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Dragon curve: Difference between revisions
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end</lang>
<div>[[File:DragonCurveRunBasic.png]]</div>
=={{header|Rust}}==
<lang rust>
use ggez::{
conf::{WindowMode, WindowSetup},
error::GameResult,
event,
graphics::{clear, draw, present, Color, MeshBuilder},
nalgebra::Point2,
Context,
};
use std::time::Duration;
// L-System to create the sequence needed for a Dragon Curve.
// This function creates the next generation given the current one
// L-System from https://www.cs.unm.edu/~joel/PaperFoldingFractal/L-system-rules.html
//
fn l_system_next_generation(current_generation: &str) -> String {
let f_rule = "f-h";
let h_rule = "f+h";
let mut next_gen = String::new();
for char in current_generation.chars() {
match char {
'f' => next_gen.push_str(f_rule),
'h' => next_gen.push_str(h_rule),
'-' | '+' => next_gen.push(char),
_ => panic!("Unknown char {}", char),
}
}
next_gen
}
// The rest of the code is for drawing the output and is specific to using the
// ggez 2d game library: https://ggez.rs/
const WINDOW_WIDTH: f32 = 700.0;
const WINDOW_HEIGHT: f32 = 700.0;
const START_X: f32 = WINDOW_WIDTH / 6.0;
const START_Y: f32 = WINDOW_HEIGHT / 6.0;
const MAX_DEPTH: i32 = 15;
const LINE_LENGTH: f32 = 20.0;
struct MainState {
start_gen: String,
next_gen: String,
line_length: f32,
max_depth: i32,
current_depth: i32,
}
impl MainState {
fn new() -> GameResult<MainState> {
let start_gen = "f";
let next_gen = String::new();
let line_length = LINE_LENGTH;
let max_depth = MAX_DEPTH;
let current_depth = 0;
Ok(MainState {
start_gen: start_gen.to_string(),
next_gen,
line_length,
max_depth,
current_depth,
})
}
}
impl event::EventHandler for MainState {
// In each repetition of the event loop a new generation of the L-System
// is generated and drawn, until the maximum depth is reached.
// Each time the line length is reduced so that the overall dragon curve
// can be seen in the window as it spirals and gets bigger.
// The update sleeps for 0.5 seconds just so that its pogression can be watched.
//
fn update(&mut self, _ctx: &mut Context) -> GameResult {
if self.current_depth < self.max_depth {
self.next_gen = l_system_next_generation(&self.start_gen);
self.start_gen = self.next_gen.clone();
self.line_length -= (self.line_length / self.max_depth as f32) * 1.9;
self.current_depth += 1;
}
ggez::timer::sleep(Duration::from_millis(500));
Ok(())
}
fn draw(&mut self, ctx: &mut Context) -> GameResult {
let grey = Color::from_rgb(77, 77, 77);
let blue = Color::from_rgb(51, 153, 255);
let initial_point_blue = Point2::new(START_X, START_Y);
clear(ctx, grey);
draw_lines(
&self.next_gen,
ctx,
self.line_length,
blue,
initial_point_blue,
)?;
present(ctx)?;
Ok(())
}
}
fn next_point(current_point: Point2<f32>, heading: f32, line_length: f32) -> Point2<f32> {
let next_point = (
(current_point.x + (line_length * heading.to_radians().cos().trunc() as f32)),
(current_point.y + (line_length * heading.to_radians().sin().trunc() as f32)),
);
Point2::new(next_point.0, next_point.1)
}
fn draw_lines(
instructions: &str,
ctx: &mut Context,
line_length: f32,
colour: Color,
initial_point: Point2<f32>,
) -> GameResult {
let line_width = 2.0;
let mut heading = 0.0;
let turn_angle = 90.0;
let mut start_point = initial_point;
let mut line_builder = MeshBuilder::new();
for char in instructions.chars() {
let end_point = next_point(start_point, heading, line_length);
match char {
'f' | 'h' => {
line_builder.line(&[start_point, end_point], line_width, colour)?;
start_point = end_point;
}
'+' => heading += turn_angle,
'-' => heading -= turn_angle,
_ => panic!("Unknown char {}", char),
}
}
let lines = line_builder.build(ctx)?;
draw(ctx, &lines, (initial_point,))?;
Ok(())
}
fn main() -> GameResult {
let cb = ggez::ContextBuilder::new("dragon curve", "huw")
.window_setup(WindowSetup::default().title("Dragon curve"))
.window_mode(WindowMode::default().dimensions(WINDOW_WIDTH, WINDOW_HEIGHT));
let (ctx, event_loop) = &mut cb.build()?;
let state = &mut MainState::new()?;
event::run(ctx, event_loop, state)
}
</lang>
=={{header|Scala}}==
Line 5,693 ⟶ 5,844:
{{omit from|AWK}}
[[Category:Geometry]]
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