| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 93 === Rendering technology has many applications in diverse fields, for example, digital archives, multimedia entertainment, inverse engineering, and even medical science. Beside the acquirement of accurate 3D geometry, how to get the best fitting feature to reconstruct the lighting reflectance of the object from different viewing direction is a critical problem. In the thesis, we use geometry-based rendering and BRFD model to represent the lighting response of materials.
The purpose of our research is to build an automatically reflectance reconstruction system, which can automatically select the most suitable BRDF model from the database to describe the input object. And the selection process operates in accordance with the characteristics of the captured pictures from different viewing directions. The system embeds five most popular BRDF models in the database, i.e. Phong, Blinn-Phong, Cook-Torrance, Ward, and Ashikhmin model. Furthermore, in order to reconstruct the reflectance characteristic of complicated materials as well, we propose an effective cluster algorithm to compute the best fitting BRDF parameters. Most of the previous approaches use monochromatic or single characteristic material, and few researches for complicated materials. The proposed algorithm uses error vector to deal with the complicated materials in terms of the process of fitting, clustering, merging and reclustering. Thus, it could make cluster process robustly and better than the previous approaches for representing real-world objects.
In the experiments, we apply the algorithm to several objects with different shape and complicated material to verity the effectiveness. The objects consist of different materials with varying reflection properties in both the diffuse and the specular part. Reflectance field is proved to be realistically reproduced from the object of complicated materials.
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