How to Create Terrain and Soften Edges in SketchUp

SketchUp’s official Help documentation explains how to create terrain with the Sandbox tools and adjust model edges with Soften Edges features. Although the pages were updated on 29 September 2026, they do not specify a particular SketchUp version for these workflows. You can start terrain work with drawn or imported contour lines, or create and shape a flat rectangular TIN. Edge properties control how lines and surfaces appear in the model.

1. Create terrain from contours or a flat surface

Contour lines can define different elevations in a terrain model. If the actual terrain does not suit the design brief—or you are creating a landscape that does not exist—you can also start with a flat TIN surface.

1. Draw or import the contour lines you plan to use. SketchUp recommends using as many contour lines as possible for better results. If the lines are excessively fragmented, simplify them by reducing the number of segments before generating the TIN. Some extensions can automate this process; the Help page suggests searching for “Contours” in the Extension Warehouse.

2. Use the Move tool to position each contour line at the appropriate elevation relative to the ground plane. You can enter the elevation in the Measurements box. From Contours generates a TIN from the lines, so you need to set their elevations in the model during this preparation step.

3. When all the contours are ready, select them with Lasso Select and activate From Contours. You’ll find the tool under Draw › Sandbox. You can also add the Sandbox tools as a toolbar from View › Toolbars.

4. SketchUp creates a TIN from the selected lines. The result is a group that you can edit like other grouped geometry.

If you are not using contour lines, you can create a starting surface with From Scratch:

1. Open From Scratch under Draw › Sandbox, then click where you want the TIN to begin.

2. Set the surface’s length and width using the mouse or by entering values in the Measurements box.

3. Select the resulting TIN and change the grid spacing in the Measurements box. The documentation does not recommend a specific spacing, so choose a value to suit your model rather than assuming a fixed one.

The surface created with From Scratch can also be edited as a group. This lets you treat both contour-based and flat-start TINs like other grouped geometry in the model.

2. Soften edges or hide geometry

Soft, Smooth, and Hide do not produce the same result in SketchUp. Soft removes an edge line from view and lets adjacent faces be selected as a single surface entity. Smooth gives faces a softer shading effect, but the line itself may remain visible. Hide removes the selected item from view, but does not turn adjacent faces into a single surface entity.

For a quick way to adjust edges, select the Eraser tool or press E. Hold Ctrl on Windows or Option on macOS to toggle Smooth Edges, then move the eraser over the lines you want to adjust. To reverse the operation, click the edges while holding Alt on Windows or Command on macOS.

For more control, select the edges first. On macOS, go to Window › Soften Edges; on Windows, go to Window › Default Tray › Soften Edges. You can also right-click the selection and choose Soften/Smooth Edges. The slider in the window sets the maximum angle included in the operation; increasing the value may soften more angles.

To see which properties have been applied to an edge, right-click it and open Entity Info; you can check or change the Soft and Smooth boxes there. If you want a line to disappear without turning its faces into a single surface entity, select the geometry and use Hide. The command is available from the right-click menu or under Edit › Hide.

3. Use in architectural and visualization projects

Architectural teams with contour lines ready can use From Contours to turn them into TIN terrain. For a conceptual landscape, or when the real terrain does not fit the design idea, From Scratch provides a flat TIN to start shaping. Because the results of both methods can be edited as groups, it is easier to handle terrain geometry as a separate element in the model.

Soften and Smooth can help basic geometry look more finished. SketchUp’s documentation says that softened edges can reduce computer memory load and improve performance in complex models, but does not promise a specific speed increase. Performance expectations should therefore be assessed based on the individual model.

The difference between Hide and Soften also matters when editing a model later. Hidden geometry remains in the model; it is simply not displayed and cannot be selected directly. To view hidden lines or objects, use View › Hidden Geometry or View › Hidden Objects. In this view, items appear faded. To make them visible again, select an item and use Unhide.

Common mistakes

Running From Contours before positioning contour lines at their elevations skips an important part of terrain preparation. Check the lines’ positions and elevations before creating the TIN, and consider simplifying lines that are heavily fragmented. The documentation does not give a specific amount of simplification.

Don’t use Smooth, Hide, and Soft interchangeably: the first affects shading, the second makes an item invisible, and Soft changes how an edge relates to adjacent faces. Hidden geometry is not deleted. To access hidden items again, turn on the Hidden Geometry or Hidden Objects view. The official documentation also notes that, to change the overall look of a model, it may be more appropriate to consider style options rather than hide individual lines.