Options

Display direction(s)

All intersecting: display the U and/or V direction of all surfaces under the cursor.

Closest to eye: display the U and/or V direction of the nearest surface under the cursor.

Surface Reversal Mode

Reverse U

Reverse the direction of the U isoparametric curves.

Reverse V

Reverse the direction of the V isoparametric curves.

Swap U and V

Swap the isoparametric curves so that the U direction becomes the V direction and vice versa.

Object edit > Fit b-spline

Creates new cubic B-spline (degree 3) curves/surfaces from linear (degree 1) geometry, such as digitized or imported CAD data.

Converting linear geometry to cubic

Create new cubic B-spline (degree 3) curves/surfaces from linear (degree 1) geometry, such as digitized or imported CAD data.

To create cubic b-spline objects from linear objects

1. Pick the linear (degree 1) curves and/or surfaces to which you want to fit cubic geometry.
2. Click the Fit b-spline icon, or choose Fit b-spline from the Object Edit palette menu.

   Fit b-spline creates new cubic b-spline curves that fit the original linear geometry, and unpicks the originals.

Tips and notes

• When creating a degree 3 surface from a degree 1 surface, the original surface cannot have two consecutive points at the exact same location (multi-knots). This restriction only applies to surfaces.
• For linear curves with very long distances between edit points, the Uniform parameterization option may create an inaccurate fit. Try using Chord length parameterization instead.

Options

Fit Type

Fit

Create a potentially less accurate curve, but reduce complexity.

Interpolate

Create a perfectly accurate curve, but with no reduction in complexity.

For example, if the original linear curve has 56 edit points, the new cubic b-spline will also have 56 edit points.

End tangents

Circle/Cubic

Choose either Circle or Cubic for two different ways of setting the end tangents. The default is Cubic.

Specify

Click this option if you know the exact values of the end tangent vectors that you want the fitted cubic geometry to have. Twelve slider fields are displayed.

Tolerance

Acceptable deviance between original and new curve/surface. The default is 0.010 cm. Only Used when Fit Type is Fit.

NoteThese options appear when End Tangents is set to Specify.

Start/End U/V Tangent

These four fields allow you to specify the exact (X,Y,Z) components of the end tangent vectors of the fitted curve or surface.

Only Start U Tangent and End U Tangent are used for curves.

Other Options

Knot Spacing

This option controls the type of curve parameterization used by the new cubic b-spline objects.

NoteThe following options apply only to surfaces.

Chord Ht Ratio

Enforce a ratio between the height of the curve off the chord (a line connecting two consecutive edit points) and the chord length. Where the ratio is exceeded, new edit points are added to the new curve.

Use this option to break up long or high-curvature spans of the original surface into shorter, simpler spans.

NoteThis option appears when Chord Ht Ratio is on.

Ratio Value

The factor by which the height must exceed the chord length before Fit b-spline adds new edit points.

For example, if the Ratio Value is 10.000, the height must be ten times the chord length before additional edit points are created. The lower the value, the more edit points will be added in high curvature areas.