Features and limitations of the LL

Features of both short and long link layouts (LL)

Reshapes the links of a graph in either an orthogonal or a direct style, without moving the nodes. Orthogonal and direct style links can be combined in the same layout.
Allows you to specify which side of the node (top, bottom, left, or right) a link can be connected to, or to preserve the existing connection points of the links.
Supports self-links (that is, links with the same origin and destination node).
Supports multiple links (that is, more than one link between the same origin and destination nodes).
Allows you to specify pinned (fixed) links that the layout algorithm cannot reshape.
Supports intergraph links of nested graphs. An intergraph link is a link whose end nodes belong to different subgraphs of a nested graph.
Supports an incremental mode: If new links are added to a drawing, the next layout takes the shapes of the old links into account.

Two layout modes: short links with a limited number of bends or long links with unlimited number of bends.

Links are placed freely in the space.
Link-to-link and link-to-node crossings are reduced, if it is possible with link shapes that have a maximum of four bends.
Links of different width are supported.
Link bundles between the same pair of nodes are supported. Optionally, the algorithm can ensure that multiple links are bundled together by giving them parallel shapes.
Automatically arranges the final segments of the links (the segments near the origin or destination node) to obtain a bundle of parallel links.
Provides two optional shapes for the self-links.
Fast algorithm with low memory footprint.

Links are placed on a grid.
Link-to-node crossings of orthogonal links are avoided, even if it introduces many bends.
Orthogonal link segments do not overlap.
Does not bundle the final segments. Instead, it distributes the links on the border of each end node according to which border has more free space.
Fast algorithm: speed and memory footprint depend on the grid spacing.

Since the Link Layout algorithm reshapes the links, it works preferably with links of type IlvPolylineLinkImage and link connectors of type IlvFreeLinkConnector.
When routing intergraph links, the incremental mode cannot be used. Due to the complexity of intergraph link routing, more crossing and overlapping can occur than when routing normal links.
In short link mode, crossing and overlapping of links with other links and nodes cannot always be avoided because the algorithm uses link shapes with a limited number of bends. This happens in particular when there are many obstacles between the end points of a link.
In long link mode, link crossing cannot always be avoided. Segments of orthogonal links that overlap are always avoided unless there is no free space remaining on the border of the end nodes. Any overlapping of nodes and links is always avoided unless one end node is inside an enclave. An enclave is an area that is surrounded by other nodes such that the area cannot be reached from the other end node, see A node inside an enclave.
In long link mode, segment overlapping or overlapping between nodes and links cannot always be avoided if the direct link style is used.
The long link mode is slower and uses more memory if the grid spacing is tiny.