Edit > Select > By Curvature selects polygons that lie in regions of a given curvature (or less).
The parameters are:
Sensitivity field (decimal value 0.0 to 1) - 0 selects all polygons; low sensitivity selects many polygons; high sensitivity selects fewer polygons; 1 selects no polygons.
Deselect Region button - Causes a selected island of polygons to be removed from the selection. Click this button, then click one or more islands of polygons in the Viewing Area to remove them from the selection. Another way to un-select polygons is to use the standard selection tools with the Ctrl key.
Reset button - restores all islands of polygons that may have been removed; re-applies the Sensitivity field to the entire polygon object.
OK button - terminates the dialog and maintains the set of selected polygons.
Cancel button - terminates the dialog without selecting any polygons.
Tip: Use Edit > Select > By Curvature to select high-curvature area, then reverse the selection by Edit > Reverse Selection so that the high-curvature regions are not affected by subsequent Polygons > Relax, Clean, or Decimate.