From: Tomas Wenström <tomas.wenstrom@gmail.com>
Date: Sat, 30 Jan 2021 14:39:46 +0000 (+0100)
Subject: Refactored level generation + fixed bug with wall finding
X-Git-Url: http://www.dolda2000.com/gitweb/?p=kaka%2Frust-sdl-test.git;a=commitdiff_plain;h=7991463123d291446f06630ae0fe0bbe2427ad23

Refactored level generation + fixed bug with wall finding
---

diff --git a/src/core/game.rs b/src/core/game.rs
index 125bd1a..e8893de 100644
--- a/src/core/game.rs
+++ b/src/core/game.rs
@@ -1,10 +1,10 @@
-use AppState;
 use ActiveState;
+use AppState;
 use common::{Point2D, Radians};
 use core::app::StateChange;
 use core::controller::Controller;
 use core::controller::ControllerManager;
-use core::level::Level;
+use core::level::{Level, LevelGenerator};
 use core::render::Renderer;
 use point;
 use sdl2::event::Event;
@@ -21,12 +21,15 @@ use time::Duration;
 #[derive(Default)]
 pub struct GameState {
     world: World,
+    lvlgen: LevelGenerator,
 }
 
 impl GameState {
     pub fn new() -> Self {
+	let lvlgen = LevelGenerator::new(0, 5);
 	GameState {
-	    world: World::new(),
+	    world: World::new(lvlgen.generate()),
+	    lvlgen,
 	}
     }
 }
@@ -58,16 +61,18 @@ impl AppState for GameState {
 		return Some(StateChange::Push(Box::new(ActiveState::new((800, 600)))))
             }
 	    Event::KeyDown { keycode: Some(Keycode::Space), .. } => {
-		self.world.level = Level::new(self.world.level.gravity);
+		self.lvlgen.seed = std::time::UNIX_EPOCH.elapsed().unwrap().as_secs() as u32;
+		self.world.level = self.lvlgen.generate();
 	    }
 	    Event::KeyDown { keycode: Some(Keycode::KpPlus), .. } => {
-		self.world.level.increase_iteration();
+		self.lvlgen.iterations += 1;
+		println!("{} iteration(s) of cellular automata", self.lvlgen.iterations);
+		self.world.level = self.lvlgen.generate();
 	    }
 	    Event::KeyDown { keycode: Some(Keycode::KpMinus), .. } => {
-		self.world.level.decrease_iteration();
-	    }
-	    Event::KeyDown { keycode: Some(Keycode::KpEnter), .. } => {
-		self.world.level.filter_regions();
+		self.lvlgen.iterations = 1.max(self.lvlgen.iterations - 1);
+		println!("{} iteration(s) of cellular automata", self.lvlgen.iterations);
+		self.world.level = self.lvlgen.generate();
 	    }
 	    _ => {}
 	}
@@ -84,9 +89,9 @@ pub struct World {
 }
 
 impl World {
-    pub fn new() -> Self {
+    pub fn new(level: Level) -> Self {
 	World {
-	    level: Level::new(point!(0.0, 0.1)),
+	    level,
 	    ..Default::default()
 	}
     }
diff --git a/src/core/level.rs b/src/core/level.rs
deleted file mode 100644
index 4937551..0000000
--- a/src/core/level.rs
+++ /dev/null
@@ -1,400 +0,0 @@
-use common::Point2D;
-use ::{point, time_scope};
-use core::render::Renderer;
-use noise::{NoiseFn, OpenSimplex, Seedable};
-use rand::Rng;
-use sprites::SpriteManager;
-
-////////// LEVEL ///////////////////////////////////////////////////////////////
-
-#[derive(Default)]
-pub struct Level {
-    pub gravity: Point2D<f64>,
-    pub grid: Grid,
-    iterations: u8,
-    walls: Vec<Vec<Point2D<isize>>>,
-}
-
-impl Level {
-    pub fn new(gravity: Point2D<f64>) -> Self {
-	let mut lvl = Level { gravity, grid: Grid::generate(10), iterations: 10, walls: vec!() };
-	lvl.filter_regions();
-	lvl
-    }
-
-    fn generate(&mut self) {
-	self.grid = Grid::generate(self.iterations);
-    }
-
-    pub fn increase_iteration(&mut self) {
