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3.1 The KI and PK Interface
The KI and the PK are interfaces for the programmer to access the modelling capabilities in the Parasolid kernel. They are standard libraries of modelling functions. The programmer calls these modelling functions in their programs. As the KI is to be phased out soon, we chose to use the PK interface. Fig. 1. Parasolid components.3D Kernel Development for Injection Mould Design 455
3.2 The Frustrum
The frustrum is a set of functions, which must be written by the applications programmer. The kernel calls them when data must be saved or retrieved. When using Parasolid, the applications programmer must first decide how to manage the storage of data, which Parasolid outputs through the frustrum. Transferring data through the frustrum usually involves writing to, or reading from, files. The format and location of the files is determined when writing the frustrum functions.
3.3 The Graphical Output (GO)
The graphical output is another set of functions, which is to be written by the applications programmer. When a call is made to the PK rendering functions, the graphical data generated are output through the GO interface. The graphical data are then passed to a 3D rendering package. OpenGL, a software interface to graphic cards, is a rendering package that is used for our purpose.
3.4 The Foreign Geometry
The foreign geometry provides functionality for the development of customised geometrical types such as in-house curves and surfaces. These are used together with the standard geometrical types for modelling within Parasolid.
4. Object-Oriented Programming Using
Visual C++ and the Microsoft Foundation Classes Object-oriented programming (OOP) has been the undisputed option for software developers. It is among the most advanced developmental tools available. The Microsoft Visual Studio is such a software package. It features several developmental tools that are meant for Internet-based and Windows-based programming. Among these tools are the Visual C++(VC++) and the Microsoft Foundation Classes (MFC). The VC++ is a powerful development tool for object-oriented programming,whereas the MFC is a framework of C++ classes that are dedicated to Windows-based programming. Together, these provided the applications programmer with powerful development features and functionalities such as auto-code generation, and wizard-based operations. These greatly improved productivity. The entire user-interface for our program is developed using the VC++ and the MFC.
5. System Design
The direct development of a 3D-based add-on application using a 3D kernel requires several issues to be addressed. They consist of 3 main stages at the highest level. First, the identification of the crucial features and functions required for the plug-in application. Secondly, the development of the design for the application framework. Lastly, the design and development of the inpidual modules in the framework with appropriate developmental tools.
5.1 Identification of Essential Modules
Parasolid, as a 3D kernel, provides only a number of libraries and a conceptual framework for 3D application development. It is thus necessary for the developers to identify and develop the other essential facilities that are provided in a 3D CAD system. In order to identify the required facilities, it is important to understand the discrepancies between the two.Table 1 summarises the main differences in the facilities provided by a 3D kernel and a 3D CAD system. Some of these facilities, such as features and parametric modelling, are both time-consuming and technically demanding to develop.As most plug-ins do not use all the facilities of the parent software, it is possible to develop only those required by the plug-ins using low-level 3D kernels, producing a stand-alone version.Items 7 to 9 in Table 1 are prerequisites for the development of 3D-based applications using Parasolid. By studying the requirements of the plug-in application, other essential facilities can be identified. A framework for the application is then proposed, based on the facilities provided by the Parasolid kernel.