#version 330

//#include "3rdParty/noise.glsl"

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);

// 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) ) );
  }

float fog(float dist) {
    dist = max(0,dist - 50);
    dist = dist * 0.05;
    dist = dist;
    return 1-exp(-dist);
}

smooth in vec3 teNormal;
smooth in vec3 tePosition;
smooth in float fogDist;
smooth in float gmix;
in vec4 teColor;

out vec4 fgColor;

uniform mat4 ViewMatrix;
uniform mat4 ProjectionMatrix;

void main(void)
{
    //fog color
    vec4 fogColor = vec4(0.6,0.7,0.8,1.0);

    //heliospheric lighting
    vec4 light = vec4(1.0,1.0,1.0,1.0);
    vec4 dark  = vec4(0.0,0.0,0.0,1.0);
    //direction to sun from origin
    vec3 lightDir = normalize(ViewMatrix * vec4(5.0,5.0,1.0,0.0)).xyz;

    float costheta = dot(teNormal, lightDir);
    float a = costheta * 0.5 + 0.5;

    //create gravel-texel
    vec3 uvw = tePosition;
    // Six components of noise in a fractal sum
    //float n = snoise(uvw * 10);
    float n = 0;
    n += 0.5 * snoise(uvw * 20.0);
    //n += 0.25 * snoise(uvw * 40.0);
    //n += 0.125 * snoise(uvw * 80.0);
    //n += 0.0625 * snoise(uvw * 160.0);
    //n += 0.03125 * snoise(uvw * 320.0);
    n = abs(n*2);//[0,1]

    //dirt
    float d = snoise(uvw);
    d += 0.5 * snoise(uvw * 2);
    d += 0.25 * snoise(uvw * 4);
    d = d/3*2 +0.5;

    //                  base, dirt, noise-level*(above 0?)*(linear blend by y)
    vec4 texBase = mix(teColor, vec4(0.45,0.27,0.1,1),d*d*step(0.01,tePosition.y)*clamp(tePosition.y/2,0,2));
    //                  stone highlights
    vec4 texHighlights = mix(texBase, vec4(0.9*n,0.9*n,0.9*n,1),n*n*n);
    //mix highlights into Color with inclination, if inclination^2 > 0.35
    vec4 texColor = mix(texBase,texHighlights, (gmix*(1-gmix))*4*(gmix*(1-gmix))*4);
    vec4 Color = texColor;

    fgColor = Color * mix(dark, light, a);
    fgColor = mix(fgColor,fogColor,fog(fogDist));
}