A new apparatus for modelling excavations

Underground space is commonly exploited both to maximise the utility of costly land in urban development and to reduce the vertical load acting on the ground. Deep excavations are carried out to construct various types of underground infrastructure such as deep basements, subways and service tunnels. Although the soil response to excavation is known in principle, designers lack practical calculation methods for predicting both short- and long-term ground movements. As the understanding of how soil behaves around an excavation in both the short and long term is insufficient and usually empirical, the judgements used in design are also empirical and serious accidents are common. To gain a better understanding of the mechanisms involved in soil excavation, a new apparatus for the centrifuge model testing of deep excavations in soft clay has been developed. This apparatus simulates the field construction sequence of a multi-propped retaining wall during centrifuge flight. A comparison is given between the new technique and the previously used method of draining heavy fluid to simulate excavation in a centrifuge model. The new system has the benefit of giving the correct initial ground conditions before excavation and the proper earth pressure distribution on the retaining structures during excavation, whereas heavy fluid only gives an earth pressure coefficient of unity and is unable to capture any changes in the earth pressure coefficient of soil inside the zone of excavation, for example owing to wall movements. Settlements of the ground surface, changes in pore water pressure, variations in earth pressure, prop forces and bending moments in the retaining wall are all monitored during excavation. Furthermore, digital images taken of a cross-section during the test are analysed using particle image velocimetry to illustrate ground deformation and soil-structure interaction mechanisms. The significance of these observations is discussed.

Development of a new apparatus for modeling deep excavation related problems in geotechnical centrifuge

Underground space is commonly exploited both to maximise the utility of costly land in urban development and to reduce the vertical load acting on the ground. Deep excavations are carried out to construct various types of underground infrastructure such as deep basements, subways and service tunnels. Although the soil response to excavation is known in principle, designers lack practical calculation methods for predicting both short- and long-term ground movements. As the understanding of how soil behaves around an excavation in both the short and long term is insufficient and usually empirical, the judgements used in design are also empirical and serious accidents are common. To gain a better understanding of the mechanisms involved in soil excavation, a new apparatus for the centrifuge model testing of deep excavations in soft clay has been developed. This apparatus simulates the field construction sequence of a multi-propped retaining wall during centrifuge flight. A comparison is given between the new technique and the previously used method of draining heavy fluid to simulate excavation in a centrifuge model. The new system has the benefit of giving the correct initial ground conditions before excavation and the proper earth pressure distribution on the retaining structures during excavation, whereas heavy fluid only gives an earth pressure coefficient of unity and is unable to capture any changes in the earth pressure coefficient of soil inside the zone of excavation, for example owing to wall movements. Settlements of the ground surface, changes in pore water pressure, variations in earth pressure, prop forces and bending moments in the retaining wall are all monitored during excavation. Furthermore, digital images taken of a cross-section during the test are analysed using particle image velocimetry to illustrate ground deformation and soil–structure interaction mechanisms. The significance of these observations is discussed.

Creation of Computer Animation from Story Descriptions

This report describes a computer system that creates simple computer animation in response to high-level, vague, and incomplete descriptions of films. It makes its films by collecting and evaluating suggestions from several different bodies of knowledge. The order in which it makes its choices is influenced by the focus of the film. Difficult choices are postponed to be resumed when more of the film has been determined. The system was implemented in an object-oriented language based upon computational entities called "actors". The goal behind the construction of the system is that, whenever faced with a choice, it should sensibly choose between alternatives based upon the description of the film and as much general knowledge as possible. The system is presented as a computational model of creativity and aesthetics.

Agency and animation: the performance of interactive game characters

As an animator and practice-based researcher with a background in games development, I am interested in technological change in the video game medium, with a focus on the tools and technologies that drive game character animation and interactive story. In particular, I am concerned with the issue of ‘user agency’, or the ability of the end user to affect story development—a key quality of the gaming experience and essential to the aesthetics of gaming, which is defined in large measure by its interactive elements. In this paper I consider the unique qualities of the video game1 as an artistic medium and the impact that these qualities have on the production of animated virtual character performances. I discuss the somewhat oppositional nature of animated character performances found in games from recent years, which range from inactive to active—in other words, low to high agency. Where procedural techniques (based on coded rules of movement) are used to model dynamic character performances, the user has the ability to interactively affect characters in real-time within the larger sphere of the game. This game play creates a high degree of user agency. However, it lacks the aesthetic nuances of the more crafted sections of games: the short cut-scenes, or narrative interludes where entire acted performances are mapped onto game characters (often via performance capture)2 and constructed into relatively cinematic representations. While visually spectacular, cut-scenes involve minimal interactivity, so user agency is low. Contemporary games typically float between these two distinct methods of animation, from a focus on user agency and dynamically responsive animation to a focus on animated character performance in sections where the user is a passive participant. We tend to think of the majority of action in games as taking place via playable figures: an avatar or central character that represents a player. However, there is another realm of characters that also partake in actions ranging from significant to incidental: non-playable characters, or NPCs, which populate action sequences where game play takes place as well as cut scenes that unfold without much or any interaction on the part of the player. NPCs are the equivalent to supporting roles, bit characters, or extras in the world of cinema. Minor NPCs may simply be background characters or enemies to defeat, but many NPCs are crucial to the overall game story. It is my argument that, thus far, no game has successfully utilized the full potential of these characters to contribute toward development of interactive, high performance action. In particular, a type of NPC that I have identified as ‘pivotal’3—those constituting the supporting cast of a video game—are essential to the telling of a game story, particularly in genres that focus on story and characters: adventure games, action games, and role-playing games. A game story can be defined as the entirety of the narrative, told through non-interactive cut-scenes as well a interactive sections of play, and development of more complex stories in games clearly impacts the animation of NPCs. I argue that NPCs in games must be capable of acting with emotion throughout a game—in the cutscenes, which are tightly controlled, but also in sections of game play, where player agency can potentially alter the story in real-time. When the animated performance of NPCs and user agency are not continuous throughout the game, the implication is that game stories may be primarily told through short movies within games, making it more difficult to define video games animation as a distinct artistic medium.