EG2016

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20 Years of the Central European Seminar on Computer Graphics
(The Eurographics Association, 2016) Ilčík, Martin; Ilčíková, Ivana; Ferko, Andrej; Wimmer, Michael; Beatriz Sousa Santos and Jean-Michel Dischler
The Central European Seminar on Computer Graphics is an annual scientific seminar for undergraduate students of computer graphics, vision and visual computing. Its main mission is to promote graphics research and to motivate students to pursue academic careers. An international committee of experts guides their research work for several months. At the end, students present their results at a three days seminar to an audience of approx. 100 students and professors. All attendants actively participate in discussions and workshops focused on academic skills and career planing for young researchers. Interactive sessions on innovation help them to identify the value of their ideas and motivate them to continue in their work.
3D Characters for Virtual Reality
(The Eurographics Association, 2016) Orvalho, Veronica; Runa, Catarina; Lewis, John P.; Augusto Sousa and Kadi Bouatouch
Creating a 3D avatar that looks like a specific person is timeconsuming, requires expert artists, expensive equipment and a complex pipeline. In this tutorial we explain the different stages of a traditional character animation pipeline: modeling, rigging and animation. But, most important we describe how each of this stages bind together and which are the challenges developers face today at each stage. Our ultimate goal is to explain stepbystep the creation of a unified facial animation pipeline. We build the tutorial over our experience on what worked, what didn't work, why we did what we did and how we are planning to improve in the future. Given the popularity of Virtual Reality since the launching of Oculus Rift, we also describe how a traditional animation pipeline can be applied in Virtual Reality, it's challenges, limitations and potential. Throughout the tutorial we introduce the theoretical background for character animation and present the current state of the art in this field. Last, we aim to trigger a discussion to analyse different lines of research that emerge by bringing together traditional character animation and Virtual Reality.
3D Modelling Framework: an Incremental Approach
(The Eurographics Association, 2016) Almeida, Luis; Menezes, Paulo; Dias, Jorge; Luis Gonzaga Magalhaes and Rafal Mantiuk
This paper presents a framework for on-line incremental 3D modeling useful for human computer interaction or telepresence applications. We aim a free viewpoint approach based on user's realistic representation to simulate a real face-to-face meeting. Our contribution includes a new adaptation of the Crust algorithm for incremental reconstruction purposes and, a confidence method that evaluates the fusion of new data into the reconstructed model, based on measure uncertainty and novelty.With depth and image information of a single RGB-D sensor, we incrementally reconstruct a mesh model by combining visual features and shape-based alignment.
A 3D Morphable Model of the Eye Region
(The Eurographics Association, 2016) Wood, Erroll; Baltrušaitis, Tadas; Morency, Louis-Philippe; Robinson, Peter; Bulling, Andreas; Luis Gonzaga Magalhaes and Rafal Mantiuk
We present the first 3D morphable model that includes the eyes, enabling gaze estimation and gaze re-targetting from a single image. Morphable face models are a powerful tool and are used for a range of tasks including avatar animation and facial expression transfer. However, previous work has avoided the eyes, even though they play an important role in human communication. We built a new morphable model of the facial eye-region from high-quality head scan data, and combined this with a parametric eyeball model constructed from anatomical measurements and iris photos. We fit our models to an input RGB image, solving for shape, texture, pose, and scene illumination simultaneously. This provides us with an estimate of where a person is looking in a 3D scene without per-user calibration - a still unsolved problem in computer vision. It also allows us to re-render a person's eyes with different parameters, thus redirecting their perceived attention.
3D Skeletons: A State-of-the-Art Report
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Tagliasacchi, Andrea; Delame, Thomas; Spagnuolo, Michela; Amenta, Nina; Telea, Alexandru; Joaquim Madeira and Gustavo Patow
Given a shape, a skeleton is a thin centered structure which jointly describes the topology and the geometry of the shape. Skeletons provide an alternative to classical boundary or volumetric representations, which is especially effective for applications where one needs to reason about, and manipulate, the structure of a shape. These skeleton properties make them powerful tools for many types of shape analysis and processing tasks. For a given shape, several skeleton types can be defined, each having its own properties, advantages, and drawbacks. Similarly, a large number of methods exist to compute a given skeleton type, each having its own requirements, advantages, and limitations. While using skeletons for two-dimensional (2D) shapes is a relatively well covered area, developments in the skeletonization of three-dimensional (3D) shapes make these tasks challenging for both researchers and practitioners. This survey presents an overview of 3D shape skeletonization. We start by presenting the definition and properties of various types of 3D skeletons. We propose a taxonomy of 3D skeletons which allows us to further analyze and compare them with respect to their properties. We next overview methods and techniques used to compute all described 3D skeleton types, and discuss their assumptions, advantages, and limitations. Finally, we describe several applications of 3D skeletons, which illustrate their added value for different shape analysis and processing tasks.
