lsystem-executor

Design

Execute L-system and shape grammars to produce visual derivations, SVG/PNG renders, and optional STL meshes

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L-System Executor

Execute parametric L-system grammars and render the results as images or meshes.

Overview

Takes a grammar definition (axiom + rewrite rules) and produces:

Step-by-step derivation showing the string at each iteration
2D turtle-graphics rendering as SVG and PNG
Optional 3D extrusion to STL (if --stl flag is passed)

Useful for investigations that produce symbolic growth grammars (urban evolution, microstructure growth, biological branching) and need a concrete visual artifact.

Usage

From a JSON grammar file:

python3 {baseDir}/scripts/lsystem_render.py --grammar grammar.json --steps 4 --output output_dir/

Inline grammar:

python3 {baseDir}/scripts/lsystem_render.py \
  --axiom "A" \
  --rules '{"A": "A[+B]A[-B]A", "B": "BB"}' \
  --angle 25 \
  --steps 4 \
  --output output_dir/

With STL export:

python3 {baseDir}/scripts/lsystem_render.py \
  --grammar grammar.json \
  --steps 3 \
  --stl \
  --output output_dir/

Grammar JSON Format

{
  "axiom": "A",
  "rules": {
    "A": "A[+B]A[-B]A",
    "B": "BB"
  },
  "angle": 25.0,
  "step_length": 10.0,
  "length_scale": 1.0,
  "title": "Urban-Material Growth Grammar"
}

Symbols

Symbol	Meaning
`F`	Move forward, drawing a line
`A-Z` (uppercase)	Move forward, drawing a line (also rewritable)
`f`	Move forward without drawing
`+`	Turn left by angle
`-`	Turn right by angle
`[`	Push position and heading onto stack
`]`	Pop position and heading from stack
`!`	Decrease line width
`>`	Multiply step length by length_scale

Outputs

The script produces in the output directory:

derivation.txt — string at each step
render.svg — vector graphics of the final structure
render.png — rasterized version (300 DPI)
render_steps.png — grid showing each derivation step side by side
grammar.json — the grammar used (for reproducibility)
render.stl — 3D mesh (only if --stl flag is used)