This survey reviews some of the most important grid generation techniques with emphasis on current trends. We provide a list of grid generation systems in use today and briefly dicuss their capabilities. The most recent literature on the subject matter is discussed.

This chapter focuses on three computer-aided geometric design (CAGD) techniques that are often needed to ''prepare'' a complex geometry for grid generation. Standard grid generation methods, as discussed in [George '91], [Knupp & Steinberg '93], and [Thompson et al. '85], assume that parametric surfaces are well parametrized and free of undesired discontinuities. We describe CAGD techniques that are extremely helpful for the preparation of complex geometries for the grid generation process.

The paper presents a technique for correcting discontinuites (holes, overlapping surfaces, and intersecting surfaces) in CAD data. The technique approximates faulty geometries by several new B-spline surfaces which match properly. Each B-spline surface is constructed from four user-defined boundary curves.

The National Grid Project has been under development at the NSF Engineering Research Center at Mississippi State University since 1991. A summary of the progress to date is presented. The project utilizes Non-Uniform Rational B-Splines (NURBS) for the geometry with a solid modeling Boundary Representation (B-Rep) data structure to represent topology. Geometry can be imported into the system via the Initial Graphics Exchange Specification (IGES), discrete XYZ's (interpolated into NURBS), or can be internally created by CAD operations. The NURBS are used parametrically both the structured and unstructured grid generation. Volumetric structured and unstructured grids are generated, visualized, and evaluated within the program, allowing the user the flexibility and control of the grid process.

A new technique for unstructured volume grid generation around closed surfaces is presented. The technique is based on iterative point insertion. Grid point density depends on distance to the surface and surface curvature. The technique is completely automatic