Recent advances in crowd simulation techniques have led to realistic agent and group behavior through elaborate behavioral models, complex motion planning algorithms and impressive physics systems. As many crowd simulation solutions typically target only specific types of environment and scenario, a variety of special-purpose methods and systems has emerged that are hard to re-configure and re-use in other contexts. Solving this situation demands a higher-level approach that takes re-use and configuration of crowds as a priority, for adequate application in a broad variety of scenarios, virtual environments and inter- action with the entities present in that environment. In this article we propose semantic crowds, a novel approach that allows one to re-use the same crowds for virtually any environment, and have them use the objects available in it in a meaningful manner, without any modification. To have the agents autonomously interact within any virtual world, we minimize in them the information relative to what objects do and how to use them. Instead, that information is stored in the objects themselves, which the agents can then query, based on what they plausibly want to achieve. To facilitate creating such crowds, we devel- oped an interactive crowd editor that provides high-level editing parameters for defining crowd templates. We illustrate the flexibility of semantic crowds by means of two cases, in which we let the same crowd populate quite differently configured airport terminal environments. These examples also highlight that this modular approach easily combines with your custom implementations of agent behavior model and/or motion planner.@en

Developing strategies to mitigate or to adapt to the threats of floods is an important topic in the context of climate changes. Many of the world’s cities are endangered due to rising ocean levels and changing precipitation patterns. It is therefore crucial to develop analytical tools that allow us to evaluate the threats of floods and to investigate the influence of mitigation and adaptation measures, such as stronger dikes, adaptive spatial planning, and flood disaster plans. Up until the present, analytical tools have only been accessible to domain experts, as the involved simulation processes are complex and rely on computational and data-intensive models. Outputs of these analytical tools are presented to practitioners (i.e., policy analysts and political decision-makers) on maps or in graphical user interfaces. In practice, this output is only used in limited measure because practitioners often have different information requirements or do not trust the direct outcome. Nonetheless, literature indicates that a closer collaboration between domain experts and practitioners can ensure that the information requirements of practitioners are better aligned with the opportunities and limitations of analytical tools. The objective of our work is to present a step forward in the effort to make analytical tools in flood management accessible for practitioners to support this collaboration between domain experts and practitioners. Our system allows the user to interactively control the simulation process (addition of water sources or influence of rainfall), while a realistic visualization allows the user to mentally map the results onto the real world. We have developed several novel algorithms to present and interact with flood data. We explain the technologies, discuss their necessity alongside test cases, and introduce a user study to analyze the reactions of practitioners to our system. We conclude that, despite the complexity of flood simulation models and the size of the involved data sets, our system is accessible for practitioners of flood management so that they can carry out flood simulations together with domain experts in interactive work sessions. Therefore, this work has the potential to significantly change the decision-making process and may become an important asset in choosing sustainable flood mitigations and adaptation strategies.@en

Procedural modelling is an attractive alternative to cut down the costs of manual content creation for virtual worlds. We discuss our declarative modelling approach to the creation of 3D virtual worlds, which integrates a variety of procedural techniques in order to enable a non-specialist user to interactively create a complete 3D virtual world in minutes. In particular, we introduce procedural sketching, a novel paradigm which allows designers to quickly specify and see the effects of their procedural modelling operations, and describe its main features as implemented in our prototype system SketchaWorld. Two main interaction modes are described, for specifying the landscape and terrain features, respectively. Our approach automatically fits all generated terrain features with their surroundings, for example by smoothing out rough terrain for roads, or creating a bridge to cross a river. It is concluded that this approach provides designers with the productivity gain of procedural methods, while still allowing for fine user control and actively supporting iterative modelling.@en

Current game worlds often fall short in providing consistency between the visual representation of the world and the way it feels, behaves, and reacts. This problem partly originates from the goaloriented and cost-effective nature of the game development process, which mostly favors ad hoc solutions for one particular game, rather than investing in concepts like reusability and emergent gameplay. In broader terms, we observe that game worlds miss semantics, and we argue that its deployment has the potential to bring about the consistency missing in their content. Therefore, we present a novel approach aimed at enriching virtual entities in game worlds with information about their roles, how they relate to others, and how they can affect and interact with players, NPCs, and with each other. We discuss several requirements to achieve these goals, and introduce a semantic model to represent game worlds. In order to support and validate this model, we have developed Entika, a framework to facilitate the deployment of semantics during game development, as well as its maintenance during run-time. Furthermore, we briefly discuss several applications that demonstrate the power of this semantic model for game worlds. After careful evaluation of our semantic game world model and framework, we conclude that a semantically rich world representation can substantially assist designers in creating much more consistent game worlds.@en

With the ever increasing costs of manual content creation for virtual worlds, the potential of creating it automatically becomes too attractive to ignore. However, for most designers, traditional procedural content generation methods are complex and unintuitive to use, hard to control, and generated results are not easily integrated into a complete and consistent virtual world. We introduce a novel declarative modeling approach that enables designers to concentrate on stating what they want to create instead of on describing how they should model it. It aims at reducing the complexity of virtual world modeling by combining the strengths of semantics-based modeling with manual and procedural approaches. This article describes two of its main contributions to procedural modeling of virtual worlds: interactive procedural sketching and virtual world consistency maintenance. We discuss how these techniques, integrated in our modeling framework SketchaWorld, build up to enable designers to create a complete 3D virtual world in minutes. Procedural sketching provides a fast and more intuitive way to model virtual worlds, by letting designers interactively sketch their virtual world using high-level terrain features, which are then procedurally expanded using a variety of integrated procedural methods. Consistency maintenance guarantees that the semantics of all terrain features is preserved throughout the modeling process. In particular, it automatically solves conflicts possibly emerging from interactions between terrain features. We believe that these contributions together represent a significant step towards providing more user control and flexibility in procedural modeling of virtual worlds. It can therefore be expected that by further reducing its complexity, virtual world modeling will become accessible to an increasingly broad group of users. @en

Semantics of 3D models is playing a crucial role in games and simulations. In this paper we propose a framework to specify semantics of large sets of 3D models with minimal human involvement. The framework consists of three modules: classification, segmentation and annotation. We associate a few models with tags representing their classes and classify the other models automatically. Once all models have been classified in different groups, we take a certain number of models as template models in each group, and segment these template models interactively. We then use the segmentation method (and parameters) of the template models to segment the rest of the models of the same group automatically. We annotate the interactively segmented parts and use an attributed adjacency graph to represent them. Automatic annotation of the rest of the models is then performed by subgraph matching. Experiments show that the proposed framework can effectively specify semantics of large sets of 3D models.@en

Object modeling for applications like CAD/CAM, simulation and computer games, has traditionally been limited to the shape of objects. Currently, a trend can be observed to add several types of semantics to object models. This observation is discussed in some detail for three modeling approaches worked on in our research group: feature modeling, including recent advances for freeform features, modeling families of objects, and modeling virtual worlds. The use of semantics in some other modeling approaches is briefly discussed. Adding semantics can ease specification and modification of an object model, help to guarantee its validity, and be useful for applications which use the model, such as process planning for manufacturing or gameplay. Much work remains to be done to determine the types of semantics most useful in practice.@en