Section: New Results

Path planning and environment analysis

Space-Time planning in dynamic environments

Participants : Fabrice Lamarche [contact] , Thomas Lopez.

When automatically populating 3D geometric databases with virtual humanoids, modeling the navigation behavior is essential since navigation is used in most exhibited behaviors. In many application fields, the need to manage navigation in dynamic environments arises (virtual worlds taking physics laws into account, numerical plants in which step stools can be moved,...). This study focuses on the following issue: how to manage the navigation of virtual entities in such dynamic environments where topology may change at any time i.e. where unpredictable accessibility changes can arise at runtime. In opposition to current algorithms, movable items are not only considered as obstacles in the environment but can also help virtual entities in their navigation.

The proposed algorithm [17] splits that problem into two complementary processes: a topology tracking algorithm and a path planning algorithm. The aim of the topology tracking algorithm is to continuously detect and update topological relations between moving objects i.e. accessibility or obstruction, while storing temporal information when recurring relations are observed. The path planning algorithm uses this information to plan a path inside the dynamic environment. The coupling of those algorithms endows a virtual character with the ability to immediately use inserted / moved object to reach previously unreachable locations. Moreover, this algorithm is able to find a path through moving platforms to reach a target located on a surface that is never directly accessible.

Automated environment analysis

Participants : Fabrice Lamarche [contact] , Carl-Johan Jorgensen.

To populate a virtual environment, modeling the navigation behavior is crucial. This behavior relies on the ability of planning a path inside a complex environment, which itself relies on an adequate representation of the environment structure. Most often, virtual environments are represented has 3D databases that are analyzed to produce data structures that are suitable for path planning and navigation. However, without any user intervention, those data structures lack of information about the nature of identified navigable zones that are crucial for navigation credibility.

We proposed an environment analysis algorithm [11] that automatically extracts a meaningful spatial representation of 3D virtual environments, suitable for spatial reasoning. This algorithm automatically differentiates indoor, outdoor and covered parts of the environment. It separates buildings into floors linked by stairs and represent floors as rooms linked by doorsteps. On this basis, we propose a natural hierarchical representation of the environment. This representation is used for spatial reasoning including zone selection and multi-criterion path planning that enhances path credibility.