Research On The Method Of Interactive 3-D Object Measurements And Its Realization

3-D measurement has capacious applications in engineering, such as its uses in machine vision, profile modeling and biomedical industry. But many 3-D measurements only can be estimated by handiwork now, for example, the area of mitral valve, the shape and size of eyepit and the volume of tumour in medicine field. With the development of computer graphics, complex objects can be observed on the computer screen, it's the foundation of computer aided 3-D measurement. Computer aided 3-D measurement can realize many complex measurements which cannot be done now, or reduce the complexity of many 3-D measurements. Biologic organ is one of the most complex 3-D objects, and the 3-D measurement of it play very important role in medicine field, so the method of biologic organ's 3-D measurement is studied in this thesis.Techniques of image recovery, image geometric correction and image segmentation are applied in this thesis to improve the quality of images, which are got from CT devices. Edge extraction and triangulation are used to complete the 3-D modeling of measuring objects. Then OpenGL graphic libraries are introduced to realize the 3-D visualization.The process of 3-D observation is detailedly studied and the transformation formulation of world coordination system and screen coordination system is listed. It's the foundation of 3-D interaction and actualization of 3-D measurement results. 3-D virtual sphere technique is used to realize the function of interactive rotation and picking method based on parallel perspective is used to realize the special characteristic points picking, so the design of 3-D interaction is completed.3-D measurement mainly includes the distance measurement between two points, and the area and volume measurement of 3-D objects. The distance measurement can be divided into linear or curvilinear distance measurement and 3-D depth measurement.A method of 3-D depth measurement following normal direction is proposed in this thesis. With the use of this method to get thickness information of facial parenchyma, the precision is increased compared with former methods. And a coordinates transformation method is proposed in calculation to simplify the 3-D calculations to 2-D calculations. This method reduces calculation complexity.A new data storage structure is designed to resolve the difficulty in arrangement of unorderly intersection points and accelerate the measuring process during curvilinear distance between two points measuring. In calculation, cubic spline curve is used to instead contour line. This method can increase the precision of curvilinear distance measurement.Finally, a digital skull-face 3-D computer aided measuring system is developed based on object-oriented software programming method. This system has completed the measurements of facial parenchyma thickness, facial distance characteristics and tumour's area and volume. It gets an upstanding effecting in facial reconstruction process, superposition identification between skulls and photos, and three-dimensional conformal radiotherapy technique.