Section: New Results
Autonomous Virtual Humans
Unifying activity scheduling and path-planning
Participants : Carl-Johan Jorgensen, Fabrice Lamarche [contact] .
Crowd distribution in cities highly depends on how people schedule their daily activities. This schedule depends on temporal constraints like appointments or shops opening times. It also relies on the city structure and the locations of the places where activities can be achieved. Personal preferences also affect this schedule: choosing favorite shops or paths for instance.
Within the framework of iSpace&Time project, we are currently working on a model that unifies activity scheduling and path planning into a single process. This process takes city topological configuration into account, as well as time constraints and personal preferences. Applied to thousands of agents, his approach allows us to credibly populate cities. Credible flows of people automatically emerge depending on the time of the day and the city topology.
Long term planning and opportunism
Participants : Philippe Rannou, Fabrice Lamarche [contact] .
Autonomous virtual characters evolve in dynamic virtual environments in which changes may be unpredictable. However, they need to behave properly and adapt their behavior to perceived changes while fulfilling their goals. We propose a system that combines long term action planning with failure anticipation and opportunism  . The system is based on a modified version of an HTN planning algorithm. It generates plans enriched with information that enable a monitor to detect relevant changes of the environment. Once those changes are detected, a plan adaptation is triggered. Such adaptations include modifying the plan to react to a predicted failure and more importantly to exploit opportunities offered by the environment.
Space-Time planning in dynamic environments
Participants : Thomas Lopez [contact] , Fabrice Lamarche [contact] .
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  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.