Graph Layout

Basic graph layout factory, currently supporting forced directed layout derived from https://github.com/chaangliu/ForceDirectedLayout

Usage

To the layout algorithm is an iterative one, so multiple calls in the layout method produce better results. Everybody should test what number of iterations suits the most.

Getting a layout instance

Use the LayoutFactory to setup an instance, currently only the so called force directed layout algorithm is implemented.

/* minimal usage example of the LayoutFactory */
 GraphLayout layout = LayoutFactory.newInstance()
                        .forced() // set type to force directed layouting
                        .width(1000) // set width of the layout space
                        .height(1000) // set height of the layout space
                        .edges(edges) // set edges to layout
                        .nodes(nodes) // set nodes to layout
                        .build(); // assemble instance

Layout your nodes

To be able to plug your nodes in the layout algorithm simply extend Nodeand Edge from the package de.boeg.graph.layout.domain. Nodes generic identifier should implement Object.hashCode() and Object.equals() because the layout works with hashes. The layout works with references to the nodes, meaning that the changes to the coordinates are directly written into the node instances.

Layout Algorithms

Currently only one algorithm is implemented

Force Direct Layout

The main idea is that each node is handled as a magnet so they are forced to diverge, while the edges are considered to be springs which pull adjacent nodes together. Natural clusters of adjacent nodes are the result. See Wikipedias Force-Directed graph drawing page to get a deeper understanding.

The LayoutFactory provides three methods that are force layout specific.

1. LayoutFactory.withEjectFactors(int e1, int e2) to configure the ejecting force factor for nodes, the first one is the usualy used one (default: 6). The second is used whenever the distance is smaller that 30 (default: 5) .
2. LayoutFactory.withMaxDeltas(int x, int y) to configure the maximal amount of distance added per iteration (default: x=3, y=3)
3. LayoutFactory.withCondenseFactor(int c) to configure the factor for the edges to pull back the nodes (default: 3)