can be exploited. We cast crowd rendering as a memory-management problem and allocate a small geometry cache on the GPU within which animated characters can be stored. This serves to augment matrix-palette skinning with baked geometry and allows animation frames to be re-used by multi-pass rendering, between multiple agents and across multiple frames. Our method builds its cache dynamically and adapts to the current simulation state through use of the page-replacement algorithms traditionally employed by virtual-memory systems. In many cases this negates the need for skinning altogether and enables thousands of characters to be rendered in real-time, each independently animated and without loss of fidelity.
Energy Aware Color Sets
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Chuang, Johnson; Weiskopf, Daniel; Moeller, Torsten
We present a design technique for colors with the purpose of lowering the energy consumption of the display device. Our approach is based on a screen space variant energy model. The result of our design is a set of distinguishable iso-lightness colors guided by perceptual principles. We present two variations of our approach. One is based on a set of discrete user-named (categorical) colors, which are analyzed according to their energy consumption. The second is based on the constrained continuous optimization of color energy in the perceptually uniform CIELAB color space. We quantitatively compare our two approaches with a traditional choice of colors, demonstrating that we typically save approximately 40 percent of the energy. The color sets are applied to examples from the 2D visualization of nominal data and volume rendering of 3D scalar fields.
Discrete Element Modelling Using a Parallelised Physics Engine
(The Eurographics Association, 2009) Longshaw, Stephen M.; Turner, Martin J.; Finch, Emma; Gawthorpe, Robert; Wen Tang and John Collomosse
Discrete Element Modelling (DEM) is a technique used widely throughout science and engineering. It offers a convenient method with which to numerically simulate a system prone to developing discontinuities within its structure. Often the technique gets overlooked as designing and implementing a model on a scale large enough to be worthwhile can be both time consuming and require specialist programming skills. Currently there are a few notable efforts to produce homogenised software to allow researchers to quickly design and run DEMs with in excess of 1 million elements. However, these applications, while open source, are still complex in nature and require significant input from their original publishers in order for them to include new features as a researcher needs them. Recently software libraries notably from the computer gaming and graphics industries, known as physics engines, have emerged. These are designed specifically to calculate the physical movement and interaction of a system of independent rigid bodies. They provide conceptual equivalents of real world constructions with which an approximation of a realistic scenario can be quickly built. This paper presents a method to utilise the most notable of these engines, NVIDIAs PhysX, to produce a parallelised geological DEM capable of supporting in excess of a million elements.
Image Statistics for Clustering Paintings According to their Visual Appearance
(The Eurographics Association, 2009) Spehr, Marcel; Wallraven, Christian; Fleming, Roland W.; Oliver Deussen and Peter Hall
Untrained observers readily cluster paintings from different art periods into distinct groups according to their overall visual appearance or 'look' [WCF08]. These clusters are typically influenced by both the content of the paintings (e.g. portrait, landscape, still-life, etc.), and stylistic considerations (e.g. the 'flat' appearance of Gothic paintings, or the distinctive use of colour in Fauve works). Here we aim to identify a set of image measurements that can capture this 'naïve visual impression of art', and use these features to automatically cluster a database of images of paintings into appearance-based groups, much like an untrained observer. We combine a wide range of features from simple colour statistics, through mid-level spatial features to high-level properties, such as the output of face-detection algorithms, which are intended to correlate with semantic content. Together these features yield clusters of images that look similar to one another despite differences in historical period and content. In addition, we tested the performance of the feature library in several classification tasks yielding good results. Our work could be applied as a curatorial or research aid, and also provides insight into the image attributes that untrained subjects may attend to when judging works of art.
Automatic Views of Natural Scenes
(The Eurographics Association, 2009) Bratkova, Margarita; Thompson, William B.; Shirley, Peter; Oliver Deussen and Peter Hall
Automatic generation of well-composed and purposeful images is useful in a variety of computer graphics applications. In this work, we explore a set of criteria based on utility, perception, and aesthetics applicable to natural outdoor scenes. We also propose a method that uses the criteria to produce renderings of terrain scenes automatically.
Scalable, Versatile and Simple Constrained Graph Layout
(The Eurographics Association and Blackwell Publishing Ltd., 2009) Dwyer, Tim; H.-C. Hege, I. Hotz, and T. Munzner
We describe a new technique for graph layout subject to constraints. Compared to previous techniques the proposed method is much faster and scalable to much larger graphs. For a graph with n nodes, m edges and c constraints it computes incremental layout in time O(nlogn+m+c) per iteration. Also, it supports a much more powerful class of constraint: inequalities or equalities over the Euclidean distance between nodes.We demonstrate the power of this technique by application to a number of diagramming conventions which previous constrained graph layout methods could not support. Further, the constraint-satisfaction method inspired by recent work in position-based dynamics is far simpler to implement than previous methods.
BRDFLab: A general system for designing BRDFs
(The Eurographics Association, 2009) Forés, Adrià; Pattanaik, Sumanta N.; Bosch, Carles; Pueyo, Xavier; Carlos Andujar and Javier Lluch
This paper introduces a novel system for interactive modeling and designing of arbitrary BRDFs. The system is able to deal with BRDFs defined in a variety of forms, such as analytical models, measured data or data obtained by simulation. The system also allows designing BRDFs from scratch using a combination of different analytical lobes. Using the programmable graphics hardware, it then performs interactive display of the designed BRDF, and its rendering on objects lit by complex illumination. The system also allows the fitting of an input BRDF defined in any form to our analytical lobe combination, so that it can be efficiently evaluated with GPU based rendering. The idea behind this work is to make available a general system for designing, fitting and rendering BRDFs, that is intuitive and interactive in nature. We plan to use this as a tool for simulation and modeling of complex physically-based BRDFs, and thus provide access to a larger variety of material models to the rendering community.

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