Advanced Curve Fitting Options

The Advanced Curve Fitting tab of the Curve and Surface Fitting dialog box allows you to set how curves are fitted through polylines, the tolerance used for curve fitting and whether any discontinuities are allowed. It is divided into two areas.

In the Curve Fitting area, you can select how CopyCAD fits the curve through the polyline from these options:

• Accurate Curve Fitting – select this option to fit the curve through points in the polyline as accurately as possible, within the constraints already set by other options in this dialog box. The distance between each polyline point and curve will be within tolerance.

• Smooth Curve Fitting – select this option to fit the curve through points in the polyline, fully utilising the curve fitting tolerance set.

• Simple Curve Fitting (through polyline segments) – select this option to fit the simplest possible curve through the polyline segments, inserting breakpoints to the tolerance set. CopyCAD considers the straight line segments between the polyline points to create a smooth curve. If the segments are within tolerance, this will create a straight line curve, even if some of the points are out of tolerance.

• Simple Curve Fitting (through polyline points) – select this option to fit the simplest possible curve through the polyline points, inserting breakpoints to the tolerance set. CopyCAD considers the polyline points to create smooth curve with high accuracy. All the polyline points must be within tolerance of the curve to create a straight line curve.

• Circular arc – select this option to fit a circular arc between the two end points, using any guide points you enter to determine the radius of the arc.

This option can only be used in singly curved curves: you cannot use a circular arc if you want to bend the curve back on itself. If you enter a guide point that is outside of the arc path, CopyCAD displays an error message, "Creating that segment failed. Returning to previous position".

Note: The Curve Fitting Tolerance is used to calculate whether a guide point is outside the arc path.

	The two Simple Curve Fitting options use the Breakpoint Insertion to Tolerance option, set in the Standard Options' Curve Parameterisation area. If a different parameterisation option is set, CopyCAD automatically changes it and displays a message to this effect.
	Note: The Curve Fitting area is also available in the Curve Fitting Options dialog box.

In the Curve Accuracy area you can set:

• the tolerance for fitting the curves to the underlying triangle model in the Curve Fitting Tolerance box.
  
  
• whether discontinuities are allowed, by clicking on the Allow Discontinuities in Curves check box to select it. For example, when it is selected, the curve can follow the boundary of the 'saddle' model accurately:

If the option is left unselected, CopyCAD maintains tangency continuity in the curve.

Note: This area is also available in the Curve Fitting Options dialog box

More:

Using the Curve and Surface Fitting Options