4 research outputs found
Ambientes virtuais povoados com simulação eficiente de detecção de colisões e planeamento de trajectos em navegação realmente 3D
Tese de Doutoramento - Área de InformáticaA tecnologia de produção de ambientes virtuais tem vindo cada vez mais a ser utilizada em projectos de animação, desenho e avaliação em diversas áreas. Mundos virtuais com níveis de detalhe consideráveis estão a começar a emergir em toda a parte, desde largas áreas das
actuais cidades até ambientes virtuais interiores mais específicos e detalhados (edifícios
habitacionais, estádios, estruturas industriais, reconstruções arqueológicas, etc). No entanto,
melhorar a aparência visual destes edifícios virtuais já não é suficiente. Com o propósito de
proporcionar novas condições de simulação a aplicações tais como o planeamento urbano,
simulações comportamentais e de fluxo de pedestres, entretenimento, etc, é necessário o
povoamento destes ambientes. Povoar estes mundos simulando a presença de vida, adiciona
um toque extra à visualização e realismo, mas infelizmente traz também carga adicional ao
sistema. Uma das lacunas da pesquisa nesta área é a representação eficiente de ambientes
densamente povoados, com simulação de navegação autónoma realmente tridimensional das
personagens, enquadradas em modelos ou cenários arbitrários. Diversas condições e áreas de
actuação são necessárias quando pretendemos simular a presença humana (através de
personagens sintéticas animadas) nestas circunstâncias, tais como a detecção de colisões,
planeamento de trajectos, algoritmos comportamentais, rendering dinâmico da geometria,
entre outros.
Nesta tese, é publicado um método transversal de modo a exibir e consolidar
comportamentos autónomos de multidões virtuais em ambientes reais de animação. O
sistema tem a capacidade de incluir um grande número de personagens lidando com mundos
3D arbitrariamente complexos, não requerendo qualquer conhecimento prévio da
geometria, e proporcionando navegação em tempo real, autónoma, e tridimensional.
Inicialmente, é apresentado um método de detecção de colisões usando técnicas
conservadoras, capaz de comportar milhares de avatares e lidar com cenas 3D de grandes
dimensões e complexidade, não necessitando de qualquer informação ou conhecimento
prévio do modelo. Este método demonstrou ser um mecanismo eficiente e escalável de
detecção de colisões entre os agentes e o ambiente 3D. Recorrendo a um mapeamento e
extracção de dados automático a partir do modelo inicial, fornece a detecção de colisões e a
interacção entre os próprios agentes virtuais, e os agentes virtuais e o ambiente que os
rodeia. Este método mostrou-se apropriado como base de implementação posterior de
algoritmos de planeamento de percursos e outros algoritmos comportamentais, onde o avatar
incorporará procedimentos de mais alto-nível.
Para projectos de desenho, simulação e testes de facilidades de navegação em locais públicos,
é importante prever as principais rotas ou fluxos a serem usados. Uma segunda aproximação
apresentada, consiste em decompor a cena 3D em partições multi-nível (para navegação em
ambientes 3D, principalmente em interiores de edifícios) criando um sistema que possa usar
este tipo de catalogação como informação relevante de modo a planear rotas de acordo com
as deslocações em várias alturas.
A outro nível, o objectivo foi também testar a base de navegação criada, desenvolvendo
mecanismos de implementação de novos e naturais comportamentos associados à navegação
das personagens virtuais, lidando com várias variáveis de interacção, permitindo um
comportamento mais realista e de reacção entre estes e o ambiente virtual. Em resumo,
foram definidos sistemas de condições, regras e propriedades capazes de produzir
comportamentos mais naturais e autónomos em personagens virtuais representativos da
conduta humana.Virtual environment technology has been increasingly used for animation projects, design and evaluation in several areas. Virtual worlds, with considerable levels of detail, are starting to emerge everywhere, from large areas of actual cities to detailed and complex virtual indoor environments (buildings, stadiums, industrials structures, archaeological
reconstructions, etc). However, improving the visual appearance of these virtual buildings is not enough anymore. In order to provide applications with new simulation conditions such as urban planning, behaviour and flow of pedestrian’s simulation, entertainment, etc, requires the populating of these virtual environments. Populating these worlds to simulate the presence of life, adds an extra touch to the visualization and credibility, but unfortunately it also brings an extra burden to the system. One of the issues of the research in this area is the representation of a densely crowded environment, simulating autonomous and real three-dimensional navigation to the virtual characters in arbitrary threedimensional models or scenarios. Several steps are required when we need simulate the human presence (by synthetic animated characters) in these circumstances, such as collision detection, path planning/finding, behavioural algorithms, dynamic rendering of geometry, amongst others.
In this thesis, a transversal approach is presented to demonstrate and consolidate autonomous virtual crowd behaviours in realistic animation environments. The system is able to include a large number of characters dealing with arbitrarily complex 3D worlds, not requiring any prior knowledge of the geometry, and providing real-time navigation,
autonomous, and really three-dimensional.
