T-FLEX Parametric CAD. Fundamentals. 2D Design

SPLINES
Main Concepts
Splines
The construction spline entities allow creating various curves. Unlike the straight construction lines, the
splines have finite length. In general, spline-handling techniques are not different from those used for other
construction entities. Nodes are created at intersections and tangency points. Graphic entities and hatch
contour segments can be constructed along splines. Spline selection is done in many commands using the
option (the same key is used for selecting other curves as well, such as functions, offset curves and
paths). T-FLEX uses NURBS-type splines.
A spline is created based on a set of nodes that represent the defining points of the spline. Therefore,
modification of the node positions will result in a change to the shape of the curve constructed based on these
points.
Splines belong to two main types: passing through the nodes directly and using the nodes as vertices of the
control polygon.
There are also closed splines.
End-point conditions can be defined for splines through points via
tangency vectors that are constructed based on nodes as well.
The control polygon nodes can be assigned weights. The more the
node’s weight, the closer the curve will pass to this node than to the
neighboring ones. Vise versa, the lesser the weight, the smaller is the
influence of the node on the curve shape.
Splines appear on the drawings as polylines made of numerous straight segments. The number of segments
and, therefore, the accuracy of the output can be controlled by specifying the number of tessellation
segments between a pairs of neighboring defining nodes. Each section of the spline will be tessellated by this
number of segments when output. The more segments are used, the higher quality and accuracy will be
achieved in the image. However, a too high number of segments may cause delays in spline handling by the
system.
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