https://github.com/mrtj/lsystem
L-System renderer in python
https://github.com/mrtj/lsystem
Last synced: 12 months ago
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L-System renderer in python
- Host: GitHub
- URL: https://github.com/mrtj/lsystem
- Owner: mrtj
- Created: 2021-01-14T17:49:03.000Z (over 5 years ago)
- Default Branch: main
- Last Pushed: 2021-01-19T13:37:06.000Z (over 5 years ago)
- Last Synced: 2025-01-16T17:30:31.234Z (over 1 year ago)
- Language: Python
- Size: 2.45 MB
- Stars: 1
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# L-System renderer
This repository contains an implementation of an *L-System* renderer.
## What is an L-System?
An *L-system* or *Lindenmayer system* is a parallel rewriting system and a type of formal grammar. An L-system consists of an *alphabet of symbols* (`actions`) that can be used to make strings, a collection of *production rules* (`rules`) that expand each symbol into some larger string of symbols, an initial *axiom string* (`axiom`) from which to begin construction, and a mechanism for translating the generated strings into geometric structures. (From [Wikipedia](https://en.wikipedia.org/wiki/L-system)).
For example a binary tree can be described in L-System as:
```python
actions = {
"A": "draw_forward",
"B": "draw_forward",
"+": "left_turn",
"-": "right_turn",
"[": "save_state",
"]": "restore_state"
}
rules = {
"A": "B[+A]-A",
"B": "BB"
}
axiom = "A"
angle = 30
```
The `angle` parameter defines the angle of the left or right turns in degrees.
When rendering the L-System one might define how much time the substition rules should be applied, in order words the maximum depth of the recursions. This parameter is called `order`.
## Usage
The LSystem library provides a default symbol -> actions mapping that conforms the [Inkspace](https://inkscape.org) L-System renderer conventions. So at minimum you should specify only the `rules` map, the initial `axiom` and the turn `angle`:
```python
from lsystem import LSystem
tree_renderer = LSystem(rules, axiom, angle)
tree_renderer.execute(tree_renderer.axiom, order=4, unit=10)
```
The `LSystem` class also contains a convenience `demo` method that draws the curve with the predefined parameters:
```python
tree_renderer.demo()
```
### json support
You can initialize the `LSystem` class also from a json file:
```python
LSystem.from_json("examples/levyc.json").demo()
```
For the available json keys refer to the documentation of the `LSystem()` constructor.
### Command line interface
```
$ python lsystem.py -h
usage: lsystem.py [-h] [-u UNIT] [-o ORDER] [-t] input_file
L-System renderer
positional arguments:
input_file json definition of the L-System
optional arguments:
-h, --help show this help message and exit
-u UNIT, --unit UNIT base unit of the drawing in pixels
-o ORDER, --order ORDER depth of the recursion
-t, --trace print tracing info to stdout
Click on the drawing window to exit.
```
## Examples
