While k-d trees are known to be effective for spatial indexing of sparse 3-d volume data, full reconstruction, e.g. due to changes to the alpha transfer function during rendering, is usually a costly operation with this hierarchical data structure. In a recent publication we showed how to port a clever state of the art k-d tree construction algorithm to a multi-core CPU architecture and by means of thorough optimization we were able to obtain interactive reconstruction rates for moderately sized to large data sets. The construction scheme is based on maintaining partial summed-volume tables that fit in the L1 cache of the multi-core CPU and that allow for fast occupancy queries. In this work we propose a GPU implementation of the parallel k-d tree construction algorithm and compare it with the original multi-core CPU implementation. We conduct a thorough comparative study that outlines performance and scalability of our implementation.

Recognizing the value of autostereoscopy for 3D displays in public contexts, we pursue the goal of large-scale, high-resolution, immersive virtual reality using lenticular displays. Our contributions include the scalable tiling of lenticular displays to large fields of view and the use of GPU image interleaving and application optimization for real-time performance. In this context, we examine several ways to improve group-viewing by combining user tracking with multi-view displays.

We introduce a technique for exploring multi-layered images by scraping arbitrary areas to determine meaningful relationships. Our system, called Wetpaint, uses perceptual depth cues to help users intuitively navigate between corresponding layers of an image, allowing a rapid assessment of changes and relationships between different views of the same area. Inspired by art diagnostic techniques, this tactile method could have distinct advantages in the general domain as shown by our user study. We propose that the physical metaphor of scraping facilitates the process of determining correlations between layers of an image because it compresses the process of planning, comparison and annotation into a single gesture. We discuss applications for geography, design, and medicine.

Streaming very-high-definition visualization data objects on top of optical networks is critical in many scientific research areas, including video streaming/conferencing, remote rendering on tiled display walls, 3D virtual reality applications, etc. Current data streaming protocols rely on UDP as well as a variety of compression techniques. However, none of the protocols scale well to the parallel streaming model of large scale graphic applications, and the existing parallel streaming protocols have limited synchronization mechanisms to synchronize the streams efficiently, and are prone to be slowed down by just one slow stream. In this paper, we propose a new parallel streaming protocol that can stream synchronized multiple Gbps media content over optical networks through reliable Cross-Stream packet coding, which not only tolerates random UDP packet loss, but also aims to achieve good synchronization performance across multiple parallel data streams with reasonable coding overhead. We simulated the approach, and the results show that our approach can generate steady throughput with fluctuating data streams.

High resolution 2D video content in high definition or higher resolutions has become widespread and video playback of such media in immersive virtual environments (VE) will be a valuable element adding more realism to VE applications. This kind of video play-back, however, has to overcome several problems. First, the data volume of video clips can reach up to hundreds of gigabytes or more depending on the length of the clips, and the data has to be streamed into virtual reality (VR) systems in real-time. Second, the interactivity of the playback screen in 3D virtual environments requires efficient rendering of each video frame. Interactivity means that the plane of the video playback screen needs to rotate, translate, and zoom in and out in 3D space as the viewer roams around in the VE. This also means that the video is not necessarily parallel to the display screen but will need to be displayed as a general quadrangle. In this work, we propose an efficient algorithm that utilizes mipmapped data, that is, multiple levels of resolutions, to provide an efficient way to interactively play back high resolution video content in VEs. In addition, we discuss several optimizations to sustain a constant frame rate, such as an optimized memory management mechanism, dynamic resolution adjustment, and predictive prefetching of data. Finally, we evaluate two video playback applications running on a virtual reality CAVE system: (1) high definition video at 3840 times 2160 pixels and (2) 32 independent 256 times 192 pixels video clips.

Industry widely employs the two-dimensional videoconferencing system as a long distance communication tool, but current limitations such as its tendency to misrepresent eye contact prevent it from becoming more widely adopted. We are exploring the possibility of a three-dimensional videoconferencing system for future interactive streaming of point cloud data, and present the preliminary research results in this paper. We have tested thus far with one sender and one receiver, using pre-recorded data for the sender. The sender, encircled by high-definition cameras, stands and speaks in a room. A cluster of computers reconstructs each frame of the camera images into a 3D point cloud and streams it across a high-speed, low-latency network. On the receiving end, a splat-based renderer employs a new algorithm to efficiently resample the points in real-time, maintaining a user-specified frame rate. Parallel hardware projects onto multiple screens while head tracking equipment records the viewer's movements, allowing the receiver to view a stereoscopic 3D representation of the sender from multiple angles. We can combine these visuals with appropriate use of multiple audio channels to forge an unparalleled virtual experience. This next step towards immersive 3D videoconferencing brings us closer to empowering worldwide collaboration between research departments.

A novel barrier strip autostereoscopic (AS) display is demonstrated using a solid-state dynamic parallax barrier. A dynamic barrier mitigates restrictions inherent in static barrier systems such as fixed view distance range, slow response to head movements, and fixed stereo operating mode. By dynamically varying barrier parameters in real time, viewers may move closer to the display and move faster laterally than with a static barrier system. Furthermore, users can switch between 3D and 2D modes by disabling the barrier. Dynallax is head-tracked, directing view channels to positions in space reported by a tracking system in real time. Such head-tracked parallax barrier systems have traditionally supported only a single viewer, but by varying the barrier period to eliminate conflicts between viewers, Dynallax presents four independent eye channels when two viewers are present. Each viewer receives an independent pair of left and right eye perspective views based on their position in 3D space. The display device is constructed using a dual-stacked LCD monitor where a dynamic barrier is rendered on the front display and the rear display produces a modulated VR scene composed of two or four channels. A small-scale head-tracked prototype VR system is demonstrated.

We present a novel method to encode four data channels in a volumetric data set, and render it at interactive frame rates with maximum intensity projection (MIP) using textured polygons. The first three channels are stored in the volume texture’s red, green, and blue components. The fourth channel is stored in the alpha channel. To achieve real-time rendering speed we are using a pixel shader.

Since the original paper of Lacroute and Levoy (1994), where the shear-warp factorization was also shown for perspective projections, a lot of work has been carried out using the shear-warp factorization with parallel projections. However, none of it has proved or improved the algorithm for the perspective projection. Also in Lacroute's Volpack library, the perspective shear-warp volume rendering algorithm is missing. This paper reports on an implementation of the perspective shear-warp algorithm, which includes enhancements for its application in immersive virtual environments. Furthermore, a mathematical proof for the correctness of the permutation of projection and warp is provided, so far a basic assumption of the shear-warp perspective projection.