Figure 1: The camera-based interface. AbstractRecent advances in mobile computing allow the users to deal with 3D interactive graphics on handheld computers. Although the computing resources and screen resolutions grow steadily, user interfaces for handheld computers do not change significantly. Consequently, we designed a new 3-DOF interface adapted to the characteristics of handheld computers. This interface tracks the movement of a target that the user holds behind the screen by analyzing the video stream of the handheld computer camera. The position of the target is directly inferred from the color-codes that are printed on it using an efficient algorithm. The users can easily interact in realtime in a mobile setting. The visualization of the data is good as the target does not occlude the screen and the interaction techniques are not dependent on the orientation of the handheld computer. We used the interface in several test applications for the visualization of large images such as maps, the manipulation of 3D models, and the navigation in 3D scenes. This new interface favors the development of 2D and 3D interactive applications on handheld computers.

Terrain rendering is an important factor in the rendering of virtual scenes. If they are large and detailed, digital terrains can represent a huge amount of data and therefore of graphical primitives to render in real-time. In this paper we present an efficient technique for outof-core rendering of pseudo-infinite terrains. The full terrain height field is divided into regular tiles which are streamed and managed adaptively. Each visible tile is then rendered using a precomputed triangle strip patch selected in an adaptive way according to an importance metric. Thanks to these two levels of adaptivity, our approach can be seen as a cross-platform technique to render terrains on any kind of devices (from slow handheld to powerful desktop PC) by only exploiting the device capacity to draw as much triangles as possible for a target frame rate and memory space.

This paper presents a fast algorithm for smooth digital elevation model interpolation and approximation from scattered elevation data. The global surface is reconstructed by subdividing it into overlapping local subdomains using a perfectly balanced binary tree. In each tree leaf, a smooth local surface is reconstructed using radial basis functions. Finally a hierarchical blending is done to create the final C 1 -continuous surface using a family of functions called Partition of Unity. We present two terrain data sets and show that our method is robust since the number of data points in the Partition of Unity blending areas is explicitly specified.

Topographic paper maps are a common support for geographical information. In the field of document analysis of this kind of support, this paper proposes an automatic approach to extract and recognize toponyms. We present a technique based on image segmentation and connected component processing. Different filtering stages ensure the consistency of plausible characters and strings. Detected text areas are used to feed an OCR software and the recognized words are analyzed and corrected. The main advantage of our technique is that no assumption is made about the character font, size or orientation. Experimental results obtained are encouraging in term of recognition efficiency.