WSCG '2006: Full Papers Proceedings

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http://hdl.handle.net/11025/6629

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Showing 1 - 20 out of 48 results

Dynamic Annotation of Interactive Environments using Object-Integrated Billboards
(Václav Skala - UNION Agency, 2006) Maass, Stefan; Döllner, Jürgen; Jorge, Joaquim; Skala, Václav
We present a technique for the dynamic annotation of three-dimensional objects in interactive virtual environments. Annotations represent textual or symbolic descriptions providing explanatory or thematic information associated with scene objects. In contrast to techniques that treat annotations as two-dimensional view-plane elements, our technique models annotations as separate three-dimensional scene elements that are automatically positioned and oriented according to the shape of the referenced object. The shape of such an object is generalized by an annotation hull and skeleton used to determine an adequate position and orientation of the annotation with respect to the viewing direction. During camera movements, annotations float along the surface of the annotation hull. Additional constraints for the generalizations provide further control about geometric and dynamical properties. In a case study, we show how this technique can be applied for annotating buildings and other components of virtual 3D city models.
A Novel Technique for Opus Vermiculatum Mosaic Rendering
(Václav Skala - UNION Agency, 2006) Battiato, S.; Di Blasi, G.; Farinella, G. M.; Gallo, G.; Jorge, Joaquim; Skala, Václav
In this paper we present a method to generate a digital mosaic starting from a raster input image. Mosaics generation of artistic quality is challenging. The basic elements, the tiles, typically small polygons, must be packed tightly, emphasizing orientations chosen by the artist. An adhoc boundaries detection have to be performed according to the directional guidelines. Different mosaic styles can be automatically rendered, depending on artistic techniques considered (“opus musivum”, “opus vermiculatum”, etc.). The proposed method is able to reproduce the colors of the original image emphasizing relevant boundaries by placing tiles along their direction. The boundaries detection is based on the statistical region merging algorithm. In particular the technique is able to reproduce the “opus vermiculatum” mosaic style. Several examples reported in the paper show how the right mixture of mathematical tools together with century proved ideas from mosaicists may lead to impressive results.
Dealing with Optical Material Properties in Computer Graphics and Vision
(Václav Skala - UNION Agency, 2006) Klein, Reinhard; Jorge, Joaquim; Skala, Václav
In the area of shape recognition tremendous advances were made during recent years. But in contrast to this success the recognition of materials is still a big challenge although for humans the identification of differnt materials is normally an easy task. In Computer Graphics we face a similar situation. While the modeling of shapes is already a highlydeveloped area the realistic modeling of the interaction of light with objects, i.e. the modeling of optical material properties, is still a great challenge. In addition, while there are straight forward techniques to measure differences between two shapes we need more sophisticated methods to judge the difference of reflection properties. From the rendering point of view these methods might even contain perceptual components. One way to obtain realistic reflection properties are measurements of real world surfaces. For arbitrary (non-fluorescent, non-phosphorescent) materials, the reflection properties can be described by the 8D reflectance field of the surface, also called BSSRDF. Since densely sampling an 8D function is currently not practical various acquisition methods have been proposed which reduce the number of dimensions by restricting the acquisition to specific classes of materials. A subsequent data modeling step is performed to interpolate missing values and compress the measured data further. In the first part of this talk we will give a brief overview over the different measurement techniques and algorithms used to capture reflection properties of different classes of objects targeted to the specific needs of computer graphics applications. Special emphasis will be given to surfaces with complex meso-structure. In the second part we will discuss some techniques we used for the validation of the measurements and the resulting renderings. Strength and limitations of different aquisition and validation techniques will be discussed and future challenges will be identified.
Real Time Simulation of Elastic Latex Hand Puppets
(Václav Skala - UNION Agency, 2006) Wüthrich, Charles A.; Augusto, Jing; Banisch, Sven; Wetzstein, Gordon; Musialski, Przemyslaw; Toll, Chrystoph; Hofmann, Tobias; Jorge, Joaquim; Skala, Václav
Children television productions have been using puppets for a long time. Since the early days of computer animation, computer puppet simulation has been researched intensively. Complex motion capture equipment allows nowadays the real time mapping of movement for virtual puppets (performance animation). However, the costs of capturing equipment are too high and the difference in the workflow make it difficult for small production teams to access and use such technology. This paper presents a system for the real time simulation of elastic latex hand puppets which are used in television productions. After an analysis of the production processes of real puppets and of the materials used for their production, the paper describes the components of the system simulating them. The system connects a high resolution visual mesh to a three-layered 3D mass spring mesh, which is used for the elastic simulation. Polygonal mesh decimation of the puppet surface model is used as a basis for generating the elastic mesh. From the decimated mesh a new metod is proposed for generating the internal layers of the mass-spring mesh. A data handglove is used for transmitting forces to the elastic mesh, indirectly moving the surface of the virtual puppet in real time. Dataglove interaction maps in a natural way the hand movements of a puppeteer to the computer model. The tradeoffs of the implementation on low cost hardware and its efficiency are also discussed.
