Approximation Tab

The Approximation tab appears in the dialog boxes of curve and surface creation commands.

This tab contains controls for:

This page discusses:

See Also
About Approximation
Automatic
  • Selected: Tolerance G0, Smoothing, Order, and Segmentation are disabled. Only Tolerance G1 and Parametrization can be specified.

    For Order and Segmentation internally preset values are used.

  • Cleared: All options are available and can be modified manually.
Defaults
If you click this button, all approximation parameters currently available and selected in the corresponding command are overwritten with the default values defined in Me > Preferences > App Preferences > 3D Modeling > Styling > ICEM Shape Design, Approximation tab.
Note: In commands where only V Segmentation can be defined, the V default value is read when selecting Defaults independently from the link setting on the Preferences Approximation tab.

Tolerance

The tolerance value defines the accuracy in which the output geometry should be created.

G0
The influence of the G0 tolerance can be controlled as follows:
  • Selected:
    • Provided that for Order and Segmentation the maximum and minimum values specified allow increasing the order, these values are increased iteratively until the deviation between the input geometry (or the theoretical results) and the approximation result exceeds the value of the G0 tolerance.
    • The value of the G0 tolerance is also available for the computation to create the theoretical results.
  • Cleared:

    The value of the G0 tolerance is now also available for the computation to create the theoretical results, i. e. the tolerance value can be edited in the text box and thus may also influence the result.

G1
The G1 tolerance is only available in commands where angle deviations can occur, e. g. Advanced Fillet command.

With the G1 tolerance the maximum angle deviation between final and theoretical result is specified. This shall guarantee that the angle between final result and selected support does not exceed the value of the G0 tolerance.

Parametrization

Standard
The result is not re-parametrized. The parameter flow of the approximation is the same as that of the input curve.
Adapt
Behaves like Standard if the selected input curve is a space curve.

If the selected input curve is a surface curve the parameter flow will be adapted either to the parametrization of the surface curve's basic surface's u- or v-direction.

Note: If the curve does not unambiguously run in U or V direction, or if it changes the direction from to V or vice versa, this option will not produce a result.
Arc Length
The curve is re-approximated with a parametrization computed according to the arc length between parametrically equidistant curve points. (The curve arc length between each pair of equidistant parameters (approximately) has same value.)

Smoothing

Allows the desired compromise between an exact approximation and a very smooth curve. The function tries to equally distribute the control points of the resulting geometry.

Order

Min.
The order is increased until it reaches this value.

For the approximation, the order can be increased until 7 at maximum.

Max.
The order is reduced until it reaches this value.

For the approximation, the order cannot exceed this value.

Fix
Increases and/or decreases the order of all selected elements until it meets exactly this value.

For the approximation, the order cannot have another value than the specified one.

Inp. (Input)
The patch is computed cell by cell and order-wise. The order in U and V direction is taken from the generating curves (guides).

Segmentation

Min.
The number of segments is increased until it reaches this value.

For the approximation, the number of segments can be arbitrarily increased.

Max.
The number of segments is reduced until it reaches this value.

For the approximation, the number of segments cannot exceed this value.

Fix
Increases and/or decreases the segmentation of all selected elements until it meets exactly this value.

For the approximation, the number of segments cannot have another value than the specified one.

Note: If in the selected geometry G2 discontinuities are found, they are transferred as sharp bends. In this case, the result may contain more segments than the maximum value specified Segmentation: Max. or Fix.