Although ray tracing produces significantly more realistic images than traditional rasterization techniques, it is still considered computationally burdensome when implemented on a head-mounted display (HMD) system that demands both wide field of view and high rendering rate. A further challenge is that to present high-quality images on an HMD screen, a sufficient number of ray samples should be taken per pixel for effective antialiasing to reduce visually annoying artifacts. In this paper, we present a novel foveated real-time rendering framework that realizes classic Whitted-style ray tracing on an HMD system. In particular, our method proposes combining the selective supersampling technique by Jin et al. [8] with the foveated rendering scheme, resulting in perceptually highly efficient pixel sampling suitable for HMD ray tracing. We show that further enhanced by foveated temporal antialiasing, our ray tracer renders nontrivial 3D scenes in real time on commodity GPUs at high sampling rates as effective as up to 36 samples per pixel (spp) in the foveal area, gradually reducing to at least 1 spp in the periphery.

Despite the expected synergistic effects, augmented and virtual reality (AR and VR, respectively) technologies still tend to be discrete entities. In this paper, we describe our effort to enable both AR and VR users to share the same physical geometric space. The geometric transformation between two world spaces, defined separately by AR and VR systems, are estimated using a specially designed tracking board. Once initially obtained, the transformation will allow users to collaborate with each other within an integrated physical environment while making the best use of both AR and VR technologies.

The simple frame-to-frame tracking used for dense visual odometry is computationally efficient, but regarded as rather numerically unstable, easily entailing a rapid accumulation of pose estimation errors. In this paper, we show that a cost-efficient extension of the frame-to-frame tracking can significantly improve the accuracy of estimated camera poses. In particular, we propose to use a multi-level pose error correction scheme in which the camera poses are reestimated only when necessary against a few adaptively selected reference frames. Unlike the recent successful camera tracking methods that mostly rely on the extra computing time and/or memory space for performing global pose optimization and/or keeping accumulated models, the extended frame-to-frame tracking requires to keep only a few recent frames to improve the accuracy. Thus, the resulting visual odometry scheme is lightweight in terms of both time and space complexity, offering a compact implementation on mobile devices, which do not still have sufficient computing power to run such complicated methods.

Abstract Compared with its competitors such as the bounding volume hierarchy, a drawback of the kd‐tree structure is that a large number of triangles are repeatedly duplicated during its construction, which often leads to inefficient, large and tall binary trees with high triangle redundancy. In this paper, we propose a space‐efficient kd‐tree representation where, unlike commonly used methods, an inner node is allowed to optionally store a reference to a triangle, so highly redundant triangles in a kd‐tree can be culled from the leaf nodes and moved to the inner nodes. To avoid the construction of ineffective kd‐trees entailing computational inefficiencies due to early, possibly unnecessary, ray‐triangle intersection calculations that now have to be performed in the inner nodes during the kd‐tree traversal, we present heuristic measures for determining when and how to choose triangles for inner nodes during kd‐tree construction. Based on these metrics, we describe how the new form of kd‐tree is constructed and stored compactly using a carefully designed data layout. Our experiments with several example scenes showed that our kd‐tree representation technique significantly reduced the memory requirements for storing the kd‐tree structure, while effectively suppressing the unavoidable frame‐rate degradation observed during ray tracing.

Abstract Visualizing dynamic participating media in particle form by fully solving equations from the light transport theory is a computationally very expensive process. In this paper, we present a computational pipeline for particle volume rendering that is easily accelerated by the current GPU. To fully harness its massively parallel computing power, we transform input particles into a volumetric density field using a GPU‐assisted, adaptive density estimation technique that iteratively adapts the smoothing length for local grid cells. Then, the volume data is visualized efficiently based on the volume photon mapping method where our GPU techniques further improve the rendering quality offered by previous implementations while performing rendering computation in acceptable time. It is demonstrated that high quality volume renderings can be easily produced from large particle datasets in time frames of a few seconds to less than a minute.

Abstract Despite recent successes in physics‐based fluid animation, generating desired fluid flow with intuitive control of its motion still remains a challenging problem in the special effects industry. In this paper, we propose a novel approach for path‐based smoke simulation that explores the theory of chemical kinetics in an aim to provide a useful animation tool. By describing intended smoke effects through chemical reaction equations and adjusting their parameters, our method allows to easily create various interesting smoke effects that were often hard to get with previous techniques. To demonstrate the effectiveness of the presented animation framework, we describe several examples of path‐based smoke animations, generated with easily understandable reaction equations and control parameters. Copyright © 2009 John Wiley & Sons, Ltd.

