Despite increasing popularity of stereo capture and display systems, creating stereo artwork remains a challenge. This paper presents a stereo painting system, which enables effective from-scratch creation of high-quality stereo artwork. A key concept of our system is a stereo layer, which is composed of two RGBAd (RGBA + depth) buffers. Stereo layers alleviate the need for fully formed representational 3D geometry required by most existing 3D painting systems, and allow for simple, essential depth specification. RGBAd buffers also provide scalability for complex scenes by minimizing the dependency of stereo painting updates on the scene complexity. For interaction with stereo layers, we present stereo paint and stereo depth brushes, which manipulate the photometric (RGBA) and depth buffers of a stereo layer, respectively. In our system, painting and depth manipulation operations can be performed in arbitrary order with real-time visual feedback, providing a flexible WYSIWYG workflow for stereo painting. Our data structures allow for easy interoperability with existing image and geometry data, enabling a number of applications beyond from-scratch art creation, such as stereo conversion of monoscopic artwork and mixed-media art. Comments from artists and experimental results demonstrate that our system effectively aides in the creation of compelling stereo paintings.

Stereoscopic 3D exploits the effects of stereopsis where the depth perception is triggered by binocular disparity, a difference in image location of an object by the left and right eyes. Despite the dissimilarity of stereo projections in terms of disparity and shape, the human visual system can find the matching stereo pair to fuse using their similarities in terms of color, size, shading, texture, shadows, that are normally present in photorealistic stereo imaging. Now if some of these elements (or depth cues) are missing, such as in non-photorealistic stereo imaging, how will it affect the depth perception and stereo fusion? In this paper, we investigate this issue by conducting a perceptual study on stereoscopic 3D line drawing, in which many of these cues have been abstracted away. We first evaluate the validity of using stereo images composed of lines only, and then compare its performance to stereo images of normal shading. We also examine the effect of changing line style as well as the prospect of using lines as an additional depth cue. Our study shows that stereo line drawing, when compared to stereo shading, does weaken the depth perception but only to a minor degree. On the other hand, modification of line style, and superimposition of stereo lines both have potentials to strengthen the perception of depth.

Despite increasing popularity of stereo capture and display systems, creating stereo artwork remains a challenge. This paper presents a stereo painting system, which enables effective from-scratch creation of high-quality stereo artwork. A key concept of our system is a stereo layer, which is composed of two RGBAd (RGBA + depth) buffers. Stereo layers alleviate the need for fully formed representational 3D geometry required by most existing 3D painting systems, and allow for simple, essential depth specification. RGBAd buffers also provide scalability for complex scenes by minimizing the dependency of stereo painting updates on the scene complexity. For interaction with stereo layers, we present stereo paint and stereo depth brushes, which manipulate the photometric (RGBA) and depth buffers of a stereo layer, respectively. In our system, painting and depth manipulation operations can be performed in arbitrary order with real-time visual feedback, providing a flexible WYSIWYG workflow for stereo painting. Comments from artists and experimental results demonstrate that our system effectively aides in the creation of compelling stereo paintings.

This paper discusses stereoscopic 3D imaging based on line drawing of 3D shapes. We describe the major issues and challenges in generating stereoscopic 3D effects using lines only, with a couple of relatively simple approaches called each-eye-based and center-eye-based. Each of these methods has its shortcomings, such as binocular rivalry and inaccurate lines. We explain why and how these problems occur, then describe the concept of stereo-coherent lines and an algorithm to extract them from 3D shapes. We also propose a simple method to stylize stereo lines that ensures the stereo coherence of stroke textures across binocular views. The proposed method provides viewers with unique visual experience of watching 2D drawings popping out of the screen like 3D.

Abstract Hierarchical culling is a key acceleration technique used to efficiently handle massive models for ray tracing, collision detection, etc. To support such hierarchical culling, bounding volume hierarchies (BVHs) combined with meshes are widely used. However, BVHs may require a very large amount of memory space, which can negate the benefits of using BVHs. To address this problem, we present a novel hierarchical‐culling oriented compact mesh representation, HCCMesh, which tightly integrates a mesh and a BVH together. As an in‐core representation of the HCCMesh, we propose an i‐HCCMesh representation that provides an efficient random hierarchical traversal and high culling efficiency with a small runtime decompression overhead. To further reduce the storage requirement, the in‐core representation is compressed to our out‐of‐core representation, o‐HCCMesh, by using a simple dictionary‐based compression method. At runtime, o‐HCCMeshes are fetched from an external drive and decompressed to the i‐HCCMeshes stored in main memory. The i‐HCCMesh and o‐HCCMesh show 3.6:1 and 10.4:1 compression ratios on average, compared to a naively compressed (e.g., quantized) mesh and BVH representation. We test the HCCMesh representations with ray tracing, collision detection, photon mapping, and non‐photorealistic rendering. Because of the reduced data access time, a smaller working set size, and a low runtime decompression overhead, we can handle models ten times larger in commodity hardware without the expensive disk I/O thrashing. When we avoid the disk I/O thrashing using our representation, we can improve the runtime performances by up to two orders of magnitude over using a naively compressed representation.

This paper presents a fast color-to-gray conversion algorithm which robustly reproduces the visual appearance of a color image in grayscale. The conversion preserves feature discriminability and reasonable color ordering, while respecting the original lightness of colors, by simple optimization of a nonlinear global mapping. Experimental results show that our method produces convincing results for a variety of color images. We further extend the method to temporally coherent color-to-gray video conversion.

Line-art illustrations are effective tools for conveying shapes and shading of complex objects. We present a set of new algorithms to render line-art illustrations of dynamic and specular (reflective and refractive) surfaces. We first introduce a real-time principal direction estimation algorithm to determine the line stroke directions on dynamic opaque objects using neighboring normal ray triplets. To render reflections or refractions in a line-art style, we develop a stroke direction propagation algorithm by using multi-perspective projections to propagate the stroke directions from the nearby opaque objects onto specular surfaces. Finally, we present an image-space stroke mapping method to draw line strokes using the computed or propagated stroke directions. We implement these algorithms using a GPU and demonstrate real-time illustrations of scenes with dynamic and specular 3D models in line-art styles.

Mobile ad hoc networks (MANETs) provide a lot of promise for many practical applications. However, MANETs are vulnerable to a number of attacks due to its autonomous nature. DoS/DDoS attacker traceback is especially challenging in MANETs for the lack of infrastructure. In this paper, we propose an efficient on-the-fly search technique, SWAT, to trace back DoS and DDoS attackers in MANETs. Our scheme borrows from small worlds, utilizes the concept of contacts, and use traffic pattern matching (TPM) and traffic volume matching (TVM) techniques. We also propose multi-directional search, in-network processing and query suppression to reduce communication overhead in energy-constrained MANETs and increase traceback robustness against spoofing and collusion. Simulation results show that SWAT successfully traces back DoS and DDoS attacker under reasonable background traffic. In addition, SWAT incurs low communication overhead (22% compared to flooding-based search).

Recently, geographic routing in wireless networks has gained attention due to several advantages of location information. Location information eliminates the necessity to set up and maintain explicit routes. These advantages allow scalability especially in dynamic and unstable wireless networks. However, no matter which technologies or techniques a location system uses, its measurements will have some amount of quantifiable inaccuracy depending on environment and system. These inaccuracies may affect the performance and even correctness of geographic routing. However, thus far, these impacts have not been studied in-depth. In this paper, we analyze the impact of location inaccuracy on geographic routing. Our study shows the significant impact of location inaccuracy on the performance of geographic routing in terms of packet drops, non-optimal paths and routing loops.