Acceptable System Latency for Gaze-Dependent Level of Detail Rendering
(The Eurographics Association, 2016) Chwesiuk, Michał; Mantiuk, Radoslaw; Luis Gonzaga Magalhaes and Rafal Mantiuk
Human visual system is unable to perceive all details in the entire field of view. High frequency features are noticeable only at a small angle of 1-2 degrees around the viewing direction. Therefore, it is a reasonable idea to render the coarser object representations for the parafoveal and peripheral visions. A core problem of this gaze-dependent level-of-detail rendering is minimisation of the system latency. In this work we measure how fast should be the whole process of rendering and visualisation to prevent that level-of-detail change will be visible for human observers. We measured in the pilot experiment that even for distant periphery, the change from coarser to fine object representation should take less than 28 ms.
Adapting Feature Curve Networks to a Prescribed Scale
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Gehre, Anne; Lim, Isaak; Kobbelt, Leif; Joaquim Jorge and Ming Lin
Feature curves on surface meshes are usually defined solely based on local shape properties such as dihedral angles and principal curvatures. From the application perspective, however, the meaningfulness of a network of feature curves also depends on a global scale parameter that takes the distance between feature curves into account, i.e., on a coarse scale, nearby feature curves should be merged or suppressed if the surface region between them is not representable at the given scale/resolution. In this paper, we propose a computational approach to the intuitive notion of scale conforming feature curve networks where the density of feature curves on the surface adapts to a global scale parameter. We present a constrained global optimization algorithm that computes scale conforming feature curve networks by eliminating curve segments that represent surface features, which are not compatible to the prescribed scale. To demonstrate the usefulness of our approach we apply isotropic and anisotropic remeshing schemes that take our feature curve networks as input. For a number of example meshes, we thus generate high quality shape approximations at various levels of detail.
Adaptive UW Image Deblurring via Sparse Representation
(The Eurographics Association, 2016) Farhadifard, Fahimeh; Radolko, Martin; T. Bashford-Rogers and L. P. Santos
We present an adaptive underwater (UW) image deblurring algorithm based on sparse representation where a blur estimation is used to guide the algorithm for the best image reconstruction. The strong blur in this medium is caused by forward scatter and is challenging since it increases by camera scene distance. It is a common practice to use methods such as dark channel prior to estimate the depth map, and use this information to improve the image quality. However, we found it not successful in the case of blur since these methods are based on haze phenomenon. We propose a simple but effective algorithm via sparse representation which establishes a blur strength estimation and uses this information for adaptive deblurring. Extensive experiments manifest the effectiveness of our method in case of small but challenging blur changes.
Advances in Geometry and Reflectance Acquisition
(The Eurographics Association, 2016) Weinmann, Michael; Langguth, Fabian; Goesele, Michael; Klein, Reinhard; Augusto Sousa and Kadi Bouatouch
This tutorial is focused on acquisition methods for geometry and reflectance as well as strategies towards an efficient acquisition pipeline to fulfill the demands of industry with respect to mass digitization of 3D contents. We provide a thorough overview of the standard methods for the acquisition of both geometry and reflectance of surfaces with different types of reflectance behavior ranging from diffuse over opaque to specular surfaces or even translucent and transparent surfaces as well as the necessary preliminaries of material appearance and setup calibration. As standard acquisition techniques are only well-suited for a limited range of surface materials, we will also discuss strategies on how an efficient, fully automatic acquisition can still be achieved when no prior information with respect to the surface reflectance behavior is available. In addition, a discussion of strategies regarding an acquisition in the wild, i.e. under uncontrolled conditions, is provided.
Agile Curriculum Design for the Creative Industries
(The Eurographics Association, 2016) Palmer, Ian J.; Ralley, J.; Davenport, D.; Beatriz Sousa Santos and Jean-Michel Dischler
The creative industries thrive on novelty and technology, demanding professionals who can innovate, deliver to demanding briefs and constantly reinvent processes to match new problems. Traditional educational approaches can deliver some of these to a high level, but the demand for graduates who can thrive in these conditions is increasing. Escape Studios has reputation for rapidly upskilling graduates and making them ‘studio ready’ and is now moving to offer degree programmes including team working skills and commercial awareness impossible to include in its existing short intensive courses. This paper outlines the design process involved in creating these new programmes and provides case studies of some experiments in studio-based learning using industry briefs, peer and self-assessment and iterative working.
