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Copy pathdensity.rs
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262 lines (228 loc) · 8.97 KB
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//! Implements a density map generator using 3D Perlin noise.
//!
//! Over the 2D height map generator, this has the advantage that terrain
//! is more interesting; overhangs and the like will be able to generate.
use crate::{block_index, noise, DensityMapGenerator, NearbyBiomes, NoiseLerper};
use bitvec::order::Local;
use bitvec::vec::BitVec;
use feather_core::biomes::Biome;
use feather_core::util::ChunkPosition;
use once_cell::sync::Lazy;
use simdnoise::NoiseBuilder;
/// A density map generator using 3D Perlin noise.
///
/// This generator should be used over the height map generator
/// when seeking correct-looking worlds;
///
/// # Implementation
/// Density calculation works as follows:
/// * Generate a base 3D Perlin nosie with settings depending
/// on the biome. Use linear interpolation on noise (this
/// is handled by `Wrapped3DPerlinNoise`)`.
/// * Depending on the density value from the noise, decide
/// whether the position is solid or air.
#[derive(Debug, Default)]
pub struct DensityMapGeneratorImpl;
impl DensityMapGenerator for DensityMapGeneratorImpl {
fn generate_for_chunk(
&self,
chunk: ChunkPosition,
biomes: &NearbyBiomes,
seed: u64,
) -> BitVec<Local, u8> {
let mut density = BitVec::from_vec(vec![0u8; 16 * 256 * 16 / 8]);
let uninterpolated_densities = generate_density(chunk, &biomes, seed);
let noise = NoiseLerper::new(&uninterpolated_densities)
.with_offset(chunk.x, chunk.z)
.generate();
for x in 0..16 {
for y in 0..256 {
for z in 0..16 {
let value = noise[noise::index(x, y, z)];
let is_solid = value < 0.0;
let index = block_index(x, y, z);
density.set(index, is_solid);
}
}
}
density
}
}
const DENSITY_WIDTH: usize = 5;
const DENSITY_HEIGHT: usize = 33;
/// Generates a 5x33x5 density array to pass to `NoiseLerper`.
///
/// This is based on Cuberite's implementation of the same function.
/// It works by having two 3D density noises, with another noise
/// to interpolate between the values of each. It then uses
/// a vertical linear gradient to determine densities of the
/// subchunks at each given Y level for a column.
///
/// # Notes
/// The density values emitted from this function should
/// be considered solid if less than 0 and air if greater
/// than 0. This is contrary to what might seem logical.
fn generate_density(chunk: ChunkPosition, biomes: &NearbyBiomes, seed: u64) -> Vec<f32> {
// TODO: generate based on biome
let x_offset = (chunk.x * (DENSITY_WIDTH as i32 - 1)) as f32;
let y_offset = 0.0;
let z_offset = (chunk.z * (DENSITY_WIDTH as i32 - 1)) as f32;
let len = DENSITY_WIDTH;
let height = DENSITY_HEIGHT;
let noise_seed = seed as i32;
// Generate various noises.
let choice_noise = NoiseBuilder::fbm_3d_offset(x_offset, len, y_offset, height, z_offset, len)
.with_seed(noise_seed)
.with_octaves(2)
.with_freq(0.001)
.generate()
.0;
let density_noise_1 =
NoiseBuilder::fbm_3d_offset(x_offset, len, y_offset, height, z_offset, len)
.with_seed(noise_seed + 1)
.with_octaves(2)
.with_freq(0.2)
.generate()
.0;
let density_noise_2 =
NoiseBuilder::fbm_3d_offset(x_offset, len, y_offset, height, z_offset, len)
.with_seed(noise_seed + 2)
.with_octaves(2)
.with_freq(0.2)
.generate()
.0;
// Additional 2D height noise for extra detail.
let height_noise = NoiseBuilder::fbm_2d_offset(x_offset, len, z_offset, len)
.with_seed(noise_seed + 3)
.with_octaves(2)
.with_freq(0.001)
.generate()
.0;
let mut result = vec![0.0; DENSITY_WIDTH * DENSITY_HEIGHT * DENSITY_WIDTH];
// Loop through subchunks and generate density for each.
for subx in 0..DENSITY_WIDTH {
for subz in 0..DENSITY_WIDTH {
// TODO: average nearby biome parameters
let (amplitude, midpoint) = column_parameters(&biomes, subx, subz);
let height = height_noise[(subz * len) + subx] * 25.0;
// Loop through Y axis of this subchunk column.
for suby in 0..DENSITY_HEIGHT {
// Linear gradient used to offset based on height.
let mut height_offset = ((suby as f32 * 8.0) - midpoint) * amplitude;
// If we are below the midpoint, increase the slope of the gradient.
