// Wood
fn shade() {
// Procedural wood: concentric growth rings warped by turbulence + fine grain.
// Only the .x channel of textures is used (value channel).
let t = time * 0.0;
// Move and scale domain; center the rings roughly in the middle of each face.
let uv2 = uv / 3.0 - vec2(1.5);
// fBm turbulence (zero-mean) to warp the rings
let n1 = sample(uv2 + vec2(t, 0.0), "fbm_perlin"); // [0,1]
let n2 = sample(uv2 * 2.0 + vec2(0.0, t*0.7), "fbm_perlin");
let turb = 0.65 * n1 + 0.35 * n2; // [0,1]
let turb_zm = (turb - 0.5) * 2.0; // [-1,1]
// Radial distance from center (log cross-section look)
let r = length(uv2);
// Warp rings by turbulence (phase modulation)
let ring_freq = 10.0; // number of rings
let ring_warp = 0.22; // strength of warp
let rings = r + ring_warp * turb_zm;
let waves = sin(rings * ring_freq);
// Map sine to ring mask; sharpen valleys to make rings thinner
let rings_mask = pow(1.0 - abs(waves), 3.0);
// Fine longitudinal grain: high-frequency value noise stretched along X
let grain_uv = vec2(uv2.x * 8.0, uv2.y * 40.0);
let g = sample(grain_uv + vec2(0.0, t*0.5), "value");
let grain = (g - 0.5) * 2.0; // zero-mean
// Base wood hues
let base_light = vec3(0.72, 0.52, 0.32);
let base_dark = vec3(0.45, 0.30, 0.16);
// Mix light/dark by ring mask
color = mix(base_light, base_dark, rings_mask);
// Apply subtle anisotropic grain as a multiplicative zero-mean factor
color *= (1.0 + 0.06 * grain);
// Optional pore streaks (cathedrals): directional bands along Y with slight turbulence
let band = uv2.y + 0.15 * turb_zm;
let cathedral = pow(1.0 - abs(sin(band * 6.0)), 4.0);
color = mix(color, color * 0.9, cathedral * 0.2);
// Roughness varies: pores are rougher, rings smoother
roughness = 0.6 + cathedral * 0.3;
// 16 Colors
//let color_steps = 16.0;
//color = floor(color * color_steps) / color_steps;
}
