Break Lines — Constraining the Terrain Surface
Draw a line, lock the terrain to it — keep path edges, swales, curbs, and terrace lips razor-sharp.
Break Lines — Constraining the Terrain SurfaceTerrain surfaces in Scapiera are smooth interpolated grids — elevation values between control points are smoothed. This is natural for organic landforms but creates problems where the ground has a genuine hard edge: the top of a retaining wall, the edge of a path, the lip of a drainage channel.
Break lines solve this by constraining the terrain interpolation to maintain the elevation values exactly along the drawn line. The terrain surface meets the break line from both sides but does not blend across it.
Break lines are a Grading Primitive — they change how the terrain interpolates, not just where vertices sit. This means a break line holds its edge even when you sculpt the surrounding terrain afterward.
Adjust break line elevation
After drawing a break line, select it (click on the line). The break line inspector appears showing:
- Vertices — the list of vertices on the break line, each with an elevation value
- Elevation Source — how the break line elevation is set:
- From Terrain (default) — each vertex takes the terrain elevation at its position at the time of drawing. The break line locks in those elevation values. - Fixed Elevation — all vertices on the break line share a single specified elevation. Useful for a level path edge or terrace lip. - Sloped — the elevation interpolates linearly from the start vertex to the end vertex. Useful for sloped drainage channels with a defined gradient.
To adjust individual vertex elevations, click a vertex in the inspector list and enter a new value, or drag the vertex on the terrain surface.
Edit and delete break lines
To edit a break line: 1. Click on the break line to select it 2. The vertices become draggable handles 3. Drag any vertex to reposition it 4. Click on the break line between vertices and drag to add a new vertex 5. Select a vertex and press Delete to remove it
To delete the entire break line, select it and press Delete.
Break lines can also be converted to path entities in the main drawing — right-click the break line and choose Convert to Drawing Path to create a 2D path annotation at the break line position.
Set the constraint type
Select the break line to open its inspector. In the Constraint type dropdown, choose Hard (snap) to make the terrain follow the line precisely — ideal for built edges like curbs, driveway lips, and stepped terraces. Choose Soft (blend) for a gentler transition that eases the terrain toward the line over a wider zone — useful for ridgelines, valley bottoms, and fence footings where a natural fade is appropriate.
Adjust the edge blend distance
The Edge blend distance field controls how far the break line's influence extends laterally from the line in meters (or feet in imperial mode). A smaller value keeps the effect narrow and tight to the line; a larger value transitions the surface more gradually on either side. For hard curb edges a value of 0.3–0.5 m is typical; for soft swales 1–3 m gives a natural valley shape.
Enable a retaining step (optional)
When the break line should hold a vertical drop — like a low wall cap, garden edge, or change of level — check the Retains terrain checkbox. Two additional fields appear: Drop height sets the size of the step in meters, and Upper side (walking along path) determines which side of the line stays at the higher elevation (Left or Right, relative to the direction you drew the line).
When you first enable Retains terrain, Drop height defaults to 0.5 m and Upper side defaults to Left. Adjust these immediately — the terrain updates live as you type so you can dial in the step visually.
Move or reshape the break line
Reselect the break line at any time. Use the standard transform handles to drag individual vertices to new positions — the terrain updates in real time as you move them. You can also change the Constraint type, Edge blend distance, Drop height, or Upper side from the inspector at any point. The break line is non-destructive and can be adjusted throughout the design process.
Delete a break line
Select the break line and press Delete (or use Edit > Delete from the menu). The terrain reverts to its natural interpolated shape at that location. If you want to temporarily suspend a break line without deleting it, you can hide the entity via the Layers panel — hidden break lines are inactive.
Deleting a break line is immediate — the terrain reverts to its interpolated shape and any vertical step is removed. If you may want to restore it, hide the layer instead of deleting.
Frequently Asked Questions
Why use a break line instead of sculpting a sharp edge by hand?
Sculpting moves vertex elevations, but the terrain interpolation still averages neighboring heights, which softens any edge you create. A break line constrains the interpolation algorithm itself, so the sharp transition is maintained precisely — even when you subsequently sculpt the terrain on either side.
What is the difference between Hard (snap) and Soft (blend)?
Hard (snap) forces the terrain to match the break line elevation exactly within the blend distance — the surface has a visible crease at the line, ideal for curbs, path edges, and terrace lips. Soft (blend) eases the terrain smoothly toward the break line elevation over the blend distance without a hard crease, which suits ridgelines, valley bottoms, and drainage swales where a gradual transition looks more natural.
How does Retains terrain differ from the Retaining Wall primitive?
Retains terrain on a break line creates a clean elevation step in the terrain surface along the line — it's suitable for low garden edges, driveway lips, or shallow level changes. The Retaining Wall primitive is designed for taller, structural walls and adds a wall geometry object with materials and height that visually represents the wall in 3D and in deliverables. For level changes over about 0.5 m that will appear in client drawings, the Retaining Wall primitive is usually the better choice.
Does the break line affect terrain analysis tools?
Yes. Because a break line changes the actual terrain surface geometry, all analysis tools reflect it — the profile tool shows the step in cross-section, the slope map shows the sharp gradient change at the line, and cut/fill calculations account for the modified surface shape. This makes break lines important to place before running any site analysis.
Can I use break lines for drainage channels and swales?
Yes — this is one of the primary use cases. Draw the break line along the centreline of the swale with vertex elevations that reflect the intended drain gradient. Use Soft (blend) constraint type with an appropriate blend distance to create the natural valley cross-section. The segmentSlopes feature lets you specify a consistent percent grade per segment, so drainage channels automatically hold the correct fall without manually adjusting every vertex elevation.