-	self.iterations += 1;
-	self.generate();
-	println!("iterate {} time(s)", self.iterations);
-    }
-
-    pub fn decrease_iteration(&mut self) {
-	self.iterations -= 1;
-	self.generate();
-	println!("iterate {} time(s)", self.iterations);
-    }
-
-    pub fn filter_regions(&mut self) {
-	self.grid.filter_regions();
-	let mut walls = vec!();
-	for mut r in self.grid.find_regions() {
-	    if r.value {
-		let mut outline = r.outline(self.grid.cell_size);
-		for i in 2..(outline.len() - 2) {
-//		    outline[i] = (outline[i - 1] + outline[i] + outline[i + 1]) / 3;
-		    outline[i] = (outline[i - 2] + outline[i - 1] + outline[i] + outline[i + 1] + outline[i + 2]) / 5;
-		}
-		walls.push(outline);
-	    }
-	}
-	self.walls = walls;
-    }
-
-    pub fn render(&mut self, renderer: &mut Renderer, _sprites: &SpriteManager) {
-	renderer.canvas().set_draw_color((64, 64, 64));
-	let size = self.grid.cell_size;
-	for x in 0..self.grid.width {
-	    for y in 0..self.grid.height {
-		if self.grid.cells[x][y] {
-		    renderer.canvas().fill_rect(sdl2::rect::Rect::new(x as i32 * size as i32, y as i32 * size as i32, size as u32, size as u32)).unwrap();
-		}
-	    }
-	}
-
-	let off = (size / 2) as i32;
-	for wall in &self.walls {
-	    for w in wall.windows(2) {
-		renderer.draw_line((w[0].x as i32 + off, w[0].y as i32 + off), (w[1].x as i32 + off, w[1].y as i32 + off), (255, 255, 0));
-	    }
-	    let last = wall.len() - 1;
-	    renderer.draw_line((wall[0].x as i32 + off, wall[0].y as i32 + off), (wall[last].x as i32 + off, wall[last].y as i32 + off), (255, 255, 0));
-	}
-    }
-}
-
-////////// GRID ////////////////////////////////////////////////////////////////
-
-
-#[derive(Default)]
-pub struct Grid {
-    pub width: usize,
-    pub height: usize,
-    pub cell_size: usize,
-    pub cells: Vec<Vec<bool>>,
-}
-
-impl Grid {
-    fn generate(iterations: u8) -> Grid {
-	time_scope!("grid generation");
-
-	let cell_size = 20;
-	let (width, height) = (2560 / cell_size, 1440 / cell_size);
-
-	let mut grid = Grid {
-	    cell_size,
-	    width,
-	    height,
-	    cells: vec!(vec!(true; height); width),
-	};
-
-	// start with some noise
-//	grid.simplex_noise();
-	grid.random_noise();
-
-	// smooth with cellular automata
-	grid.smooth(iterations);
-//	grid.smooth_until_equilibrium();
-
-	// increase resolution
-	for _i in 0..1 {
-	    grid = grid.subdivide();
-	    grid.smooth(iterations);
-	}
-
-	grid
-    }
-
-    #[allow(dead_code)]
-    fn simplex_noise(&mut self) {
-	let noise = OpenSimplex::new().set_seed(std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).unwrap().as_secs() as u32);
-	self.set_each(|x, y| noise.get([x as f64 / 12.0, y as f64 / 12.0]) > 0.055, 1);
-    }
-
-    #[allow(dead_code)]
-    fn random_noise(&mut self) {
-	let mut rng = rand::thread_rng();
-	let noise = OpenSimplex::new().set_seed(std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).unwrap().as_secs() as u32);
-	self.set_each(|_x, _y| rng.gen_range(0, 100) > (45 + (150.0 * noise.get([_x as f64 / 40.0, _y as f64 / 10.0])) as usize), 1); // more horizontal platforms
-	// let w = self.width as f64;
-	// self.set_each(|_x, _y| rng.gen_range(0, 100) > (45 + ((15 * _x) as f64 / w) as usize), 1); // opens up to the right
-    }
-
-    #[allow(dead_code)]
-    fn smooth(&mut self, iterations: u8) {
