Ground surfaces

Ground Tab

Create road-adjacent ground, free draw ground shapes, and polyline strips, with terrain conforming, height offset, materials, PCG graph support, and spline-populated static meshes. The Grounds tab is used to create and manage ground shapes around roads and in open areas. It helps fill spaces beside roads, create open ground surfaces, create closed ground areas, and build strip-like ground paths using sequential points. Ground tools are useful for verges, car parks, plazas, side areas, footpath surroundings, gravel strips, terrain fill, and any supporting environment surface that needs to sit alongside or near the road network.

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Opening the Grounds tab

Open the Road Constructor editor panel.
Use LMB to select the Ground tab icon.
Choose the required Ground workflow using the visible tool buttons and Draw Mode options.
Use the viewport to select roads, place points, inspect the ground, and confirm the result. The top row contains the main Road Constructor tabs. The Grounds tab focuses on ground creation and ground editing rather than road creation, lane editing, or marking editing.

Draw Modes overview

The Grounds tab uses three main Draw Modes: Road Anchored, Free Draw, and Polyline. These modes decide how the ground shape is created.

Road Anchored mode

Road Anchored mode keeps the workflow driven by a road edge. It is useful when you want the ground shape to start from the side of a road and preserve the road-edge contour as part of the final ground area.

Choose the Grounds tab.
Choose Road Anchored as the Draw Mode.
Use LMB on a road outer point to bind the ground to the road side.
Use LMB to place shaping points that define the outside area of the ground.
Use RMB on the opposite road outer point to close and finalise the ground shape.
Inspect the result from above and from road level to confirm the ground edge follows the intended road side.

Free Draw mode

Free Draw mode is used to create a closed ground area in open space. It is useful for shapes that do not need to be anchored directly to a road edge, such as open plazas, parking surfaces, terrain patches, landscaped areas, or custom ground islands.

Choose Free Draw as the Draw Mode.
Set Free Draw Base Height if you want the new ground to begin at a specific height.
Enable Conform To Terrain if the ground should follow the landscape height.
Adjust Terrain Height Offset if the generated ground needs to sit slightly above or below the terrain.
Use LMB in the viewport to place points around the desired outline.
Use RMB to close the shape when the outline is ready.
Review the final ground area and adjust settings if needed.

Polyline mode

Polyline mode creates a ground strip from sequential clicks. It can be used as an open strip or a closed loop, depending on the ground settings. This is useful for paths, verges, strip surfaces, boundaries, and long ground forms that follow a line rather than a filled open area.

Choose Polyline as the Draw Mode.
Set Free Draw Base Height if required.
Enable Polyline Closed Loop if the strip should close back into a loop.
Enable Conform To Terrain if the strip should follow the landscape.
Set Terrain Height Offset if the strip needs a controlled vertical offset from the terrain.
Use LMB to place strip points in sequence.
Use RMB to finish the current polyline when the outline or strip path is ready.
Inspect the generated strip and confirm whether it should remain open or close into a loop.

Mouse controls

When actively drawing, be deliberate with point placement. Place points in the order you want the edge or strip to follow. If the shape appears wrong, cancel or undo before adding too many additional points.

Conform To Terrain and Terrain Height Offset

Conform To Terrain tells the generated ground to follow the landscape instead of remaining flat at a single height. This is useful for terrain-based environments where the ground should sit naturally on hills, slopes, or uneven surfaces.

Terrain Height Offset provides fine vertical control after conforming. A small positive offset can help prevent z-fighting or the ground visually sinking into the terrain. A negative offset may be useful when the surface should sit slightly below the terrain line.

Ground Defaults

Ground Defaults apply to newly created Free Draw Ground and Polyline shapes from the Grounds tab. Road Anchored shapes still inherit and preserve their road-edge contour first before the final ground is created.
Use LMB on the asset picker, dropdowns, checkboxes, or sliders to set defaults before drawing. Defaults are most useful when you know you will create several similar ground shapes in the same session.