Conference Programme

Click here for the Afrigraph 2009 programme.

The keynote and plenary talks given at the conference are now available.

Keynote Address

Roberto Scopigno - 3D Scanning for Cultural Heritage: A Technological Exercise or a Useful Instrument

Plenary Sessions

Summary: Recreating a fully immersive perceptual experience or real virtuality, all sensory inputs need to be fully natural. In the natural environment we hear sound with two ears and this enables us to identify the direction of the sound source. In artificial listening environments where we are using loudspeakers or headphones, attempts to place a sound at a particular arbitrary location are not usually very successful. Sounds replayed over headphones are located between the headphones themselves; they are within the head. Whilst most listeners have come to accept this sound stage when replaying music, for example, on their MP3 players, the result is non-natural. The fully immersive real virtual experience requires a natural sound stage, and this paper will describe the main acoustic cues used to locate sounds and the extent to which sound can be artificially presented to provide a natural listening result.

David Levin - Shape Preserving Deformation

Summary: We discuss different ways to represent and manipulate discrete surfaces. We present the algorithms with accompanying theory motivated by classical mathematical ideas such as surface theory and moving frames, and the theory of Green's functions.

The talk reviews three works:

A. Rigid Motion Invariant Discrete Surface Representations: In this part we introduce a rigid motion invariant mesh representation based on discrete forms defined on the mesh. The reconstruction of mesh geometry from this representation requires solving two linear systems that arise from the discrete forms: The first system defines the relationship between local frames on the mesh, and the second encodes the position of the vertices via the local frames. The reconstructed geometry is unique up to a rigid transformation of the mesh. We use this representation to derive a method for shape-preserving mesh editing: We define mesh editing operations by placing user-defined constraints on the local frames and the vertex positions. These constraints are incorporated in the two linear reconstruction systems, and their solution produces a deformed surface geometry that preserves the local differential properties in the least-squares sense. Linear combination of shapes expressed with our representation enables linear shape interpolation that correctly handles rotations. We demonstrate the effectiveness of the new representation with various detail-preserving editing operators and shape morphing.
The results in this part were published in: Linear Rotation-invariant Coordinates for Meshes, SIGGRAPH 2005, special issue of ACM Transactions on Graphics, by Y. Lipman, O. Sorkine, D. Cohen-Or and D. Levin.

B. Moving Frames for Surface Deformation: This part introduces a method for mesh editing aimed at preserving shape and volume based on the theory of moving frames. It introduces two developments: The first is the minimization of a functional expressing a geometric distance measure between two isometric surfaces. The second is a local volume analysis linking the volume of an object to its surface curvature. The method is linked to the representation of meshes introduced in the previous chapter in the sense that it further dwells on the use of local frames as a mean of analyzing the local surface shape. Note that applying a rotation field to the moving frames defines an isometry. Given rotational constraints, the mesh is deformed by an optimal near-isometry map which is defined by minimizing the distance measure between the original and the deformed meshes. The resulting near-isometry nicely preserves the surface details, but, when large rotations are applied, the volumetric behavior of the model may be unsatisfactory. Using a local volume analysis, we define a scalar field by which we scale the moving frames. The scaled and rotated moving frames restore the volumetric properties of the original mesh, while properly maintaining the surface details. Our results show that even extreme deformations can be applied to meshes, with only a minimal distortion of surface details and object volume.
The results of this part were published in: Volume and Shape Preservation via Moving Frames Manipulation, ACM Transactions on Graphics (2007), by Y. Lipman, D. Cohen-Or, R. Gal and D. Levin.

C. Volume Representations and Green Coordinates: Here we introduce Green Coordinates for closed polyhedral cages. The coordinates are motivated by Green's third integral identity and respect both the vertices position and faces orientation of the cage. We show that Green Coordinates lead to space deformations with a shape-preserving property. In particular, in 2D they induce conformal mappings, which extend naturally to quasi-conformal mappings in 3D. In both cases we derive closed-form expressions for the coordinates, yielding a simple and fast algorithm for cage-based space deformation. We compare the performance of Green Coordinates with those of Mean Value Coordinates and Harmonic Coordinates and show that the advantage of the shape-preserving property is not achieved at the expense of speed or simplicity. We also show that the new coordinates extend the mapping in a natural analytic manner to the exterior of the cage, allowing the employment of partial cages.
These results are accepted and to be published in: Green Coordinates, SIGGRAPH 2008, special issue of ACM Transactions on Graphics, by Y. Lipman, D. Levin and D. Cohen-Or.

Tutorials

Dave Shreiner - The Khronos Open*L APIs: OpenGL 3.X & OpenCL

Pieter Germishuys - Game development, XNA and DirectX: putting the pieces together

Mahendra Naidoo and Frederick Smith - Practical Character Animation with ZBrush and Maya

Industry Panel

Christopher Moir and Basie von Solms - The Adoption of New Technology in the Developing World

Conference Banquet

The conference banquet will be held at the prestigious Maropeng Center at the Cradle of Humankind World Heritage Site in Gauteng.

