bevy_symbios_texture 0.2.2

//! Bark texture generator using domain-warped FBM noise.
//!
//! The algorithm:
//!  1. Precompute toroidal sin/cos lookup tables (one entry per column, one per row).
//!  2. For each pixel, sample two FBM warp layers inline to produce offsets (du, dv).
//!  3. Sample the precomputed base FBM grid via bilinear interpolation at the warped UV coordinates for the final value.
//!  4. Derive colour, roughness and a height field from the result.
//!
//! The warp layers are computed inline (no intermediate grids).  The base FBM
//! layer is precomputed into a W×H grid (~536 MB at 8 K) once, then sampled
//! via bilinear interpolation at the warped coordinates.  This trades one
//! allocation for the elimination of O(W×H) `sin`/`cos` calls that would
//! otherwise occur when evaluating the toroidal base noise at arbitrary warped
//! positions.

use std::f64::consts::TAU;

use noise::core::worley::ReturnType;
use noise::{Fbm, MultiFractal, NoiseFn, Perlin, Worley};

use crate::{
    generator::{TextureError, TextureGenerator, TextureMap, linear_to_srgb, validate_dimensions},
    noise::{ToroidalNoise, sample_grid},
    normal::{BoundaryMode, height_to_normal},
};

/// Configures the appearance of a [`BarkGenerator`].
#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
pub struct BarkConfig {
    pub seed: u32,
    /// Overall spatial scale of the bark pattern.
    pub scale: f64,
    /// Octaves for the base FBM layer.
    pub octaves: usize,
    /// Horizontal warp strength (small — creates slight lateral texture).
    pub warp_u: f64,
    /// Vertical warp strength (large — creates the fibrous streaks).
    pub warp_v: f64,
    /// Base (light) bark colour in linear RGB \[0, 1\].
    pub color_light: [f32; 3],
    /// Dark groove colour in linear RGB \[0, 1\].
    pub color_dark: [f32; 3],
    /// Normal map strength.
    pub normal_strength: f32,
    /// Blend weight of the rhytidome furrow layer \[0, 1\].  0 = pure FBM fibre,
    /// 1 = pure Worley plates.
    pub furrow_multiplier: f64,
    /// Horizontal frequency of the Worley cells (higher = narrower plates).
    pub furrow_scale_u: f64,
    /// Vertical frequency of the Worley cells (lower = longer vertical plates).
    pub furrow_scale_v: f64,
    /// Power applied to the normalised plate height.  Values < 1 fatten the
    /// plates and sharpen the V-shaped cracks between them.
    pub furrow_shape: f64,
}

impl Default for BarkConfig {
    fn default() -> Self {
        Self {
            seed: 42,
            scale: 4.0,
            octaves: 6,
            warp_u: 0.15,
            warp_v: 0.55,
            color_light: [0.45, 0.28, 0.14],
            color_dark: [0.18, 0.10, 0.05],
            normal_strength: 3.0,
            furrow_multiplier: 0.55,
            furrow_scale_u: 2.0,
            furrow_scale_v: 0.25,
            furrow_shape: 0.4,
        }
    }
}

/// Procedural bark texture generator.
///
/// Drives [`TextureGenerator::generate`] using a [`BarkConfig`].  Construct
/// via [`BarkGenerator::new`] and call `generate` directly, or spawn a
/// [`crate::async_gen::PendingTexture::bark`] task for non-blocking generation.
pub struct BarkGenerator {
    config: BarkConfig,
}

impl BarkGenerator {
    /// Create a new generator with the given configuration.
    pub fn new(config: BarkConfig) -> Self {
        Self { config }
    }
}

impl TextureGenerator for BarkGenerator {
    fn generate(&self, width: u32, height: u32) -> Result<TextureMap, TextureError> {
        validate_dimensions(width, height)?;
        let c = &self.config;

        // Three independent FBM sources with offset seeds.
        let fbm_warp_u: Fbm<Perlin> = Fbm::new(c.seed).set_octaves(c.octaves);
        let fbm_warp_v: Fbm<Perlin> = Fbm::new(c.seed.wrapping_add(100)).set_octaves(c.octaves);
        let fbm_base: Fbm<Perlin> = Fbm::new(c.seed.wrapping_add(200)).set_octaves(c.octaves);

        let warp_u_noise = ToroidalNoise::new(fbm_warp_u, c.scale);
        let warp_v_noise = ToroidalNoise::new(fbm_warp_v, c.scale);
        let base_noise = ToroidalNoise::new(fbm_base, c.scale);

        // Worley noise for rhytidome plates — frequency = 1.0 because we bake
        // the anisotropic scaling into the torus lookup tables below.
        let worley = Worley::new(c.seed.wrapping_add(300)).set_return_type(ReturnType::Distance);

        let w = width as usize;
        let h = height as usize;
        let n = w * h;

        // Precompute toroidal coordinates (W + H entries instead of W × H).
        // All three noise objects share the same `c.scale` frequency so one
        // set of lookup tables covers all of them.
        let freq = c.scale;
        let col_cos: Vec<f64> = (0..w)
            .map(|x| (TAU * x as f64 / w as f64).cos() * freq)
            .collect();
        let col_sin: Vec<f64> = (0..w)
            .map(|x| (TAU * x as f64 / w as f64).sin() * freq)
            .collect();
        let row_cos: Vec<f64> = (0..h)
            .map(|y| (TAU * y as f64 / h as f64).cos() * freq)
            .collect();
        let row_sin: Vec<f64> = (0..h)
            .map(|y| (TAU * y as f64 / h as f64).sin() * freq)
            .collect();

