State of the Art Reports
- Session Details: Tuesday, May 10, 2016 – 09:00 – 10:30
- Session Chairs: Renato Pajarola – University of Zurich
- Directional Field Synthesis, Design, and Processing
- Amir Vaxman, Marcel Campen, Olga Diamanti, Daniele Panozzo, David Bommes, Klaus Hildebrandt, Mirela Ben-Chen
- Direction fields and vector fields play an increasingly important role in computer graphics and geometry processing. The synthesis of directional fields on surfaces, or other spatial domains, is a fundamental step in numerous applications, such as mesh generation, deformation, texture mapping, and many more. The wide range of applications incentivized the definition of many types of directional fields, from vector and tensor fields, over line and cross fields, to frame and vector-set fields. Depending on the application at hand, researchers have used various notions of objectives and constraints to synthesize such fields. These notions are defined in terms of fairness, feature alignment, symmetry, or field topology, to mention just a few. To facilitate these objectives, various representations, discretizations, and optimization strategies have been developed, with varying strengths and weaknesses. This report provides a systematic overview of directional field synthesis for graphics applications, the challenges it poses, and the methods developed in recent years to address these challenges.
- Session Details: Tuesday, May 10, 2016 – 16:00 – 17:30
- Session Chairs: Paolo Cignoni – CNR-ISTI, Pisa
- 3D Skeletons: A State-of-the-Art Report
- Andrea Tagliasacchi, Thomas Delame, Michela Spagnuolo, Nina Amenta, Alexandru Telea
- 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.
- Session Details: Wednesday, May 11, 2016 – 09:00 – 10:30
- Session Chairs: Daniele Panozzo- NYU
- Laplacian Spectral Kernels and Distances for Geometry Processing and Shape Analysis
- Giuseppe Patané
- In geometry processing and shape analysis, several applications have been addressed through the properties of the spectral kernels and distances, such as commute-time, biharmonic, diffusion, and wave distances. Our survey is intended to provide a background on the properties, discretization, computation, and main applications of the Laplace-Beltrami operator, the associated differential equations (e.g., harmonic equation, Laplacian eigenproblem, diffusion and wave equations), Laplacian spectral kernels and distances (e.g., commute-time, biharmonic, wave, diffusion distances). While previous work has been focused mainly on specific applications of the aforementioned topics on surface meshes, we propose a general approach that allows us to review Laplacian kernels and distances on surfaces and volumes, and for any choice of the Laplacian weights. All the reviewed numerical schemes for the computation of the Laplacian spectral kernels and distances are discussed in terms of robustness, approximation accuracy, and computational cost, thus supporting the reader in the selection of the most appropriate method with respect to shape representation, computational resources, and target application.
- Session Details: Wednesday, May 11, 2016 – 11:00 – 12:30
- Session Chairs: Luís Paulo Santos – Universidade do Minho, Braga
- BRDF Representation and Acquisition
- Dar’ya Guarnera, Giuseppe Claudio Guarnera, Abhijeet Ghosh, Cornelia Denk, Mashuda Glencross
- 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.
- Session Details: Wednesday, May 11, 2016 – 14:00 – 15:30
- Session Chairs: Thomas Delame – Inria, Grenoble
- Semi-Regular Triangle Remeshing: A Comprehensive Study
- F. Payan, C. Roudet, B. Sauvage
- Semi-regular triangle remeshing algorithms convert irregular surface meshes into semi-regular ones. Especially in the field of computer graphics, semi-regularity is an interesting property because it makes meshes highly suitable for multi-resolution analysis. In this paper, we survey the numerous remeshing algorithms that have been developed over the past two decades. We propose different classifications to give new and comprehensible insights into both existing methods and issues. We describe how considerable obstacles have already been overcome, and discuss promising perspectives.
- Session Details: Wednesday, May 11, 2016 – 16:00 – 17:30
- Session Chairs: Rafael Bidarra – TU Delft
- A Survey of Real-Time Crowd Rendering
- A. Beacco, N. Pelechano, C. Andújar
- In this survey we review, classify and compare existing approaches for real-time crowd rendering. We first overview character animation techniques, as they are highly tied to crowd rendering performance, and then we analyze the state of the art in crowd rendering. We discuss different representations for level-of-detail (LoD) rendering of animated characters, including polygon-based, point-based, and image-based techniques, and review different criteria for runtime LoD selection. Besides LoD approaches, we review classic acceleration schemes, such as frustum culling and occlusion culling, and describe how they can be adapted to handle crowds of animated characters. We also discuss specific acceleration techniques for crowd rendering, such as primitive pseudo-instancing, palette skinning, and dynamic key-pose caching, which benefit from current graphics hardware.We also address other factors affecting performance and realism of crowds such as lighting, shadowing, clothing and variability.Finally we provide an exhaustive comparison of the most relevant approaches in the field.
- Session Details: Friday, May 13, 2016 – 09:30 – 11:00
- Session Chairs: Pere Brunet – UPC, Barcelona
- Data-Driven Shape Analysis and Processing
- Kai Xu, Vladimir G. Kim, Qixing Huang, Evangelos Kalogerakis
- Data-driven methods serve an increasingly important role in discovering geometric, structural and semantic relationships between shapes. In contrast to traditional approaches that process shapes in isolation of each other, data-driven methods aggregate information from 3D model collections to improve the analysis, modelling and editing of shapes. Data-driven methods are also able to learn computational models that reason about properties and relationships of shapes without relying on hardcoded rules or explicitly programmed instructions. Through reviewing the literature, we provide an overview of the main concepts and components of these methods, as well as discuss their application to classification, segmentation, matching, reconstruction, modelling and exploration, as well as scene analysis and synthesis. We conclude our report with ideas that can inspire future research in data-driven shape analysis and processing.