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//! Ground / dirt texture generator.
//!
//! Produces a matted, organic-looking surface by blending two FBM layers at
//! different scales. A low-frequency layer defines broad soil patches; a
//! high-frequency layer adds fine grain and pebble-like micro-detail.
use noise::{Fbm, MultiFractal, Perlin};
use crate::{
generator::{TextureError, TextureGenerator, TextureMap, linear_to_srgb, validate_dimensions},
noise::{ToroidalNoise, normalize},
normal::{BoundaryMode, height_to_normal},
};
/// Configures the appearance of a [`GroundGenerator`].
#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
pub struct GroundConfig {
/// PRNG seed for the deterministic noise pattern; different seeds give
/// statistically-different textures from otherwise-identical configs.
pub seed: u32,
/// Scale of the large soil-patch layer.
pub macro_scale: f64,
/// Octaves for the large soil-patch FBM layer.
pub macro_octaves: usize,
/// Scale of the fine-grain layer.
pub micro_scale: f64,
/// Octaves for the fine-grain FBM layer.
pub micro_octaves: usize,
/// Blend weight of the micro layer (0 = only macro, 1 = only micro).
pub micro_weight: f64,
/// Dry (light) soil colour in linear RGB \[0, 1\].
pub color_dry: [f32; 3],
/// Moist (dark) soil colour in linear RGB \[0, 1\].
pub color_moist: [f32; 3],
/// Normal map strength — larger values produce more pronounced surface detail.
pub normal_strength: f32,
}
impl Default for GroundConfig {
fn default() -> Self {
Self {
seed: 13,
macro_scale: 2.0,
macro_octaves: 5,
micro_scale: 8.0,
micro_octaves: 4,
micro_weight: 0.35,
color_dry: [0.52, 0.40, 0.26],
color_moist: [0.28, 0.20, 0.12],
normal_strength: 2.0,
}
}
}
/// Procedural ground / dirt texture generator.
///
/// Drives [`TextureGenerator::generate`] using a [`GroundConfig`]. Construct
/// via [`GroundGenerator::new`] and call `generate` directly, or spawn a
/// [`crate::async_gen::PendingTexture::ground`] task for non-blocking generation.
///
/// Noise objects are built in the constructor so that calling `generate`
/// multiple times (e.g. producing size variants of the same material)
/// does not repeat the initialisation cost.
pub struct GroundGenerator {
config: GroundConfig,
macro_noise: ToroidalNoise<Fbm<Perlin>>,
micro_noise: ToroidalNoise<Fbm<Perlin>>,
}
impl GroundGenerator {
/// Create a new generator with the given configuration.
///
/// Builds the noise objects up front so that repeated
/// calls to [`generate`](TextureGenerator::generate) skip initialisation.
pub fn new(config: GroundConfig) -> Self {
let fbm_macro: Fbm<Perlin> = Fbm::new(config.seed).set_octaves(config.macro_octaves);
let macro_noise = ToroidalNoise::new(fbm_macro, config.macro_scale);
let fbm_micro: Fbm<Perlin> =
Fbm::new(config.seed.wrapping_add(50)).set_octaves(config.micro_octaves);
let micro_noise = ToroidalNoise::new(fbm_micro, config.micro_scale);
Self {
config,
macro_noise,
micro_noise,
}
}
}
impl TextureGenerator for GroundGenerator {
fn generate(&self, width: u32, height: u32) -> Result<TextureMap, TextureError> {
validate_dimensions(width, height)?;
let c = &self.config;
let w = width as f64;
let h = height as f64;
let n = (width as usize) * (height as usize);
let mut heights = vec![0.0f64; n];
let mut albedo = vec![0u8; n * 4];
let mut roughness = vec![0u8; n * 4];
for y in 0..height {
for x in 0..width {
let idx = (y * width + x) as usize;
let u = x as f64 / w;
let v = y as f64 / h;
let macro_val = normalize(self.macro_noise.get(u, v));
let micro_val = normalize(self.micro_noise.get(u, v));
let t = macro_val * (1.0 - c.micro_weight) + micro_val * c.micro_weight;
heights[idx] = t;
let tf = t as f32;
let r = lerp(c.color_moist[0], c.color_dry[0], tf);
let g = lerp(c.color_moist[1], c.color_dry[1], tf);
let b = lerp(c.color_moist[2], c.color_dry[2], tf);
let ai = idx * 4;
albedo[ai] = linear_to_srgb(r);
albedo[ai + 1] = linear_to_srgb(g);
albedo[ai + 2] = linear_to_srgb(b);
albedo[ai + 3] = 255;
// Ground is generally rough; slight variation by moisture.
// Packed as ORM: R=Occlusion(1.0), G=Roughness, B=Metallic(0.0).
let rough = 0.80 + (1.0 - tf) * 0.15;
roughness[ai] = 255; // Occlusion = 1.0 (no shadowing)
roughness[ai + 1] = (rough * 255.0).round() as u8;
roughness[ai + 2] = 0; // Metallic = 0.0
roughness[ai + 3] = 255;
}
}
let normal = height_to_normal(
&heights,
width,
height,
c.normal_strength,
BoundaryMode::Wrap,
);
Ok(TextureMap {
albedo,
normal,
roughness,
width,
height,
})
}
}
#[inline]
fn lerp(a: f32, b: f32, t: f32) -> f32 {
a + (b - a) * t.clamp(0.0, 1.0)
}