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@@ -12,7 +12,301 @@
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Ever wondered what would happen if an Umber Hulk (or other tunneling creature) got *really* drunk, and went on a dungeon craving bender? The *Drunkard's Walk* algorithm answers the question - or more precisely, what would happen if a *whole bunch* of monsters had far too much to drink. As crazy it sounds, this is a good way to make organic dungeons.
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-As usual, we'll start with scaffolding from the previous map tutorials. We've done it enough that it should be old hat by now! In `map_builders/drunkard.rs`, build a new `DrunkardsWalkBuilder` class. We'll keep the zone-based placement from Cellular Automata - but remove the map building code.
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+## Initial scaffolding
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+
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+As usual, we'll start with scaffolding from the previous map tutorials. We've done it enough that it should be old hat by now! In `map_builders/drunkard.rs`, build a new `DrunkardsWalkBuilder` class. We'll keep the zone-based placement from Cellular Automata - but remove the map building code. Here's the scaffolding:
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+
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+```rust
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+use super::{MapBuilder, Map,
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+ TileType, Position, spawner, SHOW_MAPGEN_VISUALIZER};
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+use rltk::RandomNumberGenerator;
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+use specs::prelude::*;
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+use std::collections::HashMap;
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+
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+pub struct DrunkardsWalkBuilder {
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+ map : Map,
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+ starting_position : Position,
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+ depth: i32,
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+ history: Vec<Map>,
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+ noise_areas : HashMap<i32, Vec<usize>>
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+}
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+
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+impl MapBuilder for DrunkardsWalkBuilder {
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+ fn get_map(&self) -> Map {
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+ self.map.clone()
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+ }
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+
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+ fn get_starting_position(&self) -> Position {
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+ self.starting_position.clone()
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+ }
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+
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+ fn get_snapshot_history(&self) -> Vec<Map> {
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+ self.history.clone()
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+ }
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+
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+ fn build_map(&mut self) {
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+ self.build();
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+ }
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+
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+ fn spawn_entities(&mut self, ecs : &mut World) {
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+ for area in self.noise_areas.iter() {
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+ spawner::spawn_region(ecs, area.1, self.depth);
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+ }
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+ }
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+
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+ fn take_snapshot(&mut self) {
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+ if SHOW_MAPGEN_VISUALIZER {
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+ let mut snapshot = self.map.clone();
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+ for v in snapshot.revealed_tiles.iter_mut() {
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+ *v = true;
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+ }
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+ self.history.push(snapshot);
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+ }
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+ }
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+}
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+
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+impl DrunkardsWalkBuilder {
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+ pub fn new(new_depth : i32) -> DrunkardsWalkBuilder {
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+ DrunkardsWalkBuilder{
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+ map : Map::new(new_depth),
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+ starting_position : Position{ x: 0, y : 0 },
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+ depth : new_depth,
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+ history: Vec::new(),
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+ noise_areas : HashMap::new()
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+ }
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+ }
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+
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+ #[allow(clippy::map_entry)]
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+ fn build(&mut self) {
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+ let mut rng = RandomNumberGenerator::new();
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+
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+ // Set a central starting point
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+ self.starting_position = Position{ x: self.map.width / 2, y: self.map.height / 2 };
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+ let start_idx = self.map.xy_idx(self.starting_position.x, self.starting_position.y);
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+
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+ // Find all tiles we can reach from the starting point
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+ let map_starts : Vec<i32> = vec![start_idx as i32];
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+ let dijkstra_map = rltk::DijkstraMap::new(self.map.width, self.map.height, &map_starts , &self.map, 200.0);
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+ let mut exit_tile = (0, 0.0f32);
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+ for (i, tile) in self.map.tiles.iter_mut().enumerate() {
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+ if *tile == TileType::Floor {
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+ let distance_to_start = dijkstra_map.map[i];
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+ // We can't get to this tile - so we'll make it a wall
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+ if distance_to_start == std::f32::MAX {
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+ *tile = TileType::Wall;
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+ } else {
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+ // If it is further away than our current exit candidate, move the exit
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+ if distance_to_start > exit_tile.1 {
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+ exit_tile.0 = i;
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+ exit_tile.1 = distance_to_start;
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+ }
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+ }
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+ }
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+ }
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+ self.take_snapshot();
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+
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+ // Place the stairs
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+ self.map.tiles[exit_tile.0] = TileType::DownStairs;
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+ self.take_snapshot();
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+
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+ // Now we build a noise map for use in spawning entities later
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+ let mut noise = rltk::FastNoise::seeded(rng.roll_dice(1, 65536) as u64);
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+ noise.set_noise_type(rltk::NoiseType::Cellular);
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+ noise.set_frequency(0.08);
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+ noise.set_cellular_distance_function(rltk::CellularDistanceFunction::Manhattan);
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+
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+ for y in 1 .. self.map.height-1 {
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+ for x in 1 .. self.map.width-1 {
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+ let idx = self.map.xy_idx(x, y);
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+ if self.map.tiles[idx] == TileType::Floor {
