Development Of 3D Graphic Platform Of GLIF Pipeline Stress Analysis Software

GLIF is suitable for stress analysing of high temperature and pressure steam pipeline in large-capacity and high-parameter thermal power plant, as well as in nuclear power plant. During many years in researching and developing, and actual inspection of thousands of projects, it has met the demands of safe reliability of engineering design, and achieved the purpose of economic suitability at the same time. According to the investigation of GLIF users' circumstantialities in use in Northeast Electric Power Design Institute, we confirmed the emphases of this upgrading project. I participated in the development of 3D graphic platform of GLIF software, which required that: The data-inputting must be dealed with friendly human-computer interactive interface. Data drive the models, models to show the data. The models are on the basis of independent 3D graphic platform, lifelike, capable of rotating, translating, scaling, and revising the data by modifying the models. In the course of data inputting, the software is able to code the nodes intellectually at the request of users. The emphasis of this project lies in utilizing OpenGL to develop 3D graphic system, including drawing basic 3D image elements, coordinate transforming, colours, illumination, texture, and interactive technology, etc.. OpenGL (Open Graphics Library) is a professional graphic API produced by SGI Com., which allows programmers to describe 2D and 3D geometrical objects, and render to frame buffer. The reasons that we chose OpenGL but not DirectX were as follows: OpenGL is a software interface having nothing to do with the hardwares, being able to transplant among different operating systems, like Windows 98/NT/2000/XP, Unix, Linux, MacOS and OS/2, so that the softwares supporting OpenGL are very transplantable. OpenGL's powerful functions need not writing data of 3D models in fixed forms. Developers can use their own data directly, or else utilize the data sources of other different forms. This kind of flexibility saves time of developing greatly, and improves efficiency. OpenGL is a set of graphic standard, which follows the principles of computer graphics, and accords with optical and visual principles, so is suitable for designing visible emulational systems. It has much more advantages and convenience in interactive 3D modeling. The developing process of GLIF 3D graphic platform already realized at present is divided into several steps as follows: ⑴Realization of models Any object of true world can be described with simple points, lines and polygons in computer. Open Graphics Library provides many drawing functions of complex 3D objects, such as sphere, cone, polyhedron, etc., and complicated curves and curved surfaces, such as Bezier, Nurbs, etc., to construct virtual 3D world conveniently. Take the principles of graphics into practices through defining the attributes and operations of point, vector, especially matrix, and this is the foundation of any transformation. Utilize the drawing functions to complete drawing independent 3D pipeline-com-ponent models. ⑵Realization of transformation Any complicated image is realized by image elements through a series of transformation. Open Graphics Library provides many kinds of transformation, such as translation, rotation, scaling, orthographic and perspective projections. Projection defines viewing volume, and maps 3D images into 2D planes. Viewport transformation determines in which part the images are exported at the window. Translation and rotation are both necessary functions in CAD softwares, which are realized by a point multiplying a transformation matrix. Scaling is realized by transforming viewing volume. While the viewing volume is zoomed in, the showing size is zoomed out; On the contrary, the showing size is zoomed in, while the viewing volume zoomed out. The difficulty lies in how to assemble every independent pipeline-component models accurately. In the project we used the methods of analyzing and ploughing around. Though the latter is valid sometimes, it is inaccurate, and should be improved. ⑶Realization of special-effect The special-effect includes colour mode, illumination and material, alias and blend. We specified RGBA mode as drawing colour mode, because it could describe more colours.