Creating 3-d solid models

Two basic approaches to create solid models are : 

  (i)  Constructive solid geometry (CSG or c-rep), and

(ii)  Boundary representation (b-rep).

In CSG, the designer constructs the model basic solid primitives such as blocks, cones, spheres, cylinders, tubes and hexahedra (Figure 6.41) in combination with Boolean operations such as addition, subtraction, union and intersection. A complex model can be constructed in a building block manner, by combining the shapes or subtracting them from each other. Figure 6.42 shows the various Boolean operations using the different primitives, in constructing a solid model. An alternative name for the CSG method, set-theoritic modeling, arises from the way in which primitives are combined using the operators of set theory.