Adaptive Tesselation of Subdivision Surfaces

For a variety of reasons subdivision surfaces have developed into a prominent member of the family of freeform shapes. Based on a standard polygonal mesh a modeller can build various kinds of shapes using an arbitrary topology and special geometrical features like creases. However, the interactive display of subdivision surfaces in current scenegraph systems based on static levels of detail is unpractical, because of the exponentially increasing number of polygons during the subdivision steps. Therefore, an adaptive algorithm choosing only the necessary quads and triangles is required to obtain high-quality images at high frame rates. In this paper we present a rendering algorithm which dynamically adapts to static surface properties like curvature as well as to viewdependent properties like silhouette location and projection size. Without modifying the base mesh, the method works patchwise and tesselates each patch recursively using a new data structure, called slate. Besides these geometric properties the algorithm can also adapt to the graphics load in order to achieve a desired frame rate in the scenegraph system OpenSG

Evaluating experiences in different virtual reality setups

This paper describes the evaluation of three different scenarios in the fully immersive room-based virtual environment DAVE (Definitely Affordable Virtual Environment) and a head-mounted display, the Oculus Rift. The evaluation focuses on comparing the two immersive environments and three different scenarios (observation, emotion in a roller coaster, and interaction) in regards to typical virtual-reality characteristics, such as immersion, engagement, but also on cybersickness and the overall experience. First results indicate the DAVE environment better supports scenarios, which require the user to directly interact with the environment. The roller coaster scenario creates stronger immersion and a higher nausea-level, while the interactive task is more engaging in terms of fun

Using cognitive agent-based simulation for the evaluation of indoor wayfinding systems: A case study

This paper presents a novel approach to simulate human wayfinding behaviour incorporating visual cognition into a software agent for a computer aided evaluation of wayfinding systems in large infrastructures. The proposed approach follows the Sense-Plan-Act paradigm comprised of a model for visual attention, navigation behaviour and pedestrian movement. Stochastic features of perception are incorporated to enhance generality and diversity of the developed wayfinding simulation to reflect a variety of behaviours. The validity of the proposed approach was evaluated based on empirical data collected through wayfinding experiments with 20 participants in an immersive virtual reality environment using a life-sized 3D replica of Vienna's new central railway station. The results show that the developed cognitive agent-based simulation provides a further contribution to the simulation of human wayfinding and subsequently a further step to an effective evaluation tool for the pl anning of wayfinding and signage

Semi-Uniform, 2-Different Tessellation of Triangular Parametric Surfaces

With a greater number of real-time graphics applications moving over to parametric surfaces from the polygonal domain, there is an inherent need to address various rendering bottlenecks that could hamper the move. Scaling the polygon count over various hardware platforms becomes an important factor. Much control is needed over the tessellation levels, either imposed by the hardware limitations or by the application. Developers like to create applications that run on various platforms without having to switch between polygonal and parametric versions to satisfy the limitations. In this paper, we present SD-2 (Semi-uniform, 2-Different), an adaptive tessellation algorithm for triangular parametric surfaces. The algorithm produces well distributed and semi-uniformly shaped triangles as a result of the tessellation. The SD-2 pattern requires new approaches for determining the edge tessellation factors, which can be fractional and change continuously depending on view parameters. The factors are then used to steer the tessellation of the parametric surface into a collection of triangle strips in a single pass. We compare the tessellation results in terms of GPU performance and surface quality by implementing SD-2 on PN patches

A new modeling framework for multi-scale simulation of hydraulic fracturing and production from unconventional reservoirs

This paper describes a new modeling framework for microscopic to reservoir-scale simulations of hydraulic fracturing and production. The approach builds upon a fusion of two existing high-performance simulators for reservoir-scale behavior: the GEOS code for hydromechanical evolution during stimulation and the TOUGH+ code for multi-phase flow during production. The reservoir-scale simulations are informed by experimental and modeling studies at the laboratory scale to incorporate important micro-scale mechanical processes and chemical reactions occurring within the fractures, the shale matrix, and at the fracture-fluid interfaces. These processes include, among others, changes in stimulated fracture permeability as a result of proppant behavior rear-rangement or embedment, or mineral scale precipitation within pores and microfractures, at µm to cm scales. In our new modeling framework, such micro-scale testing and modeling provides upscaled hydromechanical parameters for the reservoir scale models. We are currently testing the new modeling framework using field data and core samples from the Hydraulic Fracturing Field Test (HFTS), a recent field-based joint research experiment with intense monitoring of hydraulic fracturing and shale production in the Wolfcamp Formation in the Permian Basin (USA). Below, we present our approach coupling the reservoir simulators GEOS and TOUGH+ informed by upscaled parameters from micro-scale experiments and modeling. We provide a brief overview of the HFTS and the available field data, and then discuss the ongoing application of our new workflow to the HFTS data set