Unreal Engine Landscape Spline guide: Shape roads and paths to terrain

Unreal Engine’s Landscape Spline tools can be used to create roads, paths, fences and other linear features that follow the terrain. In the workflow described in Epic Games’ official documentation, you can edit spline control points and segments, place meshes on the terrain, and—once you add the required edit layer—change terrain elevation to follow the spline. The documentation page does not specify a particular Unreal Engine version, so the steps below are based on the interface and feature names in that official documentation.

1. Create a spline and shape its path

1. In the Landscape editing tools, open the Manage tab and select the Spline tool.

2. Ctrl + left-click on the terrain to create the first control point. Repeat to connect a new point to the previous one and extend the path.

3. Alternatively, select a control point and Alt + left-drag to add a new point and segment. Dragging outward from a point at the end of the path extends the spline; dragging onto an existing segment splits the path.

4. Select control points and use the move and rotate tools to reposition them. Drag the tangents that appear when you select a segment or point to adjust the segment’s curve.

To connect one spline to another, select one spline, then Ctrl + left-click on the other. Ctrl + left-clicking on a segment splits the path by adding a new control point at that location. These methods let you build a route in sections and refine it later, rather than having to draw it perfectly in one go.

2. Modify terrain to follow the spline

Creating a spline alone does not change the Landscape heightmap. To do that, create a new edit layer in the Edit Layer Stack and choose Spline Edit Layer. Once the layer is added, the Landscape responds to spline changes, allowing you to raise or lower the terrain to match the spline path.

The height transition is softened using the width and falloff values on either side of the spline. Half-Width on control points sets the spline’s half-width, while Side Falloff defines the transition area on both sides. In the segment or control point properties, Raise Terrain raises the terrain and Lower Terrain lowers it. The official documentation associates raising terrain with roads built on embankments, and lowering it with rivers and ditches.

To have the spline paint a layer on the terrain, use the relevant segment’s Layer Name property. The width and edge transition of the paint are also affected by the control points’ width and falloff settings. This lets you edit the route geometry, terrain surface and layer painting together.

3. Place meshes along the spline

1. Select the Static Mesh you want to use in the Content Browser.

2. Click a spline control point on the Landscape. In the Level Editor’s Details panel, use the Segments button in the Landscape Spline section to apply the mesh to the spline segments.

3. If there are no entries under Spline Meshes in the Landscape Spline Meshes section, add one using the plus icon. Expand the new entry and assign the selected Static Mesh using the Assign icon next to Mesh.

4. To assign a mesh to a single control point only, select that point and use the Mesh section in the Details panel.

For segment meshes, Scale to Width scales the mesh to match the spline’s width, while Forward Axis and Up Axis determine the mesh’s orientation along the spline. Offset shifts the mesh relative to the spline. If you define multiple meshes on the same spline, they are applied in a random order; Random Seed controls the order. If the mesh appears reversed or scaled unexpectedly, check these properties and the mesh’s axes.

The first two rows give the defaults stated in the documentation; they are not recommendations that apply unchanged to every project. Whether the mesh conforms to the spline’s width is also controlled by Scale to Width; the documentation does not specify one universal value for this property.

4. Nanite use and version note

The Unreal Engine 5.3 release notes describe an experimental first implementation of spline mesh components with Nanite meshes. To enable the feature, the notes specify adding the following line to the settings file:

r.Nanite.AllowSplineMeshes=1

The feature is described as experimental in the UE 5.3 notes. Epic warns that enabling it may affect culling performance across Nanite and that culling issues are known to occur with excessive deformation. Therefore, test the results with the project and meshes you intend to use rather than enabling the setting directly in a production scene. This note does not mean that Landscape Splines work the same way in every version.

Common mistakes

• Terrain does not change: Creating a spline is not enough; check that a Spline Edit Layer has been added to the Edit Layer Stack.

• Mesh is not added to segments: Check the Segments selection in the Details panel and confirm that a mesh has been assigned under Landscape Spline Meshes.

• Road edges look harsh: Review the Half-Width and Side Falloff values on the control points, as well as the segment’s raise or lower setting.

• Mesh orientation or order is unexpected: Check the mesh’s Forward Axis and Up Axis properties; if multiple meshes are in use, Random Seed affects their order.

Impact on architecture and archviz workflows

Architecture teams creating site plans, access roads, pedestrian routes or boundary features on terrain can benefit from the spline workflow, since they can edit the path by changing its control points. The same method can also be used to apply meshes along a route and shape the terrain to follow it in real-time archviz scenes. However, the source documentation does not specify hardware requirements; it does warn about performance impact for the Nanite spline mesh feature in UE 5.3. Confirm the version in use, mesh orientation, terrain layer and licensing terms before starting a project.