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+ let cell_value_f = noise.get_noise(x as f32, y as f32) * 10240.0;
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+ let cell_value = cell_value_f as i32;
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+
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+ if self.noise_areas.contains_key(&cell_value) {
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+ self.noise_areas.get_mut(&cell_value).unwrap().push(idx);
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+ } else {
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+ self.noise_areas.insert(cell_value, vec![idx]);
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+ }
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+ }
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+ }
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+ }
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+ }
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+}
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+
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+```
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+
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+We've kept a lot of the work from the Cellular Automata chapter, since it can help us here also. We also go into `map_builders/mod.rs` and once again force the "random" system to pick our new code:
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+
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+```rust
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+pub fn random_builder(new_depth: i32) -> Box<dyn MapBuilder> {
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+ /*let mut rng = rltk::RandomNumberGenerator::new();
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+ let builder = rng.roll_dice(1, 4);
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+ match builder {
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+ 1 => Box::new(BspDungeonBuilder::new(new_depth)),
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+ 2 => Box::new(BspInteriorBuilder::new(new_depth)),
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+ 3 => Box::new(CellularAutomotaBuilder::new(new_depth)),
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+ _ => Box::new(SimpleMapBuilder::new(new_depth))
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+ }*/
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+ Box::new(DrunkardsWalkBuilder::new(new_depth))
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+}
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+```
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+
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+## Don't Repeat Yourself (The DRY principle)
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+
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+Since we're re-using the exact code from Cellular Automata, we should take the common code and put it into `map_builders/common.rs`. This saves typing, saves the compiler from repeatedly remaking the same code (increasing your program size). So in `common.rs`, we refactor the common code into some functions. In `common.rs`, we create a new function - `remove_unreachable_areas_returning_most_distant`:
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+
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+```rust
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+/// Searches a map, removes unreachable areas and returns the most distant tile.
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+pub fn remove_unreachable_areas_returning_most_distant(map : &mut Map, start_idx : usize) -> usize {
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+ let map_starts : Vec<i32> = vec![start_idx as i32];
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+ let dijkstra_map = rltk::DijkstraMap::new(map.width, map.height, &map_starts , map, 200.0);
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+ let mut exit_tile = (0, 0.0f32);
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+ for (i, tile) in map.tiles.iter_mut().enumerate() {
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+ if *tile == TileType::Floor {
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+ let distance_to_start = dijkstra_map.map[i];
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+ // We can't get to this tile - so we'll make it a wall
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+ if distance_to_start == std::f32::MAX {
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+ *tile = TileType::Wall;
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+ } else {
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+ // If it is further away than our current exit candidate, move the exit
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+ if distance_to_start > exit_tile.1 {
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+ exit_tile.0 = i;
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+ exit_tile.1 = distance_to_start;
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+ }
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+ }
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+ }
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+ }
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+
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+ exit_tile.0
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+}
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+```
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+
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+We'll make a second function, `generate_voronoi_spawn_regions`:
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+
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+```rust
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+/// Generates a Voronoi/cellular noise map of a region, and divides it into spawn regions.
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+#[allow(clippy::map_entry)]
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+pub fn generate_voronoi_spawn_regions(map: &Map, rng : &mut rltk::RandomNumberGenerator) -> HashMap<i32, Vec<usize>> {
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+ let mut noise_areas : HashMap<i32, Vec<usize>> = HashMap::new();
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+ let mut noise = rltk::FastNoise::seeded(rng.roll_dice(1, 65536) as u64);
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+ noise.set_noise_type(rltk::NoiseType::Cellular);
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+ noise.set_frequency(0.08);
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+ noise.set_cellular_distance_function(rltk::CellularDistanceFunction::Manhattan);
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+
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+ for y in 1 .. map.height-1 {
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+ for x in 1 .. map.width-1 {
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+ let idx = map.xy_idx(x, y);
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+ if map.tiles[idx] == TileType::Floor {
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+ let cell_value_f = noise.get_noise(x as f32, y as f32) * 10240.0;
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+ let cell_value = cell_value_f as i32;
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+
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+ if noise_areas.contains_key(&cell_value) {
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+ noise_areas.get_mut(&cell_value).unwrap().push(idx);
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+ } else {
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+ noise_areas.insert(cell_value, vec![idx]);
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+ }
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+ }
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+ }
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+ }
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+
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+ noise_areas
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+}
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+```
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+
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+Plugging these into our `build` function lets us reduce the boilerplate section considerably:
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+
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+```rust
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+// Find all tiles we can reach from the starting point
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+let exit_tile = remove_unreachable_areas_returning_most_distant(&mut self.map, start_idx);
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+self.take_snapshot();
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+
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+// Place the stairs
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+self.map.tiles[exit_tile] = TileType::DownStairs;
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+self.take_snapshot();
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+
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+// Now we build a noise map for use in spawning entities later
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+self.noise_areas = generate_voronoi_spawn_regions(&self.map, &mut rng);
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+```
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+
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+In the example, I've gone back to the `cellular_automata` section and done the same.