Abstract The signed distance field for a polygonal model is a useful representation that facilitates efficient computation in many visualization and geometric processing tasks. Often it is more effective to build a local distance field only within a narrow band around the surface that holds local geometric information for the model. In this paper, we present a novel technique to construct a volumetric local signed distance field of a polygonal model. To compute the local field efficiently, exactly those cells that cross the polygonal surface are found first through a new voxelization method, building a list of intersecting triangles for each boundary cell. After their neighboring cells are classified, the triangle lists are exploited to compute the local signed distance field with minimized voxel‐to‐triangle distance computations. While several efficient methods for computing the distance field, particularly those harnessing the graphics processing unit's (GPU's) processing power, have recently been proposed, we focus on a CPU‐based technique, intended to deal flexibly with large polygonal models and high‐resolution grids that are often too bulky for GPU computation.

Abstract While linear interpolation has been used frequently in computer graphics, higher‐order interpolation is often desirable in applications requiring higher‐order accuracy. In this paper, we study how interpolation filters, employed to resample such data as velocity, density, and temperature in simulating the equations of fluid dynamics, affect the animation of fluids. For this purpose, we have designed a controllable local cubic interpolation scheme that offersG1(orC1) continuity globally. It is based on monotonic splines so does not suffer from undue overshooting. Furthermore, it is possible to control the general behavior of the interpolation through a global tension parameter, providing a continuous spectrum of linear to cubic interpolation. We analyze how this controllable interpolation filter may be effectively used to enhance the visual reality for physically based fluid animation. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract With the increased sophistication and use of heated gas, fire, and explosion simulations in computer graphics applications, there is a corresponding impetus to improve the visual realism in the rendering of such simulated phenomena. In visualizing these turbulent fluids, an appropriate incorporation of their incandescent properties into the rendering significantly enhances the realism of visual effects. In this paper, we effectively synthesize the light emission phenomena of hot gaseous fluids by extending the photon mapping global illumination method. In particular, we add two new photon maps to capture the thermal radiation effects. First, we define anemissionphoton map to store the photons emitted within hot gaseous fluids. Second, we utilize additionalflashandflash reflectionphoton maps, which are effective in creating a visual effect of light that intensively and instantly propagates outside hot gaseous fluids, visually capturing shock waves. Our current technique, while based on the theory of blackbody radiation, is parameterized to enable an animator to generate a wide range of visual effects with fairly intuitive user control. We demonstrate the effectiveness of our new rendering technique and user‐controlled generation of visual effects with several example pictures and animations. Copyright © 2005 John Wiley & Sons, Ltd.

The increased programmability of graphics hardware allows efficient graphical processing unit (GPU) implementations of a wide range of general computations on commodity PCs. An important factor in such implementations is how to fully exploit the SIMD computing capacities offered by modern graphics processors. Linear expressions in the form of ȳ = Ax̄ + b̄, where A is a matrix, and x̄, ȳ and b̄ are vectors, constitute one of the most basic operations in many scientific computations. In this paper, we propose a SIMD code optimization technique that enables efficient shader codes to be generated for evaluating linear expressions. It is shown that performance can be improved considerably by efficiently packing arithmetic operations into four-wide SIMD instructions through reordering of the operations in linear expressions. We demonstrate that the presented technique can be used effectively for programming both vertex and pixel shaders for a variety of mathematical applications, including integrating differential equations and solving a sparse linear system of equations using iterative methods.

When interactive real-time applications are developed with very large volume data, the use of lossy compression is often inevitable. Lossy compression schemes generally encode data without consideration of the purpose of visualization that is actually performed, which often results in inefficient compression. In this paper, we present a new method for classifying voxels according to their importance in visualization, and assigning appropriate weights to them. The associated weight information can be combined with lossy compression schemes to reduce the visual degradation of reconstructed images, resulting in higher compression rates and visual fidelity. Test results demonstrate that the proposed technique improves both the amount of compression and the quality of visualization significantly.

This paper presents a new 3D RGB image compression scheme designed for interactive real-time applications. In designing our compression method, we have compromised between two important goals: high compression ratio and fast random access ability, and have tried to minimize the overhead caused during run-time reconstruction. Our compression technique is suitable for applications wherein data are accessed in a somewhat unpredictable fashion, and real-time performance of decompression is necessary. The experimental results on three different kinds of 3D images from medical imaging, image-based rendering, and solid texture mapping suggest that the compression method can be used effectively in developing real-time applications that must handle large volume data, made of color samples taken in three- or higher-dimensional space.

While 2D texture mapping is one of the most powerful rendering techniques that make 3D objects appear visually interesting, it suffers from visual artifacts produced when 2D image patterns are wrapped onto the surface of objects with arbitrary shapes. On the other hand, 3D texture mapping generates highly natural visual effects in which objects appear carved from lumps of materials rather than laminated with thin sheets as in 2D texture mapping. Storing 3D texture images in a table for fast mapping computations, instead of evaluating procedures on the fly, however, has been considered impractical due to the extremely high memory requirements. In this paper, we present a new effective method for 3D texture mapping designed for real-time rendering of polygonal models. Our scheme attempts to resolve the potential texture memory problem arising from the very large size of 3D images by compressing them using a wavelet-based encoding method. The experimental results on various non-trivial 3D textures and polygonal models show that high compression rates are achieved with few visual artifacts in the rendered image and a small impact on rendering time. The simplicity of our compression-based scheme will make it possible to implement practical 3D texture mapping in software/hardware rendering systems including the real-time 3D graphics APIs like OpenGL and Direct3D.