// This creates smoother terrain.
if height_offset < 0.0 {
height_offset *= 4.0;
}
// When we are near sky limit, decrease
// the slope. This ensures that very tall
// mountains don't artificially cut off
// at Y=256.
if suby > 26 {
height_offset += (suby as f32 - 28.0) / 4.0;
}
let index = DENSITY_WIDTH * suby + subx + DENSITY_WIDTH * DENSITY_HEIGHT * subz;
let choice = choice_noise[index] * 100.0;
let density_1 = density_noise_1[index] * 50.0;
let density_2 = density_noise_2[index] * 50.0;
// Average between two density values based on choice weight.
result[index] = lerp(density_1, density_2, choice) + height_offset + height;
}
}
}
result
}
/// Elevation height field, used to weight
/// the averaging of nearby biome heights.
static ELEVATION_WEIGHT: Lazy<[[f32; 19]; 19]> = Lazy::new(|| {
let mut array = [[0.0; 19]; 19];
for (x, values) in array.iter_mut().enumerate() {
for (z, value) in values.iter_mut().enumerate() {
let mut x_squared = x as i32 - 9;
x_squared *= x_squared;
let mut z_sqaured = z as i32 - 9;
z_sqaured *= z_sqaured;
*value = 10.0 / (x_squared as f32 + z_sqaured as f32 + 0.2).sqrt();
}
}
array
});
/// Computes the target amplitude and midpoint for the
/// given column, using a 9x9 grid of biomes
/// around the column to determine a weighted average.
///
/// The X and Z parameters are the coordinates of the subchunk
/// within the chunk, not the block coordinate.
fn column_parameters(biomes: &NearbyBiomes, x: usize, z: usize) -> (f32, f32) {
let x = x as i32 * (DENSITY_WIDTH as i32 - 1);
let z = z as i32 * (DENSITY_WIDTH as i32 - 1);
let mut sum_amplitudes = 0.0;
let mut sum_midpoints = 0.0;
let mut sum_weights = 0.0;
// Loop through columns in 9x9 grid and compute weighted average of amplitudes
// and midpoints.
for block_x in -9..=9 {
for block_z in -9..=9 {
let abs_x = x + block_x;
let abs_z = z + block_z;
let biome = biomes.biome_at(abs_x, abs_z);
let (amplitude, midpoint) = biome_parameters(biome);
let weight = ELEVATION_WEIGHT[(block_x + 9) as usize][(block_z + 9) as usize];
sum_amplitudes += amplitude * weight;
sum_midpoints += midpoint * weight;
sum_weights += weight;
}
}
sum_amplitudes /= sum_weights;
sum_midpoints /= sum_weights;
(sum_amplitudes, sum_midpoints)
}
/// Returns the amplitude and midpoint for a given biome
/// type as a tuple in that order.
///
/// All original values were taken from Cuberite's source,
/// so all credit for this function goes to their team
/// for the presumably highly laborious effort
/// involved in finding these values.
fn biome_parameters(biome: Biome) -> (f32, f32) {
match biome {
Biome::Beach => (0.2, 60.0),
Biome::BirchForest => (0.1, 64.0),
Biome::BirchForestHills => (0.075, 64.0),
Biome::TallBirchHills => (0.075, 68.0),
Biome::TallBirchForest => (0.1, 64.0),
Biome::SnowyBeach => (0.3, 62.0),
Biome::Taiga => (0.3, 62.0),
Biome::TaigaHills => (0.075, 68.0),
Biome::DesertHills => (0.075, 68.0),
Biome::DeepOcean => (0.17, 35.0),
Biome::Desert => (0.15, 62.0),
Biome::Mountains => (0.045, 75.0),
Biome::MountainEdge => (0.1, 70.0),
Biome::WoodedMountains => (0.04, 80.0),
Biome::FlowerForest => (0.1, 64.0),
Biome::Forest => (0.1, 64.0),
Biome::Jungle => (0.1, 63.0),
Biome::Ocean => (0.12, 45.0),
Biome::Plains => (0.3, 62.0),
Biome::Savanna => (0.3, 62.0),
Biome::SavannaPlateau => (0.3, 85.0),
Biome::StoneShore => (0.075, 60.0),
Biome::SunflowerPlains => (0.3, 62.0),
Biome::Swamp => (0.25, 59.0),
// TODO: finish this list
_ => (0.3, 62.0),
}
}
/// Interpolates between two values based on the given
/// weight.
///
/// The weight is clamped to [0.0, 1.0].
fn lerp(a: f32, b: f32, weight: f32) -> f32 {
if weight < 0.0 {
return a;
} else if weight > 1.0 {
return b;
}
a + (b - a) * weight
}
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