From BlenderWiki

	Warning
	This feature is not yet in the official version of Blender and currently only available in a branch (see here)

Line Sets

The Line Set settings determine which parts of the existing geometry are taken into account for calculating the output of the Freestyle renderer. You can (and should) use more than one Line Set to achieve more sophisticated results.

Selection by Visibility

There are 3 options for selecting edges by visibility:

Visible

Only lines occluded by no surfaces are rendered.

Hidden

Lines occluded by at least one surface are rendered.

QI Range (Quantitative Invisibility Range)

Lines occluded by a range of surfaces [min/max] are rendered.

Visible lines	Hidden lines	QI Range: 0-6
QI Range: 1-2	QI Range: 1-4	QI Range: 3-4

	Combining visibility levels
	Use separate Line Styles to combine visibility types to achieve technical drawing styles.

Selection by Edge Types

Edge Types are the basic algorithms for the selection of lines from geometry. When using the Parameter Editor you have to choose at least one Edge Type in order to get a render output but several Edge Types can be combined in one Line Set. Edge Types can also be excluded from calculation by pressing the X next to them.

Silhouette

Silhouette edge detection finds feature edges of interest that constitute a basis of line drawing in Freestyle. The output is affected by the Kr derivative Epsilon setting.

Border

Draws only on on the edges of unclosed meshes. Depends on Mesh Structure.

Crease

Shows only edges whose adjecent faces form an angle greater than the defined Crease Angle.

Ridge

Draws ridges. Very similar results to valley. Depends on your Sphere Radius settings.

Valley

Draws valleys. Very similar results to ridge. Depends on Sphere Radius

Suggestive Contour

Draws some lines which would form the contour of the mesh if the viewport was shifted. Depends on your settings for Kr Derivative Epsilon and Sphere Radius. Further information here

Material Boundary

Draws lines where two materials meet on the same object.

Edge Marks

Draws lines on Edges which where marked in edit mode via Mesh » Edges » Mark Freestyle Edge. See also Freestyle Edges

Contour

Draws the contour lines.

External Contour

Draws the contour lines, but only on the outer edges.

Silhouette	Border	Crease
Ridge	Valley	Suggestive Contour
Material Boundary	Edge Marks	Contour
External Contour

Selection by Face Marks

Draws edges of faces which were marked in edit mode via Mesh » Faces » Mark Freestyle Face See also Freestyle Edges

Selection by Group

You can in- or exclude groups of objects for line calculation. To do this select the objects you want in a group and press CtrlG. See also Grouping Objects

Then check Selection by Group in the Line Style panel and select the group you already defined. You can choose to in- or exclude groups of objects.

Selection by Image Border

If checked, Freestyle only takes geometry within the image border into consideration for line calculation. This reduces render times but increases continuity problems when geomtry is moved out of and into camera view.