Main Content

Resolve Triangulation Issues in Junctions

In RoadRunner, a junction represents the complex intersection of multiple roadways, defining a space where multiple surfaces compete for influence over the junction's final surface representation. Even in simple intersections, roads can vary by width, length, bank angle, and elevation. Roads also vary by features such as medians, curbs, and sidewalks, which need to be gracefully clipped from the final result. The goal of RoadRunner software is to unify these overlapping regions into a single representation suitable for simulation use cases. This unification often requires triangulating the junction surface to export into various formats. This task is nontrivial and can often lead to undesirable artifacts in the final junction triangulation.

To avoid common triangulation issues, use these tips.

Adjust Road Elevations

RoadRunner continually detects overlaps with neighboring roads and automatically creates junctions for any roads which overlap within 2 vertical meters. However, given that each road is fully independent, it is possible to create intersections that vary in grade, which can cause undesirable triangulation artifacts. One way to resolve this issue is to adjust road elevations to match as closely as possible within the junction.

From within the Road Plan Tool, the RoadRunner 2D Profile editor displays all overlapping roads for any selected road. You can use the tool to raise or lower any road to match the height of other roads by selecting and dragging either the height profile nodes or spans. Dragging a span is equivalent to dragging the nodes on either end.

Bank Roads

When two or more roads that intersect have different slopes, the intersections might need to be banked to better align the road surfaces. The RoadRunner Cross Section Tool offers an interface to adjust road bank at lane boundary locations. To use this tool, select the road you want to edit, select a cross section, and adjust the banking by using the 2D Cross section editor window.

Use Slip Connections

RoadRunner offers a way to enforce height constraints between roads that have a dependent relationship, such as a freeway and a freeway offramp. By creating slip roads, the end height and slope of the slip road is constrained to that of the master road. To build a slip road, use the Slip Road Tool to pull a slip road off of any other road in your scene.