Parameters

The Orthogonal Link Layout uses generic parameters, common to other graph layouts, and specific parameters applicable in orthogonal link layouts only. Refer to the following sections for general information on parameters among the graph layouts:

The Orthogonal Link Layout parameters are described in detail in this topic under:

Generic Parameters

The IlvOrthogonalLinkLayout class supports the following Layout Parameters in IlvGraphLayout as defined in the class IlvGraphLayout:

The following comments describe the particular way in which these parameters are used by this subclass.

Allowed Time

The layout algorithm stops if the allowed time setting has elapsed. (For a description of this layout parameter in the IlvGraphLayout class, see Allowed Time.)

Preserve Fixed Links

The layout algorithm does not reshape the links that are specified as fixed. (For more information on link parameters in the IlvGraphLayout class, see Preserve Fixed Links .)

Specific Parameters

The following parameters are specific to the IlvOrthogonalLinkLayout class:

Dimensional Parameters

Dimensional Parameters for the Orthogonal Link Layout Algorithm illustrates the dimensional parameters used in the Orthogonal Link Layout algorithm. These parameters are:

Dimensional Parameters for the Orthogonal Link Layout Algorithm

Link Offset

The layout algorithm computes the final connecting segments of the links (that is, the segments near the origin and destination nodes) in order to obtain parallel lines spaced at a user-defined distance. Since the links can have different widths, it takes into account the width of the links, when computing the offset. To specify the offset, use the method:

void setLinkOffset(IlUInt offset);

To obtain the current value, use the method:

IlUInt getLinkOffset() const;

Minimum Final Segment Length

You can specify a minimum value for the length of the final connecting segments of the links (that is, the segments near the origin and destination nodes) using the method:

void setMinFinalSegmentLength(IlUInt length);

To obtain the current value, use the method:

IlUInt getMinFinalSegmentLength() const;

The default value is 10.

Link Style

The layout algorithm provides two link styles. To specify the link style, the following method can be used:

void setLinkStyle(IlvLayoutLinkStyle style);

The valid values for style are:

  • IlvLayoutOrthogonalLinkStyle

The links are reshaped to a polygonal line of alternating horizontal and vertical segments. Orthogonal Link Drawing Produced with the Orthogonal Link Option shows a layout produced with this style. This is the default.

  • IlvLayoutDirectLinkStyle

The links are reshaped to a polygonal line composed of three segments: a straight-line segment that starts and ends with a small horizontal or vertical segment. Orthogonal Link Drawing Produced with the Direct Links Option shows a layout produced with this style.

Note

The layout algorithm calls the method ensureReshapeableLinks on the attached graph model to ensure that all the links can be reshaped as needed, including their connection points. With an IlvGrapher, this method may replace links with the appropriate type of link and install the appropriate link connector on the nodes. For details on this method, see the Reference Manual. For details on the graph model, see Using the Graph Model.

 

Note

The link style requires links in an IlvGrapher that can be reshaped. Links of type IlvLinkImage, IlvOneLinkImage, IlvDoubleLinkImage, IlvOneSplineLinkImage, and IlvDoubleSplineLinkImage cannot be reshaped. You can use the class IlvPolylineLinkImage instead.

To obtain the current choice, use the following method:

IlvLayoutLinkStyle getLinkStyle() const;

Number of Optimization Iterations

The link shape optimization is stopped if the number of iterations exceeds the allowed number of iterations or the time exceeds the Allowed Time. To specify this number, use the method:

void setAllowedNumberOfIterations(IlUInt iterations);

To obtain the current value, use the method:

IlUInt getAllowedNumberOfIterations() const

Note

You may want to disable the link shape optimization by setting the number of iterations to zero in order to increase the speed of the layout process.

Same Shape for Multiple Links

You can force the layout algorithm to compute the same shape for all the links having common origin and destination nodes. The links will have parallel shapes. To enable or disable this option, use the method:

void setSameShapeForMultipleLinks(IlBoolean option);

To obtain the current value, use the method:

IlBoolean isSameShapeForMultipleLinks() const;

The default value is IlFalse.

Link Crossing Penalty

The computation of the shape of the links is driven by the objective to minimize a cost function, which is proportional to the number of link-to-link and link-to-node crossings. By default, these two types of crossings have equal weights. You can increase or decrease the weight of the link-to-node crossings using the method:

void setLinkToNodeCrossingPenalty(IlUInt penalty);

The default value is 1. To increase the possibility of obtaining a layout with no link-to-node crossings (or with only a few crossings), set the parameter to a value greater than one. For example, set penalty to 5.

To obtain the current value, use the method:

IlUInt getLinkToNodeCrossingPenalty() const;

You can also increase or decrease the weight of the link-to-link crossings using the method:

void setLinkToLinkCrossingPenalty(IlUInt penalty);

The default value is 1. To increase the possibility of obtaining a layout with no link-to-link crossings (or with a only few crossings), set the parameter to a value greater than one. For example, set penalty to 5.

To obtain the current value, use the method:

IlUInt getLinkToLinkCrossingPenalty() const;