# Differential Growth Rust

![example1](https://github.com/DriesCruyskens/differential-growth-rs/raw/main/images/example1.gif)

## Overview
 
This crate provides a very easy to use Differential Growth algorithm as well as an example sketch using the excellent [nannou](https://crates.io/crates/nannou) crate.
It's as simple as providing a Vec of starting points, calling [`DifferentialGrowth::tick()`] to advance one iteration of the algorithm and obtaining the new state
using [`DifferentialGrowth::get_points()`].

Get up and running quickly by using an included point generator function like [`generate_points_on_circle()`] to generate your starting points.

Having a basic knowledge of the differential growth algorithm is highly recommended:
- <https://inconvergent.net/generative/differential-line/>
- <https://inconvergent.net/2016/shepherding-random-growth/>

## Example

The best way to understand this crate is by taking a look at `/example` folder. You can run it on any platform running `cargo run --example example`.

Otherwise, below is a quick reference on how to use this crate.

```rust
# use differential_growth::{generate_points_on_circle, DifferentialGrowth};
# use nalgebra::Point2; 
# use nannou::{event::Update, prelude::*, window, App, Frame};

// Generate a set of starting points.
// You do not have to use the included helper function,
// you could for example pass points drawn by the mouse.
let starting_points: Vec<Point2<f64>> = generate_points_on_circle(0.0, 0.0, 10.0, 10);
// Instantiate DifferentialGrowth.
// the choice of input parameters is very import to the
// succesful working of the algorithm. A value to big or too small
// or a wrong combination of values can make the algorithm behave
// like it doesn't work.
// Here I've provided values that I tested and like.
let mut dg = DifferentialGrowth::new(starting_points, 1.5, 1.0, 14.0, 1.1, 5.0);

// Advance the algorithm 1 iteration.
dg.tick();

// Get the newly calculated points.
let points_to_draw: Vec<Point2<f64>> = dg.get_points();

// draw the result by
// - drawing a line between consecutive Vec elements.
// - drawing a line between the first and the last element.
```

## References
- http://www.codeplastic.com/2017/07/22/differential-line-growth-with-processing/
- https://processing.org/examples/flocking.html
- https://inconvergent.net/2016/shepherding-random-growth/
- https://inconvergent.net/generative/differential-line/
- http://www.dgp.toronto.edu/~karan/artexhibit/mazes.pdf