Tham khảo tài liệu 'machine learning and robot perception - bruno apolloni et al (eds) part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6 3D Modeling of Real-World Objects Using Range and Intensity Images 245 a b Fig. Close-up view of the model before and after integration frequently required we must also obtain the reflectance data of the object surface. In general there are two approaches for acquiring the reflectance data. The first approach employs one of the many parametric reflectance models and estimates the reflectance parameters for each data point by using multiple images taken from different viewpoints and under different lighting conditions 27 30 33 48 49 . Once the reflectance parameters are estimated it is possible to visualize the object under any novel lighting condition from any novel viewpoint. We will describe this approach in greater depth in Section . The second approach instead of using a parametric reflectance model utilizes only a set of color images of the object. Some methods 15 47 exploit the use of view dependent texture maps. For each viewing direction of the 3D model a synthetic image for texture mapping is generated by interpolating the input images that were taken from the directions close to the current viewing direction. The synthetic image simulates what would have been the image taken from the current viewing direction thus it provides a correct texture to the 3D model. Other methods 42 60 store a series of N textures for each triangle where the textures are obtained from the color images taken from different viewpoints under known light source directions. The N textures are compressed by applying the Principal Components Analysis and a smaller number of textures that approximate basis functions of the viewing space are computed. These basis functions are then interpolated to represent the texture of each triangle from a novel viewpoint. Although the second approach provides realistic visualization from an 246 J. Park and G. N. DeSouza arbitrary viewpoint without estimating reflectance parameters for each data point one of the major drawbacks is the .
