Fabrice Lamarche

A review of classification algorithms for EEG-based brain-computer interfaces

In this paper we review classification algorithms used to design brain-computer interface (BCI) systems based on electroencephalography (EEG). We briefly present the commonly employed algorithms and describe their critical properties. Based on the literature, we compare them in terms of performance and provide guidelines to choose the suitable classification algorithm(s) for a specific BCI.

A real-time cinematography system for interactive 3D environments

Developers of interactive 3D applications, such as computer games, are expending increasing levels of effort on the challenge of creating more narrative experiences in virtual worlds. As a result, there is a pressing requirement to automate an essential component of a narrative -- the cinematography -- and develop camera control techniques that can be utilized within the context of interactive environments in which actions are not known in advance. Such camera control algorithms should be capable of enforcing both low-level geometric constraints, such as the visibility of key subjects, and more elaborate properties related to cinematic conventions such as characteristic viewpoints and continuity editing. In this paper, we present a fully automated real-time cinematography system that constructs a movie from a sequence of low-level narrative elements (events, key subjects actions and key subject motions). Our system computes appropriate viewpoints on these narrative elements, plans paths between viewpoints and performs cuts following cinematic conventions. Additionally, it offers an expressive framework which delivers notable variations in directorial style. Our process relies on a viewpoint space partitioning technique in 2D that identifies characteristic viewpoints of relevant actions for which we compute the partial and full visibility. These partitions, to which we refer as Director Volumes, provide a full characterization over the space of viewpoints. We build upon this spatial characterization to select the most appropriate director volumes, reason over the volumes to perform appropriate camera cuts and rely on traditional path-planning techniques to perform transitions. Our system represents a novel and expressive approach to cinematic camera control which stands in contrast to existing techniques that are mostly procedural, only concentrate on isolated aspects (visibility, transitions, editing, framing) or do not encounter for variations in directorial style.

A Spatio-temporal Reasoning System for Virtual Camera Planning

The problem of virtual camera planning consists in computing camera paths in virtual environments that satisfy given cinematographic properties. In this article, we present a spatio-temporal query system for reasoning over the cinematographic expressiveness of a dynamic 3D scene. We offer a declarative language with quantifiers based on a first order logic representation. Prior to any query, we fully characterize each spatial and temporal region of the search-space according to a broad set of properties. We rely on interval-based constraint techniques to guarantee the completeness of the characterization. Then in order to answer a query, we build a digraph that connects over space and time the areas satisfying the request. The exploration of this digraph together with its connectivity properties provide the user with the identification of distinct classes of solutions as well as the full set of camera paths with their temporal validity. Applications are found in film prototyping, e.g. when a director needs to explore the staging, shot and editing possibilities in real world, by using virtual environments, or in automated and semi-automated editing.

Automated Staging for Virtual Cinematography

While the topic of virtual cinematography has essentially focused on the problem of computing the best viewpoint in a virtual environment given a number of objects placed beforehand, the question of how to place the objects in the environment with relation to the camera (referred to as staging in the film industry) has received little attention. This paper first proposes a staging language for both characters and cameras that extends existing cinematography languages with multiple cameras and character staging. Second, the paper proposes techniques to operationalize and solve staging specifications given a 3D virtual environment. The novelty holds in the idea of exploring how to position the characters and the cameras simultaneously while maintaining a number of spatial relationships specific to cinematography. We demonstrate the relevance of our approach through a number of simple and complex examples.