New option to specify the angular threshold for detecting crease edges.

An entry "Crease Angle" has been added to the Layers tab of the Render
buttons, to allow users to specify an angle (between 0 and 180) used for
crease edge detection.  An edge is considered a crease edge if the angle
between two faces sharing the edge is smaller than the threshold.  The
default value is 134.43 degrees (for backward compatibility).  Be aware
that a larger threshold leads to a larger number of feature edges and
thus a larger memory consumption.

release/scripts/ui/properties_render.py

@@ -182,6 +182,7 @@ class RENDER_PT_layers(RenderButtonsPanel):
             col = split.column()
             col.label(text="Freestyle:")
             freestyle = rl.freestyle_settings
+            col.prop(freestyle, "crease_angle", text="Crease Angle")
             col.prop(freestyle, "sphere_radius", text="Sphere Radius")
             col.prop(freestyle, "ridges_and_valleys", text="Ridges and Valleys")
             col.prop(freestyle, "suggestive_contours", text="Suggestive Contours")