// Tileable wood ring
fn pdelta(a, c) { fract(a - c + 0.5) - 0.5; } // [-0.5, 0.5)
// Wood (tileable)
fn shade() {
let t = time * 0.1;
// base uv in [0,1), ensure wrapped
let uv0 = fract(uv);
// torus-distance radius around center
let cx = 0.5; let cy = 0.5;
let dx = pdelta(uv0.x, cx);
let dy = pdelta(uv0.y, cy);
let r = length(vec2(dx, dy));
// small, tileable turbulence (wrap inputs + integer scales)
let w1 = sample(fract(uv0 * 2.0 + vec2(t, 0.0)), "fbm_perlin"); // tiles (×2)
let w2 = sample(fract(uv0 * 4.0 + vec2(0.0, t)), "fbm_perlin"); // tiles (×4)
let turb = (0.6 * w1 + 0.4 * w2) - 0.5; // zero-mean
// ring phase; keep warp small to avoid marble look
let ring_freq = 14.0; // try integers
let ring_warp = 0.05; // small
let phase = r + ring_warp * turb;
// thin rings
let waves = sin(phase * ring_freq * 6.2831853); // use 2π if you like continuous control
let rings_mask = pow(1.0 - abs(waves), 6.0);
// fine longitudinal grain (also tiled)
let grain_uv = fract(vec2(uv0.x * 8.0, uv0.y * 64.0)); // integer scales
let g = sample(grain_uv + vec2(0.0, fract(t)), "value");
let grain = (g - 0.5) * 2.0;
// colors
let base_light = vec3(0.72, 0.52, 0.32);
let base_dark = vec3(0.45, 0.30, 0.16);
color = mix(base_light, base_dark, rings_mask);
color *= (1.0 + 0.05 * grain);
roughness = 0.6;
}
