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ezu

Geometry

Features -> Features transforms. They rewrite geometry before anything is painted, so downstream paint ops stay simple.

20 ops: bbox, boundary, buffer, centroid, contour, convex-hull, dash, densify, dot-density, feature-boolean, hatch, medial-axis, resample, simplify, smooth, transform, triangulate, voronoi, voronoi-fracture, wave.

Ops with no demo image below produce no visible result on their own — they feed other nodes rather than paint.

bbox

Section titled “bbox”

Axis-aligned bounding box of every input vertex (pooled across polygons, lines, and points), emitted as a single rectangular polygon.

A tile rendered with bbox
The bounding box of every input vertex — here, a shrunken cloud of water centroids. style
Field Type Required Description
features @node yes Reference to another node (@name).

boundary

Section titled “boundary”

Convert each polygon to its boundary rings (exterior + holes) as polylines. Existing polylines and points pass through.

A tile rendered with boundary
Polygon rings turned into lines — the coastline of every water body. style
Field Type Required Description
features @node yes Reference to another node (@name).

buffer

Section titled “buffer”

Minkowski sum / offset with a disk. Polygons accept negative distance for erosion; lines and points are inflated by |distance|.

A tile rendered with buffer
Roads dilated into polygons, then filled. style
Field Type Required Description
distance number | $param | @node yes Offset distance in tile pixels. Positive inflates, negative erodes (polygons only).
features @node yes Reference to another node (@name).
join miter | round | bevel no —

centroid

Section titled “centroid”

Replace input geometry with one point per polygon / polyline centroid.

A tile rendered with centroid
One point per input polygon, drawn as a dot. style
Field Type Required Description
features @node yes Reference to another node (@name).
include-lines boolean no —
include-polygons boolean no —

contour

Section titled “contour”

Isolines from a ScalarField (marching squares with linear sub-cell interpolation), chained into polylines. One feature group per level with properties {"level": <number>}, so data-driven paint can style by level. Levels are base + k·interval, or the explicit levels array (which overrides both), clamped by min/max. Chain dem → contour → stroke for elevation contours, or density → contour → stroke for point-density isolines.

Field Type Required Description
base number | $param | @node no Offset the interval grid: levels sit at base + k·interval.
field @node yes Reference to another node (@name).
interval number | $param | @node no Spacing between levels, in field units. Required unless levels is given.
levels array of number | string no Explicit levels to extract; overrides interval/base. A level may be a $param; the list is sorted and de-duplicated per render.
max number no Emit no level above this value.
min number no Emit no level below this value.

convex-hull

Section titled “convex-hull”

Convex hull of every input vertex as a single polygon.

A tile rendered with convex-hull
The convex hull of every input vertex — here, a shrunken cloud of water centroids. style
Field Type Required Description
features @node yes Reference to another node (@name).

dash

Section titled “dash”

Cut polylines into dash/gap segments. Lengths are in canvas pixels (consistent with *-px brush parameters). Polygons and points pass through unchanged.

A tile rendered with dash
Coastlines cut into dashes before painting. style
Field Type Required Description
dash-px number (0…∞) | $param | @node yes —
features @node yes Reference to another node (@name).
gap-px number (0…∞) | $param | @node yes —
phase-px number | $param | @node no Initial offset into the dash/gap pattern, in pixels. May be negative.

densify

Section titled “densify”

Insert intermediate vertices so no segment of any polyline or polygon ring exceeds target-px. Original vertices are preserved.

Field Type Required Description
features @node yes Reference to another node (@name).
target-px number (0…∞) yes —

dot-density

Section titled “dot-density”

Scatter points inside polygons at a per-feature areal density (dot density map).

A tile rendered with dot-density
Dots spread over the landmass at 12,000 people per km², one dot per 100 people. A real dot density map reads the density from each feature with density-expr instead of stating one constant. style
Field Type Required Description
density number (0…∞) | $param | @node no Constant density in units per square kilometre, used where density-expr is absent.
density-expr — no Per-feature MapLibre expression giving density in units per square kilometre, e.g. [“/”, [“get”, “POP”], [“get”, “AREA_KM2”]].
dot-value number | $param | @node no Units one dot stands for. 100 means one dot per 100 people.
features @node yes Reference to another node (@name).
jitter number (0…1) | $param | @node no How far a dot may stray from its cell centre, as a fraction of the cell. 0 leaves a visible grid.
seed integer (0…∞) no Lattice salt; change it to reshuffle the dots without changing their density.
spacing-px number | $param | @node no Lattice cell size in screen pixels. One dot per cell at most, so this caps how dense the scatter can get.

feature-boolean

Section titled “feature-boolean”

Polygon boolean operation between two Features inputs. Subject = a, clip = b. Lines and points on either input are dropped — booleans are defined on polygons only.

Field Type Required Description
a @node yes Reference to another node (@name).
b @node yes Reference to another node (@name).

hatch

Section titled “hatch”

Parallel-line hatching of input polygons.

