a gpu/webgl version of http://mainisusuallyafunction.blogspot.com/2011/10/quasicrystals-as-sums-of-waves-in-plane.html

gistfile1.txt

// paste this into http://www.iquilezles.org/apps/shadertoy/ for pictures!
// this is a gpu/webgl version of http://mainisusuallyafunction.blogspot.com/2011/10/quasicrystals-as-sums-of-waves-in-plane.html
// 'implementation' by @mmalex for http://news.ycombinator.com/item?id=3153835
// sorry for the unrolled loop, on my gpu/chrome combo, a for loop gives 0 output :(
// cant be bothered to work out why.
#ifdef GL_ES
precision highp float;
#endif
uniform float time;
uniform vec2 resolution;
void main(void)
{
 vec2 p = -1.0 + 2.0 * gl_FragCoord.xy / resolution.xy;
 float t=time*4.0; // change this for more speed
 vec2 up=vec2(32.0,0.0); // change this for finer/coarser stripes
 float s = 0.43388373911755; // sin and cos of pi / 7
 float c = 0.90096886790241;
 vec2 temp;
 float sum=cos(dot(p,up)+t);
 temp=up; up.x=dot(temp,vec2(c,s)); up.y=dot(temp,vec2(-s,c)); sum+=cos(dot(p,up)+t);
 temp=up; up.x=dot(temp,vec2(c,s)); up.y=dot(temp,vec2(-s,c)); sum+=cos(dot(p,up)+t);
 temp=up; up.x=dot(temp,vec2(c,s)); up.y=dot(temp,vec2(-s,c)); sum+=cos(dot(p,up)+t);
 temp=up; up.x=dot(temp,vec2(c,s)); up.y=dot(temp,vec2(-s,c)); sum+=cos(dot(p,up)+t);
 temp=up; up.x=dot(temp,vec2(c,s)); up.y=dot(temp,vec2(-s,c)); sum+=cos(dot(p,up)+t);
 temp=up; up.x=dot(temp,vec2(c,s)); up.y=dot(temp,vec2(-s,c)); sum+=cos(dot(p,up)+t);
 float a1=sum*0.25+0.5;
 gl_FragColor = vec4(a1,a1,a1,1.0);
}