// 4D Multi-octave Simplex noise.
//
// For each octave, a higher frequency/lower amplitude function will be added to the original.
// The higher the persistence [0-1], the more of each succeeding octave will be added.
float simplexNoise( const int octaves, const float persistence, const float scale, const float4 &v ) {
float total = 0;
float frequency = scale;
float amplitude = 1;
// We have to keep track of the largest possible amplitude,
// because each octave adds more, and we need a value in [-1, 1].
float maxAmplitude = 0;
for( int i=0; i < octaves; i++ ) {
total += simplexRawNoise( v.x() * frequency, v.y() * frequency, v.z() * frequency, v.w() * frequency ) * amplitude;
frequency *= 2;
maxAmplitude += amplitude;
amplitude *= persistence;
}
return total / maxAmplitude;
}
// 4D Scaled Simplex raw noise.
//
// Returned value will be between loBound and hiBound.
float simplexScaledRawNoise( const float loBound, const float hiBound, const float x, const float y, const float z, const float w ) {
return simplexRawNoise(x, y, z, w) * (hiBound - loBound) / 2 + (hiBound + loBound) / 2;
}