-	let distance = 1;
-	for _i in 0..iterations {
-	    let mut next = vec!(vec!(true; self.height); self.width);
-	    for x in distance..(self.width - distance) {
-	    	for y in distance..(self.height - distance) {
-		    match Grid::neighbours(&self.cells, x, y, distance) {
-			n if n < 4 => next[x][y] = false,
-			n if n > 4 => next[x][y] = true,
-			_ => next[x][y] = self.cells[x][y]
-		    }
-		}
-	    }
-	    if self.cells == next {
-		break; // exit early
-	    } else {
-		self.cells = next;
-	    }
-	}
-    }
-
-    #[allow(dead_code)]
-    fn smooth_until_equilibrium(&mut self) {
-	let distance = 1;
-	let mut count = 0;
-	loop {
-	    count += 1;
-	    let mut next = vec!(vec!(true; self.height); self.width);
-	    for x in distance..(self.width - distance) {
-		for y in distance..(self.height - distance) {
-		    match Grid::neighbours(&self.cells, x, y, distance) {
-			n if n < 4 => next[x][y] = false,
-			n if n > 4 => next[x][y] = true,
-			_ => next[x][y] = self.cells[x][y]
-		    };
-		}
-	    }
-	    if self.cells == next {
-		break;
-	    } else {
-		self.cells = next;
-	    }
-	}
-	println!("{} iterations needed", count);
-    }
-
-    fn neighbours(grid: &Vec<Vec<bool>>, px: usize, py: usize, distance: usize) -> u8 {
-	let mut count = 0;
-	for x in (px - distance)..=(px + distance) {
-	    for y in (py - distance)..=(py + distance) {
-		if !(x == px && y == py) && grid[x][y] {
-		    count += 1;
-		}
-	    }
-	}
-	count
-    }
-
-    fn set_each<F: FnMut(usize, usize) -> bool>(&mut self, mut func: F, walls: usize) {
-    	for x in walls..(self.width - walls) {
-    	    for y in walls..(self.height - walls) {
-    		self.cells[x][y] = func(x, y);
-    	    }
-    	}
-    }
-
-    fn subdivide(&mut self) -> Grid {
-	let (width, height) = (self.width * 2, self.height * 2);
-	let mut cells = vec!(vec!(true; height); width);
-	for x in 1..(width - 1) {
-	    for y in 1..(height - 1) {
-		cells[x][y] = self.cells[x / 2][y / 2];
-	    }
-	}
-	Grid {
-	    cell_size: self.cell_size / 2,
-	    width,
-	    height,
-	    cells
-	}
-    }
-
-    fn find_regions(&self) -> Vec<Region> {
-	time_scope!("finding all regions");
-	let mut regions = vec!();
-	let mut marked = vec!(vec!(false; self.height); self.width);
-	for x in 0..self.width {
-	    for y in 0..self.height {
-		if !marked[x][y] {
-		    regions.push(self.get_region_at_point(x, y, &mut marked));
-		}
-	    }
-	}
-	regions
-    }
-
-    fn get_region_at_point(&self, x: usize, y: usize, marked: &mut Vec<Vec<bool>>) -> Region {
-	let value = self.cells[x][y];
-	let mut cells = vec!();
-	let mut queue = vec!((x, y));
-	marked[x][y] = true;
-
-	while let Some(p) = queue.pop() {
-	    cells.push(p);
-	    for i in &[(-1, 0), (1, 0), (0, -1), (0, 1)] {
-		let ip = (p.0 as isize + i.0, p.1 as isize + i.1);
-		if ip.0 >= 0 && ip.0 < self.width as isize && ip.1 >= 0 && ip.1 < self.height as isize {
-		    let up = (ip.0 as usize, ip.1 as usize);
-		    if self.cells[up.0][up.1] == value && !marked[up.0][up.1] {
-			marked[up.0][up.1] = true;
-			queue.push(up);
-		    }
-		}
-	    }
-	}
-
-	Region { value, cells }
-    }
-
-    fn delete_region(&mut self, region: &Region) {
-	for c in &region.cells {
-	    self.cells[c.0][c.1] = !region.value;
-	}
-    }
-
-    pub fn filter_regions(&mut self) {
-	let min_wall_size = 0.0015;
