KodeLife fragment shader sketch

00_blot9.md

blot9.glsl

#version 150

uniform float time;
uniform sampler2D prevFrame;
uniform sampler2D texture0;
uniform vec2 resolution;
uniform vec3 spectrum;
out vec4 fragColor;

vec2 fade(vec2 x) { return x * x * x * (x * (x * 6 - 15) + 10); }

vec2 phash(vec2 p)
{
    p = fract(mat2(1.2989833, 7.8233198, 6.7598192, 3.4857334) * p);
    p = ((2384.2345 * p - 1324.3438) * p + 3884.2243) * p - 4921.2354;
    return normalize(fract(p) * 2 - 1);
}

float cnoise(vec2 p)
{
    vec2 ip = floor(p);
    vec2 fp = fract(p);
    float d00 = dot(phash(ip), fp);
    float d01 = dot(phash(ip + vec2(0, 1)), fp - vec2(0, 1));
    float d10 = dot(phash(ip + vec2(1, 0)), fp - vec2(1, 0));
    float d11 = dot(phash(ip + vec2(1, 1)), fp - vec2(1, 1));
    fp = fade(fp);
    return mix(mix(d00, d01, fp.y), mix(d10, d11, fp.y), fp.x);
}

void main(void)
{
    vec2 uv = gl_FragCoord.xy / resolution;
    float aspect = resolution.x / resolution.y;
    float amp = spectrum.x;
    
    // eye texture
    float tex = texture(texture0, uv * vec2(1, -1)).r;
    
    // polar coordinate
    vec2 p = (uv - 0.5) * vec2(aspect, 1);
    p = vec2(atan(p.y, p.x), length(p));
    
    // displacement
    p.x += cnoise(vec2(p.y * 20, time)) * 0.08 / (p.y + 0.1);
    
    // bring back to uv space
    uv = vec2(cos(p.x), sin(p.x)) * p.y;
    uv = uv / vec2(aspect, 1) + 0.5;
    
    // feedback
    float fb = texture(prevFrame, uv).r * 0.998;
    
    // blending
    float c = mix(fb, tex, smoothstep(0.4, 1, amp));
    
    // color gradient
    float t = time + amp;
    float c1 = 0.5 + sin(c * 12.12 + t * 1.11) * 0.5;
    float c2 = 0.5 + sin(c * 11.33 + t * 1.73) * 0.5;
    fragColor = vec4(1, c1, c2, 0) * c;
}

It does not run with copy/pasting the code alone because this shader requires an eye texture (an image file) in variable texture0 (line 38), prevFrame (line 52) and an audio input with spectrum split input (line 35). After adding these inputs, it still doesn't show anything.

The reason is that in the last line fragColor = vec4(1, c1, c2, 0) * c; the parameter for alpha should be 1.0, not 0. After fixing these issues, the shader shows something.