// Author: Stefan Gustavson
// Title: Classic 3D cellular noise

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform float u_time;

// Cellular noise ("Worley noise") in 3D in GLSL.
// Copyright (c) Stefan Gustavson 2011-04-19. All rights reserved.
// This code is released under the conditions of the MIT license.
// See LICENSE file for details.

// Permutation polynomial: (34x^2 + x) mod 289
vec3 permute(vec3 x) {
  return mod((34.0 * x + 1.0) * x, 289.0);
}

// Cellular noise, returning F1 and F2 in a vec2.
// 3x3x3 search region for good F2 everywhere, but a lot
// slower than the 2x2x2 version.
// The code below is a bit scary even to its author,
// but it has at least half decent performance on a
// modern GPU. In any case, it beats any software
// implementation of Worley noise hands down.

vec2 cellular(vec3 P) {
	#define K 0.142857142857 // 1/7
	#define Ko 0.428571428571 // 1/2-K/2
	#define K2 0.020408163265306 // 1/(7*7)
	#define Kz 0.166666666667 // 1/6
	#define Kzo 0.416666666667 // 1/2-1/6*2
	#define jitter 1.0 // smaller jitter gives more regular pattern

	vec3 Pi = mod(floor(P), 289.0);
 	vec3 Pf = fract(P) - 0.5;

	vec3 Pfx = Pf.x + vec3(1.0, 0.0, -1.0);
	vec3 Pfy = Pf.y + vec3(1.0, 0.0, -1.0);
	vec3 Pfz = Pf.z + vec3(1.0, 0.0, -1.0);

	vec3 p = permute(Pi.x + vec3(-1.0, 0.0, 1.0));
	vec3 p1 = permute(p + Pi.y - 1.0);
	vec3 p2 = permute(p + Pi.y);
	vec3 p3 = permute(p + Pi.y + 1.0);

	vec3 p11 = permute(p1 + Pi.z - 1.0);
	vec3 p12 = permute(p1 + Pi.z);
	vec3 p13 = permute(p1 + Pi.z + 1.0);

	vec3 p21 = permute(p2 + Pi.z - 1.0);
	vec3 p22 = permute(p2 + Pi.z);
	vec3 p23 = permute(p2 + Pi.z + 1.0);

	vec3 p31 = permute(p3 + Pi.z - 1.0);
	vec3 p32 = permute(p3 + Pi.z);
	vec3 p33 = permute(p3 + Pi.z + 1.0);

	vec3 ox11 = fract(p11*K) - Ko;
	vec3 oy11 = mod(floor(p11*K), 7.0)*K - Ko;
	vec3 oz11 = floor(p11*K2)*Kz - Kzo; // p11 < 289 guaranteed

	vec3 ox12 = fract(p12*K) - Ko;
	vec3 oy12 = mod(floor(p12*K), 7.0)*K - Ko;
	vec3 oz12 = floor(p12*K2)*Kz - Kzo;

	vec3 ox13 = fract(p13*K) - Ko;
	vec3 oy13 = mod(floor(p13*K), 7.0)*K - Ko;
	vec3 oz13 = floor(p13*K2)*Kz - Kzo;

	vec3 ox21 = fract(p21*K) - Ko;
	vec3 oy21 = mod(floor(p21*K), 7.0)*K - Ko;
	vec3 oz21 = floor(p21*K2)*Kz - Kzo;

	vec3 ox22 = fract(p22*K) - Ko;
	vec3 oy22 = mod(floor(p22*K), 7.0)*K - Ko;
	vec3 oz22 = floor(p22*K2)*Kz - Kzo;

	vec3 ox23 = fract(p23*K) - Ko;
	vec3 oy23 = mod(floor(p23*K), 7.0)*K - Ko;
	vec3 oz23 = floor(p23*K2)*Kz - Kzo;

	vec3 ox31 = fract(p31*K) - Ko;
	vec3 oy31 = mod(floor(p31*K), 7.0)*K - Ko;
	vec3 oz31 = floor(p31*K2)*Kz - Kzo;

	vec3 ox32 = fract(p32*K) - Ko;
	vec3 oy32 = mod(floor(p32*K), 7.0)*K - Ko;
	vec3 oz32 = floor(p32*K2)*Kz - Kzo;

	vec3 ox33 = fract(p33*K) - Ko;
	vec3 oy33 = mod(floor(p33*K), 7.0)*K - Ko;
	vec3 oz33 = floor(p33*K2)*Kz - Kzo;

	vec3 dx11 = Pfx + jitter*ox11;
	vec3 dy11 = Pfy.x + jitter*oy11;
	vec3 dz11 = Pfz.x + jitter*oz11;

	vec3 dx12 = Pfx + jitter*ox12;
	vec3 dy12 = Pfy.x + jitter*oy12;
	vec3 dz12 = Pfz.y + jitter*oz12;