-	println!("grid size: ({}, {}) = {} cells", self.width, self.height, self.width * self.height);
-	println!("min wall size: {}", (self.width * self.height) as f64 * min_wall_size);
-
-	// delete all smaller wall regions
-	for r in self.find_regions().iter().filter(|r| r.value) {
-	    let percent = r.cells.len() as f64 / (self.width * self.height) as f64;
-	    if percent < min_wall_size {
-		println!("delete wall region of size {}", r.cells.len());
-		self.delete_region(r);
-	    }
-	}
-
-	// delete all rooms but the largest
-	let regions = self.find_regions(); // check again, because if a removed room contains a removed wall, the removed wall will become a room
-	let mut rooms: Vec<&Region> = regions.iter().filter(|r| !r.value).collect();
-	rooms.sort_by_key(|r| r.cells.len());
-	rooms.reverse();
-	while rooms.len() > 1 {
-	    self.delete_region(rooms.pop().unwrap());
-	}
-    }
-}
-
-////////// REGION //////////////////////////////////////////////////////////////
-
-struct Region {
-    value: bool,
-    cells: Vec<(usize, usize)>,
-}
-
-impl Region {
-    fn enclosing_rect(&self) -> (usize, usize, usize, usize) {
-	let mut min = (usize::MAX, usize::MAX);
-	let mut max = (0, 0);
-	for c in &self.cells {
-	    if      c.0 < min.0 { min.0 = c.0; }
-	    else if c.0 > max.0 { max.0 = c.0; }
-	    if      c.1 < min.1 { min.1 = c.1; }
-	    else if c.1 > max.1 { max.1 = c.1; }
-	}
-	(min.0, min.1, 1 + max.0 - min.0, 1 + max.1 - min.1)
-    }
-
-    pub fn outline(&mut self, scale: usize) -> Vec<Point2D<isize>> {
-	let rect = self.enclosing_rect();
-	let (ox, oy, w, h) = rect;
-	let grid = self.grid(&rect);
-	let mut marked = vec!(vec!(false; h); w);
-	let mut outline = vec!();
-
-	let (mut p, mut dir) = self.find_first_point_of_outline(&rect, &grid);
-//	println!("starting at {:?} with dir {:?}", p, dir);
-	marked[p.x as usize][p.y as usize] = true;
-	loop {
-	    outline.push((p + (ox as isize, oy as isize)) * scale as isize);
-	    let result = self.find_next_point_of_outline(&grid, p, dir);
-	    p = result.0;
-	    dir = result.1;
-//	    println!("next at {:?} with dir {:?}", p, dir);
-	    if marked[p.x as usize][p.y as usize] {
-		// we're back at the beginning
-		break;
-	    }
-	    marked[p.x as usize][p.y as usize] = true;
-	}
-
-	outline
-    }
-
-    fn grid(&self, rect: &(usize, usize, usize, usize)) -> Vec<Vec<bool>> {
-	let (x, y, w, h) = rect;
-	let mut grid = vec!(vec!(false; *h); *w);
-	for c in &self.cells {
-	    grid[c.0 - x][c.1 - y] = true;
-	}
-	grid
-    }
-
-    fn find_first_point_of_outline(&self, rect: &(usize, usize, usize, usize), grid: &Vec<Vec<bool>>) -> (Point2D<isize>, Point2D<isize>) {
-	let (ox, oy, w, h) = rect;
-	let is_outer_wall = (ox, oy) == (&0, &0); // we know this is always the outer wall of the level
-    	for x in 0..*w {
-    	    for y in 0..*h {
-		if is_outer_wall && !grid[x][y] {
-		    return (point!(x as isize, y as isize - 1), point!(0, 1)) // one step back because we're not on a wall tile
-		}
-		else if !is_outer_wall && grid[x][y] {
-		    return (point!(x as isize, y as isize), point!(1, 0))
-		}
-    	    }
-    	}
-	panic!("no wall found!");
-    }
-
-    fn find_next_point_of_outline(&self, grid: &Vec<Vec<bool>>, p: Point2D<isize>, dir: Point2D<isize>) -> (Point2D<isize>, Point2D<isize>) {
-	let left = match dir.into() {
-	    (-1, 0) => (0, 1),