Enhanced Billboards for Model Simplification
(Václav Skala - UNION Agency, 2006) Vichitvejpaisal, Phongvarin; Kanongchaiyos, Pizzanu; Jorge, Joaquim; Skala, Václav
A set of billboards can represent 3D models for extreme simplification in real-time rendering. Unlike conventional polygon method, billboard-based technique has the rendering time of the model proportional to its contribution to the image. Thus, it has an automatically built-in Level of Detail. However, previous techniques still have limited viewing angle and do not accurately represent the model. We present an adaptive rendering method using enhanced billboards. First, each enhanced billboard, representing portion of the model, is defined to have four maps: depth map, normal map, color map and transparency map. The model is then projected onto a number of viewing planes in different viewing directions. Consequently, these enhanced billboards are rendered based on ray-height-field intersection algorithm implemented on GPU. This representation can maintain the geometry and the silhouette of the model with no limit in viewing direction. Moreover, real-time rendering is supported.
Video-Based Rendering Of Traffic Sequences
(Václav Skala - UNION Agency, 2006) Vanaken, Cedric; Mertens, Tom; Bekaert, Philippe; Jorge, Joaquim; Skala, Václav
Video-based rendering is a viable alternative to traditional realistic image synthesis techniques. It avoids the burden of timeconsuming modeling and expensive global illumination simulation. In this paper we propose a video-based synthesis and animation system for fixed viewpoint scenes that feature rigid objects. We examplify this by using traffic video sequences. In a first stage, we extract vehicles and their trajectories from the example footage using an intuitive semi-automatic segmentation technique. Subsequently, the resulting vehicle “sprites” are dimensionally reduced using PCA in order to effectively extrapolate trajectories from incomplete sequences. Background, occlusions and shadows cast by vehicles are extracted as well. We show that convincing new footage can be synthesized readily from a single input video. Any number and variety of cars can be inserted, and their trajectories can be edited to simulate such traffic scenarios as lane changes and traffic jams.
Úvodní strany
(Václav Skala - UNION Agency, 2006) Jorge, Joaquim; Skala, Václav; Jorge, Joaquim; Skala, Václav
A New Approach to Urban Modelling Based on LIDAR
(Václav Skala - UNION Agency, 2006) Tse, Rebecca (Oi Chi); Gold, Christopher; Kidner, Dave; Jorge, Joaquim; Skala, Václav
Estimating building forms from LIDAR data has usually been done by attempting to fit standardized building types to the residual data points after an estimated bare earth terrain surface has been removed. We propose an approach based on segmenting the raw data into high and low regions, and then modelling the walls and roofs by extruding the triangulated terrain surface (TIN) using CAD-type Euler operators. The segmentation may be done by the addition of building boundary data to the TIN so as to force triangle edges to match the boundaries, and then using Euler operators to extrude the building, producing vertical walls rather than the more usual sloping walls formed from TIN models alone. If boundary data is not available then an automated segmentation method based on adaptive Voronoi cells may be used, so that each cell contains either high or low LIDAR data, but not both. This prismatic model, with flat-topped cells, approximates the building forms without hypothesizing specific building types. Once the segmentation is achieved, and the walls constructed, we attempt to model the roofs by calculating the eigenvalues and eigenvectors of the vector normals of the TIN sections within the building boundaries. The smallest eigenvalue gives a predicted roof orientation, and the resulting roof profile is then modelled.
Improved Illumination Estimation for Photon Maps in Architectural Scenes
(Václav Skala - UNION Agency, 2006) Tobler, F.; Maierhofer, Stefan; Jorge, Joaquim; Skala, Václav
The photon map algorithm provides a number of advantages for fast global illumination algorithms. In order to calculate the illumination at each point in a scene, the photon density needs to be estimated. Standard estimation methods will have problems with typical architectural scenes, as walls and corners will lead to undesirable light and shadow leaks. We introduce a new method for estimating photon density in photon maps, that is especially suited for calculating global illumination in architectural scenes. By providing additional information using a limited number of ray-casts, shadow and light leaks can be significantly reduced, thereby resulting in a significant improvement in the speed and accuracy of global illumination algorithms based on photon maps.
