The Filtering Utility dialog is used to separate long wavelength components from short wavelength components in the surface.  The filter cutoff is the wavelength of the separation.  Two filters are available in this utility:  Spline and Gaussian.  The spline filter has some advantages.  The main advantage being that the filtered surface, and residual surface, are the same size as the original unfiltered surface after processing.  The Gaussian filter algorithm must remove data along the edges of the surface, therefore, the filtered and residual surfaces are smaller in size than the original unfiltered surface.

 

The filter cutoff can be changed by moving the knob in the user interface.  A value can also be entered into the edit box.  The preview images will update a few seconds after changing this value or immediately if the Enter key is pressed.

 

The "filtered" surface contains the component wavelengths of the surface that are shorter than the selected filter cutoff wavelength.  The "residual" surface contains the component wavelengths of the surface that are longer than the selected filter cutoff wavelength.  There will always be some overlap of wavelength components very near the filter cutoff to the "roll off" of the selected filter.

 

 

To create a new surface of the short wavelength components, check the 'Filtered Surface' checkbox then click the OK button to close the dialog.  To create a new surface of the long wavelength components, check the Residual Surface' checkbox then click the OK button to close the dialog.  To close the dialog without creating a new surface, click the Cancel button.