Investigation On The Key Technology Of Virtual Scene Rendering Based On Image

Interactive, immersion, and imagination are the objectives for virtual reality system, while reality and realtime are contradicted during VR system construction. Traditional virtual scene coustruction method based on geometry is on the basis of computer graphics; the depth information of scene can be obtained directly, which offers a convenient interactive mode between user and the scene. Also, user can change their viewpoint freely. However complexity of this method is entirely depends on virtual scene, and it is difficult to realize on common harder platform. A completely brandnew method-image based rendering is proposed recently, which uses image as the carrier of information. This method uses pixel as rendering element, rendering is just the process of resample and reorganize former pixel. Advantages of this method are rendering speed independent of scene complexity and high fidelity. So it becomes a hot reseach spot in virtual reality field.This dissertation concentrates on the key technology of virtual scene rendering based on image. Aimed at the needs of virtual panoramic space construction, we emphatic research the image stitching method; image based relighting method and image resolution enhancement method. Generally, the main research points in this paper are as follows:Image Stitching is one of the key technology in virtual reality construction,we proposes two ambient light independent panorama mosaics methods based on feature: image stitching algorithm based on stationary wavelet decomposition and homomorphic filtering, and image stitching algorithm based on ring projection and energy function optimization. The first algorithm uses stationary wavelet decomposition to extract feature sequences in image templates. Then color transform or homomorphic filtering can be used to adjust the global brightness of images to solve the problem of difference illumination, thus a pleasure stitching result can be achived. The second algorithm uses ring projection to extract feature sequences in image templates, which overpasses the local area limit in tradition methods. While blending factors are gained from energy function that contains image gradient, which conquer the blur and mackle problems in the overlap area using tradition linear weight function. Thus we can gain pleasure visual effect using these two methods in image mosaics with notable illumination difference.Illumination is an important factor for scene generation, we proposes a pure image based rendering method to synthesis image under arbitrary illumination condition. In this method, Singular Value Decomposition (SVD) was used analytically to derive environment light part and properties of scenes from sampled images, which were taken from the same view point under different point illumination condition. For images rendering under novel lighting conditions, direct illumination effect is calculated using lambertain model; while indirect illumination one was added by environment light part derived before. So feature of this method is that it supplies a good algorithm to synthesis image in arbitrary illumination environment.Aimed at the needs of high image resolution and zooming browse in virtual environment, this paper research algorithm of image resolution enhancement. In the case of one frame, we presented a novel image zooming algorithm based on maximum a posteriori (MAP) probability theory and maximum entropy principle, which anisotropy interpolate pixels using gradient information self-adaptively. In the case of multi-frames, we presented a super-resolution reconstruction algorithm based on generalized MAP theory and maximum entropy principle. By introduce bifilter into traditional MAP algorithm, we anisotropy interpolate pixels using gradient information and geometry distance self-adaptively. Experiment shows that our algorithm holds higher signal/noise ratio and better vision quality.Aimed at the needs of virtualized relationship in virtual environment, we introduce non-photorealistic rendering into virtual reality and presented a novel algorithm for virtualized relationship generation in image based virtual environment based on line integral convolution. First, structure tensor is calculated to gain vector field for characterizing local structure of image. And then, total variation partial difference equation is imposed for smoothing vector field. Based on this we use line integral convolution for guide the stroke to generate virtual special effect image with fluctuant sense. Last, mergering with original real image, cylindrical panorama with virtualized relationship controlled by time can be generated, which accomplished the character of surpass the time and space in virtual reality system.Aimed at the needs of divagation in virtual environment, we define the position chain, time chain, zooming chain and virtulized chain. Also, a divagation strategy is proposed for vitural panorama space containing position relationship, time relationship, zooming relationship and virtualized relationship.