A Study On Key Methods And Techniques Of Rendering For Spatial Dataset Visualization

Visualization for spatial dataset has received increasing attention and has reached a great achievement in the field of medicine, geoscience, astronomy, chemistry, mechanical engineering et al. It is release a large number of engineer and technologist from large scale and fussy data. Rendering technique for visualization is a fundamental tool by which the spatial dataset are outputted and transformed into meaningful visual images. The rendering quality is promising for recognition of original data to engineer and technologist. Besides, the application of graphics rendering for visualization is very wide and spreads most field of industry and society. It is foreseeable that this technique will be more and more important in the future. Visualization for rendering research covers illumination model, texture technique and graphics generation.Illumination model is one of the commonest rendering techniques. Physically-based reflectance models typically represent light scattering as a function of surface geometry at the pixel level. With changes in viewing resolution, the geometry imaged within a pixel can undergo significant variations that can result in changing reflectance characteristics. To address these transformations, we present a multiresolution reflectance framework based on geometric descriptors appropriate for representing reflectance effects over different scales. Since these quantities must be efficiently determined with respect to resolution, they are recorded at multiple resolution levels in mipmaps, for which we present a technique for efficient filtering of these distribution-based parameters. This framework can be used with common geometry-based reflectance functions, and can be implemented in graphics hardware for real-time processing. With this multiresolution reflectance technique, our system can rapidly render the fine reflectance detail that is customarily disregarded in multiresolution rendering methods.Texture mapping and caching is playing a key role in many study for visualization. Most previous automatic texture mapping algorithms have suffered from been too slowly or could only use a limit set of feature points of the model. We introduce in this paper a new constrained-based method for automatic texture mapping that deal with these problems for planar meshes. Our critical improvements include generalizing feature point to feature curve to fit some application and also simplified computation through efficient weighted of texture mapping. We generalize by parameterizing each vertex at two passes. Firstly we compute all the possible mapping along the feature curve consecutively where every triangle that consists of the computed vertex and two points in the curve can be deduced a conformal mapping result with minimum deformations. Then we combine all the possible mapping using normalization distribution to get the final one. Our results show that this texture mapping algorithm makes a great mapping for the planar meshes. Besides, this paper proposes a system that improves the texturing technique for large scale terrain visualization. A texture mapping method based on overlap sampling is presented for tiling textures without seams during initialization phase. And then this paper defines a texture error, presents its detail math expression and proves that it has very good character. An algorithm based on the texture error proposed to confirm texture resolution considers not only screen projection but also position. Finally advanced estimate method can control schedule for texture release that unload possible invisible texture patches to induce data commute of main and second memory. The experiments show that result has high quality with high speed.Model simplification is an important tool for graphics generation. At first, given the framework of incremental mesh simplification based on edge collapse, the paper proposes a mesh simplification algorithm using an improved approach for measuring simplification error. The algorithm uses edge collapse to simplify the triangle mesh and maintains...