Hybrid transparency is an approach for real-time approximation of order-independent transparency. Our hybrid approach combines an accurate compositing, of a few core transparent layers, with a quick approximation, for the remaining layers. Its main advantage, the ability to operate in bounded memory without noticeable artifacts, enables its usage with high scene complexity and image resolution, which other approaches fail to handle. Hybrid transparency is suitable for highly-parallel execution, can be implemented in current GPUs and further improved, with minimal architecture changes. We present quality, memory, and performance analysis and comparisons which demonstrate that hybrid transparency is able to generate high-quality images at competitive frames rates and with the lowest memory consumption among comparable OIT techniques.

Path planning is an active topic in the literature, and efficient navigation over non-planar surfaces is an open research question. In this work we present a novel technique for navigation of multiple agents over arbitrary triangular domains. The proposed solution uses a fast hierarchical computation of geodesic distances over triangular meshes to allow interactive frame rates, and a GPU-based collision avoidance technique to guide individual agents. Unlike most previous work, the method imposes no limitations on the surface over which the agents are moving, and can naturally deal with non-planar meshes of arbitrary genus and curvature. Moreover, the implementation is a hybrid CPU/GPU algorithm that explores the current trend of increasing the number of CPU cores and GPU programmability. This approach exploits the best qualities in each processor, thus achieving very high performance.

Abstract There is a vast number of applications that require distance field computation over triangular meshes. State‐of‐the‐art algorithms have quadratic or sub‐quadratic worst‐case complexity, making them impractical for interactive applications. While most of the research on this subject has been focused on reducing the computation complexity of the algorithms, in this work we propose an approximate algorithm that achieves similar results working in lower resolutions of the input meshes. The creation of lower resolution meshes is the essence of our proposal. The idea is to identify regions on the input mesh that can be unfolded into planar regions with minimal area distortion (i.e. quasi‐developable charts). Once charts are computed, their interior is re‐triangulated to reduce the number of triangles, which results in a collection of simplified charts that we call a base mesh. Due to the properties of quasi‐developable regions, we are able to compute distance fields over the base mesh instead of over the input mesh. This reduces the memory footprint and data processed for distance computations, which is the bottleneck of these algorithms. We present results that are one order of magnitude faster than current exact solutions, with low approximation errors.

Abstract We present the first computer graphics algorithm designed to simulate the aurora, a natural phenomenon of great visual beauty and considerable scientific interest. The algorithm is based on the current understanding of the physical origin of this natural display. The aurorae are mainly caused by high‐energy electrons originating in the sun and entering the earth's atmosphere in narrow regions centered on the magnetic poles. These electrons collide with atmospheric atoms, which are excited to higher energy levels. The excited atoms emit rapidly varying visible light in a curtain‐like volume as they return to lower energy levels, thereby creating the aurora. By simulating these light emissions along with the spatial and temporal distribution of the entering electrons, we are able to render the major visual aspects of auroral displays. The applicability of this auroral model for rendering and scientific purposes is illustrated through comparisons of synthetic images with photographs of real auroral displays. Copyright © 2003 John Wiley & Sons, Ltd.

We present an algorithm to simulate the aurora borealis, commonly known as the "northern lights", a natural phenomenon of great visual beauty and considerable scientific interest. The algorithm is based on the current understanding of the physical origin of the aurora. This natural display is mainly caused by high-energy electrons originating in the Sun and entering the Earth's atmosphere in narrow regions centered on the magnetic poles. These electrons collide with atmospheric atoms which are excited to higher energy levels. The excited atoms emit rapidly varying visible light in a curtain-like volume as they return to lower energy levels thereby creating the aurora. By simulating these light emissions along with the spatial and temporal distribution of the entering electrons, we are able to render the major visual aspects of auroral displays. This approach also allows the representation of time-dependent features that characterize the dynamic nature of the aurorae. The applicability of this auroral model for artistic and research purposes is illustrated through comparisons of synthetic images with photographs of real auroral displays.

We present a system for rendering very complex 3D models at interactive rates.We select a subset of the model as preferred viewpoints and partition the space into virtual cells.Each cell contains near geometry, rendered using levels of detail and visibility culling, and far geometry, rendered as a textured depth mesh.Our system automatically balances the screen-space errors resulting from geometric simplification with those from textureddepth-mesh distortion.We describe our prefetching and data management schemes, both crucial for models significantly larger than available system memory.We have successfully used our system to accelerate walkthroughs of a 13 million triangle model of a large coal-fired power plant and of a 1.7 million triangle architectural model.We demonstrate the walkthrough of a 1.3 GB power plant model with a 140 MB cache footprint.

This paper presents a new method for interactive rendering of globally illuminated static scenes. Global illumination is decomposed into view-independent (diffuse) and view-dependent (non-diffuse) components. The two are recombined during rendering using a hybrid geometry- and image-based approach along with multi-pass blending techniques. This approach allows the preprocessing of both components and the fast rendering of globally illuminated scenes. The view-independent component uses a traditional precomputed geometry-based radiosity solution that is rendered using standard graphics hardware. The view-dependent component is decomposed into “what is reflected ” (radiance with depth) and “how it is reflected ” (BRDF), and precomputed and rendered using image-based approaches. Radiance is stored as images with depth, and rendered using perspective reprojection; the BRDF is decomposed into an integration of incoming radiance and a directional modulation. The radiance integration term is approximated by convolving the reflected image with precomputed kernel textures based on material properties. The directional modulation is stored as a reflectance modulation texture based on material properties and is rendered using spheremapping during a blending pass.

A study by Slater, et al., [1995] indicated that naive subjects in an immersive virtual environment experience a higher subjective sense of presence when they locomote by walking-in-place (virtual walking) than when they push-button-fly (along the floor plane).We replicated their study, adding real walking as a third condition.Our study confirmed their findings.We also found that real walking is significantly better than both virtual walking and flying in ease (simplicity, straightforwardness, naturalness) as a mode of locomotion.The greatest difference in subjective presence was between flyers and both kinds of walkers.In addition, subjective presence was higher for real walkers than virtual walkers, but the difference was statistically significant only in some models.Follow-on studies show virtual walking can be substantially improved by detecting footfalls with a head accelerometer.As in the Slater study, subjective presence significantly correlated with subjects' degree of association with their virtual bodies (avatars).This, our strongest statistical result, suggests that substantial potential presence gains can be had from tracking all limbs and customizing avatar appearance.An unexpected by-product was that real walking through our enhanced version of Slater's visual-cliff virtual environment (Figure 1) yielded a strikingly compelling virtual experience-the strongest we and most of our visitors have yet experienced.The most needed system improvement is the substitution of wireless technology for all links to the user.

Wepresenta method to speed up walkthmttghs of static scenes.It involves the cmatiort of acmttimsous C1 radiosity reconstruction for adaptively sampled tegiotts.This mpmaentation is a unitied solution to handle usuestricted quadtrees and T-vertices, and allows for the generation of multiple different levels-of-detail of the radiosity function, which are represented as texture maps.The method also involves the use of hardwase bicublc filtering for the mdiosity shading.Both techniques allow improvenmts in performance and memory usage while preserving visual appearance.