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3DS Objects

Z-axis of a 3DS Object is a privileged one. All lines of the object are parameterized by the local z coordinate.

Every 3DS Object has a Base. Base is an array of points on the object's axis ( z-axis ). We call these points Base Knots. A generic 3D Object has at least two knots: minimal and maximal values of z coordinate for the object. Knots are used to define plot of different parameters of the surface against axis of the object. These plots are called Profiles. For example, x coordinate of a 3D Curve is a function of z coordinate. Its plot against z normally represented as a strip of lines (or arcs). Knots are points of z-axis where those segments are joined. For the default case of two knots, each such a strip will have only one segment. Adding extra knots allows creation of more complex geometry and approximation of any shape. Programmatically the set of knots is managed by IAxiBase interface. 

The simplest surface is a patch.  A patch is a piece of surface between two 3D Curved Segments.

When base of a Generic 3D Object has more than two knots, surface of the object consists of Patch Strips.

Surface of a 3DS object consists of Patch Strips. Patch Strips are joined together by their edges. Edges of patch strips are 3D Curve Elements. In a sense surface of a 3DS object can be considered as a strip of Patch Strips.

Each 3DS object keeps current z-axis position called cross position. Plane orthogonal to axis of the object at the cross position (and parallel to x and y plane) we call