Yoshimasa Tokuyama

3D terrain reconstruction based on contours

In 3D terrain reconstruction, the differences of shape and topology among contours in adjacent sections cause a difficulty as the tiling problem of branching terrain. In this paper, we present a brief and pure geometrical algorithm to reconstruct 3D terrain based on contours. The merit of our method is that the tiling rules guarantee arbitrary branching terrain can be divided into correct topology.

Reconstruction Method of Trimmed Surfaces Maintaining G1-Continuity with Adjacent Surfaces

In 3D CAD systems, reconstruction of trimmed surfaces is one of the important research topics. When 3D CAD data is exchanged between different CAD systems, it does not deliver the specifications of CAD systems completely. Therefore, we have to correct the CAD data, such as moving the point in order to fill gaps. Generally, CAD data is expressed by set of trimmed surfaces. Then, we need to modify the trimmed surfaces. It is necessary, however, to modify the trimmed surface shape so as to maintain geometrical consistency of the boundary edges and surfaces in direct modeling, and this is a big restriction. It is effective to apply a new free-form surface to a closed region enclosed with the modified edges because the consistency of a trimmed surface can be maintained. Many shapes with holes or concave shapes are included in CAD data. Moreover, it is necessary to consider maintaining G1-continuity with adjacent surfaces, but it is difficult to reconstruct the trimmed surface by the conventional surface fittin...

Virtual Reconstruction and Visualization of Pre and Proto Historic Landscapes in Srilanka

3D Computer graphics and advanced media technologies have long been used to preserve or virtually visualize cultural heritage sites. While a number of research work on preservation and virtual reconstructions of archeological sites in Europe and Egypt, less effort has been spent on introducing new technologies to visualize and preserve cultural heritage sites in some other regions of the world like south Asia. This research presents a case study focused on the virtual visualization and simulation of pre and proto historic landscapes in Sri Lanka. The transition between prehistory and protohistory of Sri Lanka is not precisely clear, that would have occurred in the mid or late Holocene. Recently, archeological researchers have focused on the proto historic culture of the Uda Walave River Basin in Sri Lanka. This area has identified as an environmentally optimal area apt to probe the question of pre and proto historic transition in Sri Lanka. The main goal of this paper is to visualize and virtually reconstruct pre and proto historic culture in the Uda Walave River Basin; based on recent archeological data and findings.

High-quality Approximation Technique for Two G1-continuous Offset Surfaces

This paper proposes a technique for approximating two G1-continuous offset surfaces. Since offset surfaces are in general not rational representation, spline approximations of offset surfaces are widely used. However, when two G1-continuous offset surfaces are approximated using existing methods, the shape data quality is reduced because gaps or creases arise between two approximated surfaces. Our technique generates two G1-continuous approximated surfaces represented by C1-continuous bicubic B-spline surfaces. The approximated surfaces are higher quality than those generated using existing methods, because no gaps or creases arise between those surfaces.

Real-time rendering of colour-shift effect of metallic materials

The directional-dependent effects of the materials are responsible for our perception of certain materials being realistic or not. Some materials consist of colour pigments, and these cause directional-dependent colour variations (or colour-shifts). For instance, we can observe a colour-shift effect of metallic materials, which means the changing of colour from metallic colour to pigment colour depending on the direction of incident illumination and direction of view. The most common criticism of existing analytical Bidirectional Reflectance Distribution Function (BRDF) models is that these models are inadequate to generate colour-shift effect of materials for realistic real-time rendering. This paper introduces a visually plausible shading model to generate colour-shift effect of metallic materials by modifying specular component with illumination and view dependent sheen. The developed shaders have intuitive parameters, which can generate different kinds of metallic effects for real-time rendering, including visually plausible gold, brass, silver, bronze and copper effects for real-time rendering.