Pixel-Composer/shaders/sh_perlin/sh_perlin.fsh

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//
// Simple passthrough fragment shader
//
varying vec2 v_vTexcoord;
varying vec4 v_vColour;
uniform vec2 u_resolution;
uniform vec2 position;
uniform float scale;
uniform float bright;
uniform int iteration;
float random (in vec2 st) {
return fract(sin(dot(st.xy, vec2(12.9898, 78.233))) * 43758.5453123);
}
float noise (in vec2 st) {
vec2 i = floor(st);
vec2 f = fract(st);
// Four corners in 2D of a tile
float a = random(i);
float b = random(i + vec2(1.0, 0.0));
float c = random(i + vec2(0.0, 1.0));
float d = random(i + vec2(1.0, 1.0));
// Cubic Hermine Curve. Same as SmoothStep()
vec2 u = f * f * (3.0 - 2.0 * f);
// Mix 4 coorners percentages
return mix(mix(a, b, u.x), mix(c, d, u.x), u.y);
}
void main() {
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vec2 pos = position + v_vTexcoord * scale;
float amp = pow(2., float(iteration) - 1.) / (pow(2., float(iteration)) - 1.);
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float n = 0.;
for(int i = 0; i < iteration; i++) {
n += noise(pos) * amp;
amp *= .5;
pos *= 2.;
}
gl_FragColor = vec4(vec3(n), 1.0);
}