+float snoise(vec3 v)
+ {
+ const vec2 C = vec2(1.0/6.0, 1.0/3.0) ;
+ const vec4 D = vec4(0.0, 0.5, 1.0, 2.0);
+
+// First corner
+ vec3 i = floor(v + dot(v, C.yyy) );
+ vec3 x0 = v - i + dot(i, C.xxx) ;
+
+// Other corners
+ vec3 g = step(x0.yzx, x0.xyz);
+ vec3 l = 1.0 - g;
+ vec3 i1 = min( g.xyz, l.zxy );
+ vec3 i2 = max( g.xyz, l.zxy );
+
+ // x0 = x0 - 0.0 + 0.0 * C.xxx;
+ // x1 = x0 - i1 + 1.0 * C.xxx;
+ // x2 = x0 - i2 + 2.0 * C.xxx;
+ // x3 = x0 - 1.0 + 3.0 * C.xxx;
+ vec3 x1 = x0 - i1 + C.xxx;
+ vec3 x2 = x0 - i2 + C.yyy; // 2.0*C.x = 1/3 = C.y
+ vec3 x3 = x0 - D.yyy; // -1.0+3.0*C.x = -0.5 = -D.y
+
+// Permutations
+ i = mod289(i);
+ vec4 p = permute( permute( permute(
+ i.z + vec4(0.0, i1.z, i2.z, 1.0 ))
+ + i.y + vec4(0.0, i1.y, i2.y, 1.0 ))
+ + i.x + vec4(0.0, i1.x, i2.x, 1.0 ));
+
+// Gradients: 7x7 points over a square, mapped onto an octahedron.
+// The ring size 17*17 = 289 is close to a multiple of 49 (49*6 = 294)
+ float n_ = 0.142857142857; // 1.0/7.0
+ vec3 ns = n_ * D.wyz - D.xzx;
+
+ vec4 j = p - 49.0 * floor(p * ns.z * ns.z); // mod(p,7*7)
+
+ vec4 x_ = floor(j * ns.z);
+ vec4 y_ = floor(j - 7.0 * x_ ); // mod(j,N)
+
+ vec4 x = x_ *ns.x + ns.yyyy;
+ vec4 y = y_ *ns.x + ns.yyyy;
+ vec4 h = 1.0 - abs(x) - abs(y);
+
+ vec4 b0 = vec4( x.xy, y.xy );
+ vec4 b1 = vec4( x.zw, y.zw );
+
+ //vec4 s0 = vec4(lessThan(b0,0.0))*2.0 - 1.0;
+ //vec4 s1 = vec4(lessThan(b1,0.0))*2.0 - 1.0;
+ vec4 s0 = floor(b0)*2.0 + 1.0;
+ vec4 s1 = floor(b1)*2.0 + 1.0;
+ vec4 sh = -step(h, vec4(0.0));
+
+ vec4 a0 = b0.xzyw + s0.xzyw*sh.xxyy ;
+ vec4 a1 = b1.xzyw + s1.xzyw*sh.zzww ;
+
+ vec3 p0 = vec3(a0.xy,h.x);
+ vec3 p1 = vec3(a0.zw,h.y);
+ vec3 p2 = vec3(a1.xy,h.z);
+ vec3 p3 = vec3(a1.zw,h.w);
+
+//Normalise gradients
+ vec4 norm = taylorInvSqrt(vec4(dot(p0,p0), dot(p1,p1), dot(p2, p2), dot(p3,p3)));
+ p0 *= norm.x;
+ p1 *= norm.y;
+ p2 *= norm.z;
+ p3 *= norm.w;
+
+// Mix final noise value
+ vec4 m = max(0.6 - vec4(dot(x0,x0), dot(x1,x1), dot(x2,x2), dot(x3,x3)), 0.0);
+ m = m * m;
+ return 42.0 * dot( m*m, vec4( dot(p0,x0), dot(p1,x1),
+ dot(p2,x2), dot(p3,x3) ) );
+ }
+
+#pragma glslify: export(snoise)