#version 120

vec3 mod289(vec3 x)
{
  return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 mod289(vec4 x)
{
  return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 permute(vec4 x)
{
  return mod289(((x*34.0)+1.0)*x);
}

vec4 taylorInvSqrt(vec4 r)
{
  return 1.79284291400159 - 0.85373472095314 * r;
}

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);
  vec3 i = floor(v + dot(v, C.yyy) );
  vec3 x0 = v - i + dot(i, C.xxx) ;
  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 );
  vec3 x1 = x0 - i1 + C.xxx;
  vec3 x2 = x0 - i2 + C.yyy;
  vec3 x3 = x0 - D.yyy;
  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 ));
  float n_ = 0.142857142857;
  vec3 ns = n_ * D.wyz - D.xzx;
  vec4 j = p - 49.0 * floor(p * ns.z * ns.z);
  vec4 x_ = floor(j * ns.z);
  vec4 y_ = floor(j - 7.0 * x_ );
  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 = 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);
  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;
  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) ) );
}

varying vec4 vColor;
varying vec3 v_texCoord3D;
varying float vUncertainty;
uniform sampler2D texture;
uniform float noiseDensity;

vec2 mix_random_noise(vec2 inputCoord, float uncertainty)
{
  vec3 uvw = v_texCoord3D + noiseDensity * vec3(snoise(v_texCoord3D + vec3(0.0f, 0.0f, 1.0f)),
                                         snoise(v_texCoord3D + vec3(43.0f, 17.0f, 1.0f)),
                                         snoise(v_texCoord3D + vec3(-17.0f, -43.0f, 1.0f)));
  float n = snoise(uvw - vec3(0.0f, 0.0f, 1.0f));
  n += 0.5f * snoise(uvw * 2.0f - vec3(0.0f, 0.0f, 1.4f));
  n += 0.25f * snoise(uvw * 4.0f - vec3(0.0f, 0.0f, 2.0f));
  n += 0.125f * snoise(uvw * 8.0f - vec3(0.0f, 0.0f, 2.8f));
  n += 0.0625f * snoise(uvw * 16.0f - vec3(0.0f, 0.0f, 4.0f));
  n += 0.03125f * snoise(uvw * 32.0f - vec3(0.0f, 0.0f, 5.6f));
  n = n * 0.7f - 0.5f;

  return mix(inputCoord, vec2(n, n), uncertainty);
}

void main()
{
  // offset the texture coordinate by the uncertainty value
  float uncertainty = clamp(vUncertainty, 0.0f, 1.0f);
  vec2 coord = mix_random_noise(gl_TexCoord[0].xy, uncertainty);
  gl_FragColor = vColor * texture2D(texture, coord);
}
