Landscape Splines

Splines for carving Landscape, modifying blendmask and deforming meshes into roads.

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Landscape Splines are a flexible system for creating any linear feature that needs to conform to a Landscape, and can even push and pull the terrain to better facilitate building these features. They are created and edited using the spline tool in the Landscape tool.

The Spline tool is best used to make streets or paths in the environment, but in general, it can be used for any mesh that must conform to the terrain, such as cobblestone walls or long straight rows of corn.

Creating a Spline

  1. Under Manage, select Edit Splines.

    Spline Tool

  2. Press Ctrl + Left-click to set your spline's first control point. The control point's sprite looks like a bumpy, brown-and-white boulder.

    A Spline control point

  3. Press Ctrl + Left-click again to create another control point and connect it to the first point by a spline segment. The selection changes to the new control point so that you can repeat this action and add more control points.

    A second spline control point

    Alternatively, you can use ALT + Left Mouse Button (LMB) Drag to create a new spline control point and segment. Select an existing control point and ALT+LMB Drag in the direction you want to place the new point. If you select the point at either end of the spline, ALT+LMB Drag adds a new segment and extends the spline. As you drag the point, you will see what the new segment will look like in the viewport.

Joining and Splitting Splines

To join two splines, select one spline and then Ctrl + Left-click on the other.

To split a spline, press Ctrl + Left-click on a segment. This splits the segment at that point and inserts a new control point.

In addition to Ctrl + Left-click, you can use ALT+LMB Drag to split a spline. Select a spline point on either side of the segment and ALT+LMB Drag the cursor towards an existing segment to split the path.
If Use Auto Rotate Control Point is enabled, after you release the cursor, the spline point auto-rotates to maintain a smooth spline.

Enable_AutoRotate.png

Adding a Static Mesh Actor to a Spline

  1. In the Content Browser, find and select the Static Mesh asset that you want to use with your spline.

  2. Click on a spline control point on your Landscape.

  3. In the Level Editor's Details panel, in the Landscape Spline section, next to Select all connected, click Segments. This ensures that the Static Mesh is added to all the spline's segments.

    All Segments

  4. In the Landscape Spline Meshes section, under Spline Meshes, if there is no element, click the plus icon (Plus Icon) to add one.

    Add Mesh

  5. Expand the element you just added. Next to Mesh, click the Assign arrow icon (Assign) to assign the selected Static Mesh.

    Mesh Added

You can also assign a Static Mesh to an individual control point by selecting that control point and assigning the Static Mesh in the Details panel, in the Mesh section.

Editing a Spline

Spline control points respond as you would expect to the translation and rotation tools, but the scale tool brings up a different tool, spline tangents.

Segment tangent scale tool

If a segment is selected, it shows the tangents at each end of the segment, and if a control point is selected, it shows the tangents of all connected segments. You can adjust the scale of the tangent by dragging the end of it, which alters how curved the segment of spline is.

Applying Splines to the Landscape

The Apply Splines to Landscape button modifies the Landscape heightmap and layer weightmaps with the spline information. The heightmap is raised or lowered to fit the spline, with a smooth cosine-blended falloff on either side. This is controlled by the width and falloff properties of the spline control points, and the Raise/Lower Terrain option on the individual spline segments. The Texture layer that is painted (if any) is specified in the Layer Name property of the individual spline segments, and the painting is affected by the spline width and falloff settings in the control points.

Spline Properties

The properties of the selected control points or segments are displayed in the Level Editor's Details panel.

Control Point Properties

Property

Description

Location

Position of the control point relative to the Landscape.

Rotation

Rotation of the control point, and controls the direction of the tangent of any attached spline segments.

Width

Width of the spline, and shown as solid lines. Affects all connected segments.

Side Falloff

The width of the cosine-blended falloff region on either side of the spline, and shown as dotted lines.

End Falloff

Control point at the end of a spline with only one attached segment. The length of the cosine-blended falloff region smoothly ends the spline segment.

Layer Name

Name of the painted blendmask layer when applying the spline to the Landscape.

Raise Terrain

Raises the Landscape to match spline when applying the spline to the Landscape. Good for roads on embankments.

Lower Terrain

Lowers the Landscape to match spline when applying the spline to the Landscape. Good for rivers and ditches.

Spline Segment Properties

Property

Description

Landscape Spline Segment

Connections

Settings specific to the two control points attached to the segment.

Connections Sub-Properties

Tangent Len

Scale of the tangent at this point, and controls the segment curve. Negative tangents cause the segment to connect to the back of the control point.

Socket Name

Socket on the control point connected to the end of the segment.

Layer Name

Name of the painted blendmask layer when applying the spline to the Landscape.

Raise Terrain

Raises the Landscape to match spline when applying the spline to the Landscape. Good for roads on embankments.

Lower Terrain

Lowers the Landscape to match spline when applying the spline to the Landscape. Good for rivers and ditches.

Landscape Spline Meshes

Spline Meshes

The meshes applied to the spline. Multiple meshes will be applied in random order controlled by the random seed.

Spline Meshes Sub-Properties (per mesh used)

Mesh

The Static Mesh applied to the spline.

Material Overrides

Overrides the Static Mesh's assigned Material with a different Material for the spline.

Center H

Determines whether to horizontally center the mesh on the spline or use the mesh's origin.

Offset

Offsets the mesh from the spline (units are in mesh-space, unscaled by the spline).

Scale to Width

Determines whether to scale the mesh to fit the spline width or to use the mesh as-is.

Scale

Multiplier to the size of the mesh. If Scale to Width is enabled, the Scale specified here is relative to the spline width. Otherwise, it is relative to the mesh's natural size.

Forward Axis

Chooses the forward axis of the Spline Mesh.

Up Axis

Chooses the Up axis of the Spline Mesh.

Random Seed

Controls the application order of multiple spline meshes to the spline.

Enable Collision

Enables collision on spline meshes.

Cast Shadow

Enables the casting of shadows by the mesh.

Controls Reference

Controls

Operation

Left Mouse Button

Selects a control point or segment.

Shift + Left Mouse Button (LMB)

Selects multiple control points or segments.

Ctrl + A

Selects all control points connected to the currently selected control points and/or all segments connected to the currently selected segment.

Ctrl + LMB

  • Adds a new control point, and automatically connects to any selected control points.

  • With a control point or multiple control points selected, creates a segment joining any selected control points to the new control point.

  • With a segment selected, splits the segment at that point and inserts a new control point.

ALT + LMB Drag

  • With a control point selected, adds a new control point and translates it in the direction of the drag.

  • Splits the path when dragged through an existing segment.

  • Adds a new segment when dragged away from either end of the spline.

Del

Deletes the selected control points or segments.

R

Automatically calculate rotation for selected spline control points.

T

Automatically flip the tangents for the selected control points / segments.

F

Flips selected spline segments (only affects meshes on the spline).

End

Snaps the selected control points to the Landscape below.

Additional Lanscape Resources

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