Real-Time Massive 3D Data Capture and Geometry Processing
(Václav Skala - UNION Agency, 2006) Taubin, Gabriel; Jorge, Joaquim; Skala, Václav
In Geometry Processing, a field which has developed during the last ten years, concepts from applied mathematics, computer science, and engineering are used to design efficient algorithms for the acquisition, manipulation, animation and transmission of complex 3D models. A number of methods have been proposed to smooth, denoise, edit, compress, transmit, re-parameterize, and animate very large polygon meshes, based on topological and combinatorial methods, signal processing techniques, constrained energy minimization, and the solution of partial differential equations. In particular, polygon models, which are used in most graphics applications, require considerable amounts of storage, even when they only approximate precise shapes with limited accuracy, and must be compressed by several orders of magnitude for fast network access. In this talk I will present some of our early contributions to the field, and some related ongoing research projects. I will also describe the state of our work towards the apparently unrelated goal of building Visual Sensor Networks with 1000s of cameras for real time capture and processing of 3D data.
The Hierarchical Ray Engine
(Václav Skala - UNION Agency, 2006) Szécsi, László; Jorge, Joaquim; Skala, Václav
Due to the success of texture based approaches, ray casting has lately been confined to performing preprocessing in realtime applications. Though GPU based ray casting implementations outperform the CPU now, they either do not scale well for higher primitive counts, or require the costly construction of spatial hierarchies. We present an improved algorithm based on the Ray Engine approach, which builds a hierarchy of rays instead of objects, completely on the graphics card. Exploiting the coherence between rays when displaying refractive objects or computing caustics, realtime frame rates are achieved without preprocessing. Thus, the method fills a gap in the realtime rendering repertoire.
Exposing Application Graphics to a Dynamic Heterogeneous Network
(Václav Skala - UNION Agency, 2006) Stavrakakis, John; Lau, Zhen-Jock; Lowe, Nick; Takatsuka, Masahiro; Jorge, Joaquim; Skala, Václav
With the abundance of high performance personal computers, rendering thousands to millions of polygons per second is an inexpensive task. In recent years, there have been advances in networking technologies that have enabled applications to become distributed over a network and many applications require this functionality. These applications can range from driving a large display, collaborating over an internet, or supporting pervasive environments. Solutions currently exist in providing graphics over a network. However, they are usually targeted to satisfy particular problem domains or are otherwise difficult to adopt as applications require major adjustment. OpenGL R is a graphics drawing library. Although many applications have made use of this API, few provide direct interaction within networked environments. In this paper we present Lumino, a framework that enables graphics from an existing OpenGL application to become available to a dynamic heterogeneous network. What differentiates Lumino from prior work is that it provides this functionality to existing unmodified applications at a very low level and is capable of supporting flow control, quality and scalability. Moreover, it is targeted at wide adoption and will be released under a Free Software license.
Hierarchical texture compression
(Václav Skala - UNION Agency, 2006) Stachera, Jerzy; Rokita, Przemyslaw; Jorge, Joaquim; Skala, Václav
Visualizing Dynamic Etching in MEMS VR-CAD Tool
(Václav Skala - UNION Agency, 2006) Sitte, Renate; Cai, Jie; Jorge, Joaquim; Skala, Václav
In this paper we introduce our virtual etching as part of MAGDA a CAD system for Micro Electro Mechanical Systems (MEMS). Virtual prototyping visualizations require fast algorithms for visualization that are suitable for interactive design. Modern MEMS simulators do not offer dynamic visualizations for etching. Etching progress is time dependent, typically calculated with Finite Element Analysis, which has too slow a calculation time, hence is not suitable for interactive design. Etching progress is important in MEMS with small dimensions, where Silicon technology must be used, with its repeated cycles of deposition and lithography/etching until the desired structure is formed. While etching performance is well known from the Integrated Circuit processing, it is not so predictable in MEMS because the shapes are more complex. Underetching is not desired in IC technology, but it is crucial in shaping MEMS structures. We use a Marker/String method for the progressive mesh as a faster method suitable for interactive design. The method is not known much for etching; but used in other applications. We have found a way of overcoming swallowtail conditions that appear on corners. We are also able to simulate underetching. In this paper we demonstrate the progress of etching using a circular lithography mask calculated in 2D then rotated, and a square mask calculated in 3D. In both cases we are able to simulate underetching. The method can be extended into larger material removal CAD visualizations. In this way we made a step towards filling a long existing need in virtual prototyping.
Grafting Locomotive Motions
(Václav Skala - UNION Agency, 2006) Shanbhag, Shrinath; Chandran, Sharat; Jorge, Joaquim; Skala, Václav
The notion of transplanting limbs to enhance a motion capture database is appealing and has been recently introduced [Sha04], [Ike04]. A key difficulty in the process is identifying believable combinations. Not all transplantations are successful; we also need to identify appropriate frames in the different clips that are “cutpasted.” In this paper, we describe motion grafting, a method to synthesize new believable motion using existing motion captured data. In our deterministic scheme designed for locomotive actions, motion grafts increase the number of combinations by mixing independent kinematics chains with a base motion in a given clip. Our scheme uses a cluster graph data structure to establish correlation among grafts so that the result is believable and synchronized.
