Any network analysis in the Rhino UNA toolbox requires at least two geometry inputs—first, an input analysis network along which all trips are computed, and second, Origin and Destination points, where movement starts or ends.

The Add Curves to Network tool prompts you to select curves that you want to build your network out of. Select all the curves you want to involve in the network and press enter. This will automatically turn the selected curves into a network and build an adjacency matrix that is used for analysis.

In order for network analyses to work, network curves need to provide continuity between the Origin and Destination points you analyze (see Figure 45). If your network curves do not share a common end node, then Origin and Destination points found on different network segments might not be topologically connected to each other. If one curve ends on top of another, but the latter does not have a node at the intersection (e.g. T intersection with no shared endpoints), then there is no topological continuity between the two curves. Curves that intersect without sharing a common node can be used to model three-dimensional overpasses or underpasses.

The tool can accept any kinds of curves to participate in networks—lines, polylines, curves, arcs, etc. Networks of these curves can either be planar (2D) or three-dimensional, as long as adjacent curves share a common end node with each other. While 2D networks may be adequate for representing street and building networks in urban settings, 3D networks offer additional opportunities for analyzing circulation systems and layouts within buildings or in multi-layered urban infrastructure systems.

For visual clarity, the default settings in the UNA Graphic Options will visualize dead-ends or “naked edges” of the network with little black crosses (Figure 46). You can turn these black crosses off in the Graphic Options by turning off Nodes. The black crosses can be useful to visualize where your network might contain topological errors. In Figure 46, for instance, the first and second intersections from the top have topology issues. On the first intersection, a black cross is drawn, indicating that one or more curves around that node has a dead end and does not connect to any other curve. On the second node, a red warning with a numeric value “2” is displayed. This warning, which can also be toggled on or off in the Graphics Options using the NodeD2 setting, detects “degree 2” nodes—that is nodes that have exactly two curves intersecting at the node. In this case it signals two polylines meeting at right angles, instead of four segments sharing an endpoint.