Surface model construction History

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... 

Fillet surfaces are created along a common edge of two surfaces or between two surfaces having no common edge. A fillet surface is created as an individual surface entity. The model saves information about the original and the fillet surface in the history of the model construction. The radius of a fillet can be ... 

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... 

Fig. 11. Surface temperature and pCOi, histories for some rooted models with current Fndge = 2 x 10 moles a . These are compared with the the standard rootless model (Fig. 6). Also shown for comparison is Berner s (1997) Phanerozoic pC02 curve. By choosing favourable parameters (a = 0.4, p = 0.3) we are able to construct a model that maintains a clement Earth using CO2 alone through most of Earth history. However, such a model badly violates Rye et al. s constraint on PCO2 (Fig. 7). It is also worth asking whether such models can be consistent with cold climates at the end of Precambrian time.

Figure 12 shows surface temperature and pCOz histories. These focus on Archaean and Hadean time. Results are shown for the different heat-flow histories. The models with ejecta weathering use equation (19). By construction these are... 

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