Aiming High: Undergraduate Research Projects in Computer Graphics and Animation
(The Eurographics Association, 2016) Anderson, Eike Falk; Adzhiev, Valery; Fryazinov, Oleg; Beatriz Sousa Santos and Jean-Michel Dischler
Among educators, the promotion of undergraduate research is a much debated topic, with issues arising from questions as to how it can be integrated with undergraduate degree programmes and how to structure its delivery. Undergraduate research is also considered important by employers, as can be seen in case of the computer game development and visual effects industries who demand that universities produce graduate software developers with not only vocational but also with rather advanced research skills. In this paper we present a successful undergraduate research course, implemented for one of our undergraduate degree programmes. It includes teaching and learning focussed on the nature of small team research and development as encountered in the creative industries dealing with computer graphics, computer animation and game development. We discuss our curriculum design and issues in conducting undergraduate research that we have identified through several iterations of the course.
Algorithms and Techniques for Virtual Camera Control
(The Eurographics Association, 2016) Ranon, Roberto; Christie, Marc; Lino, Christophe; Augusto Sousa and Kadi Bouatouch
Camera control is required in nearly all interactive 3D applications and presents a particular combination of different technical challenges. This tutorial will present recent and novel research ideas to handling a user's viewpoint on a scene in interactive, semi-automatic, and fully declarative camera control situations, covering a range of techniques from path-planning, visibility computation, optimal viewpoint computation and continuity editing. A specific part of the tutorial will be dedicated to virtual cinematography, and how it can draw inspiration from data and knowledge in real cinematography. Our presentation will include numerous live examples from both commercial systems and research prototypes, running in Unity and Motion Builder systems. Some of the tools, algorithms and datasets that will be presented will be also made, for the first time, available to the community.
Animation Setup Transfer for 3D Characters
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Avril, Quentin; Ghafourzadeh, Donya; Ramachandran, Srinivasan; Fallahdoust, Sahel; Ribet, Sarah; Dionne, Olivier; Lasa, Martin de; Paquette, Eric; Joaquim Jorge and Ming Lin
We present a general method for transferring skeletons and skinning weights between characters with distinct mesh topologies. Our pipeline takes as inputs a source character rig (consisting of a mesh, a transformation hierarchy of joints, and skinning weights) and a target character mesh. From these inputs, we compute joint locations and orientations that embed the source skeleton in the target mesh, as well as skinning weights to bind the target geometry to the new skeleton. Our method consists of two key steps. We first compute the geometric correspondence between source and target meshes using a semi-automatic method relying on a set of markers. The resulting geometric correspondence is then used to formulate attribute transfer as an energy minimization and filtering problem. We demonstrate our approach on a variety of source and target bipedal characters, varying in mesh topology and morphology. Several examples demonstrate that the target characters behave well when animated with either forward or inverse kinematics. Via these examples, we show that our method preserves subtle artistic variations; spatial relationships between geometry and joints, as well as skinning weight details, are accurately maintained. Our proposed pipeline opens up many exciting possibilities to quickly animate novel characters by reusing existing production assets.
Anisotropic Diffusion Descriptors
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Boscaini, Davide; Masci, Jonathan; Rodolà, Emanuele; Bronstein, Michael M.; Cremers, Daniel; Joaquim Jorge and Ming Lin
Spectral methods have recently gained popularity in many domains of computer graphics and geometry processing, especially shape processing, computation of shape descriptors, distances, and correspondence. Spectral geometric structures are intrinsic and thus invariant to isometric deformations, are efficiently computed, and can be constructed on shapes in different representations. A notable drawback of these constructions, however, is that they are isotropic, i.e., insensitive to direction. In this paper, we show how to construct direction-sensitive spectral feature descriptors using anisotropic diffusion on meshes and point clouds. The core of our construction are directed local kernels acting similarly to steerable filters, which are learned in a task-specific manner. Remarkably, while being intrinsic, our descriptors allow to disambiguate reflection symmetries. We show the application of anisotropic descriptors for problems of shape correspondence on meshes and point clouds, achieving results significantly better than state-of-the-art methods.
Augmenting Physical Maps: an AR Platform for Geographical Information Visualization
(The Eurographics Association, 2016) Nóbrega, Rui; Jacob, João; Rodrigues, Rui; Coelho, António; Sousa, A. Augusto de; Luis Gonzaga Magalhaes and Rafal Mantiuk
Physical maps of a city or region are important pieces of geographical information for tourists and local citizens. Unfortunately the amount of information that can be presented on a piece of paper is limited. In order to extend the map information we propose an augmented reality (AR) system, ARTourMap, for additional information visualization and interaction. This system provides an abstraction layer to develop applications based on the concept of separated logic map tiles taking advantage of a multi-target system where several regions of the map trigger different superimposed graphics. This allows the map to be folded, to be partially occluded, and to have dematerialized information. To demonstrate the proposed system ARTourMap, three layers were developed: a location-based game with points of interest (POIs), a 3D building visualization and an historical map layer.