-	    (0, 1) => (1, 0),
-	    (1, 0) => (0, -1),
-	    (0, -1) => (-1, 0),
-	    _ => (0, 0),
-	};
-	let right = match dir.into() {
-	    (0, 1) => (-1, 0),
-	    (1, 0) => (0, 1),
-	    (0, -1) => (1, 0),
-	    (-1, 0) => (0, -1),
-	    _ => (0, 0),
-	};
-	if self.check(p + dir, grid) {
-//	    println!("{:?} is true", p + dir);
-	    if self.check(p + dir + left, grid) {
-//		println!("going left to {:?}", p + dir + left);
-		return (p + dir + left, left.into())
-	    } else {
-		return (p + dir, dir)
-	    }
-	} else {
-//	    println!("{:?} is false", p + dir);
-	    if self.check(p + dir + right, grid) {
-//		println!("going right to {:?}", p + dir + right);
-		return (p + dir + right, dir)
-	    } else {
-//		println!("going right from p to {:?}", p + right);
-		return (p + right, right.into())
-	    }
-	}
-    }
-
-    fn check(&self, p: Point2D<isize>, grid: &Vec<Vec<bool>>) -> bool {
-	if p.x < 0 || p.x >= grid.len() as isize || p.y < 0 || p.y >= grid[0].len() as isize {
-	    false
-	} else {
-	    grid[p.x as usize][p.y as usize]
-	}
-    }
-}
diff --git a/src/core/level/lvlgen.rs b/src/core/level/lvlgen.rs
new file mode 100644
index 0000000..3dcc3a7
--- /dev/null
+++ b/src/core/level/lvlgen.rs
@@ -0,0 +1,351 @@
+use {point, time_scope};
+use common::Point2D;
+use super::{Grid, Level};
+use noise::{NoiseFn, OpenSimplex, Seedable};
+use rand::Rng;
+
+////////// LEVEL GENERATOR /////////////////////////////////////////////////////
+
+#[derive(Default)]
+pub struct LevelGenerator {
+    pub seed: u32,
+    pub iterations: u8,
+}
+
+impl LevelGenerator {
+    pub fn new(seed: u32, iterations: u8) -> Self{
+	LevelGenerator { seed, iterations }
+    }
+
+    pub fn generate(&self) -> Level {
+	time_scope!("grid generation");
+
+	let cell_size = 20;
+	let (width, height) = (2560 / cell_size, 1440 / cell_size);
+
+	let mut grid = Grid {
+	    cell_size,
+	    width,
+	    height,
+	    cells: vec!(vec!(true; height); width),
+	};
+
+	// start with some noise
+//	self.simplex_noise(&mut grid);
+	self.random_noise(&mut grid);
+
+	// smooth with cellular automata
+	self.smooth(&mut grid);
+//	grid.smooth_until_equilibrium(&mut grid);
+
+	// increase resolution
+	for _i in 0..1 {
+	    grid = self.subdivide(&mut grid);
+	    self.smooth(&mut grid);
+//	    self.smooth_until_equilibrium(&mut grid);
+	}
+
+	self.filter_regions(&mut grid);
+
+	let walls = self.find_walls(&grid);
+	Level {
+	    gravity: point!(0.0, 0.1),
+	    grid,
+	    walls,
+	}
+    }
+
+    #[allow(dead_code)]
+    fn simplex_noise(&self, grid: &mut Grid) {
+	let noise = OpenSimplex::new().set_seed(self.seed);
+	self.set_each(grid, |x, y| noise.get([x as f64 / 12.0, y as f64 / 12.0]) > 0.055, 1);
+    }
+
+    #[allow(dead_code)]
+    fn random_noise(&self, grid: &mut Grid) {
+	let mut rng: rand::prelude::StdRng = rand::SeedableRng::seed_from_u64(self.seed as u64);
+	let noise = OpenSimplex::new().set_seed(self.seed);
+	self.set_each(grid, |_x, _y| rng.gen_range(0, 100) > (45 + (150.0 * noise.get([_x as f64 / 40.0, _y as f64 / 10.0])) as usize), 1); // more horizontal platforms
+	// let w = self.width as f64;
+	// self.set_each(|_x, _y| rng.gen_range(0, 100) > (45 + ((15 * _x) as f64 / w) as usize), 1); // opens up to the right
+    }
+
+    #[allow(dead_code)]
+    fn smooth(&self, grid: &mut Grid) {
+	let distance = 1;
+	for _i in 0..self.iterations {