	vec3 dx13 = Pfx + jitter*ox13;
	vec3 dy13 = Pfy.x + jitter*oy13;
	vec3 dz13 = Pfz.z + jitter*oz13;

	vec3 dx21 = Pfx + jitter*ox21;
	vec3 dy21 = Pfy.y + jitter*oy21;
	vec3 dz21 = Pfz.x + jitter*oz21;

	vec3 dx22 = Pfx + jitter*ox22;
	vec3 dy22 = Pfy.y + jitter*oy22;
	vec3 dz22 = Pfz.y + jitter*oz22;

	vec3 dx23 = Pfx + jitter*ox23;
	vec3 dy23 = Pfy.y + jitter*oy23;
	vec3 dz23 = Pfz.z + jitter*oz23;

	vec3 dx31 = Pfx + jitter*ox31;
	vec3 dy31 = Pfy.z + jitter*oy31;
	vec3 dz31 = Pfz.x + jitter*oz31;

	vec3 dx32 = Pfx + jitter*ox32;
	vec3 dy32 = Pfy.z + jitter*oy32;
	vec3 dz32 = Pfz.y + jitter*oz32;

	vec3 dx33 = Pfx + jitter*ox33;
	vec3 dy33 = Pfy.z + jitter*oy33;
	vec3 dz33 = Pfz.z + jitter*oz33;

	vec3 d11 = dx11 * dx11 + dy11 * dy11 + dz11 * dz11;
	vec3 d12 = dx12 * dx12 + dy12 * dy12 + dz12 * dz12;
	vec3 d13 = dx13 * dx13 + dy13 * dy13 + dz13 * dz13;
	vec3 d21 = dx21 * dx21 + dy21 * dy21 + dz21 * dz21;
	vec3 d22 = dx22 * dx22 + dy22 * dy22 + dz22 * dz22;
	vec3 d23 = dx23 * dx23 + dy23 * dy23 + dz23 * dz23;
	vec3 d31 = dx31 * dx31 + dy31 * dy31 + dz31 * dz31;
	vec3 d32 = dx32 * dx32 + dy32 * dy32 + dz32 * dz32;
	vec3 d33 = dx33 * dx33 + dy33 * dy33 + dz33 * dz33;

	// Sort out the two smallest distances (F1, F2)
#if 0
	// Cheat and sort out only F1
	vec3 d1 = min(min(d11,d12), d13);
	vec3 d2 = min(min(d21,d22), d23);
	vec3 d3 = min(min(d31,d32), d33);
	vec3 d = min(min(d1,d2), d3);
	d.x = min(min(d.x,d.y),d.z);
	return sqrt(d.xx); // F1 duplicated, no F2 computed
#else
	// Do it right and sort out both F1 and F2
	vec3 d1a = min(d11, d12);
	d12 = max(d11, d12);
	d11 = min(d1a, d13); // Smallest now not in d12 or d13
	d13 = max(d1a, d13);
	d12 = min(d12, d13); // 2nd smallest now not in d13
	vec3 d2a = min(d21, d22);
	d22 = max(d21, d22);
	d21 = min(d2a, d23); // Smallest now not in d22 or d23
	d23 = max(d2a, d23);
	d22 = min(d22, d23); // 2nd smallest now not in d23
	vec3 d3a = min(d31, d32);
	d32 = max(d31, d32);
	d31 = min(d3a, d33); // Smallest now not in d32 or d33
	d33 = max(d3a, d33);
	d32 = min(d32, d33); // 2nd smallest now not in d33
	vec3 da = min(d11, d21);
	d21 = max(d11, d21);
	d11 = min(da, d31); // Smallest now in d11
	d31 = max(da, d31); // 2nd smallest now not in d31
	d11.xy = (d11.x < d11.y) ? d11.xy : d11.yx;
	d11.xz = (d11.x < d11.z) ? d11.xz : d11.zx; // d11.x now smallest
	d12 = min(d12, d21); // 2nd smallest now not in d21
	d12 = min(d12, d22); // nor in d22
	d12 = min(d12, d31); // nor in d31
	d12 = min(d12, d32); // nor in d32
	d11.yz = min(d11.yz,d12.xy); // nor in d12.yz
	d11.y = min(d11.y,d12.z); // Only two more to go
	d11.y = min(d11.y,d11.z); // Done! (Phew!)
	return sqrt(d11.xy); // F1, F2
#endif
}

void main(void) {
	vec2 st = gl_FragCoord.xy/u_resolution.xy;
	st *= 10.;

	vec2 F = cellular(vec3(st,u_time));
	float dots = smoothstep(0.05, 0.1, F.x);
	float n = F.y-F.x;

	n *= dots;
	gl_FragColor = vec4(n, n, n, 1.0);
}