3DS Geometry
Zaxis of a 3DS geometry is a privileged one. All lines of the object
are parameterized by the local z coordinate.
Every 3DS geometry has a Base. Base is an array
of points on the object's axis ( zaxis ). We call these points Base
Knots. A 3DS geometry 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 model 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 zaxis 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 3DS surface is a patch. A patch is a
piece of surface between two 3D Curved Segments.
When base of a 3DS has more than two knots, surface of the
object consists of Patch Strips.
Surface of 3DS geometry 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.
