Steve C. Maddock

Accurate multidimensional Poisson-disk sampling

We present an accurate and efficient method to generate samples based on a Poisson-disk distribution. This type of distribution, because of its blue noise spectral properties, is useful for image sampling. It is also useful for multidimensional Monte Carlo integration and as part of a procedural object placement function. Our method extends trivially from 2D to 3D or to any higher dimensional space. We demonstrate results for up to four dimensions, which are likely to be the most useful for computer graphics applications. The method is accurate because it generates distributions with the same statistical properties of those generated with the brute-force dart-throwing algorithm, the archetype against which all other Poisson-disk sampling methods are compared. The method is efficient because it employs a spatial subdivision data structure that signals the regions of space where the insertion of new samples is allowed. The method has O(N log N) time and space complexity relative to the total number of samples. The method generates maximal distributions in which no further samples can be inserted at the completion of the algorithm. The method is only limited in the number of samples it can generate and the number of dimensions over which it can work by the available physical memory.

A Serious Game for Traffic Accident Investigators.

In Dubai, traffic accidents kill one person every 37 hours and injure one person every 3 hours. Novice traffic accident investigators in the Dubai police force are expected to ‘learn by doing’ in this intense environment. Currently, they use no alternative to the real world in order to practice. This paper argues for the use of an alternative learning environment, where the novice investigator can feel safe in exploring different investigative routes without fear for the consequences. The paper describes a game‐based learning environment that has been built using a game engine. The effectiveness of this environment in improving the performance of traffic accident investigators is also presented. Fifty‐six policemen took part in an experiment involving a virtual traffic accident scenario. They were divided into two groups: novices (0 to 2 years experience) and experienced personnel (with more than 2 years experience). The experiment revealed significant performance improvements in both groups, with the improvement reported in novices significantly higher than the one reported in experienced personnel. Both groups showed significant differences in navigational patterns (e.g. distances travelled and time utilization) between the two training sessions.

Ray casting implicit fractal surfaces with reduced affine arithmetic

A method is presented for ray casting implicit surfaces defined by fractal combinations of procedural noise functions. The method is robust and uses affine arithmetic to bound the variation of the implicit function along a ray. The method is also efficient due to a modification in the affine arithmetic representation that introduces a condensation step at the end of every non-affine operation. We show that our method is able to retain the tight estimation capabilities of affine arithmetic for ray casting implicit surfaces made from procedural noise functions while being faster to compute and more efficient to store.

Physically-based forehead animation including wrinkles

Physically‐based animation techniques enable more realistic and accurate animation to be created. We present a fully physically‐based approach for efficiently producing realistic‐looking animations of facial movement, including animation of expressive wrinkles. This involves simulation of detailed voxel‐based models using a graphics processing unit‐based total Lagrangian explicit dynamic finite element solver with an anatomical muscle contraction model, and advanced boundary conditions that can model the sliding of soft tissue over the skull. The flexibility of our approach enables detailed animations of gross and fine‐scale soft‐tissue movement to be easily produced with different muscle structures and material parameters, for example, to animate different aged skins. Although we focus on the forehead, our approach can be used to animate any multi‐layered soft body.

Game portability using a service-oriented approach

Game assets are portable between games. The games themselves are, however, dependent on the game engine they were developed on. Middleware has attempted to address this by, for instance, separating out the AI from the core game engine. Our work takes this further by separating the game from the game engine, and making it portable between game engines. The game elements that we make portable are the game logic, the object model, and the game state, which represent the games brain, and which we collectively refer to as the game factor, or G-factor. We achieve this using an architecture based around a service-oriented approach. We present an overview of this architecture and its use in developing games. The evaluation demonstrates that the architecture does not affect performance unduly, adds little development overhead, is scaleable, and supports modifiability.

Evaluation of A Viseme-Driven Talking Head

This paper introduces a three-dimensional virtual head for use in speech tutoring applications. The system achieves audiovisual speech synthesis using viseme-driven animation and a coarticulation model, to automatically generate speech from text. The talking head was evaluated using a modified rhyme test for intelligibility. The audiovisual speech animation was found to give higher intelligibility of isolated words than acoustic speech alone.

A constraint-based approach to visual speech for a Mexican-Spanish talking head

A common approach to produce visual speech is to interpolate the parameters describing a sequence of mouth shapes, known as visemes, where a viseme corresponds to a phoneme in an utterance. The interpolation process must consider the issue of context-dependent shape, or coarticulation, in order to produce realistic-looking speech. We describe an approach to such pose-based interpolation that deals with coarticulation using a constraint-based technique. This is demonstrated using a Mexican-Spanish talking head, which can vary its speed of talking and produce coarticulation effects.

Game logic portability

Many game engines integrate the game logic with the graphics engine. In this paper we separate the two, thus making the logic portable between game engines. In our architecture the logic is represented as an ontology and a set of rules for a particular application domain. A mediator with an embedded rules-engine links the logic to a suitable game engine.We demonstrate our architecture in two ways. First, we show a traffic accident scenario running on two different game engines, with a separate mediator for each engine. The logic type is smart-terrain logic, with participants triggering events based on interaction and proximity tests. In the second demonstration (a simple first-person shooting game) we show the extensibility and performance of the architecture to control non-player characters quickly manoeuvring using proximity tests and waypoints.

Planar Bones for MPEG-4 facial animation

This paper proposes a deformation technique called Planar Bones, derived from surface-oriented free form deformations, and explores its application to the context of facial animation. The warping method proposed uses as the control input a polygonal mesh, which is built as a triangulation of the feature points defined by MPEG-4 (Motion Picture Experts Group). A strong correspondence between the facial geometry and this control structure is maintained throughout the animation, overcoming the issues of many of the current systems defined using this standard.

Sketching faces

Faces can be modelled using a number of techniques. Existing faces can be transferred to a digital form using equipment such as laser scanners. New faces can be constructed using commercial modelling tools, or using specialist software, e.g. Photo-fit software. We present a technique that can create a 3D head using intuitive 2D sketching techniques. This involves bringing together two types of graphics applications: sketching interfaces and systems used to create 3D faces, through the mediation of a statistical model.