Draw a curve, type a rule, get a fence

Placing modular pieces along a path by hand is slow, and every change to the path means doing it again. PCG Spline Grammar brings the idea of Unreal Engine 5's PCG Spline Grammar to Blender: describe each module once, write a rule such as Pillar,[{Fence:3,Gate},Pillar]*, and the curve fills itself. Edit the curve and every piece re-fits.

A tiny grammar

• A,B,C: place modules one after another
• {A,B,C}: pick one at random
• {A:5,B:1}: weighted random pick
• [A,B,C]: treat several modules as one group
• <A,B,C>: fallback, try A, then B, then C
• A*3: repeat n times
• ...*: keep placing until the curve is full

Brackets nest as deep as you like, and the Seed input gives a new random layout that follows the same rule.

Features

• Modules of any length: each module is measured from its bounds (or a size you type) and fitted along the curve.
• Spline Mesh mode: bend a module along the curve for rails, pipes, cables and kerbs.
• Padding and orientation: forward and back padding, forward axis, custom up or curve normal, random transform ranges.
• Fully procedural: change the curve, the rule or the seed and the layout rebuilds instantly.
• Geometry Nodes only: no scripts, no add-on.

Great for

Fences and walls, railways, pipes and cables, building facades, sci-fi corridors, roads with lamps and kerbs, level layout blockouts.

What's included

• 3 node assets: Module Info Piece, Combine Module Infos, Spline Grammar
• Example scene with grammar presets

Requirements

Blender 5.2 or newer (uses Bundles and Closures, new in Blender 5).