Spline Points and Alignment¶

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The shape of the structure is set by the spline at the actor's root. Points can be edited by hand or laid out with one of the tools (SplinePointsAlignTool).

Editing by hand¶

Select the actor — the spline component becomes active in the viewport. From there it behaves like any USplineComponent:

Alt-drag a point to add a new one; Delete removes the selected one.
Drag the tangent handles to change curvature.
Each point has a Spline Point Type in the Details panel: Curve (smooth), Linear (corner), Constant.

If an alignment tool is selected it does not wipe hand edits: a tool only runs when its own settings change (see "Non-sticky tools" below).

Common parameters¶

Parameter	Purpose
Mode (`ESplineCraftUseMode`)	`Concrete` / `Line` / `Curve` — the global placement strategy. See Line vs Curve Mode.
Visible Last Point Elements	show the posts and knobs at the last point of an open spline (`bCloseSection`).
Spline Close Loop	close the spline into a loop. Unavailable for the Line, Sinusoid, Arc, Spiral, Zigzag and Catenary tools.
Num Spline Points	how many points the selected tool builds (for tools that build a shape from scratch).
Design Notes	a free-text note on the actor.

The Utils panel¶

The Tool dropdown only shows the options of the selected tool; the rest are hidden. Every dropdown entry has a tooltip. The Apply Point Layout button lays the points out again manually — for when you actually want it.

Alignment tools (Tool)¶

Manual¶

Points are placed by hand. No tool touches the spline.

Line¶

A straight run of evenly spaced points. Step — spacing (m). Needs ≥ 2 points.

Rectangle¶

A closed rectangle. Clockwise, Rectangle Length (X) / Rectangle Width (Y) (m), Bevel — corner bevel (m). A point is always placed on every corner (4, or 8 with a bevel); the rest are spread along the edges in proportion to edge length, so the spacing is as even as possible all the way round even on a non-square rectangle. Needs ≥ 4 points (≥ 8 with a bevel — the count is raised to that if it is lower).

Ellipse¶

A closed ellipse, evenly divided into the requested number of points. Clockwise, Diameter X / Diameter Y (m). Needs ≥ 3 points.

Sinusoid¶

A sine wave along the X axis. Amplituda (m), Frequency. Optional random spread of the amplitude (Random Settings), which can be turned off with Ignore Random Settings.

Uniform¶

Redistributes the points that already exist evenly along the spline. Use Every Nodal Point — how many nodes to align through; Vertical Points — stand the points upright.

Bind To Surface¶

Drops the points that already exist onto the surface below them by tracing straight down. Vertical Points — stand the points upright; Additional Vertical Shift (cm); Trace Distance Above / Trace Distance Below — how far up and down to search for a surface (cm). Keep "above" small so a bridge or roof overhead is not picked up instead.

Arc¶

Part of an ellipse. Diameter X / Diameter Y (m), Start Angle — starting angle (0 points along +X), Sweep Angle — how far it sweeps (90 = a quarter, 180 = a half), Clockwise. Even Spacing (on by default) — equal steps along the curve; turn it off to step by angle.

Regular Polygon¶

A closed regular polygon with equal sides. Diameter (m), Start Angle — rotates the shape in place (e.g. stand a hexagon on a flat side instead of a corner), Sharp Corners — keep the sides straight (off — the shape rounds into a blob), Clockwise. Needs ≥ 3 points.

Spiral¶

A spiral, and a helix once it has height. Start Diameter / End Diameter (m) — the diameter changes from start to end; Turns — number of turns (fractions allowed); Height — total rise (m; 0 = a flat spiral); Clockwise; Even Spacing. Good for spiral stairs, ramps, wells.

Zigzag¶

Points alternate to either side of the X axis. Step — step along X (m), Amplitude — swing to the side (m), Vertical — swing up and down instead of sideways (a saw-tooth profile), Sharp Corners — keep the corners sharp (off — you get a wave).

Catenary¶

The curve a chain takes when it hangs freely. Span — distance between the two ends (m; the ends stay level with the actor), Sag — how far the middle drops below its ends (m). A negative value turns the curve over and arches it upwards — the shape of an arched bridge. Even Spacing — equal steps along the curve (equal chain links); turn it off to step by X. For chain fences between bollards, rope barriers, garlands, cables — and, with a negative value, arched bridges and vaults.

Follow Spline¶

Copies the points of another actor's spline — a road, a river, a cliff edge, a ready path — so the structure runs along it. Reference Actor — an actor with a spline component (it cannot follow itself); Lateral Offset — run this far to one side (m; positive is the right-hand side looking along the reference); Reverse Direction — walk from end to start; Match Reference Height — take height from the reference (ride its rises and dips) or keep every point level with the actor. Each point's type (smooth/corner) and the closed-loop state are carried over from the reference, so sharp road junctions stay sharp.

About Even Spacing¶

Equal steps of angle are not equal steps of distance once the arc's two diameters differ or a spiral's radius grows: without Even Spacing the posts bunch up where the curvature is higher. On an elliptical arc the step spread drops from about 3× to 1.05×, on a spiral from 5.5× to 1.25×.

Non-sticky tools¶

A tool rebuilds the spline only when one of its own settings changes — the tool itself, Num Spline Points, or a field of its options struct. So: turn the parameters and the shape updates live; drag a point and the edit survives. The Apply Point Layout button lays the points out again when you want a clean start. Saved scenes do not change visually: the points sit in the level, they are not recomputed on load.