In terrain visualization, the quadtree is the most frequently used data structure for progressive mesh generation. The quadtree provides an efficient level of detail selection and view frustum culling. However, most applications using quadtrees are performed on the CPU, because the pointer and recursive operation in hierarchical data structure cannot be manipulated in a programmable rendering pipeline. We present a quadtree-based terrain rendering method for GPU (Graphics Processing Unit) execution that uses vertex splitting and triangle splitting. Vertex splitting supports a level of detail selection, and triangle splitting is used for crack removal. This method offers higher performance than previous CPU-based quadtree methods, without loss of image quality. We can then use the CPU for other computations while rendering the terrain using only the GPU.

In this paper, we discuss both effective approaches in specification process, formal specification and reuse, and focus on providing an integrated and systematic supportbased on them. Preparing the specification model which mediates an image of the designer and another representation of it in formal method, the designer can specify the target system incrementally and smoothly. As for the specification model, we employ LTS on the early step of specification process because of its understandability for the designer. Moreover, reuse of specification leads to reduction of the cost and time, defining retrieval mechanism of reusable cases from database by mathematically calculating similarity of them. For the reuse mechanism, we define a new concept of similarity on LTS as the criterion of case retrieval, which enables more flexible matching between the besigner's requirement and the existing case than any other traditional schema on LTS, and show the case retrieval algorithm. Integration of two approaches brings us the great improvement of the productivity on system development.

This paper presents an effective application of Net-theory for all the stages of the communication protocol development process. Net-theory provides a basic mathematical model and tool for development of communication protocol. The special usability of Net-theory is that 1) visual representation of the system's stadic/dynamic structure, so that users may easily understand the represented contents, 2) formal specifications based on mathematical basis of Net-theory admit automatic verification, implementation and conformance testing. We have seen that Net-theory which has the above usability can provide a systematic and advanced paradigm for effective communication protocol development.

This paper presents unique specification environments for LOTOS, which is one of FDTs (Formal Description Techniques) developed in ISO. We first discuss the large gap in terms of syntax and semantics between informal specifications at the early stage of specification design and formal specifications based on FDT such as LOTOS. This large gap has been bridged by human intelligent works thus far. In order to bridge the large gap, we have designed user-friendly specification environments for FDTs. The outlines of SEGL (Specification Environment for G-LOTOS), CBP (Concept-Based Programming environment) and MBP (Model-Based Programming environment) are described. The effectiveness of software development under such an environment is demonstrated using application examples from OSI and non-OSI protocols.

Massive digital elevation models require a large number of geometric primitives that exceed the throughput of the existing graphics hardware. For the interactive visualization of these datasets, several adaptive reconstruction methods that reduce the number of primitives have been introduced over the decades. Quadtree triangulation, based on subdivision of the terrain into rectangular patches at different resolutions, is the most frequently used terrain reconstruction method. This usually accomplishes the triangulation using LOD (level-of-detail) selection and crack removal based on geometric errors. In this paper, we present bimodal vertex splitting, which performs LOD selection and crack removal concurrently on a GPU. The first mode splits each vertex for LOD selection and the second splits each vertex for crack removal. By performing these two operations concurrently on a GPU, we can efficiently accelerate the rendering speed by reducing the computation time and amount of transmission data in comparison with existing quadtree-based rendering methods.