Intersection Of Mesh Surfaces And Construction Offset Line On Surfaces

Surface and Surface Intersection and offset of curves on surface are important operations in CAD/CAM, and had been widely used in various applications, such as surface trimming, numerical control machining, solid modeling. There are, in general, two ways to represent a surface for the purpose of visualization and computation. One is to use analytical surface patches via functions such as Coon's patches, B-splines or NURBS surfaces. Another is to use discrete data structures such as tessellate facets and triangular facets. For engineering applications, surfaces defined by discrete data are widely adopted, because it has many strongpoint, such as easy expression, universal application, flexibility etc. This dissertation focused on the intersection of triangulated surfaces and the offset of the intersection line on triangulated surface. The following is the main research work.1,In this dissertation, some algorithms on surface intersection and offset of curves on surface are analyzed; some problems and relatively measures are pointed out.2,A new surface intersection algorithm based on bounding box is proposed. The algorithm filtered some triangles that is impossible to intersect by using bounding box; then introducing background grid, it sorted the triangles into different background grid and calculated the intersection line segment between two triangles that is on the same background grid; connecting all the intersection line segments by tracing the neighbor of intersecting triangles, a intersection line/loop is formed.3,The development kits are Visual C++ and OpenGL. Some examples demonstrate availability of the surface intersection algorithm based on bounding box.4,Offset of curves on triangular mesh is analyzed. In this dissertation, a better algorithm is proposed by combining Holla's algorithm, polygonal chain intersection algorithm and improved polygonal chain intersection algorithm. this algorithm adopts scan lines to improve the efficiency of removing global invalid loop.5,The Proposed algorithms are further verified in configuration offset curves on triangulated spherical surfaces. The development kits are Visual C++ and OpenGL.