noiseFunctions top-level property

String noiseFunctions

Implementation

final String noiseFunctions = '''
  const float PI = 3.14159265;

  //	Simplex 3D Noise
  //	by Ian McEwan, Ashima Arts
  //
  vec4 permute(vec4 x){return mod(((x*34.0)+1.0)*x, 289.0);}
  vec4 taylorInvSqrt(vec4 r){return 1.79284291400159 - 0.85373472095314 * r;}

  //
  float simplex3(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 * C
    vec3 x1 = x0 - i1 + 1.0 * C.xxx;
    vec3 x2 = x0 - i2 + 2.0 * C.xxx;
    vec3 x3 = x0 - 1. + 3.0 * C.xxx;

    // Permutations
    i = mod(i, 289.0 );
    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
    // ( N*N points uniformly over a square, mapped onto an octahedron.)
    float n_ = 1.0/7.0; // N=7
    vec3  ns = n_ * D.wyz - D.xzx;

    vec4 j = p - 49.0 * floor(p * ns.z *ns.z);  //  mod(p,N*N)

    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 = 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 fractal3(
  //   vec3 v,
  //   float sharpness,
  //   float period,
  //   float persistence,
  //   float lacunarity,
  //   int octaves
  // ) {
  //   float n = 0.0;
  //   float a = 1.0; // Amplitude for current octave
  //   float max_amp = 0.0; // Accumulate max amplitude so we can normalize after
  //   float P = period;  // Period for current octave

  //   for(int i = 0; i < octaves; i++) {
  //       n += a * simplex3(v / P);
  //       a *= persistence;
  //       max_amp += a;
  //       P /= lacunarity;
  //   }

  //   // Normalize noise between [0.0, amplitude]
  //   return n / max_amp;
  // }

  // float fractal3(vec3 p, float sharp, float per, float pers, float lac, int lodLimit) {
  //   float total = 0.0;
  //   float frequency = 1.0 / per;
  //   float amplitude = 1.0;

  //   // Use a constant max (e.g., 12) so the shader compiles everywhere
  //   for (int i = 0; i < 12; i++) {
  //     if (i >= lodLimit) break; // This is the performance "Magic"

  //     total += simplex3(p * frequency) * amplitude;

  //     frequency *= lac;
  //     amplitude *= pers;
  //   }
  //   return total;
  // }

  float fractal3(vec3 p, float sharp, float per, float pers, float lac, float lodLimit) {
      float total = 0.0;
      float frequency = 1.0 / per;
      float amplitude = 1.0;

      // We still loop to a constant max
      for (int i = 0; i < 12; i++) {
          float fi = float(i);

          // SMOOTH TRANSITION LOGIC
          // If we are below the floor of the limit, add full noise.
          // If we are at the limit, add a fraction of the noise.
          // If we are above, stop.
          float multiplier = clamp(lodLimit - fi, 0.0, 1.0);

          if (multiplier > 0.0) {
              total += simplex3(p * frequency) * amplitude * multiplier;
              frequency *= lac;
              amplitude *= pers;
          } else {
              break;
          }
      }
      return total;
  }

  float terrainHeight(
    int type,
    vec3 v,
    float amplitude,
    float sharpness,
    float offset,
    float period,
    float persistence,
    float lacunarity,
    float octaves
  ) {
    float h = 0.0;

    if (type == 1) {
      h = amplitude * simplex3(v / period);
    }
    else if (type == 2) {
      h = amplitude * fractal3(
        v,
        sharpness,
        period,
        persistence,
        lacunarity,
        octaves);
      h = amplitude * pow(max(0.0, (h + 1.0) / 2.0), sharpness);
    }
    else if (type == 3) {
      h = fractal3(
        v,
        sharpness,
        period,
        persistence,
        lacunarity,
        octaves);
      h = amplitude * pow(max(0.0, 1.0 - abs(h)), sharpness);
    }

    // Multiply by amplitude and adjust offset
    return max(0.0, h + offset);
  }
''';