Curves defined by fitting to points
When you add a curve by fitting it to a set of points there are two different methods you can select in the From drop-down list to specify the points:
- Points — Specify points by directly indicating one by one all the points you want the curve to fit
- ASCII file — Specify points by loading an ASCII file containing the coordinates of the points you want the curve to fit.
You can control the following characteristics of the curve (remember the values you enter must comply with the fundamental relationship between
control points, degree, continuity and number of arcs for a NURBS):
- The curve Degree and Continuity
- If the Automatic option is selected in the Approximation drop-down list under More Options, you will have to specify the Arc number (the number of arcs that compose the curve)
- If the Select arc joints option is selected in the Approximation drop-down list, you will have to indicate the Arc joints.
- The Parameterization type. Depending on your choice, the resulting curve can have an arc-length parametrization (the sample points are spaced as equal arc-length along the curve), a uniform parameterization (the sample points are equally spaced in the domain of the curve) or an arc-length parameterization based on the chord length between the fitting points.
In addition, under Advanced Options, further options are available to define the tolerances used to control the sampling:
- Max. sampled chord error — the maximum distance between the chord (between two adjacent sample points) and the curve.
- Max. sampled torsion error
— the maximum angle between the normals at two adjacent sample points.
- Max. sampled arc length — the maximum value for the length of the chord between two adjacent sample points.
Notice that the first and last points specified are in fact interpolated and become the start point and end point of the curve, respectively.
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