Sets the Composite Collider to generate closed outlines for the merged Collider geometry consisting of only edges.
The outline geometry is equivalent to using an EdgeCollider2D with the chains of edges all connected. While all the edges are closed (the end edge connects to the start edge), nothing will collide in the interior of such geometry, that is it will not overlap. A collision or trigger will be registered only if the edges are in contact with a Collider.
This is usually the most efficient geometry to use as it produces far less edges. Continuous edges do not cause unwanted collisions because all edges are connected. Unwanted collisions is where two separate Colliders get in contact even though both are aligned perfectly. Use this type of geometry to produce platform surfaces where other Colliders are to move without any interference from unwanted collisions.
Any interior holes caused by the the composite edges surrounding it, does not cause any interior overlap but is another closed off section of the new Composite Collider shape.