Papers

TITLE	AUTHORS	ORGANIZATION (Primary Author)	COUNTRY (Primary Author)
Virtual Relighting of a Roman Statue Head from Herculaneum, A Case Study	Jassim Happa, Mark Williams, Glen Turley, Piotr Dubla and Graeme Earl	The Digital Laboratory, University of Warwick	UK
Revisiting District Six: A Case Study of Digital Heritage Reconstruction from Archival Photographs	Christopher De Kadt, James Gain and Patrick Marais	University of Cape Town	South Africa
Pick-by-Vision comes on Age: Evaluation of an Augmented Reality supported Picking System in an real Storage Environment	Rupert Reif, Willibald Günthner, Björn Schwerdtfeger and Gudrun Klinker	TU München	Germany
Associating fonts with musical genres	Jukka Holm and Antti Aaltonen	Nokia Research Center	Finland
Analytic simplification of animated characters	Bruce Merry, Patrick Marais and James Gain	ARM	UK
Simulating crowd phenomena in African markets	Flora Ponjou Tasse, Kevin Glass and Shaun Bangay	Rhodes University	South Africa
Virtual Reality Training Applications for the Mining Industry	Etienne van Wyk and Ruth de Villiers	Tshwane University of Technology	South Africa
Particle-based Fluid Flow Visualization on Meshes	Khalid Djado and Richard Egli	Université de Sherbrooke	Canada
Visual quality of the ground in 3D models: Using color-coded images to blend aerial photos with tiled detail-textures	Mattias Roupé and Mikael Johansson	Chalmers University of Technology	Sweden
Using An Implicit Min/Max KD-Tree for Doing Efficient Terrain Line of Sight Calculations	Bernardt Duvenhage	The Council for Scientific and Industrial Research	South Africa
An Efficient Parameters Estimation Method for Automatic Patch-based Texture Synthesis	Jakrapong Narkdej and Pizzanu Kanongchaiyos	Chulalongkorn University	Thailand
Programmable Transitions for Video Stream Editing	Alexandre Hardy	University of Johannesburg	South Africa

Posters

Visualization of Web Browsing From Tags Sequence - Chao Wu (Zhejiang University, China)

Abstract: In this paper, we describe a method to visualize and analyze users' browsing activities on Internet. The raw data we use are the sequence of bookmarks' tags in Del.icio.us, which can indicate a user's browsing history. Due to the difficulty to investigate textual data, we use visualization method called "Chromogram", which maps the textual data to color-based diagrams. After applying the method on data in Del.icio.us, we found some patterns of users' web browsing, such as theme-based browsing and diversity.

Efficient Rendering Of Large Geometric Objects Using Geometry Images - Daniel Walker (University of Johannesburg, South Africa)

Abstract: The poster introduces an algorithm that renders an object at different levels of detail, with emphasis on the silhouette. Geometry images are used to represent the object and a chunked LOD approach is used to render the various detail levels. Normal maps are used to supplement detail in areas of lower detail.

Distributed Rendering - Sean O'Reilly and Peter van Onselen (University of Johannesburg, South Africa)

Abstract: This poster outlines our implementation of a Sort Last algorithm for a distributed rendering system.

Artworks

Paul Abro's Fireflies' Lullaby - Adrian Burger (South Africa)

Abstract: Fireflies' Lullaby tells the story of a boy who dreams of changing the world. It is a 2D animated music video, and uses various software techniques, drawing and painting methods to simulate the visual style and appeal of children's storybook illustration.

Created entirely in Adobe Photoshop, Illustrator, After Effects and Premiere.

DRAWING - Juliana Alvarenga (Brazil)

