Region Border

Name	Type	Description
領域 regions	RegionMap Required	境界を取り出す RegionMap です

Name	Type	Description
画像 output	Image	透明背景に境界線だけを描いた画像です

Parameters

Name	Type	Default	Range	Description / Options
近傍 connectivity	Enum	Four	—	境界判定に使う近傍ルールです 4近傍`Four` 上下左右だけを見て境界を作ります 8近傍`Eight` 斜め接触も境界として扱います
配置 placement	Enum	BothSides	—	領域境界のどちら側にピクセルを置くかです両側`BothSides` 境界の両側を塗ります片側`ForwardSide` 右・下方向を基準に片側だけ塗ります小さいID側`LowerIdSide` 隣接する領域のうちIDが小さい側だけ塗ります大きいID側`HigherIdSide` 隣接する領域のうちIDが大きい側だけ塗ります辺スキャン`EdgeScan` 右・下方向の境界辺を1回だけ拾って塗ります
太さ thickness	Int	1	1–8	境界線のピクセル太さです
色 color	Color	[1,1,1,1]	—	境界線の色です

Overview

Extracts the boundaries between regions in a RegionMap as a line image on a transparent background. It produces the lines between surfaces—mortar joints in paving stones, divisions between strata, or outlines around individual faces. The go-to setup overlays it on the fill from region_fill.

Category: Generate / Region / Render
Use cases: surface boundaries in water or rock, divider lines in pixel art, and boundary extraction for downstream masks

Usage tips

The standard composite takes region_fill (fill) and region_border (lines) from the same RegionMap, then overlays them with blend. This lets you adjust line color and thickness independently from the fill.
For a pixel-art-like 1px line, use placement = ForwardSide. The default BothSides colors both sides, so some areas effectively look 2px thick.
To process the line itself, such as retaining only the lower side for a shadow, use LowerIdSide / HigherIdSide to select one side.

Related nodes

region_fill — the fill to overlay
region_boundary_trace — organize boundaries as line data
region_distance — create a gradient from boundaries instead of lines
blend — composite lines with the fill

Placement

Value	Description
`BothSides`	The current standard mode. It colors both sides of a boundary, so some areas effectively appear 2px thick even with `thickness=1`.
`ForwardSide`	Colors only one side using the right/down direction as reference. Use it to quickly create 1px boundaries.
`LowerIdSide`	Colors only the side belonging to the lower-ID region of two adjacent regions.
`HigherIdSide`	Colors only the side belonging to the higher-ID region of two adjacent regions.
`EdgeScan`	Collects each boundary edge in the right/down direction once. Use it when edges between cells should take priority over diagonal contact.

How to use

Connect Region Cells.regions -> Region Border.regions to draw lines only where regions touch. Overlay the result on Region Fill with Blend to adjust surfaces and boundaries separately.

If the input RegionMap loops horizontally or vertically, opposite edges are also treated as connected during boundary detection. Boundaries at the seams of tiled material inherit the loop settings from the generator.

Pixel-perfect lines with L-corner removal, like Path Stroke, are intended for a downstream node that converts boundaries to Path or PixelLine, rather than this node. Region Border remains focused on extracting boundary candidates from region IDs.

Use this node when you want to overlay boundaries immediately as an image. Use Region Boundary Trace when you need to organize them as line data, select only boundaries between particular IDs, or clean up short protrusions.

Input Ports

Output Ports