Performing a Curvature Analysis

This task shows how to analyze the curvature of curves, or surface boundaries.

This command is only available with:

  • FreeStyle Shaper

  • Generative Shape Design 2

  • Wireframe and Surface for Building 1.

Open the FreeStyle_10.CATPart document.

  When analyzing surface boundaries
  • if you select the surface, the analysis is performed on all its boundaries
  • if you select a specific boundary, the analysis is performed only on this boundary.
    Make sure the Geometrical Element Filter selection mode is active from the User Selection Filter toolbar. This mode lets you select sub- elements.
  1. Click the Porcupine Analysis icon:

  1. Select the curve.

  • The Curvature Analysis dialog box appears.

  • Automatically the curvature comb is displayed on the selected curve:

  1. Click the More... button in the Curvature Analysis dialog box.

  • Select the Project on Plane checkbox to analyze the projected curve in the selected plane referenced by the compass.

  • If you unselect the Project On Plane option, the analysis is performed according to the curve orientation.
    This is the default option.

  1. Use the spinners to adjust the number of strikes and modify the density.

  1. You can also decide to halve the number of spikes in the comb clicking as many times as wished the /2 button.


This option is particularly useful when the geometry is too dense to be read but the resulting curve may not be smooth enough for your analysis needs.

You could just as well double the number of spikes using the X2 button.

  1. Similarly, click the /2 button to fine-tune the amplitude (size) of the spikes, and re-compute the analysis curve accordingly.

  1. Click Curvilinear to switch from the Parametric discretization mode to the Curvilinear analysis. You will get something like this:

  1. Select the Automatic option optimizes the spikes length so that even when zooming in or out, the spikes are always visible.

  1. Select the Logarithm and the Particular options to display the logarithmic values in the 3D geometry.


Displaying these values does not modify the analysis.

  1. Click Reverse, you will get something like this:



That is the analysis opposite to what was initially displayed. This is useful when from the current viewpoint, you do not know how the curve is oriented.

  1. Use the Particular checkbox to display at anytime the minimum and the maximum points.

  • Inflection points are displayed only if the Project on Plane and Particular checkboxes are checked.

  • The Inverse Value option displays the inverse value in Radius when the Curvature option is selected, or in Curvature when the Radius option is selected. This option does not recalculate Max and Min type values, it displays only the inverse values and Max and Min location for the selected type are still displayed.


You can right-click on any of the spikes and select Keep this Point to keep the current point at this location.
A appears in the specification tree. 
If you check the Particular option, you have more contextual commands:

Take care that all these contextual commands are applicable not only to the curve where you have right-clicked the spike but to all the curves involved in the analyses.

  • Keep all inflection points: keep all the inflection points.

  • Keep local minimum: keep all the points corresponding to all the minima except the minimal minimum.

  • Keep local maximum: keep all the points corresponding to all the maxima except the maximal maximum.

  • Keep global minimum: keep only the point corresponding to the minimal minimum.

  • Keep global maximum: keep only the point corresponding to the maximal maximum.

  • Keep all minimum: keep all the points corresponding to all the minima.

  • Keep all maximum: keep all the points corresponding to all the maxima.

  1. Finally, click the icon to display the curvature graph:

The curvature amplitude and parameter of the analyzed curve is represented in this diagram.

When analyzing a surface or several curves, i.e. when there are several curvature analyses on elements that are not necessarily of the same size for example, you can use different options to view the analyses. 


For example, when analyzing a surface, by default you obtain this diagram, where the curves color match the ones on the geometry.

  • Same vertical length : all curves are displayed according to the same vertical length, regardless of the scale:

  • Same origin : all curves are displayed according to a common origin point on the Amplitude scale:

  • Vertical logarithm scale : all curves are displayed according to a logarithm scale for the Amplitude, and a linear scale for the Curve parameter:

Depending on the chosen option, values displayed in the diagram are updated.
The last icon is used to reframe the diagram within the window, as you may move and zoom it within the window.

  1. Right-click a curve and choose one of the following options from the contextual menu:

  • Remove: removes the curve

  • Drop marker: adds in the specification tree

  • Change color: displays the Color selector dialog box that enables you to change the color of the curve.

  1. Slide the pointer over the diagram to display the amplitude at a given point of the curve.
    You can slide the pointer over the diagram and the 3D analysis.
    Click the x in the top right corner to close the diagram.

  1. Click OK in the Curvature Analysis dialog box once you are satisfied with the performed analysis.


The analysis (identified as Curvature Analysis.x) is added to the specification tree.

In case of clipping, you may want to temporarily modify the Depth Effects' Far and Near Limits. See Setting Depth Effects in Infrastructure User Guide.