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Tree Layout

Tree layout requires a tree or a collection of trees as its input. A tree is a graph that contains no undirected cyclic edge path.

General Tab

Layout Style

The layout style determines the overall style of the resulting tree layout. The remaining option tabs allow for the configuration of the chosen layout style in more detail.

Directed
The tree will be laid out hierarchically with the root node at the top. This is a good choice for directed trees with a unique root node and a moderate number of nodes on a single hierarchy level. This layout style uses the input graph as a sketch to determine the order of siblings at a common node. This means that the order of x-coordinates of the nodes in the input graph determines the order of siblings in the resulting layout.
Balloon
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.
Horizontal-Vertical
The children of a node will be either arranged on a horizontal or on a vertical line. The edges will be routed orthogonally in a bus-like fashion. This layout can be very compact if the user has chosen the right alignment type for the children of a node. Subgraphs rooted at selected nodes will be laid out vertically. Subgraphs rooted at unselected nodes will be laid out horizontally.
Compact
Generates compact orthogonal tree drawings. As a layout constraint a preferred aspect ratio (relation of width to height) can be given. This is especially useful when the graph should fit perfectly on a page of given size.

Allow General Graphs

Whether non-tree graphs should be processed, too. (Normally, only proper tree-structured graphs are processed.)

Routing Style for Non-Tree Edges

Determines the routing style for all non-tree edges.
(Note: Tree and non-tree edges are determined automatically.)

Organic
Organic routing.
Orthogonal
Orthogonal routing.
Straight-Line
Straight-line routing.

Act on Selection Only

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

Directed Tab

These options configure the layout style Directed in more detail.

Minimal Node Distance

Determines the minimal distance between the siblings of a node.

Minimal Layer Distance

Determines the minimal distance between parent and child nodes.

Orientation

Determines the main layout orientation. The layouter tries to arrange nodes in such a way that all edges point in the main layout direction.

Top to Bottom
The main layout orientation will be from top to bottom. Note that the documentation for the other layout options assumes that this default layout orientation is being used.
Bottom to Top
The main layout orientation will be from bottom to top.
Left to Right
The main layout orientation will be from left to right.
Right to Left
The main layout orientation will be from right to left.

Port Style

Determines the port assignment policy to be used.

Node Centered
Ports will be placed in the center of the corresponding nodes.
Border Centered
Ports will be placed in the center of the border of the corresponding nodes.
Border Distributed
Ports will be distributed along the border of the corresponding nodes.

Consider Node Labels

Whether or not node labels should be considered during layout calculation.

Consider Edge Labels

Whether or not edge labels should be considered during layout calculation.

Orthogonal Edge Routing

If set, all edges will be routed orthogonally in a bus-like fashion. If not set, the edges will be routed as straight-line segments.

Edge Bus Alignment

Determines the relative placement of the bus-like routing of edges that connect to child nodes.

Child Alignment

Determines the placement of same-level child nodes relative to each other. 0.0 means alignment at the top side of the nodes, 1.0 at the bottom side.

Leaf Layout Policy

This option determines the placement of leaf nodes. Leaf nodes are nodes that have no child nodes. Depending on the selected leaf layout policy, an optimal area utilization can be achieved.

Siblings in Same Layer
This setting configures the algorithm to place siblings (leaf nodes with the same parent node) in the same layer. This means that all sibling nodes are aligned on the same horizontal line. This option is useful in order to make a graph more vertically compact.
Stacked (left)
This setting configures the algorithm for a stacked style of leaf nodes. This allows you to make a graph more horizontally compact. "Left" means, that all leaf nodes are placed left of the corresponding bus axis.
Stacked (right)
This setting configures the algorithm for a stacked style of leaf nodes. This allows you to make a graph more horizontally compact. "Right" means, that all leaf nodes are placed right of the corresponding bus axis.
Stacked (left and right)
This setting configures the algorithm for a stacked style of leaf nodes. This allows you to make a graph more horizontally compact. "Left and right" means, that the leaf nodes are placed both left and right of the corresponding bus axis.
Stacked (auto)
This setting configures the algorithm for a stacked style of leaf nodes. This allows you to make a graph more horizontally compact. The second advantage of the setting is, that it tries to balance all bus heights. For each subtree that consists of leaf nodes only, the algorithm decides about the style. Depending on the number of leaf nodes, "Stacked (right)" or "Stacked (left and right)" will be used.
All in Same Layer
This results in a Dendrogram-like style and places all leaf nodes of the tree in the same layer (one horizontal line for all leaf nodes of the tree). A Dendrogram layout is often applied in computational biology in order to show clustering of genes.

Enforce Global Layering

If set, the algorithm ensures that all nodes of same depth are placed in the same layer. This means, that all nodes which have the same distance to the root node (distance = number of edges on the shortest path connecting two nodes), are placed on the same horizontal line.
This setting is useful, if the hierarchical structure of the tree should be more distinguished.

Balloon Tab

These options configure the layout style Balloon in more detail.

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.

Preferred Child Wedge

This setting determines the angular range of the sector that will be reserved for the children of a node. The possible angular 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 original circular order of child nodes around each parent node will be maintained.

Horizontal-Vertical Tab

These options configure the layout style Horizontal-Vertical in more detail. Subgraphs rooted at selected nodes will be laid out vertically. Subgraphs rooted at unselected nodes will be laid out horizontally.

Horizontal Spacing

The minimal horizontal distance between adjacent nodes.

Vertical Spacing

The minimal vertical distance between adjacent nodes.

Compact Tab

These options configure the layout style Compact in more detail. Children rooted at selected nodes will be laid out in vertical columns. Children rooted at unselected nodes will be laid out in horizontal rows.

Horizontal Spacing

The minimal horizontal distance between adjacent nodes.

Vertical Spacing

The minimal vertical distance between adjacent nodes.

Bend Distance

Determines the preferred minimal distance between two consecutive bends, between source port and first bend, and between target port and last bend. In other words, this setting determines the preferred minimal length for the line segments of an edge path.

Use Aspect Ratio of View

The current aspect ratio of the view will be used to determine the preferred aspect ratio of the calculated drawing.

Preferred Aspect Ratio

Determines the preferred aspect ratio (width by height) of the resulting layout. This option allows for creating layouts which for example fit perfectly onto the page of a book.

This option will only be respected if the Use Aspect Ratio of View option is disabled.