3DS Curves
Note: The definitions below are related only to this particular type of
object: Generic 3D Object (3DO)
The simplest 3D curve is a 3D Curved Segment. 3D Curved segments are always
oriented along z axis of the current object . z-coordinates of its ends are knots
of the current object. Another necessary property of a 3d segment is that its
projections to z, x and z, y planes are arcs or straight lines.
3D Curved Segment.
A 3D Curve is a strip of joined 3D Curved Segments. Any 3D Curve in a given
3D Object consists of n-1 3D Curved segments, where n is the
number of base knots in the Object.
Active 3D View. 3D Curve with two Curved Segments and three base knots.
In our definition of a 3D curve we include 3D lines too, considering them as a
special case of a curve with zero value of curvature.
Edges of 3D surface patches are 3D curves. 3D curves can also exist as a
standalone curve. Standalone curve is a Generic 3D Object. It has its local
frame. A standalone 3D Curve can be created with the New Object dialog (Model
menu>New Object>Curve) or by deleting an edge from a single surface patch
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