Load Balancing on Cluster-Based Multi Projector Display Systems
(Václav Skala - UNION Agency, 2006) Roth, Marcus; Riess, Patrick; Reiners, Dirk; Jorge, Joaquim; Skala, Václav
Sort- rst or image space parallel rendering has been the subject of a signi cant amount of research. Its limited scalability is well known. Nevertheless, sort- rst has noticeable advantages over other approaches: it has moderate and predictable communication overhead, and it has no problems with multipass or transparent rendering. Especially for multi-projector display systems, driven by a cluster of standard PCs with limited network bandwidth, it is the rst choice to achieve interactive frame rates. In this paper we present an approach to do load balancing for arbitrary multi projector systems, based on a sort- rst approach.
Agents Based Visualization and Strategies
(Václav Skala - UNION Agency, 2006) Roard, Nicolas; Jones, Mark W.; Jorge, Joaquim; Skala, Václav
This paper describes a flexible visualization architecture based on software agents, which enables the abstraction and reuse of rendering strategies. Using a reification of the rendering environment, the system is able to add new rendering strategies (such as distributed rendering or progressive rendering) to an existing pipeline, without any modification of the other components (controls components, display components, rendering algorithms, etc. ). The ability of changing strategies on the fly leads to a better adaptability to runtime constraints. The system uses an agent-based graphic pipeline, where each agent/component can be located on different computers; communications between agents use XML/RPC and data stream in order to easily integrate existing code in the system. Agents can add specific behavior to graphic pipelines, such as saving environments to reuse them, adapt information and knowledge from another pipeline, and generally modify and improve the entire system. Various visualization and control clients exist, enabling collaboration between platforms such as PDAs, Windows, Linux, MacOS X, and Web (using Java applets).
An efficient continuous level of detail model for foliage
(Václav Skala - UNION Agency, 2006) Rebollo, C.; Remolar, I.; Chover, M.; Ripollés, O.; Jorge, Joaquim; Skala, Václav
Outdoor scenes require vegetation to make them look realistic. Current hardware cannot afford real-time rendering of these scenes because of the large number of polygons. Multiresolution modelling has been successfully presented as a solution to the problem of efficient manipulation of highly detailed polygonal surfaces. This article describes a new continuous multiresolution hardware-oriented model that can represent tree foliage with different levels of detail. The multiresolution model presented in this paper, Level of Detail Foliage, takes advantage of the programmable rendering pipelines nowadays available in most video cards. The geometry of the foliage is divided into a number of clusters, in some of which the detail can change while the rest of the clusters remain unaltered. This division of the foliage remarkably diminishes the number of vertices sent to the graphics system because only the information of the changed clusters are updated. The independent clusters condition a data structure that makes the time required for visualisation of the foliage more efficient. Here we present the data structure and the retrieval algorithms, which favour the extraction of an appropriate level of detail for rendering.
A simple construction method for sequentially tidying up 2D online freehand sketches
(Václav Skala - UNION Agency, 2006) Qin, Shengfeng; Wright, David K.; Jordanov, Ivan; Jorge, Joaquim; Skala, Václav
This paper presents a novel constructive approach to sequentially tidying up 2D online freehand sketches for further 3D interpretation in a conceptual design system. Upon receiving a sketch stroke, the system first identifies it as a 2D primitive and then automatically infers its 2D geometric constraints related to previous 2D geometry (if any). Based on recognized 2D constraints, the identified geometry will be modified accordingly to meet its constraints. The modification is realized in one or two sequent geometric constructions in consistence with its degrees of freedom. This method can produce 2D configurations without iterative procedures to solve constraint equations. It is simple and easy to use for a real-time application. Several examples are tested and discussed
Real-time rendering of complex surfaces defined by atlas of discoids
(Václav Skala - UNION Agency, 2006) Piranda, Benoît; Magdelaine, Sylvain; Arquès, Didier; Jorge, Joaquim; Skala, Václav
This paper expounds a new method of complex surfaces rendering permitting to visualize atlas of discoids in real-time. The atlas of discoids allow to define surfaces very easily without the topological constraints we could get with the classical methods such as polygons meshes ones. Our basic model is completed by many algorithms permitting either to reconstruct implicit surfaces or to calculate the global illumination using radiosity algorithm. But up to now, no fast viewing method has been proposed for this modeling algorithm. We present here a real time rendering algorithm which exploits the recent extensions of OpenGL library and the possibilities offered by GPU like the shaders programs to perform non standard fragments mixing operations.

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