綺麗な海

float hash12(vec2 p) {
    vec3 p3  = fract(p.xyx * .1031);
    p3 += dot(p3, p3.yzx + 33.33);
    return fract((p3.x + p3.y) * p3.z);
}

float noise(vec2 p) {
    vec2 i = floor(p);
    vec2 f = fract(p);
    f = f * f * (3.0 - 2.0 * f);

    float a = hash12(i);
    float b = hash12(i + vec2(1.0, 0.0));
    float c = hash12(i + vec2(0.0, 1.0));
    float d = hash12(i + vec2(1.0, 1.0));

    return mix(mix(a, b, f.x), mix(c, d, f.x), f.y);
}

float fbm(vec2 p) {
    float f = 0.0;
    p *= 1.5;
    float amp = 0.5;
    for (int i = 0; i < 5; i++) {
        f += amp * noise(p);
        p *= 2.0;
        amp *= 0.5;
    }
    return f;
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = (fragCoord * 2.0 - iResolution.xy) / iResolution.y;

    float time = iTime * 0.15;

    // Domain warping to create organic, swirling patterns reminiscent of water currents
    vec2 q = vec2(fbm(uv * 1.0 + time * 0.5), fbm(uv * 1.0 + time * 0.5 + vec2(5.2, 1.3)));
    q = q * 2.0 - 1.0;

    vec2 r = vec2(fbm(uv * 1.0 + q * 1.5 - time * 0.3), fbm(uv * 1.0 + q * 1.5 - time * 0.3 + vec2(7.3, 2.1)));
    r = r * 2.0 - 1.0;

    // Final noise value, influenced by both layers of warping, creating the main flow
    float f = fbm(uv * 1.5 + r * 1.0 + time * 0.2);

    // Add another layer of noise for finer details, like light caustics or subtle surface variations
    float surfaceDetail = fbm(uv * 4.0 + f * 2.0 + time * 0.4);
    
    // Combine noise values, enhance contrast and brightness for more defined "light" areas
    float finalNoise = f + surfaceDetail * 0.5;
    finalNoise = pow(finalNoise, 1.5);

    // Color palette: a gradient from deep sea blues to lighter aquas and hints of foamy white
    vec3 col = vec3(0.0);
    // Darker base for deep water
    col = mix(vec3(0.05, 0.15, 0.25), vec3(0.1, 0.35, 0.5), smoothstep(0.0, 0.6, finalNoise));
    // Mid-tones for clearer water
    col = mix(col, vec3(0.2, 0.6, 0.8), smoothstep(0.3, 0.8, finalNoise));
    // Highlights for surface foam or strong light penetration
    col = mix(col, vec3(0.8, 0.95, 1.0), smoothstep(0.7, 1.0, finalNoise));
    
    // Apply a subtle blue-green tint to enhance the "sea" feel
    col *= vec3(0.95, 1.05, 1.1); 

    // Add a soft, subtle vignette to focus the view
    float len_uv = length(uv);
    float vignette = smoothstep(1.1, 0.6, len_uv);
    col *= vignette;
    
    fragColor = vec4(col, 1.0);
}