About Conversion

This section deals with basic concepts you should know before beginning with converting curves and surfaces.

This page discusses:

See Also
Approximation Tab
Converting Curves
Converting Surfaces

Each CAD system developed today, manages the geometry produced through their own set of tolerances and approximation algorithms. As a result of the approximations used in other CAD systems, it becomes critical on how geometry is created and managed when mixing this data within ICEM Shape Design. Today this data management process involves a lot of manual work using commands such as Conversion, Smoothing, Matching.

To address the data management process in a more efficient manner, ICEM Shape Design commands must be designed in a way that they can handle data coming from everywhere.

Within the Class A process, the more traditional approach for users is to obtain geometry output of a maximum order 7 and by having less segments and with a minimum deviation from the original input geometry. As this is not always possible users prefer to have better control over the output.

Approximation

You can convert curves and surfaces without approximating them if you deselect the Approximation check box on the Options tab of the corresponding dialog boxes.

Cell Structure

You can influence the cell structure of the result curves and surfaces.

Use Input Cell Structure
Each cell of a domain is approximated separately. The Cell Fusion options are not available.
Enable Cell Fusion
All adjacent cells of a domain whose transition quality among each other corresponds at least the value specified in Continuity, are approximated as one entity (segmentation of the domain in continuity ranges).
The Segmentation will be applied to each continuity range.
The transition parameters will be used as preferential parameters for further processing with the settings on the Approximation tab.
Manage Cell Boundaries (Curves only)
You can move, insert, and delete cell boundaries of curves using handles or the context menu at the cell boundaries, or the options Add Cell Boundaries, Remove Cell Boundaries, and Add / Remove Cell Boundaries in the drop-down list.
Important: To enable this option on the Output tab of the Curve Conversion dialog box must be selected the Single-Result option.
Note: The Cell Fusion options are not available.

Cell Fusion - Continuity

Note: The Cell Fusion options are only available if Enable Cell Fusion is selected.

The cells are only merged if at least the specified continuity is kept. To keep the number of segments as low as possible, when using G0 continuity, the tolerance will not be considered when approximating, independently from the approximation parameters set.

For Curve Conversion, Keep Input Cell Structure option is available. After the approximation operation, the resulting geometry is re-broken at the transitions.

Special Parameterization Methods for Surface Conversion

In addition to the general approximation options, the following Parametrization methods are available for the Surface Conversion command:

Curvature
The parametrization is calculated from the curvature distribution of the input surface.
Average
The parametrization is calculated from the spatial deformation (Arc Length) and the curvature distribution (Curvature) of the input surface.

The command may be carried out several times to find out the optimal parametrization method. With the parametrization methods Curvature and Average, shape and control point distribution of the result surface can be optimized. The following example shows the results created with the parametrization methods Arc Length and Curvature:

Conversion of a multi-segment spline surface to a single-segment surface



Conversion with parametrization method Arc Length



The deviation of the result from the input surface is within the allowed tolerance. However, the conversion result shows unwanted inflections at the indicated locations.

Conversion with parametrization method Curvature

The accuracy of the result surface is within the specified tolerance. The conversion result reflects the shape of the input surface without inflections.

Edge Alignment for Surface Conversion

You can align the converted surface result to the selected support surfaces by imposing continuity conditions along the edges of the converted surfaces.

Important: The Edge Alignment options in the Surface Conversion dialog box are only available if the Support check box and support surfaces are selected.
Continuity
Aligns the converted surfaces to the support surfaces with the selected continuity.
Influence
Specifies how much the converted surfaces are influenced by the alignment of the support surfaces.
Max. Distance
The support surfaces are used for edge alignment, if the distance between edges of the selected surfaces and the support surfaces is smaller than the specified value.