        // Anisotropic torus tables for the Worley furrow layer.
        // High U frequency → narrow horizontal spacing (many columns of plates).
        // Low V frequency  → wide vertical spacing (long plates, deep fissures).
        let f_freq_u = c.scale * c.furrow_scale_u;
        let f_freq_v = c.scale * c.furrow_scale_v;
        let f_col_cos: Vec<f64> = (0..w)
            .map(|x| (TAU * x as f64 / w as f64).cos() * f_freq_u)
            .collect();
        let f_col_sin: Vec<f64> = (0..w)
            .map(|x| (TAU * x as f64 / w as f64).sin() * f_freq_u)
            .collect();
        let f_row_cos: Vec<f64> = (0..h)
            .map(|y| (TAU * y as f64 / h as f64).cos() * f_freq_v)
            .collect();
        let f_row_sin: Vec<f64> = (0..h)
            .map(|y| (TAU * y as f64 / h as f64).sin() * f_freq_v)
            .collect();

        // Precompute the base noise on a regular grid using the torus LUTs
        // (O(W+H) trig calls).  The warped lookup then becomes a cheap
        // bilinear interpolation rather than per-pixel sin/cos evaluation.
        let base_grid = sample_grid(&base_noise, width, height);

        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..h {
            let nz = row_cos[y];
            let nw = row_sin[y];
            let v = y as f64 / h as f64;

            let f_nz = f_row_cos[y];
            let f_nw = f_row_sin[y];

            for x in 0..w {
                let nx = col_cos[x];
                let ny = col_sin[x];
                let u = x as f64 / w as f64;

                // Compute warp offsets using precomputed torus coordinates.
                let du = warp_u_noise.get_precomputed(nx, ny, nz, nw) * c.warp_u;
                let dv = warp_v_noise.get_precomputed(nx, ny, nz, nw) * c.warp_v;

                // Sample the precomputed base grid at the warped UV coordinates.
                // Bilinear interpolation wraps toroidally — no trig per pixel.
                let raw = bilinear_sample_torus(&base_grid, w, h, u + du, v + dv);
                let t = normalize(raw); // [0, 1]

                // --- Worley rhytidome plates ---
                // Sample anisotropic Worley on a 4D torus: U-axis uses high
                // frequency (narrow plates), V-axis uses low frequency (tall plates).
                let f_nx = f_col_cos[x];
                let f_ny = f_col_sin[x];
                let furrow_raw = worley.get([f_nx, f_ny, f_nz, f_nw]);
                // Invert: boundaries (furrow_raw ≈ 1) → 0 (deep crack);
                //         centres  (furrow_raw ≈ -1) → 1 (raised plate).
                let furrow_norm = (0.5 - furrow_raw * 0.5).clamp(0.0, 1.0);
                // powf < 1 widens the plateau and keeps cracks narrow and sharp.
                let plate_height = furrow_norm.powf(c.furrow_shape);

                // Blend fibrous FBM micro-detail with macro rhytidome plates.
                let t_final = t * (1.0 - c.furrow_multiplier) + plate_height * c.furrow_multiplier;

                let idx = y * w + x;
                heights[idx] = t_final;

                // Colour: lerp between dark and light by height value.
                let r = lerp(c.color_dark[0], c.color_light[0], t as f32);
                let g = lerp(c.color_dark[1], c.color_light[1], t as f32);
                let b = lerp(c.color_dark[2], c.color_light[2], t as f32);

                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;

                // Roughness: grooves (dark, low t) are rougher.
                // Packed as ORM: R=Occlusion(1.0), G=Roughness, B=Metallic(0.0).
                let rough = 0.6 + (1.0 - t as f32) * 0.35;
                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,
        })
    }
}

// --- helpers ----------------------------------------------------------------

#[inline]
fn lerp(a: f32, b: f32, t: f32) -> f32 {
    a + (b - a) * t.clamp(0.0, 1.0)
}

/// Map a raw noise sample from `[-1, 1]` to `[0, 1]`.
#[inline]
fn normalize(v: f64) -> f64 {
    v * 0.5 + 0.5
}

/// Bilinearly interpolate a value from a toroidal (seamlessly tiling) grid.
///
/// `u` and `v` are in UV space and may fall outside `[0, 1]`; they are wrapped
/// before sampling so the lookup is always valid.  This is used to fetch the
/// domain-warped base noise value without additional `sin`/`cos` calls.
#[inline]
fn bilinear_sample_torus(grid: &[f64], w: usize, h: usize, u: f64, v: f64) -> f64 {
    // Wrap UV into [0, 1).
    let u = u.rem_euclid(1.0);
    let v = v.rem_euclid(1.0);

    // Convert to fractional pixel coordinates.
    let px = u * w as f64;
    let py = v * h as f64;

    let x0 = px as usize % w;
    let y0 = py as usize % h;
    let x1 = (x0 + 1) % w;
    let y1 = (y0 + 1) % h;

    let fx = px.fract();
    let fy = py.fract();

    let v00 = grid[y0 * w + x0];
    let v10 = grid[y0 * w + x1];
    let v01 = grid[y1 * w + x0];
    let v11 = grid[y1 * w + x1];

    v00 * (1.0 - fx) * (1.0 - fy) + v10 * fx * (1.0 - fy) + v01 * (1.0 - fx) * fy + v11 * fx * fy
}