Читать книгу Computer Aided Design and Manufacturing - Zhuming Bi - Страница 66

In solid modelling, the geometry of an object is modelled by a set of solid primitives, which are assembled into an object using composition operations. The modelling procedure to combine elemental solids using composition operations is commonly known as Constructive Solid Geometry (CSG) modelling. The geometric representation from solid modelling gives complete information about physical objects. CSG modelling is based on the following assumptions:

1 A constitutive object is a rigid solid; the object has a concrete and invariant shape not affected by spatial location or position.

2 An object fills the space occupied by it homogeneously; the inside positions of the object are always connected to the complementary of the model through boundary surfaces.

3 The extension of an object is finite; the model can be mapped to a 2D plan for computer visualization.

4 An object can be generated as a composition of a finite number of solid primitives and the modelled object model can be stored in a computer.

5 An object can be modelled as a closed set in terms of rigid solid motions.