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+
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+This is basically the same code we had before (hence, it isn't explained here), but wrapped in a function (and taking a mutable map reference - so it changes the map you give it, and the starting point as parameters).
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+
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+## Walking Drunkards
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+
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+The basic idea behind the algorithm is simple:
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+
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+1. Pick a central starting point, and convert it to a floor.
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+2. We count how much of the map is floor space, and iterate until we have converted a percentage (we use 50% in the example) of the map to floors.
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+ 1. Spawn a drunkard at the starting point. The drunkard has a "lifetime" and a "position".
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+ 2. While the drunkard is still alive:
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+ 1. Decrement the drunkard's lifetime (I like to think that they pass out and sleep).
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+ 2. Roll a 4-sided dice.
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+ 1. If we rolled a 1, move the drunkard North.
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+ 2. If we rolled a 2, move the drunkard South.
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+ 3. If we rolled a 3, move the drunkard East.
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+ 4. If we rolled a 4, move the drunkard West.
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+ 3. The tile on which the drunkard landed becomes a floor.
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+
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+That's really all there is to it: we keep spawning drunkards until we have sufficient map coverage. Here's an implementation:
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+
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+```rust
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+// Set a central starting point
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+self.starting_position = Position{ x: self.map.width / 2, y: self.map.height / 2 };
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+let start_idx = self.map.xy_idx(self.starting_position.x, self.starting_position.y);
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+self.map.tiles[start_idx] = TileType::Floor;
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+
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+let total_tiles = self.map.width * self.map.height;
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+let desired_floor_tiles = (total_tiles / 2) as usize;
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+let mut floor_tile_count = self.map.tiles.iter().filter(|a| **a == TileType::Floor).count();
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+let mut digger_count = 0;
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+let mut active_digger_count = 0;
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+
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+while floor_tile_count < desired_floor_tiles {
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+ let mut did_something = false;
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+ let mut drunk_x = self.starting_position.x;
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+ let mut drunk_y = self.starting_position.y;
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+ let mut drunk_life = 400;
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+
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+ while drunk_life > 0 {
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+ let drunk_idx = self.map.xy_idx(drunk_x, drunk_y);
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+ if self.map.tiles[drunk_idx] == TileType::Wall {
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+ did_something = true;
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+ }
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+ self.map.tiles[drunk_idx] = TileType::DownStairs;
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+
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+ let stagger_direction = rng.roll_dice(1, 4);
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+ match stagger_direction {
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+ 1 => { if drunk_x > 2 { drunk_x -= 1; } }
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+ 2 => { if drunk_x < self.map.width-2 { drunk_x += 1; } }
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+ 3 => { if drunk_y > 2 { drunk_y -=1; } }
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+ _ => { if drunk_y < self.map.height-2 { drunk_y += 1; } }
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+ }
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+
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+ drunk_life -= 1;
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+ }
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+ if did_something {
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+ self.take_snapshot();
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+ active_digger_count += 1;
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+ }
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+
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+ digger_count += 1;
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+ for t in self.map.tiles.iter_mut() {
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+ if *t == TileType::DownStairs {
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+ *t = TileType::Floor;
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+ }
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+ }
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+ floor_tile_count = self.map.tiles.iter().filter(|a| **a == TileType::Floor).count();
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+}
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+println!("{} dwarves gave up their sobriety, of whom {} actually found a wall.", digger_count, active_digger_count);
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+```
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+
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+This implementation expands a lot of things out, and could be *much* shorter - but for clarity, we've left it large and obvious. We've also made a bunch of things into variables that could be constants - it's easier to read, and is designed to be easy to "play" with values. It also prints a status update to the console, showing what happened.
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+
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+If you `cargo run` now, you'll get a pretty nice open map:
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+
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+.
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+
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**The source code for this chapter may be found [here](https://github.com/thebracket/rustrogueliketutorial/tree/master/chapter-28-drunkards-walk)**
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Herbert Wolverson