+	    let mut next = vec!(vec!(true; grid.height); grid.width);
+	    for x in distance..(grid.width - distance) {
+	    	for y in distance..(grid.height - distance) {
+		    match self.neighbours(&grid.cells, x, y, distance) {
+			n if n < 4 => next[x][y] = false,
+			n if n > 4 => next[x][y] = true,
+			_ => next[x][y] = grid.cells[x][y]
+		    }
+		}
+	    }
+	    if grid.cells == next {
+		break; // exit early
+	    } else {
+		grid.cells = next;
+	    }
+	}
+    }
+
+    #[allow(dead_code)]
+    fn smooth_until_equilibrium(&self, grid: &mut Grid) {
+	let distance = 1;
+	let mut count = 0;
+	loop {
+	    count += 1;
+	    let mut next = vec!(vec!(true; grid.height); grid.width);
+	    for x in distance..(grid.width - distance) {
+		for y in distance..(grid.height - distance) {
+		    match self.neighbours(&grid.cells, x, y, distance) {
+			n if n < 4 => next[x][y] = false,
+			n if n > 4 => next[x][y] = true,
+			_ => next[x][y] = grid.cells[x][y]
+		    };
+		}
+	    }
+	    if grid.cells == next {
+		break;
+	    } else {
+		grid.cells = next;
+	    }
+	}
+	println!("{} iterations needed", count);
+    }
+
+    fn neighbours(&self, grid: &Vec<Vec<bool>>, px: usize, py: usize, distance: usize) -> u8 {
+    	let mut count = 0;
+    	for x in (px - distance)..=(px + distance) {
+    	    for y in (py - distance)..=(py + distance) {
+    		if !(x == px && y == py) && grid[x][y] {
+    		    count += 1;
+    		}
+    	    }
+    	}
+    	count
+    }
+
+    fn set_each<F: FnMut(usize, usize) -> bool>(&self, grid: &mut Grid, mut func: F, walls: usize) {
+    	for x in walls..(grid.width - walls) {
+    	    for y in walls..(grid.height - walls) {
+    		grid.cells[x][y] = func(x, y);
+    	    }
+    	}
+    }
+
+    fn subdivide(&self, grid: &mut Grid) -> Grid {
+	let (width, height) = (grid.width * 2, grid.height * 2);
+	let mut cells = vec!(vec!(true; height); width);
+	for x in 1..(width - 1) {
+	    for y in 1..(height - 1) {
+		cells[x][y] = grid.cells[x / 2][y / 2];
+	    }
+	}
+	Grid {
+	    cell_size: grid.cell_size / 2,
+	    width,
+	    height,
+	    cells
+	}
+    }
+
+    fn find_regions(&self, grid: &Grid) -> Vec<Region> {
+	time_scope!("finding all regions");
+	let mut regions = vec!();
+	let mut marked = vec!(vec!(false; grid.height); grid.width);
+	for x in 0..grid.width {
+	    for y in 0..grid.height {
+		if !marked[x][y] {
+		    regions.push(self.get_region_at_point(grid, x, y, &mut marked));
+		}
+	    }
+	}
+	regions
+    }
+
+    fn get_region_at_point(&self, grid: &Grid, x: usize, y: usize, marked: &mut Vec<Vec<bool>>) -> Region {
+	let value = grid.cells[x][y];
+	let mut cells = vec!();
+	let mut queue = vec!((x, y));
+	marked[x][y] = true;
+
+	while let Some(p) = queue.pop() {
+	    cells.push(p);
+	    for i in &[(-1, 0), (1, 0), (0, -1), (0, 1)] {
+		let ip = (p.0 as isize + i.0, p.1 as isize + i.1);
+		if ip.0 >= 0 && ip.0 < grid.width as isize && ip.1 >= 0 && ip.1 < grid.height as isize {
+		    let up = (ip.0 as usize, ip.1 as usize);
+		    if grid.cells[up.0][up.1] == value && !marked[up.0][up.1] {
+			marked[up.0][up.1] = true;
+			queue.push(up);
+		    }
+		}
+	    }
+	}
+
+	Region { value, cells }
+    }
+
+    fn delete_region(&self, grid: &mut Grid, region: &Region) {
+	for c in &region.cells {
+	    grid.cells[c.0][c.1] = !region.value;
+	}