A tile rendered with hatch
Parallel-line hatching of the landmass polygons. style
Field Type Required Description
angle-deg number | $param | @node no Hatch direction (degrees, CCW from +X).
features @node yes Reference to another node (@name).
phase number | $param | @node no Per-line offset in spacing units (0..1 cycles through one period).
spacing number (0…∞) | $param | @node yes Perpendicular spacing between consecutive lines, in tile pixels.

medial-axis

Section titled “medial-axis”

Approximate medial axis of each input polygon, emitted as polylines. Smaller densify-px → more accurate but slower; min-branch-px prunes short side branches after stitching.

A tile rendered with medial-axis
The skeleton of each polygon — a river’s centreline from its bank. style
Field Type Required Description
densify-px number (0.5…∞) | $param | @node no —
features @node yes Reference to another node (@name).
min-branch-px number (0…∞) | $param | @node no —

resample

Section titled “resample”

Resample each polyline / polygon ring to evenly-spaced vertices at spacing-px along arc length. Original vertices are not preserved.

Field Type Required Description
features @node yes Reference to another node (@name).
spacing-px number (0…∞) yes —

simplify

Section titled “simplify”

Douglas-Peucker simplify polylines and polygon rings; points pass through.

A tile rendered with simplify
Coastlines simplified with a generous tolerance, so the loss is visible. style
Field Type Required Description
epsilon number (0…∞) | $param | @node yes Max perpendicular distance a vertex may be from the simplified line, in tile pixels.
features @node yes Reference to another node (@name).

smooth

Section titled “smooth”

Chaikin corner-smoothing over each input polyline and polygon ring. Each iteration roughly doubles the vertex count; 2–3 iterations are usually enough.

A tile rendered with smooth
Coastlines smoothed, rounding off the vertex-to-vertex corners. style
Field Type Required Description
features @node yes Reference to another node (@name).
iterations integer (0…8) no —

transform

Section titled “transform”

Translate / rotate / scale every input vertex. Rotation happens around pivot (defaults to the origin) before the final translation. The scalar fields take a $param or an @node port and follow it per render; the [x, y] arrays are literal, and seed the matching scalars. Uniform scale multiplies the per-axis factors.

A tile rendered with transform
Water polygons scaled about their own centre. style
Field Type Required Description
features @node yes Reference to another node (@name).
pivot array of number no Literal [x, y] rotation centre in feature space.
rotation-deg number | $param | @node no —
scale number | $param | @node no —
scale-x number | $param | @node no —
scale-xy array of number no Literal per-axis scale. scale-x / scale-y override it; uniform scale multiplies it.
scale-y number | $param | @node no —
translate array of number no Literal [x, y] shift. translate-x / translate-y override it.
translate-x number | $param | @node no —
translate-y number | $param | @node no —

triangulate

Section titled “triangulate”

Delaunay triangulation of the input’s point set. Each triangle becomes a closed polygon. Polygons and lines on input are ignored.

A tile rendered with triangulate
Delaunay mesh over the building centroids. The op triangulates points, so polygons come through centroid first. style
Field Type Required Description
features @node yes Reference to another node (@name).

voronoi

Section titled “voronoi”

Voronoi diagram of the input’s point set. Output is a Features value carrying the Voronoi edges as polylines (each polyline is a single 2-point edge). Polygons and lines in the input are ignored — use centroid to derive points from them.

A tile rendered with voronoi
Voronoi cells around each input point. style
Field Type Required Description
features @node yes Reference to another node (@name).

voronoi-fracture

Section titled “voronoi-fracture”

Fracture each polygon in features into Voronoi sub-cells using the points in seeds as Voronoi sites. Cells are clipped against the source polygon. Lines/points on features and lines/polygons on seeds are ignored.

A tile rendered with voronoi-fracture
Polygons shattered into Voronoi shards — the crackle-glaze effect. style
Field Type Required Description
features @node yes Reference to another node (@name).
seeds @node yes Reference to another node (@name).

wave

Section titled “wave”

Displace polylines laterally with a sine wave. Lengths in canvas pixels. Sharp corners may kink (no tangent smoothing). Polygons/points pass through.

A tile rendered with wave
Road geometry perturbed sideways — the wobble behind hand-drawn styles. style
Field Type Required Description
amplitude-px number | $param | @node yes Peak lateral deviation in pixels. May be negative to flip phase.
features @node yes Reference to another node (@name).
noise-amp-px number | $param | @node no Peak 1D-value-noise jitter added on top of the sine, in pixels. 0 = pure sine (default).
noise-scale-px number (0.5…∞) | $param | @node no Cell length of the noise jitter along arc length, in pixels. Defaults to wavelength-px.
phase-px number | $param | @node no Offset into the wave at the polyline start, in pixels.
samples-per-wavelength number (2…256) no Subdivisions per wavelength. Higher = smoother but more vertices. Default 16.
seed integer (0…∞) no Optional explicit u32 seed for the world-anchored 2D value noise. Default: a fixed constant so adjacent tiles agree across the seam.
wavelength-px number (0.5…∞) | $param | @node yes —

Map renders on this site are made fromOpenStreetMap data viaProtomaps (© OpenStreetMap contributors), elevation from Re:Earth Terrain,Mapterhorn andEGM2008 (NGA), and aerial imagery from GSI Japan(© 国土地理院). The painterly styles use CC0 brushes byDavid Revoy.