Noise 3

noise.cpp

/* Linear interpolation */
float lerp(float a, float b, float x) {
   return a * (1 - x) + b * x;
}

/* Trigonometric interpolation */
float terp(float a, float b, float x) {
  float ft = x * 3.1415927f;
  float f = (1 - cosf(ft)) * 0.5f;

  return a * (1 - f) + b * f;
}

/* Noise interpolation */
float interpolateNoise(const float x, const float y) {
  int   ix = (int)x;
  float fx = x - ix;

  int   iy = (int)y;
  float fy = y - iy;

  float v1 = smoothNoise(ix, iy),
        v2 = smoothNoise(ix + 1, iy),
        v3 = smoothNoise(ix, iy + 1),
        v4 = smoothNoise(ix + 1, iy + 1);

  float i1 = terp(v1, v2, fx),
        i2 = terp(v3, v4, fx);

  return terp(i1, i2, fy);
}