Initially, a method for efficient and scalable conservative collision detection is presented, that is able to deal with large and complex 3D scenes with thousands of avatars, not requiring any prior knowledge of model. This method demonstrated to be a fast, efficient and scalable collision detection process between virtual agents and the 3D environment. Using an automatic data extraction and mapping process from the initial graphical model, it provides collisions detection and interaction between virtual agents, as well as virtual agents and the environment that encircles them. This method proved to be appropriate as a basis for further implementation of path planning/finding algorithms and other behaviours algorithms.
For design projects, simulation and the study of crowd behaviour facilities in public places, it is however important to be able to predict heavily used routes or peak flows. The second approach presented, consists in decomposing the 3D scene in multi-level sub-divisions (for navigation in 3D environments such as indoor building) creating a system that can use this type of cataloguing as relevant information to planning and finding routes, according to the movements at the various levels of heights.
At another level, the goal was testing the base of navigation, developing mechanisms for new and natural behaviour implementations associated with virtual characters navigation, dealing with some interaction variables, representing a more realistic react/interact behaviour. In summary, autonomous conditions systems, rules and properties were defined, that are capable to produce behaviours representative of human condition
Efficient conservative collision detection for populated virtual worlds
Large virtual worlds, with considerable level of detail are starting to emerge everywhere, from large areas of
actual cities to archaeological detailed reconstructions of sites. Populating a virtual world adds an extra touch
to the visualization of these worlds, but unfortunately it also brings an extra burden to the system. Several tasks
are required when adding animated characters to a virtual world, such as collision detection, path planning and
other AI algorithms, rendering of dynamic geometry, amongst others. In here a method for efficient and scalable
conservative collision detection, that is able to deal with large scenes and thousands of avatars, is presented. This
method does not perform exact collision detection, hence it is conservative. The method is suitable as a basis for
path planning algorithms and other AI algorithms where an avatar is often regarded as ’something’ that can be
bounded by a cylinder, or a box. The algorithm is capable of dealing with arbitrarily complex 3D worlds, and
does not require any a priori knowledge of the geometry
Path planning for complex 3D multilevel environments
The continuous development of graphics hardware is
contributing to the creation of 3D virtual worlds with
high level of detail, from models of large urban areas, to
complete infrastructures, such as residential buildings,
stadiums, industrial settings or archaeological sites, to
name just a few. Adding virtual humans or avatars adds
an extra touch to the visualization providing an enhanced
perception of the spaces, namely adding a sense of scale,
and enabling simulations of crowds. Path planning for
crowds in a meaningful way is still an open research
field, particularly when it involves an unknown polygonal
3D world. Extracting the potential paths for navigation in
a non automated fashion is no longer a feasible option
due to the dimension and complexity of the virtual
environments available nowadays. This implies that we
must be able to automatically extract information from
the geometry of the unknown virtual world to define
potential paths, determine accessibilities, and prepare a
navigation structure for real time path planning and path
finding. A new image based method is proposed that
deals with arbitrarily a priori unknown complex virtual
worlds, namely those consisting of multilevel passages
(e.g. over and below a bridge). The algorithm is capable
of extracting all the information required for the actual
navigation of avatars, creating a hierarchical data
structure to help both high level path planning and low
level path finding decisions. The algorithm is image
based, hence it is tessellation independent, i.e. the
algorithm does not rely on the underlying polygonal
structure of the 3D world. Therefore, the number of
polygons does not have a significant impact on the
performance, and the topology has no weight on the
results.Fundação para a Ciência e a Tecnologi
Path planning for complex 3D multilevel environments
The continuous development of graphics hardware is
contributing to the creation of 3D virtual worlds with
high level of detail, from models of large urban areas, to
complete infrastructures, such as residential buildings,
stadiums, industrial settings or archaeological sites, to
name just a few. Adding virtual humans or avatars adds
an extra touch to the visualization providing an enhanced
perception of the spaces, namely adding a sense of scale,
and enabling simulations of crowds. Path planning for
crowds in a meaningful way is still an open research
field, particularly when it involves an unknown polygonal
3D world. Extracting the potential paths for navigation in
a non automated fashion is no longer a feasible option
due to the dimension and complexity of the virtual
environments available nowadays. This implies that we
must be able to automatically extract information from
the geometry of the unknown virtual world to define
potential paths, determine accessibilities, and prepare a
navigation structure for real time path planning and path
finding. A new image based method is proposed that
deals with arbitrarily a priori unknown complex virtual
worlds, namely those consisting of multilevel passages
(e.g. over and below a bridge). The algorithm is capable
of extracting all the information required for the actual
navigation of avatars, creating a hierarchical data
structure to help both high level path planning and low
level path finding decisions. The algorithm is image
based, hence it is tessellation independent, i.e. the
algorithm does not use the underlying polygonal structure
of the 3D world. Therefore, the number of polygons as
well as the topology, do not affect the performance