Solid Modeling

Solid modeling is a consistent set of principles for mathematics and modeling of three dimensional solids. Due to its importance on physical fidelity, solid modeling is distinguished from the related areas of geometric modeling and computer graphics. The principles of geometric and solid modeling from the foundation of computer aided design and in general support creation, exchange, animation, interrogation, and annotation of digital models of physical objects.

Solid Modeling

A three dimensional object, for example; a cube is represented as a set of six separate faces in solid modeling. However the faces might be grouped to make a single object, there is no internal representation of the objects in solid modeling. On other hand, with the solid modeling program, an object is represented internally as single object made up joint faces.

It is especially useful in engineering applications, with a solid modeling representation it is possible to calculate physical properties of the object and to check for object interference. It is also useful to generate instructions to create physical models with computer controlled machinery.

The basic limitations of solid modeling, mostly due to the large data structures, limit its use to the creation of relatively small objects. Solid modeling is used in the architecture mostly in the conceptual stages of a design, due to that reason. The use of the solid modeling for creating the building model is problematic, not only because of the limitations of the tool but also because of the established professional practices in the building industry.

Solid objects can be generated in different ways:

• Sweeping a two dimensional entity, it is similar operation as the one used to generate 3d surface objects.
• Primitive installation, inserting an instance of a given language of solid primitives.
• By combining the existing solids with Boolean operators, the resulting object is a solid, which can be used to create the new solids.

Boolean Operators

The power of solid modeling gets not only from its internal representation, but it gets mostly from the set of Boolean operation that is used to create new solids from the existing ones. The operators are same as in the set theory: union, subtraction and intersection.

Solid Representation

There are different techniques to represent solids that have been developed so far, among them spatial partitioning, boundary representation and construction solid geometry.

Questions:

• What is solid modeling?
• What are the ways of generating solid objects?