Research Of Key Techniques In Image Based Rendering System On Mobile Devices

Interactive scene walkthroughs have long been an important application area of computer graphics. Traditional methods to implement the walkthrough systems is that first building up the geometry models of the virtual scene and then rendering the scene through graphics hardware pipelines. With the rapid explosion of the Internet and the mobile devices, more and more wireless networks are deployed nowadays. People can access the Internet, share data, play games anywhere at any time with the assistance of the mobile devices. But real-time rendering of complex 3D scenes on mobile devices is still a challenging task. The main reason is that mobile devices have limited computational capabilities and are lack of powerful 3D graphics hardware support, so can't afford to the geometry based scene rendering.Image-Based Rendering (IBR) is an alternative way for traditional geometry rendering. It can synthesize photo-realistic novel views using recorded images captured from real-world or synthetic scenes. The rendering cost of IBR is independent of scene' s complexity. IBR is more suitable for visualizing 3D world on mobile devices since the rendering process requires less computational resources than that of the traditional geometry rendering.In this dissertation, we focus on the key techniques for remote walkthrough systems on mobile devices. The dissertation is organized as following:In the chapter 1, we first gave an overview for how to realize a walkthrough system on mobile devices. And introduced the related techniques, such as image based rendering, security and network transmition. After analyzed the recently research states in the field of remote walkthrough system, we affirmed the research contents and setup the architecture of the paper.The main content in the chapter 2 was to design a remote rendering system on mobile devices. Firstly we studied the properties of the mobile devices and the wireless networks. Then we briefly described the methods of image based rendering, and proposed the whole structure for remote rendering system. At the last, we realized the remote walkthrough system on mobile devices and show the experiment results.With the explosion of the mobile communication market, more and more handheld devices act as the clients in the Internet. For protecting privacies, the applications on the Internet should integrate digital signature schemes. Since handheld devices havepoor computational capacities and limited battery life times, traditional computation intensive digital signature protocols that based on asymmetric cryptographic algorithms are not suitable for mobile devices. In chapter 3, we proposed a Server Based Signature (SBS) scheme for mobile devices. Besides achieving the same security level of the traditional digital signature protocols, the SBS scheme also: 1) Minimizes the computation complexity on the mobile devices; 2) Minimizes the communication between the signer and the verifier. Application results show that our scheme was very useful in mobile communication systems.To protect the copyrights of the scene data in image based rendering system was the main objective in the chapter 4. Digital watermark was now the most appropriate and widely used technique for copyright protection of digital images. In this chapter, a robust wavelet based digital watermark algorithm was proposed and implemented. The experiment results approved this algorithm meet the goal for protecting the copyright of the images.In the chapter 5, we presented an adaptive panoramic video streaming scheme for distributed image based rendering (IBR) systems. Real-time rendering of complex 3D scene on mobile devices was still a challenging task. The main reason was that mobile devices have limited computational capabilities and are lack of powerful 3D graphics hardware support. In such systems, server should take most of the computing job and than transmit the required image segments to client. So the efficient network transmission was vital for client to smoothly synthesize attractive 3D scenes. The proposed streaming scheme fulfilled this task by probing the mobile network's status and then effective adjusted the sending data to avoid network congestion and jitter. Pre-fetching and cache management were also considered for efficient memory usage and reducing transmission requests. Experimental results show that the adaptive panoramic video streaming scheme was useful for the distributed IBR systems.In the last chapter, the main works and contributes in the dissertation were concluded, the future works were also prospected.