Interactive 3D Marking Of Dimensions And Tolerances For The Solid Model Based On HOOPS

With the rapid development of computer technology, the 3D model of product design has been widely used, whose process not only needs shape design of the product structure, but marks 3d size and tolerance of 3d model, in order to exchange information of the designed product. Adding the function of 3d dimensioning and tolerance dimensioning to 3d solid modeling software with independent copyright is of great significance to the practical application of the 3d design software.HOOPS, one of the most popular advanced graphics engine internationally at present, is widely used in many CAD software systems like SolidWorks. In this paper, HOOPS’ architecture, graphic drawing mechanism and application program interface are deeply studied, and the graphics environment and interactive tools needed by the 3d dimensioning, text dimensioning and tolerance dimensioning are developed and constructed.The paper aims to perfect the function of 3d CAD solid modeling software. Based on the existing 3D solid modeling system JhSolid, adopting the object-oriented design, some graphics functions of JhSolid are developed, which uses computer graphics, computer science, Parasolid modeling kernel, HOOPS graphics engine and so on. Specific graphical functions developed are as follows:First, display multiple patterns of the text in a 3D scene on the basis of text display technology of HOOPS. Second,3D scale is designed by using 3d graphics display and scene technology, and 3d scale is displayed dynamically via HOOPS and drawing tools are also developed. Third, adopted object-oriented technology, the intelligent tagging function of 3d dimension is designed, which can make intelligent judgments on dimension types according to the chosen geometric elements and display dimension dynamically in real time. In addition,3d roughness and geometrical tolerance can be marked interactively, that is, if given 3d geometric elements, the type of tolerance can be determined automatically. Facing to the object, the class hierarchy of dimensions, text symbols and tolerances is constructed, making it possible for dimensions, text symbols and tolerances to be amend, edited and stored, and mixed with the existing modeling system.The functions of size dimensioning, text symbol dimensioning and tolerance dimensioning are programmed, debugged and tested, which proves the programs have successfully realized the above-mentioned function and that the presented methods are correct and practical.