Overview
Spline Tools adds a powerful Scene View toolbar overlay to Unity's built-in Spline system. Select any GameObject with a SplineContainer and the toolbar appears automatically, giving you instant access to a complete set of spline editing tools.
The toolbar is organized into three groups: Tool Buttons that each open a dedicated overlay panel, Toggle Buttons that stay active regardless of the selected tool, and Action Buttons for quick-access to common workflows.
Early Access
Spline Tools is released as Early Access at a discount price. Features will be added and functionality will change depending on Feedback.
Discount
Everyone who supported me with any of these assets will get this asset at a discount:
Tool Buttons
* Flow - Click-drag on surfaces to paint splines freehand. Supports tension control, auto/manual point reduction, extend and replace modes, closed loops, and surface layer filtering. A Terrain Flow mode traces downhill paths across Unity Terrain in real time while you drag spline knots.
* Shape - Generate preset shapes including Line, Rectangle, Rounded Rectangle, Circle, Landscape (Perlin noise) and Race Track (procedural with self-intersection resolution). Pipette buttons pick dimensions from existing splines. Auto Apply for instant feedback.
* Create - Derive new splines from existing ones. Create parallel offset copies, generate bounding box splines around GameObjects, or compute the 2D convex hull. Optional Align to Surface snapping.
* Align - Snap knots to terrain or any surface via raycasting. Flatten along X, Y or Z using the selected knot's local axes. Configurable layer mask, ray distance, height offset and normal alignment.
* Smooth - Curvature-aware relaxation that targets sharp corners with configurable iterations, strength and angle threshold. Jitter mode adds controlled randomness to break up uniform paths.
* Scale - Expand or contract splines from their centroid. Uniform or per-axis scaling with an axis mask.
* Structure - Subdivide, unsubdivide, reduce knots (Ramer-Douglas-Peucker), distribute evenly, distribute at fixed intervals, reverse direction, unroll rotations, and mirror across any axis.
* Object - Copy and paste spline data between SplineContainers. Clear all splines from a container.
* Options - Configure the Gizmo visualiser (per-axis normals, spline length, segment distances) and Snap behaviour (ray distance, height offset, normal alignment) from a single panel.
Toggle Buttons
* Gizmo - Visualise spline normals, total length and segment distances in the Scene View. Each axis can be toggled independently with customizable colours. Stays active with any tool.
* Snap - Automatically snap knots to the closest surface while dragging them. Zero overhead when disabled.
Action Buttons
* Edit Mode - Enter spline edit mode instantly without navigating Unity's dropdown menus.
* Draw Spline - Activate Unity's spline creation tool with a single click.
* Knot Tool - Click on a curve to insert knots. Hold Ctrl to delete, Shift for free-placement.
* Select Tool - Brush-select knots by dragging. Shift-drag to add, Ctrl-drag to remove from the selection.
Additional Features
* Instant Edit Mode - Double-click gameobject to enter spline edit mode
* Pivot - Center the main handle at the spline centroid
* Popout - Show tool overlay content in editor window
* Pin - Show multiple tool panels as editor windows simultaneously for quick access
Preferences
Toolbar visibility modes, text label toggles, customisable gizmo colours, screen-relative or world-space normal length, and debug logging - all from Unity's Editor Preferences.
Requirements
Screenshots
The screenshots show the asset in use with various toolbar overlays which are available for the individual toolbar items.
Support & Feedback
With Unity's UI Toolkit being in flux it's nearly impossible to test in all Unity versions. The asset was developed in Unity 6.0 with all future Unity versions in mind. If you encounter an issue or if you just have questions feel free to contact me any time. See my publisher page for contact information.