Validating Stereoscopic Volume Rendering

The evaluation of stereoscopic displays for surface-based renderings is well established in terms of accurate depth perception and tasks that require an understanding of the spatial layout of the scene. In comparison direct volume rendering (DVR) that typically produces images with a high number of low opacity, overlapping features is only beginning to be critically studied on stereoscopic displays. The properties of the specific images and the choice of parameters for DVR algorithms make assessing the effectiveness of stereoscopic displays for DVR particularly challenging and as a result existing literature is sparse with inconclusive results. In this thesis stereoscopic volume rendering is analysed for tasks that require depth perception including: stereo-acuity tasks, spatial search tasks and observer preference ratings. The evaluations focus on aspects of the DVR rendering pipeline and assess how the parameters of volume resolution, reconstruction filter and transfer function may alter task performance and the perceived quality of the produced images. The results of the evaluations suggest that the transfer function and choice of recon- struction filter can have an effect on the performance on tasks with stereoscopic displays when all other parameters are kept consistent. Further, these were found to affect the sensitivity and bias response of the participants. The studies also show that properties of the reconstruction filters such as post-aliasing and smoothing do not correlate well with either task performance or quality ratings. Included in the contributions are guidelines and recommendations on the choice of pa- rameters for increased task performance and quality scores as well as image based methods of analysing stereoscopic DVR images

3D Mesh Simplification Techniques for Enhanced Image Based Rendering

Three dimensional videos and virtual reality applications are gaining wide range of popularity in recent years. Virtual reality creates the feeling of 'being there' and provides more realistic experience than conventional 2D media. In order to feel the immersive experience, it is important to satisfy two important criteria namely, visual quality of the video and timely rendering. However, it is quite impractical to satisfy these goals, especially on low capability devices such as mobile phones. Careful analysis of the depth map and further processing may help in achieving these goals considerably. Advanced developments in the graphics hardware tremendously reduced the time required to render the images to be displayed. However, along with this development, the demand for more realism tend to increase the complexity of the model of the virtual environment. Complex models require millions of primitives which subsequently means millions of polygons to represent it. Wise selection of rendering technique offer one of the ways to reduce the rendering speed. Mesh-based rendering is one of the techniques which enhances the speed of rendering as compared to its counterpart pixel based rendering. However, due to the demand for richer experience, the number of polygons required, always seem to exceed the number of polygons the graphics hardware can efficiently render. In practice, it is not feasible to store large number of polygons because of storage limitations in mobile phone hardware. Furthermore, number of polygons increase the rendering speed, which would necessitate more powerful devices. Mesh simplification techniques offer solution to deal with complex models. These methods simplify unimportant and redundant part of the model which helps in reducing the rendering cost without negatively effecting the visual quality of the scene. Mesh simplification has been extensively studied, however, it is not applied to all the areas. For example, depth is one of the areas where general available simplification methods are not very well suitable as most of the methods do not consider depth discontinuities very well. Moreover, some of the state of the art methods are not capable of handling high resolution depth maps. In this thesis, an attempt is made to address the problem of combining the depth maps with mesh simplification. Aim of the thesis is to reduce the computational cost of rendering by taking the homogeneous and planar areas of the depth map into account, while still maintaining suitable visual quality of the rendered image. Different depth decimation techniques are implemented and compared with the available state of the art methods. We demonstrate that the depth decimation technique which fits the plane to depth area and considers the depth discontinuities, outperforms the state of the art methods clearly

Selective rendering for efficient ray traced stereoscopic images

Depth-related visual effects are a key feature of many virtual environments. In stereo-based systems, the depth effect can be produced by delivering frames of disparate image pairs, while in monocular environments, the viewer has to extract this depth information from a single image by examining details such as perspective and shadows. This paper investigates via a number of psychophysical experiments, whether we can reduce computational effort and still achieve perceptually high-quality rendering for stereo imagery. We examined selectively rendering the image pairs by exploiting the fusing capability and depth perception underlying human stereo vision. In ray-tracing-based global illumination systems, a higher image resolution introduces more computation to the rendering process since many more rays need to be traced. We first investigated whether we could utilise the human binocular fusing ability and significantly reduce the resolution of one of the image pairs and yet retain a high perceptual quality under stereo viewing condition. Secondly, we evaluated subjects' performance on a specific visual task that required accurate depth perception. We found that subjects required far fewer rendered depth cues in the stereo viewing environment to perform the task well. Avoiding rendering these detailed cues saved significant computational time. In fact it was possible to achieve a better task performance in the stereo viewing condition at a combined rendering time for the image pairs less than that required for the single monocular image. The outcome of this study suggests that we can produce more efficient stereo images for depth-related visual tasks by selective rendering and exploiting inherent features of human stereo vision

Evaluation of optimisation techniques for multiscopic rendering

A thesis submitted to the University of Bedfordshire in fulfilment of the requirements for the degree of Master of Science by ResearchThis project evaluates different performance optimisation techniques applied to stereoscopic and multiscopic rendering for interactive applications. The artefact features a robust plug-in package for the Unity game engine. The thesis provides background information for the performance optimisations, outlines all the findings, evaluates the optimisations and provides suggestions for future work. Scrum development methodology is used to develop the artefact and quantitative research methodology is used to evaluate the findings by measuring performance. This project concludes that the use of each performance optimisation has specific use case scenarios in which performance benefits. Foveated rendering provides greatest performance increase for both stereoscopic and multiscopic rendering but is also more computationally intensive as it requires an eye tracking solution. Dynamic resolution is very beneficial when overall frame rate smoothness is needed and frame drops are present. Depth optimisation is beneficial for vast open environments but can lead to decreased performance if used inappropriately