This interface can be used to translate between X-Topology and Napa Curve and Surface definitions. On export, X-Topology will be converted as faithfully as possible to a text file of Napa Curve and Surface definitions. The import will process the Napa Curve and Surface definitions and attempt to generate a corresponding X-Topology Curve and Surface representations.
The main objective of this interface is to transfer the design intent from one system to another. It therefore treats the imported data as a set of instructions on how to regenerate definition rather than as precise description of geometrical representations. This means that the descriptions of curves, the locations of data points, tangents, compatible constraints and intersections are transfered. However, both systems use different approaches to generate the curve and will be unlikely that the geometry generated by each system will match. If an exact translation is required, formats such as DXF and IGES are more appropriate but design intent will be lost.
Fundamental Differences between Curve Geometry in Napa and X-Topology
As X-Topology and Napa Curves are both based on a cross sectional curve modelling approach, they share many fundamental concepts. However, there are many smaller differences between the two definitions which make translation diffcult. The biggest difference is that X-Topology curves consist of 3D points while Napa curves consist of 2D Points which are projected onto a location surface to generate a 3D representation. It is not possible to import any Napa curves which have non-planar location surfaces and not possible to export any X-Topology curves which cannot be represented within a plane. Furthermore, any planar Napa curves which may reference a curve which is non-planar cannot be exported. In addition, Napa supports the ability to define arbitrary tangent angles at points, a feature not supported by X-Topology curves unless the angle is parallel to a principle axis. In this case, the interface will attempt to ignore the tangent angles unless they are parallel to a principle axis. The import translator will feedback any errors that occur during process so that the user may attempt to correct any problems or know that translation is not possible.
Note: This translator has been developed without access to Napa and although every effort has been made to capture the file format some oversights may remain. If you encounter a problem importing/exported and believe it warrants investigation given the differences between the two systems I would be very grateful if you could forward the details and any data to me.
|BSpline Suface List|
|Interpolating Cubic BSpline|