Surface model construction Modification

The construction history of a loft surface and its offset can be followed in Figure 7-37. The entities used in the construction of a surface are called constructors. Two section curves and two limiting curves are the constructors of loft surface 1. The offset of loft surface 1 was generated using the offset value. When any of the constructors is changed, the associative surfaces change accordingly. The history of surface model construction provides the link between surface model and the elements that were used for its creation as the constructors. Modification of a surface model is... 

The boundary representation must allow all necessary geometric operations during construction, modification, and application of the model such as intersection by curves and surfaces, and modification of continuity conditions. 

Surface modeling produces boundary representations of surfaces with or without a history of model construction. The development and modification of complex curves and surfaces needs information about how existing curve and surface entities... 

Form features are created as solids by a task based choice of volume modification, surface integration, and conditioning model construction operations as available in the modeling system. Hybrid modelers apply shape modification such as primary and volume combinations as an auxiliary means of part construction. Besides the integration of separately created surface, a surface can be constructed as a boundary of a solid by using one of the surface creation rules and as a swept, lofted, etc., volume feature. 

With the tools developed in Chapters 1 through 3, it is possible to construct models of the emission and reflection of gas layers over a solid surface. Such models, with increasing complexity, including scattering, are the subject of Chapter 4. However, it is impossible to separate a study of planetary systems by remote sensing from the instmments which record the data. Inferences of atmospheric and surface parameters require the analysis of observed spectra, which have been subjected to modifications characteristic of the instruments used. In Chapter 5 we consider... 

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