+    }
+
+    fn filter_regions(&self, grid: &mut Grid) {
+	let min_wall_size = 0.0015;
+	println!("grid size: ({}, {}) = {} cells", grid.width, grid.height, grid.width * grid.height);
+	println!("min wall size: {}", (grid.width * grid.height) as f64 * min_wall_size);
+
+	// delete all smaller wall regions
+	for r in self.find_regions(grid).iter().filter(|r| r.value) {
+	    let percent = r.cells.len() as f64 / (grid.width * grid.height) as f64;
+	    if percent < min_wall_size {
+		// println!("delete wall region of size {}", r.cells.len());
+		self.delete_region(grid, r);
+	    }
+	}
+
+	// delete all rooms but the largest
+	let regions = self.find_regions(grid); // check again, because if a removed room contains a removed wall, the removed wall will become a room
+	let mut rooms: Vec<&Region> = regions.iter().filter(|r| !r.value).collect();
+	rooms.sort_by_key(|r| r.cells.len());
+	rooms.reverse();
+	while rooms.len() > 1 {
+	    self.delete_region(grid, rooms.pop().unwrap());
+	}
+    }
+
+    fn find_walls(&self, grid: &Grid) -> Vec<Vec<Point2D<isize>>> {
+	let mut walls = vec!();
+	for r in self.find_regions(&grid) {
+	    if r.value {
+		let mut outline = r.outline(grid.cell_size);
+		for i in 2..(outline.len() - 2) {
+//		    outline[i] = (outline[i - 1] + outline[i] + outline[i + 1]) / 3;
+		    outline[i] = (outline[i - 2] + outline[i - 1] + outline[i] + outline[i + 1] + outline[i + 2]) / 5;
+		}
+		walls.push(outline);
+	    }
+	}
+	walls
+    }
+}
+
+////////// REGION //////////////////////////////////////////////////////////////
+
+struct Region {
+    value: bool,
+    cells: Vec<(usize, usize)>,
+}
+
+impl Region {
+    fn enclosing_rect(&self) -> (usize, usize, usize, usize) {
+	let mut min = (usize::MAX, usize::MAX);
+	let mut max = (0, 0);
+	for c in &self.cells {
+	    if      c.0 < min.0 { min.0 = c.0; }
+	    else if c.0 > max.0 { max.0 = c.0; }
+	    if      c.1 < min.1 { min.1 = c.1; }
+	    else if c.1 > max.1 { max.1 = c.1; }
+	}
+	(min.0, min.1, 1 + max.0 - min.0, 1 + max.1 - min.1)
+    }
+
+    pub fn outline(&self, scale: usize) -> Vec<Point2D<isize>> {
+	let rect = self.enclosing_rect();
+	let (ox, oy, w, h) = rect;
+	let grid = self.grid(&rect);
+	let mut marked = vec!(vec!(false; h); w);
+	let mut outline = vec!();
+	let mut directions = vec!((1, 0), (1, 1), (0, 1), (-1, 1), (-1, 0), (-1, -1), (0, -1), (1, -1)); // 8 directions rotating right from starting direction right
+
+	let mut p = self.find_first_point_of_outline(&rect, &grid);
+	marked[p.x as usize][p.y as usize] = true;
+	loop {
+	    outline.push((p + (ox as isize, oy as isize)) * scale as isize);
+	    self.find_next_point_of_outline(&grid, &mut p, &mut directions);
+	    if marked[p.x as usize][p.y as usize] {
+		// we're back at the beginning
+		break;
+	    }
+	    marked[p.x as usize][p.y as usize] = true;
+	}
+
+	outline
+    }
+
+    #[allow(dead_code)]
+    fn print_grid(&self, grid: &Vec<Vec<bool>>) {
+	let w = grid.len();
+	let h = grid[0].len();
+	let mut g = vec!(vec!(false; w); h);
+    	for x in 0..w {
+    	    for y in 0..h {
+		g[y][x] = grid[x][y];
+	    }
+	}
+	println!("grid {} x {}", w, h);
+	print!("    ");
+	for n in 0..w {
+	    print!("{}", n % 10);
+	}
+	println!();
+	for (n, row) in g.iter().enumerate() {
+	    print!("{:>3}|", n);
+	    for col in row {
+		print!("{}", if *col { "#" } else { " " });
