Принципы генерации ландшафтов на сферической поверхности (4 стр)

lowp float snoise(in mediump vec3 v){
  const lowp vec2 C = vec2(0.16666666666,0.33333333333);
  const lowp vec4 D = vec4(0,.5,1,2);
  lowp vec3 i  = floor(C.y*(v.x+v.y+v.z) + v);
  lowp vec3 x0 = C.x*(i.x+i.y+i.z) + (v - i);
  lowp vec3 g = step(x0.yzx, x0);
  lowp vec3 l = (1. - g).zxy;
  lowp vec3 i1 = min( g, l );
  lowp vec3 i2 = max( g, l );
  lowp vec3 x1 = x0 - i1 + C.x;
  lowp vec3 x2 = x0 - i2 + C.y;
  lowp vec3 x3 = x0 - D.yyy;
  i = mod(i,289.);
  lowp vec4 p = permute( permute( permute(
    i.z + vec4(0., i1.z, i2.z, 1.))
  + i.y + vec4(0., i1.y, i2.y, 1.))
  + i.x + vec4(0., i1.x, i2.x, 1.));
  lowp vec3 ns = .142857142857 * D.wyz - D.xzx;
  lowp vec4 j = -49. * floor(p * ns.z * ns.z) + p;
  lowp vec4 x_ = floor(j * ns.z);
  lowp vec4 x = x_ * ns.x + ns.yyyy;
  lowp vec4 y = floor(j - 7. * x_ ) * ns.x + ns.yyyy;
  lowp vec4 h = 1. - abs(x) - abs(y);
  lowp vec4 b0 = vec4( x.xy, y.xy );
  lowp vec4 b1 = vec4( x.zw, y.zw );
  lowp vec4 sh = -step(h, vec4(0));
  lowp vec4 a0 = b0.xzyw + (floor(b0)*2.+ 1.).xzyw*sh.xxyy;
  lowp vec4 a1 = b1.xzyw + (floor(b1)*2.+ 1.).xzyw*sh.zzww;
  lowp vec3 p0 = vec3(a0.xy,h.x);
  lowp vec3 p1 = vec3(a0.zw,h.y);
  lowp vec3 p2 = vec3(a1.xy,h.z);
  lowp vec3 p3 = vec3(a1.zw,h.w);
  lowp vec4 norm = inversesqrt(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;
  lowp vec4 m = max(.6 - vec4(dot(x0,x0), dot(x1,x1), dot(x2,x2), dot(x3,x3)), 0.);
  return .5 + 12. * dot( m * m * m, vec4( dot(p0,x0), dot(p1,x1),dot(p2,x2), dot(p3,x3) ) );
}

float perlin(vec3 v) {
    vec3 p = floor(v), f = fract(v);
  f = f*f*(3.-2.*f);
  float n = p.x + dot(p.yz,vec2(157,113));
  vec4 s1 = mix(permute(n+vec4(0,157,113,270)),permute(n+vec4(1,158,114,271)),f.x);
  return mix(mix(s1.x,s1.y,f.y), mix(s1.z,s1.w,f.y), f.z);
}

float noise3(vec3 v){
    v *= 64.; // emulates 64x64 noise texture
    return ( perlin(v) + perlin(v+11.5) )/2.;
}