Interactive visualization of very large volume data has been recognized as a task requiring great effort in a variety of science and engineering fields. In particular, such data usually places considerable demands on run‐time memory space. In this paper, we present an effective 3D compression scheme for interactive visualization of very large volume data, that exploits the power of wavelet theory. In designing our method, we have compromised between two important factors: high compression ratio and fast run‐time random access ability. Our experimental results on the Visual Human data sets show that our method achieves fairly good compression ratios. In addition, it minimizes the overhead caused during run‐time reconstruction of voxel values. This 3D compression scheme will be useful in developing many interactive visualization systems for huge volume data, especially when they are based on personal computers or workstations with limited memory.

A plenoptic function is a parameterized function describing the flow of light in space, and has served as a key idea in building some of the recent image based rendering systems. The paper presents a new representation scheme, called a spherical light field, of the plenoptic function, that is based on spheres. While methods using spherical coordinates are thought to require substantially more computation than those using planar or cylindrical coordinates, we show that spheres can also be used efficiently in representing and resampling the flow of light. Our image based rendering algorithm is different from the previous systems, the light field and lumigraph, in that it is an "object space" algorithm that can be easily embedded into the traditional polygonal rendering system. Our method is easily accelerated by 3D graphics boards that support the primitive functionality, such as viewing and smooth shading. In addition, we introduce an encoding scheme based on wavelets for compression of the huge data resulting from sampling of the spherical light field. The proposed technique can be easily adapted to compress the light field and lumigraph data, and offers as high compression ratios as the previous methods. Furthermore, it naturally creates a multi resolutional representation of the light flow that can be exploited effectively in the future applications. We show how to access the compressed data efficiently using a modified significance map and an incremental decoding technique, and report experimental results on several test data sets.

Splatting is an object space direct volume rendering algorithm that produces images of high quality, but is computationally expensive like many other volume rendering algorithms. The paper presents a new technique that enhances the speed of splatting without trading off image quality. This new method reduces rendering time by employing a simple indexing mechanism which allows to visit and splat only the voxels of interest. It is shown that this algorithm is suitable for the dynamic situation in which viewing parameters and opacity transfer functions change interactively. We report experimental results on several test data sets of useful site and complexity, and discuss the cost/benefit trade off of our method.

In this article, we characterize the solution space of low-degree, implicitly defined, algebraic surfaces which interpolate and/or least-squares approximate a collection of scattered point and curve data in three-dimensional space. The problem of higher-order interpolation and least-squares approximation with algebraic surfaces under a proper normalization reduces to a quadratic minimization problem with elegant and easily expressible solutions. We have implemented our algebraic surface-fitting algorithms, and included them in the distributed and collaborative geometric environment SHASTRA. Several examples are given to illustrate how our algorithms are applied to algebraic surface design.

Polyhedron "smoothing" is an efficient construction scheme for generating complex boundary models of solid physical objects.This paper presents efficient algorithms for generating families of curved solid objects with boundaty topology related to an input polyhedron.Individual faces of a polyhedron are replaced by low degree implicit algebraic surface patches with local support.These quintic patches replace the @ contacts of planar facets with C' continuity along all irtterpatch boundaries.Selection of suitable instances of implicit surfaces as well as local control of the individual surface patches are achieved via simultaneouss interpolation and weighted least-squares approximation.

This paper presents an efficient algorithm called Hermite interpolation, for constructing low-degree algebraic surfaces, which contain, with C 1 or tangent plane continuity, any given collection of points and algebraic space curves having derivative information. Positional as well as derivative constraints on an implicitly defined algebraic surface are translated into a homogeneous linear system, where the unknowns are the coefficients of the polynomial defining the algebraic surface. Computaional details of the Hermite interpolation algorithm are presented along with several illustrative applications of the interpolation technique to construction of joining or blending surfaces for solid models as well as fleshing surfaces for curved wire frame models. A heuristic approach to interactive shape control of implicit algebraic surfaces is also given, and open problems in algebraic surface design are discussed.

We present a simple characterization of the lowest degree, implicitly defined, real algebraic surfaces, which smoothly contain any given number of points and algebraic space curves, of arbitrary degree. The characterization is constructive, yielding efficient algorithms for generating families of such algebraic surfaces. Smooth containment of space curves yields C1-continuous surface fitting, and is a generalization of standard Hermite interpolation applied to fitting curves through point data, equating derivatives at those points. We deal with the containment and matching of “normals” (vectors orthogonal to tangents), possibly varying along the entire span of the space curves. Such Hermite interpolated surfaces prove useful as “blending” or “joining” surfaces for solid models as well as “fleshing” surfaces for curved wireframe models.