+	    }
+	    println!("|");
+	}
+    }
+
+    fn grid(&self, rect: &(usize, usize, usize, usize)) -> Vec<Vec<bool>> {
+	let (x, y, w, h) = rect;
+	let mut grid = vec!(vec!(false; *h); *w);
+	for c in &self.cells {
+	    grid[c.0 - x][c.1 - y] = true;
+	}
+	grid
+    }
+
+    fn find_first_point_of_outline(&self, rect: &(usize, usize, usize, usize), grid: &Vec<Vec<bool>>) -> Point2D<isize> {
+	let (ox, oy, w, h) = rect;
+	let is_outer_wall = (ox, oy) == (&0, &0); // we know this is always the outer wall of the level
+    	for x in 0..*w {
+    	    for y in 0..*h {
+		if is_outer_wall && !grid[x][y] {
+		    return point!(x as isize, y as isize - 1); // one step back because we're not on a wall tile
+		}
+		else if !is_outer_wall && grid[x][y] {
+		    return point!(x as isize, y as isize);
+		}
+    	    }
+    	}
+	panic!("no wall found!");
+    }
+
+    fn find_next_point_of_outline(&self, grid: &Vec<Vec<bool>>, p: &mut Point2D<isize>, directions: &mut Vec<(isize, isize)>) {
+	directions.rotate_left(2);
+	loop {
+	    let d = directions[0];
+	    if self.check(*p + d, grid) {
+		*p += d;
+		break;
+	    }
+	    directions.rotate_right(1);
+	}
+    }
+
+    fn check(&self, p: Point2D<isize>, grid: &Vec<Vec<bool>>) -> bool {
+	if p.x < 0 || p.x >= grid.len() as isize || p.y < 0 || p.y >= grid[0].len() as isize {
+	    false
+	} else {
+	    grid[p.x as usize][p.y as usize]
+	}
+    }
+}
diff --git a/src/core/level/mod.rs b/src/core/level/mod.rs
new file mode 100644
index 0000000..b70cdb8
--- /dev/null
+++ b/src/core/level/mod.rs
@@ -0,0 +1,56 @@
+use common::Point2D;
+use core::render::Renderer;
+use sprites::SpriteManager;
+
+mod lvlgen;
+
+pub use self::lvlgen::LevelGenerator;
+
+////////// LEVEL ///////////////////////////////////////////////////////////////
+
+#[derive(Default)]
+pub struct Level {
+    pub gravity: Point2D<f64>,
+    pub grid: Grid,
+    walls: Vec<Vec<Point2D<isize>>>,
+}
+
+impl Level {
+    // pub fn new(gravity: Point2D<f64>) -> Self {
+    // 	let seed = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).unwrap().as_secs() as u32;
+    // 	let mut lvl = Level { gravity, grid: Grid::generate(seed, 10), iterations: 10, walls: vec!() };
+    // 	lvl.filter_regions();
+    // 	lvl
+    // }
+
+    pub fn render(&mut self, renderer: &mut Renderer, _sprites: &SpriteManager) {
+	renderer.canvas().set_draw_color((64, 64, 64));
+	let size = self.grid.cell_size;
+	for x in 0..self.grid.width {
+	    for y in 0..self.grid.height {
+		if self.grid.cells[x][y] {
+		    renderer.canvas().fill_rect(sdl2::rect::Rect::new(x as i32 * size as i32, y as i32 * size as i32, size as u32, size as u32)).unwrap();
+		}
+	    }
+	}
+
+	let off = (size / 2) as i32;
+	for wall in &self.walls {
+	    for w in wall.windows(2) {
+		renderer.draw_line((w[0].x as i32 + off, w[0].y as i32 + off), (w[1].x as i32 + off, w[1].y as i32 + off), (255, 255, 0));
+	    }
+	    let last = wall.len() - 1;
+	    renderer.draw_line((wall[0].x as i32 + off, wall[0].y as i32 + off), (wall[last].x as i32 + off, wall[last].y as i32 + off), (255, 255, 0));
+	}
+    }
+}
+
+////////// GRID ////////////////////////////////////////////////////////////////
+
+#[derive(Default)]
+pub struct Grid {
+    pub width: usize,
+    pub height: usize,
+    pub cell_size: usize,
+    pub cells: Vec<Vec<bool>>,
+}