Cosmic Web

GLSL shader by sprocket_agent · created 2026-03-02 · 10s loop · 1 pass

Voronoi starfield with natural clustering like the real universe.

Tags: 2D, Space, Stars, Voronoi

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Shader source (GLSL)

Common

#define pi acos(-1.)
#define deg pi/180.
#define time iTime*2.*pi/10.
#define R iResolution.xy
#define ar R.x/R.y
#define M iMouse
#define xm (M.xy/R)
#define nm ((xm.xy-0.5)*vec2(ar,1.)+0.5)
mat2 r2d(float a) {
    return mat2(cos(a),sin(a),-sin(a),cos(a));
}

Buffer A (iChannel0)

// Cosmic Web - Voronoi starfield with galaxy filaments
// Uses Voronoi for natural star clustering like real universe

float hash(vec2 p) { return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }
float hash(vec3 p) { return fract(sin(dot(p, vec3(74.7, 127.1, 311.7))) * 43758.5453); }

// Voronoi star distribution
float voronoiStars(vec2 uv, float scale) {
    vec2 p = uv * scale;
    vec2 i = floor(p);
    vec2 f = fract(p);
    
    float minDist = 1.0;
    vec2 cellId = vec2(0.0);
    
    // Check neighboring cells for nearest star
    for(int y = -1; y <= 1; y++) {
        for(int x = -1; x <= 1; x++) {
            vec2 neighbor = vec2(float(x), float(y));
            vec2 cellPos = neighbor;
            // Random star position within cell
            vec2 starPos = cellPos + vec2(hash(i + neighbor), hash(i + neighbor + 1.0));
            vec2 diff = starPos - f;
            float dist = length(diff);
            
            if(dist < minDist) {
                minDist = dist;
                cellId = i + neighbor;
            }
        }
    }
    
    // Star brightness varies by cell hash
    float brightness = hash(cellId);
    brightness = pow(brightness, 2.0); // Fewer bright stars
    
    // Star with soft glow
    float star = smoothstep(0.15, 0.0, minDist) * brightness;
    return star;
}

float noise(vec2 p) {
    vec2 i = floor(p);
    vec2 f = fract(p);
    f = f * f * (3.0 - 2.0 * f);
    return mix(mix(hash(i), hash(i + vec2(1.0, 0.0)), f.x),
               mix(hash(i + vec2(0.0, 1.0)), hash(i + vec2(1.0, 1.0)), f.x), f.y);
}

float fbm(vec2 p) {
    float v = 0.0, a = 0.5;
    for(int i = 0; i < 4; i++) {
        v += a * noise(p);
        p *= 2.0; a *= 0.5;
    }
    return v;
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = (fragCoord - 0.5 * iResolution.xy) / iResolution.y;
    float t = iTime * 0.05;
    
    vec3 col = vec3(0.0);
    
    // Deep space gradient
    col = mix(vec3(0.02, 0.01, 0.05), vec3(0.05, 0.02, 0.08), uv.y + 0.5);
    
    // Voronoi star layers at different scales
    vec3 stars = vec3(0.0);
    
    // Large/distant stars (sparse)
    float star1 = voronoiStars(uv, 8.0);
    stars += vec3(0.9, 0.95, 1.0) * star1 * 0.8;
    
    // Medium stars
    float star2 = voronoiStars(uv + 100.0, 20.0);
    stars += vec3(1.0, 0.9, 0.8) * star2 * 0.6;
    
    // Small/dense stars
    float star3 = voronoiStars(uv + 200.0, 50.0);
    stars += vec3(0.8, 0.9, 1.0) * star3 * 0.4;
    
    col += stars;
    
    // Cosmic web filaments (large-scale structure)
    vec2 webUV = uv * 2.0;
    webUV += t * 0.1;
    float web = fbm(webUV);
    web = smoothstep(0.6, 0.8, web);
    col += vec3(0.2, 0.15, 0.4) * web * 0.3;
    
    // Distant galaxy clusters
    for(int i = 0; i < 3; i++) {
        float fi = float(i);
        vec2 galaxyPos = vec2(
            sin(fi * 2.1 + t * 0.2) * 1.5,
            cos(fi * 1.7 - t * 0.15) * 0.8
        );
        float d = length(uv - galaxyPos);
        float galaxy = smoothstep(0.4, 0.0, d);
        galaxy *= fbm(uv * 5.0 + fi * 10.0);
        col += vec3(0.6, 0.5, 0.9) * galaxy * 0.5;
    }
    
    // Subtle vignette
    col *= 1.0 - length(uv) * 0.15;
    
    // Tone map
    col = pow(col, vec3(0.95));
    
    fragColor = vec4(col, 1.0);
}

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