Balloon layout requires a tree or a collection of trees as its input. The tree will be routed in a quasi-radial style which we call balloon style. This is a good choice for undirected, dense, or huge trees with a high number of nodes on a single hierarchy level. Note: If the input is a general graph (not a tree), the layout is applied to a spanning tree of the graph.

## General Tab

### Root Node Policy

Determines which node should be used as root of the tree.

- Directed Root
- Chooses a node with indegree zero, if present. A good choice for directed rooted trees.
- Center Root
- Chooses the root such that the depth of the resulting tree gets minimized.
- Weighted Center Root
- Chooses the root such that the number of paths between any two nodes that traverse the root is maximal. This seems to be a natural root for undirected trees.

### Routing Style for Non-Tree Edges

Determines the routing style for all non-tree edges if the input graph is a general graph (not a tree).

(Note: Tree and non-tree edges are determined automatically.)

- Organic
- Organic routing.
- Orthogonal
- Orthogonal routing.
- Straight-Line
- Straight-line routing.
- Bundled
- Bundled routing. Edge paths will be routed such that the common parts of different edges are to some degree merged into a bundled part.

### Act on Selection Only

Whether or not to act on selected nodes and edges that are connected to selected nodes only.

### Preferred Child Wedge

This setting determines the angular range of the sector that will be reserved for the children of a node. The possible angluar range lies between 1 and 359. The remaining angular range (360-x) will be automatically used to accommodate the edge that connects to the root node.

The smaller the chosen value, the more one will gain the impression that the nodes drive away from their root nodes and the center of the graph.

Generally speaking, the compactness of the layout will decrease with smaller values. Very small values will lead to layouts that consume a lot of space.

### Preferred Root Wedge

This setting determines the angular range of the sector that will be reserved around the root node of the graph to accommodate the attached subtrees.

### Minimal Edge Length

Determines the minimal length of an edge.

### Compactness Factor

This parameter influences the length of the tree-edges as it is computed by the layouter. The smaller the compactness factor, the shorter the tree-edges and the more compact the overall layout. The bigger the compactness factor the more difficult, and hence slower, the layout computation.

### Allow Overlaps

If activated, this option further increases compactness of the resulting layout but may introduce slight node overlaps.

### Use Drawing As Sketch

If activated, the original circular order of child nodes around each parent node will be maintained.

### Place Children Interleaved

If activated, the children (successors) of each node in the tree will possibly be placed in an interleaved fashion, i.e., such that the successors of a node are placed at different distances in an alternating way. Enabling this option may produce more compact results for large graphs. Note that if there is enough space within the desired child wedge of a node all children may be placed without interleaving.

### Straighten Chains

Specifies whether chains within the graph shall be drawn straight or not. Straightening all chains may lead to smoother, more symmetric results.

### Bundling strength

Determines how tightly the edges are merged/bundled for *Routing Style for Non-Tree Edges* `Bundled`

. The higher this value, the stronger the connection of the bundled edges.

## Labeling Tab

### Place Edge Labels

If activated, edge labels will be placed by the layout algorithm. Note that this option only works for edge labels with a free edge label model. Hence, all edge labels automatically receive such a model.

### Node Labeling

Specifies how to place node labels.

- None
- Automatic node labeling is deactivated.
- Horizontal
- All node labels are placed horizontally centered on the corresponding node. There will be no overlaps between node labels and other graph elements.
- Ray-like at Leaves
- Node labels of leaf nodes get the same orientation as the nodes’ incoming edge. These labels will be placed outside the node. Note that this style can only be applied to node labels having a free node label model. Hence, all node labels automatically receive such a model. There will be no overlaps between node labels and other graph elements.
- Consider Position
- The algorithm considers the current position of the node labels, i.e., the node labels keep their relative position and do not overlap with other graph elements.

### Auto-Flip Node Labels

If activated, node labels will be automatically flipped if they would be upside-down.