Thicken

Converts a thin path into a closed shape with thickness — open paths get end caps, closed paths become donut topology.

Category: Shape Ops Menu path: Shape Ops > Thicken

Ports

Port	Type	Direction	Description
shape_in	shape	input	Source shape (open or closed paths)
out	shape	output	Closed thickened shape

Parameters

Param	Type	Default	Description
width	scalar	10	Total thickness in comp pixels. The output extends ±width/2 perpendicular to each path's tangent
cap	enum	Round	End-cap style for open paths: Butt (flat), Round (semi-circle), Square (extends half-width along tangent)
join	enum	Miter	Corner-join style for the offset polyline. v1 uses miter direction with miterLimit clamp; Round and Bevel fall back to bevel-style clamping past the limit
miterLimit	scalar	4	Max miter scale factor. Acute corners exceeding this fall back to a bevel-style clamp (same convention as SVG / CSS)

Expose Channels

When enabled (E button on node header), adds input ports that override params via edge connections:

Port	Type	Overrides
width_in	scalar	width

How It Works

For each input path, Thicken:

1. Linearizes the path — bezier segments are sampled into a polyline (16 samples per segment).
2. Generates two offset polylines by shifting each vertex along its outward normal (bisector of adjacent edge tangents), one to each side at distance ±width/2. Miter length scales by 1/cos(angle/2); acute corners exceeding miterLimit clamp.
3. Builds the output contour:
   • Open paths — the forward offset, an end cap, the reverse offset, a start cap, all stitched into a single closed contour.
   • Closed paths — the outer and inner offsets become two separate closed paths. Output fill_rule is forced to NonZero so DrawShape renders the donut correctly (outer filled, inner cut out).

The output uses fresh PointIds. Per-vertex attributes from the input do not carry over (resampling changes vertex topology); per-path attributes (color, strokeWidth, opacity from ShapeAttributes) propagate to each output contour. A clean sequential index attribute is regenerated on the output points.

Usage Examples

Basic: thicken a trimmed line

Line → TrimPath(start: 0, end: 0.6) → Thicken(width: 12) → DrawShape (fillEnabled: true). The trimmed segment becomes a filled rectangle/capsule that can be styled, masked, or further processed as geometry.

Donut from a closed shape

Circle(radius: 100) → Thicken(width: 8) → DrawShape. Produces a ring. Equivalent to combining a +4 and -4 OffsetPath manually, but topology is correct out of the box.

Animated stroke fill

Path → Thicken(width: keyframed 0 → 30) → DrawShape. The stroke grows from invisible to its full thickness over time as a geometric region (animatable in ways a render-time stroke isn't).

Boolean ops on stroke regions

Line → Thicken → ShapeBoolean(Subtract) ← OtherShape → DrawShape. Cut chunks out of a thickened path using boolean ops — only possible because Thicken's output is a closed region with area.

Round-cap pen tip

EditableShape → Thicken(cap: Round, width: 20) → DrawShape. Gives the same visual result as DrawShape's stroke + round cap, but as geometry that can be deformed, animated, or chained into further shape ops.

Tips

• Open vs closed input matters. Open paths get caps; closed paths become donut topology. Force a closed input by setting closed: true on EditableShape, or close downstream of TrimPath if needed.
• Bezier sampling is fixed at 16 per segment in v1. For very long curves, downstream ResampleShape can smooth the result. For very short straight segments, no sampling cost.
• Per-vertex attributes are dropped. Topology changes too much to carry them through meaningfully. If you need per-vertex styling, run ShapeAttributes after Thicken.
• Compared to DrawShape's stroke: DrawShape's strokeWidth is a render-time effect — pixels only. Thicken produces a real geometric region you can boolean, deform, sample, or pipe back into another shape op. Use DrawShape's stroke for simple visual strokes; use Thicken when you need the area as data.

Related Nodes

• OffsetPath — parallel curve at signed distance; useful for inflating/contracting closed shapes without changing topology
• TrimPath — common upstream when you want to thicken only a segment of a path
• ResampleShape — post-Thicken smoothing for fewer / more uniform vertices
• ShapeBoolean — boolean ops on thickened regions
• DrawShape — rasterize the result; for a stroke effect with no extra geometry, prefer DrawShape's built-in stroke
• RoundCorners — round the corners produced by Thicken's miter clamps