Feature-based solid modeling

Also known as feature-based solid modeling, parametric modeling is a 3-D computer drawing program. 

Figure 4-21 Modification of the form-feature based solid model by the surface model.

B-rep models are not feature-based. In order to convert a B-rep model into a feature-based solid model, the embedded solid features must be recognized, and a feature tree that... 

The situation described here is based on a simple one-electron model which can hardly be expected to predict the behaviour of complex many-electron systems in quantitative detail. There can be no doubt however, that the qualitative picture is convincing and probably that the broad principles of electronic behaviour in solids have been identified. The most significant feature of the model is the band structure that makes no sense except in terms of the electron as a wave. Important, but largely unexplored aspects of solid-state reactions and heterogeneous catalysis must also relate to the nearly-free models of electrons in solids. 

Some of the representations used in a generative process-planning system include GT code, line drawing, special language, symbolic representation, solid model, CSG, B-Rep, feature-based model. Extract and decompose features from a geometric model. 

A solid mcxlel fully describes the shape, size, and volume of the object It provides a complete set of geometric data about the object for further applications. These may include mass properties calculation, kinematic analysis, stress analysis, and manufacmring. Solid mcxieling uses a feature-based concept that a part is geometrically composed of a combination of several identifiable features, such as blcxrks, holes, and slots to model parts. 

A typical process of feature driven part modeling is illustrated in Figure 8-2. Base feature FF/, is created as a tabulated solid, starting from contour Cpph, sketched in its place in the reference plane RPj. Feature FFi, is modified by volume adding features FFp and FFr starting from contours Cppp and Cppr, respectively. Rib feature FFr needs reference plane RP2 outside of the part. RP2 is not included in the boundary of the part, but it is included in the part model. Features FFp and FFr are modified by draft conditioning features FFd2 and FF u, respectively. 

Two models exist vdiich are in a sense complementary and allow valence transitions to be discussed. The Anderson localization model is mostly applied in a parametric scheme, and allows many phenomena to be considered together as resulting fi om hybridisation effects in the conduction band. However, atomic effects are not so well accounted for in this picture essentially, they are added in by hand. Another proach is the quasi-atomic double-well model. This scheme is not parametric, since it is based on ab initio Hartree-Fock calculations. It accounts for atomic aspects, such as the general region of the Periodic Table vriiere such phenomena are encountered. Also, it provides a mechanism for localization (orbital collapse). Finally, it allows one to understand and explain the properties of rather special states (the extended 4f states) which are delocalized, but retain certain atomic features. However, this model is unable to incorporate solid state efifects in a simple way. 

Fig. 6. Illustration of GFR algorithm, (a) imported surface model with hole surface selected, (b) hole recognized and removed, extruded face of cylinder selected, (c) cylindrical extrusions recognized, base block extrusion face selected, and (d) all features recognized and mapped to solid model...

Once the sketch profile is parameterized, it can be extruded to generate an extrusion feature for the base block (Fig. 18b). The same steps can be followed to create more solid features, and Boolean operations can be employed to union, subtract, or intersect solid features for a fully parameterized solid model. The final solid model is analyzed by using Accuracy... 

Venkataraman, S. Sohoni, M Kulkarni, V. A Graph-Based Framework for Feature Recognition, Sixth ACM Symposium on Solid Modeling and Applications, 2001, 194-205. DOI 10.1145/376957.376980 ZCorp, www.zcorp.com... 

---