dithering and drunken stupor

Author: moni-dz

dither.glsl

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+// Simple "dithering" effect
+// (c) moni-dz (https://github.com/moni-dz)
+// CC BY-NC-SA 4.0 (https://creativecommons.org/licenses/by-nc-sa/4.0/)
+
+// Packed bayer pattern using bit manipulation
+const float bayerPattern[4] = float[4](
+    0x0514, // Encoding 0,8,2,10
+    0xC4E6, // Encoding 12,4,14,6
+    0x3B19, // Encoding 3,11,1,9
+    0xF7D5  // Encoding 15,7,13,5
+);
+
+float getBayerFromPacked(int x, int y) {
+    int idx = (x & 3) + ((y & 3) << 2);
+    return float((int(bayerPattern[y & 3]) >> ((x & 3) << 2)) & 0xF) * (1.0 / 16.0);
+}
+
+#define LEVELS 2.0 // Available color steps per channel
+#define INV_LEVELS (1.0 / LEVELS)
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord)
+{
+    vec2 uv = fragCoord * (1.0 / iResolution.xy);
+    vec3 color = texture(iChannel0, uv).rgb;
+ 
+    float threshold = getBayerFromPacked(int(fragCoord.x), int(fragCoord.y));
+    vec3 dithered = floor(color * LEVELS + threshold) * INV_LEVELS;
+
+    fragColor = vec4(dithered, 1.0);
+}

drunkard.glsl

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+// Drunken stupor effect using fractal Brownian motion and Perlin noise
+// (c) moni-dz (https://github.com/moni-dz) 
+// CC BY-NC-SA 4.0 (https://creativecommons.org/licenses/by-nc-sa/4.0/)
+
+vec2 hash2(vec2 p) {
+    uvec2 q = uvec2(floatBitsToUint(p.x), floatBitsToUint(p.y));
+    q = (q * uvec2(1597334673U, 3812015801U)) ^ (q.yx * uvec2(2798796415U, 1979697793U));
+    return vec2(q) * (1.0/float(0xffffffffU)) * 2.0 - 1.0;
+}
+
+float perlin2d(vec2 p) {
+    vec2 i = floor(p);
+    vec2 f = fract(p);
+    vec2 u = f*f*(3.0-2.0*f);
+
+    return mix(mix(dot(hash2(i + vec2(0.0,0.0)), f - vec2(0.0,0.0)),
+                   dot(hash2(i + vec2(1.0,0.0)), f - vec2(1.0,0.0)), u.x),
+               mix(dot(hash2(i + vec2(0.0,1.0)), f - vec2(0.0,1.0)),
+                   dot(hash2(i + vec2(1.0,1.0)), f - vec2(1.0,1.0)), u.x), u.y);
+}
+
+#define OCTAVES 10     // How many passes of fractal Brownian motion to perform
+#define GAIN 0.5       // How much should each pixel move
+#define LACUNARITY 2.0 // How fast should each ripple be per pass
+
+float fbm(vec2 p) {
+    float sum = 0.0;
+    float amp = 0.5;
+    float freq = 1.0;
+    
+    for(int i = 0; i < OCTAVES; i++) {
+        sum += amp * perlin2d(p * freq);
+        freq *= LACUNARITY;
+        amp *= GAIN;
+    }
+    
+    return sum;
+}
+
+
+#define NOISE_SCALE 1.0      // How distorted the image you want to be
+#define NOISE_INTENSITY 0.05 // How strong the noise effect is
+#define ABERRATION true      // Chromatic aberration
+#define ABERRATION_DELTA 0.1 // How strong the chromatic aberration effect is
+#define ANIMATE true
+#define SPEED 0.4            // Animation speed
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord)
+{
+    vec2 uv = fragCoord/iResolution.xy;
+    float time = ANIMATE ? iTime * SPEED : 0.0;
+ 
+    vec2 noisePos = uv * NOISE_SCALE + vec2(time);
+    float noise = fbm(noisePos) * NOISE_INTENSITY;
+
+    vec3 col;
+
+    if (ABERRATION) {
+        col.r = texture(iChannel0, uv + vec2(noise * (1.0 + ABERRATION_DELTA))).r;
+        col.g = texture(iChannel0, uv + vec2(noise)).g;
+        col.b = texture(iChannel0, uv + vec2(noise * (1.0 - ABERRATION_DELTA))).b;
+    } else {
+        vec2 distortedUV = uv + vec2(noise);
+        col = texture(iChannel0, distortedUV).rgb;
+    }
+
+    fragColor = vec4(col, 1.0);
+}