Controlling the contact levels of details for fast and precise haptic collision detection

For accurate and stable haptic rendering, collision detection for interactive haptic applications has to be done by filling in or covering target objects as tightly as possible with bounding volumes （spheres, axis-aligned bounding boxes, oriented bounding boxes, or polytopes）. In this paper, we propose a method for creating bounding spheres with respect to the contact levels of details （CLOD）, which can fit objects while maintaining the balance between high speed and precision of collision detection. Our method is composed mainly of two parts： bounding sphere formation and two-level collision detection. To specify further, bounding sphere formation can be divided into two steps： creating spheres and clustering spheres. Two-level collision detection has two stages as well： fast detection of spheres and precise detection in spheres. First, bounding spheres are created for initial fast probing to detect collisions of spheres. Once a collision is probed, a more precise detection is executed by examining the distance between a haptie pointer and each mesh inside the colliding boundaries. To achieve this refmed level of detection, a special data structure of a bounding volume needs to be defined to include all mesh information in the sphere. After performing a number of experiments to examine the usefulness and performance of our method, we have concluded that our algorithm is fast and precise enough for haptic simulations. The high speed detection is achieved through the clustering of spheres, while detection precision is realized by voxel-based direct collision detection. Our method retains its originality through the CLOD by distance-based clustering.

Modelling occupant behaviour for urban scale simulation:Review of available approaches and tools

Urban building energy modelling(UBEM)is considered one of the high-performance computational tools that enable analyzing energy use and the corresponding emission of different building sectors at large scales.However,the efficiency of these models relies on their capability to estimate more realistic building performance indicators at different temporal and spatial scales.The uncertainty of modelling occupants'behaviours(OB)aspects is one of the main reasons for the discrepancy between the UBEM predicted results and the building's actual performance.As a result,research efforts focused on improving the approaches to model OB at an urban scale considering different diversity factors.On the other hand,the impact of occupants in the current practice is still considered through fixed schedules and behaviours pattern.To bridge the gap between academic efforts and practice,the applicability of OB models to be integrated into the available UBEM tools needs to be analyzed.To this end,this paper aims to investigate the flexibility and extensibility of existing UBEM tools to model OB with different approaches by(1)reviewing UBEM's current workflow and the main characteristics of its inputs,(2)reviewing the existing OB models and identifying their main characteristics and level of details that can contribute to UBEM accuracy,(3)providing a breakdown of the occupant-related features in the commonly used tools.The results of this investigation are relevant to researchers and tool developers to identify areas for improvements,as well as urban energy modellers to understand the different approaches to model OB in available tools.

Domino Tiling:A New Method of Real-Time Conforming Mesh Construction for Rendering Changeable Height Fields

In this paper we present a novel GPU-oriented method of creating an inherently continuous triangular mesh for tile-based rendering of regular height fields. The method is based on tiling data-independent semi-regular meshes of non-uniform structure, a technique that is quite different from other mesh tiling approaches. A complete, memory efficient set of mesh patterns is created by an off-line procedure and stored into the graphics adapter＇s memory at runtime. At rendering time, for each tile, one of the precomputed mesh patterns is selected for rendering. The selected mesh pattern fits the required level of details of the tile and ensures seamless connection with other adjacent mesh patterns, like in a game of dominoes. The scalability potential of the proposed method is demonstrated through quadtree hierarchical grouping of tiles. The efficiency is verified by experimental results on height fields for terrain representation, where the method achieves high frame rates and sustained triangle throughput on high resolution viewports with sub-pixel error tolerance. Frame rate sensitivity to real-time modifications of the height field is measured, and it is shown that the method is very tolerant and consequently well tailored for applications dealing with rapidly changeable phenomena represented by height fields.