Abstract: L'analogie peut être pensée en tant que transposition, déplacement de relations d'un champ spécifique de la connaissance vers un autre. A partir de la notion d'apollinien et de dionysiaque chez Nietzsche, nous pouvons affirmer que le langage est la représentation symbolique et nécessaire de la connaissance. Ce langage-métaphore agit comme protection contre l'expérience dionysiaque destructrice, dans laquelle le sujet est confondu avec l'objet. Au moment où le sujet se sépare de l'objet, le langage est généré par le biais d'une élaboration rationnelle de l'observateur, jusqu'alors dissolu dans l'ivresse de l'expérience intuitive. Le corps humain s'affirme aussi comme créateur de langages lorsqu'il manifeste des altérations fonctionnelles caractéristiques des maladies. Le déplacement des connaissances du domaine médical homéopathique vers l'art utilise l'analogie pour construire un langage imagétique, métaphorique de la connaissance qui a traversé le corps de l'artiste dans cette expérimentation. Le développement de la vídeo DESENHO (DESSIN) culmine dans la jonction d'images du corps de l'auteur avec le corps de l'animal qui produit la teinture de sépia, utilisée dans la production du médicament homéopathique Sepia Officinalis, indiqué pour les cas d'affections rénales. Le passage d'ultrasonographies des reins aux dessins en sépia projetés sur le corps à l'aide de rétroprojeteur, la rétroprojection étant ensuite photographiée sur diapositives et la projection de ces diapositives filmées en vídeo constitue une métaphore de la dynamisation – príncipe de l'homéopathie selon lequel l'augmentation de la dilution engendre une plus grande puissance. Après la réalisation de ce travail, exhibé dans plusieurs festivals internationaux d'arts, des effets de guérison de problèmes rénaux chroniques ont été vérifiés, traités ici non comme vérité scientifique, mais comme fait poétique. Ce travail propose qu'il soit vraisemblable que des analogies entre science et art puissent élargir la puissance des divers champs de la connaissance.

Coinage Project: Girl #3 - Jin Wan Park (Chung-Ang Univ., South Korea)

Abstract: New type of mosaic: Multi-layered Stack Mosaic with photos of rotatable objects. The algorithm uses multi-layered Photomosaics with database enrichment by elements rotation. The benefit of this algorithm is that not only an that artist can produce the digital mosaic with relatively small size database without degrading the quality of mosaic but also that the Multi-layered Stack Mosaic generates unique and strong artistic expression which gives an illusion of piled stackable objects. Since the result has a unique visual style, we could exhibit series of our mosaic images at galleries such as Epson Color Imaging Contest and Leonardo MIT Press. One of the main goals of this artwork is merging technology and art in one place. For this project, I suggested an algorithm, the multi-layered photo mosaic with limited database of stackable objects. The result image has very direct message, but my intention is not a anti-capitalism campaign. If someone questions my opinion of the money, I can answer it easily. Buying people with money, only human being can perform, and it helps or destroy people who need it desperately. Money can buy almost anything today, even times, but sympathy is not one of them.

Fear: Book Deconstructed - Leslie Nobler Farber (Wm. Paterson University, USA)

Join-Manual Deconstructed - Leslie Nobler Farber (Wm. Paterson University, USA)

Liquidator - Johannes Schmid and Mark Pauly (ETH Zürich, Switzerland)

Abstract: Making fluid simulations behave any different from what the physical model prescribes is a challenging task. With existing methods, control is usually exerted by scripting force fields or by importing key-framed data. We have implemented a system that allows the user to design fluid animations using a simple and intuitive sketching interface. Each stroke, sketched using a mouse or a tablet input device, induces forces that either attract or repel fluid, or alter its velocity vector. Using this simple control paradigm, many effects can be achieved, ranging from detailed touch-up edits on existing flow simulations to completely synthetic fluid behaviour for special effects or artistic applications.

The combination of physics-based simulation and sketch-based interaction yields a highly versatile system for fluid flow animation. Simulation provides physically plausible fluid behavior as well as geometric and dynamic complexity enabling a compelling flow animation. Sketching control forces allows intuitive flow design and supports full expressive freedom by transcending the laws of physics to create fluids that behave according to the animators goals.

This animated short movie showcases the potential of sketched fluid control. Except for the forces that cause the fluid to form a human shape, all flow movement that differs from the natural behavior of liquids has been achieved by guiding the fluid using only a few mouse strokes.

Don't Take a Risk! - Rodrigo Santos (Sant Studio, Brazil)

Abstract: Cartoon 3d animation produced by Sant Studio from São Paulo, Brazil. Don't Take a Risk! has been screened in national and international festivals including events like Annecy International Animated Film Festival, Orlando Siggraph Eureka! Computer Animation Festival, China International Animation Digital Arts Festival, Holland Animation Film Festival, Animest and Sibgrapi Video Festival Brazilian Symposium on Computer Graphics and Image Processing.

Don't Take a Risk! is an ad animation. This video shows that things can get really bad if you try to make a Caipirinha, the famous brazillian drink but don't have the skills to do it.

Maratinho - Rodrigo Santos (Sant Studio, Brazil)

Abstract: Maratinho is an ad animation produced by Sant Studio from São Paulo, Brazil. ILU had an unexpected adventure when he was riding a bicycle.

Mr. Lucky Navio Pirata (Mr. Lucky - Submarine) - Rodrigo Santos (Sant Studio, Brazil)

Colégio Equipe - Surpresa (Colégio Equipe - Surprise) - Rodrigo Santos (Sant Studio, Brazil)

Força Construtiva - Dia das Crianças (Força Construtiva - Children's Day) - Rodrigo Santos (Sant Studio, Brazil)

Rose Dollz - Hi-Fi - Rodrigo Santos (Sant Studio, Brazil)