Nicolas Chevassus

Passive control architecture for virtual humans

In the present paper, we introduce a new control architecture aimed at driving virtual humans in interaction with virtual environments, by motion capture. It brings decoupling of functionalities, and also of stability thanks to passivity. We show projections can break passivity, and thus must be used carefully. Our control scheme enables task space and internal control, contact, and joint limits management. Thanks to passivity, it can be easily extended. Besides, we introduce a new tool as for manikins control, which makes it able to build passive projections, so as to guide the virtual manikin when sharp movements are needed.

Field-of-view tests for a virtual cockpit application

The virtual cockpit application aims to perform ergonom- ics studies on future aircraft cockpits, directly from digital mock-ups. This is made possible by immersing a user in a digital mock-up with the help of virtual reality devices. The challenge is then to reproduce a realistic and exact visual environment. To do that, some visual criteria have to be determined: the necessary values of visual acuity, temporal resolution, and field of view. Some of them are easy to find, but the field-of-view requirement is far more subjective and complex to evaluate. We present tests which have helped us to determine the necessary and sufficient values of field of view for such an ap- plication. We advise then to use a field of view higher than 75 deg, for ergonomic studies and good performances of the users, and up to 133 deg to increase visual comfort. These results will be used for the specification of a head-mounted display for the application.

A formal description of preparation processes for geometric models to improve downstream activities integration in the design process

In order to better integrate downstream applications - like simulation or virtual reality based applications - within design cycles, geometric data extracted from the digital mock-up need to be prepared and adapted to the needs and the constraints of these applications. In this paper, we propose to formalize the preparation process from the digital mock-up to an adapted database (AD). These processes allow not only transforming geometric data, but also creating a link between the initial data and the AD. The current computer implementation shows how this processes can be described and saved, in order to automate and capitalize processes, reduce preparation time, and finally enhance downstream applications integration within design.

Processes to Integrate Design With Downstream Applications Through Product Shapes Adaptation

In the aeronautics industry, various stages of a product development process such as physical phenomena (like stress, strain, and thermal ones) or virtual reality simulations are regarded as product views and based on different digital shapes of the same physical component. The shape adaptation processes needed to progress from one stage of the product development process to another one, the multiple shapes needed for a simulation at a given stage of this process are analyzed and shape adaptation operators are presented. Then, it is shown why geometric models adaptation processes from the design stage to downstream applications are important in an industrial design context, and why this is a concurrent engineering enabler. Subsequently, we show how shapes adaptation processes can be achieved through their appropriate formalization and representation using direct acyclic graphs connected to the scene structure of a simulation and the product structure used as input. A process data structure is also proposed to describe shape adaptation processes and ease their reuse. Finally, based on two EADS case studies, we illustrate how methods and criteria can be set up to produce adapted shapes from computer-aided design data in a controlled and integrated manner.

Digital mock-up database simplification with the help of view and application dependent criteria for industrial virtual reality application

Aircraft cockpits are advanced interfaces dedicated to the interaction and exchange of observations and commands between the pilot and the flying system. The design process of cockpits is benefiting from the use of Virtual Reality technologies: early ergonomics and layout analysis through the exploration of numerous alternatives, availability all along the cockpit life cycle of a virtual product ready for experimentation, reduced usage of costly physical mock-ups. Nevertheless, the construction of a virtual cockpit with the adequate performances is very complex. Due to the fact that the CAD based digital mock-up used for setting up the virtual cockpit is very large, one challenge is to achieve interactivity while maintaining the quality of rendering. The reduction of the information contained in the CAD database shall achieve a sufficient frame rate without degradation of the geometrical visual quality of the virtual cockpit which would alleviate the relevance of ergonomics and layout studies. This paper proposes to control the simplification process by using objective criteria based on considerations about the cockpit application and the visual performances of human beings. First, it presents the results of studies on the characteristics of the Human Visual System linked to virtual reality and visualization applications. Illustrated by first results, it establishes how to control simplifications in a rational and automatic way.