Automatic Portrait Segmentation for Image Stylization
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Shen, Xiaoyong; Hertzmann, Aaron; Jia, Jiaya; Paris, Sylvain; Price, Brian; Shechtman, Eli; Sachs, Ian; Joaquim Jorge and Ming Lin
Portraiture is a major art form in both photography and painting. In most instances, artists seek to make the subject stand out from its surrounding, for instance, by making it brighter or sharper. In the digital world, similar effects can be achieved by processing a portrait image with photographic or painterly filters that adapt to the semantics of the image. While many successful user-guided methods exist to delineate the subject, fully automatic techniques are lacking and yield unsatisfactory results. Our paper first addresses this problem by introducing a new automatic segmentation algorithm dedicated to portraits. We then build upon this result and describe several portrait filters that exploit our automatic segmentation algorithm to generate high-quality portraits.
BlendForces: A Dynamic Framework for Facial Animation
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Barrielle, Vincent; Stoiber, Nicolas; Cagniart, Cédric; Joaquim Jorge and Ming Lin
In this paper we present a new paradigm for the generation and retargeting of facial animation. Like a vast majority of the approaches that have adressed these topics, our formalism is built on blendshapes. However, where prior works have generally encoded facial geometry using a low dimensional basis of these blendshapes, we propose to encode facial dynamics by looking at blendshapes as a basis of forces rather than a basis of shapes. We develop this idea into a dynamic model that naturally combines the blendshapes paradigm with physics-based techniques for the simulation of deforming meshes. Because it escapes the linear span of the shape basis through time-integration and physics-inspired simulation, this approach has a wider expres- sive range than previous blendshape-based methods. Its inherent physically-based formulation also enables the simulation of more advanced physical interactions, such as collision responses on lip contacts.
Boundary Detection in Particle-based Fluids
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Sandim, Marcos; Cedrim, Douglas; Nonato, Luis Gustavo; Pagliosa, Paulo; Paiva, Afonso; Joaquim Jorge and Ming Lin
This paper presents a novel method to detect free-surfaces on particle-based volume representation. In contrast to most particlebased free-surface detection methods, which perform the surface identification based on physical and geometrical properties derived from the underlying fluid flow simulation, the proposed approach only demands the spatial location of the particles to properly recognize surface particles, avoiding even the use of kernels. Boundary particles are identified through a Hidden Point Removal (HPR) operator used for visibility test. Our method is very simple, fast, easy to implement and robust to changes in the distribution of particles, even when facing large deformation of the free-surface. A set of comparisons against state-of-the-art boundary detection methods show the effectiveness of our approach. The good performance of our method is also attested in the context of fluid flow simulation involving free-surface, mainly when using level-sets for rendering purposes.
BRDF Representation and Acquisition
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Guarnera, Dar'ya; Guarnera, Giuseppe Claudio; Ghosh, Abhijeet; Denk, Cornelia; Glencross, Mashhuda; Joaquim Madeira and Gustavo Patow
Photorealistic rendering of real world environments is important in a range of different areas; including Visual Special effects, Interior/Exterior Modelling, Architectural Modelling, Cultural Heritage, Computer Games and Automotive Design. Currently, rendering systems are able to produce photorealistic simulations of the appearance of many real-world materials. In the real world, viewer perception of objects depends on the lighting and object/material/surface characteristics, the way a surface interacts with the light and on how the light is reflected, scattered, absorbed by the surface and the impact these characteristics have on material appearance. In order to re-produce this, it is necessary to understand how materials interact with light. Thus the representation and acquisition of material models has become such an active research area. This survey of the state-of-the-art of BRDF Representation and Acquisition presents an overview of BRDF (Bidirectional Reflectance Distribution Function) models used to represent surface/material reflection characteristics, and describes current acquisition methods for the capture and rendering of photorealistic materials.
Building Construction Sets by Tiling Grammar Simplification
(The Eurographics Association and John Wiley & Sons Ltd., 2016) Kalojanov, Javor; Wand, Michael; Slusallek, Philipp; Joaquim Jorge and Ming Lin
This paper poses the problem of fabricating physical construction sets from example geometry: A construction set provides a small number of different types of building blocks from which the example model as well as many similar variants can be reassembled. This process is formalized by tiling grammars. Our core contribution is an approach for simplifying tiling grammars such that we obtain physically manufacturable building blocks of controllable granularity while retaining variability, i.e., the ability to construct many different, related shapes. Simplification is performed by sequences of two types of elementary operations: non-local joint edge collapses in the tile graphs reduce the granularity of the decomposition and approximate replacement operations reduce redundancy. We evaluate our method on abstract graph grammars in addition to computing several physical construction sets, which are manufactured using a commodity 3D printer.

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