ADAMS的CSG实体介绍.pdfVIP

What is Constructive Solid Geometry? Contents 1.0 Introduction: Intelligent Geometry 2.0 Constructive Solid Geometry Defined 3.0 Constructive Solid Geometry in Action 3.1 Basic CSG Operations 3.2 Intermediate CSG Operations 3.3 Advanced CSG Operations 4.0 Conclusion 1.0 Introduction: Intelligent Geometry Constructive solid geometry (CSG) is a type of intelligent geometry that gives the programmer extra information. CSG uses simple objects called “solids”, constructed according to geometric rules. The special properties of CSG solids allow mathematical operations that are not possible with an arbitrary polygon mesh. It’s no wonder that games like Half-Life 2, Doom 3, and Unreal Tournament 2004 rely on CSG as the basis of their world geometry. 2.0 Constructive Solid Geometry Defined CSG solids are simple convex objects, made out of intersecting coplanar faces: Convex means that all faces point out away from each other: Coplanar means that all the vertices of a face lie along the same plane: The top right vertex has been moved inwards to make the selected face non-coplanar. Concave objects can be created using multiple convex solids: This concave solid still follows the rules of CSG; each individual solid is convex. 3.0 Constructive Solid Geometry In Action The special properties of CSG solids allow mathematical operations that are not possible with an arbitrary polygon mesh. CSG solids are made out of intersecting coplanar faces. Each face has an ascertainable plane equation, defined as a 3D vector, plus a distance from the origin: Each face has a normal indicating the direction it points, and a distance from the origin. The intersection of the planes defines the solid. 3.1 Basic CSG Operations Two equations form the basis of more complex operations. Equation for distance between a point and a plane The sign of the result indicates whether the point is in front of or behind