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n/fractal: use hurst parameters consistently

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This commit is contained in:
Danny Robson 2015-06-02 00:15:02 +10:00
parent e98709bfc6
commit bc1c576297
8 changed files with 91 additions and 46 deletions
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9
noise/fractal/fbm.hpp
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@ -37,12 +37,14 @@ namespace util { namespace noise { namespace fractal {
using seed_t = uint64_t;
static constexpr unsigned DEFAULT_OCTAVES = 8;
static constexpr T DEFAULT_H = 1;
static constexpr T DEFAULT_FREQUENCY = T(0.1);
static constexpr T DEFAULT_LACUNARITY = 2;
static constexpr T DEFAULT_AMPLITUDE = 1;
static constexpr T DEFAULT_GAIN = 1 / T(2);
static constexpr T DEFAULT_GAIN = 1 / DEFAULT_LACUNARITY;
fbm (unsigned octaves,
T H,
T frequency,
T lacunarity,
T amplitude,
@ -52,6 +54,7 @@ namespace util { namespace noise { namespace fractal {
seed_t seed;
unsigned octaves;
T H;
T frequency;
T lacunarity;
@ -61,6 +64,10 @@ namespace util { namespace noise { namespace fractal {
B basis;
constexpr T operator() (util::point<2,T>) const;
private:
T invAH;
T invGH;
};
} } }

11
noise/fractal/fbm.ipp
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@ -25,6 +25,7 @@ namespace util { namespace noise { namespace fractal {
///////////////////////////////////////////////////////////////////////////
template <typename T, typename B>
fbm<T,B>::fbm (unsigned _octaves,
T _H,
T _frequency,
T _lacunarity,
T _amplitude,
@ -32,11 +33,14 @@ namespace util { namespace noise { namespace fractal {
seed_t _seed):
seed (_seed),
octaves (_octaves),
H (_H),
frequency (_frequency),
lacunarity (_lacunarity),
amplitude (_amplitude),
gain (_gain),
basis (_seed)
basis (_seed),
invAH (std::pow (amplitude, -H)),
invGH (std::pow (gain, H))
{
CHECK_NEQ (octaves, 0);
CHECK_NEQ (frequency, 0);
@ -48,6 +52,7 @@ namespace util { namespace noise { namespace fractal {
template <typename T, typename B>
fbm<T,B>::fbm ():
fbm<T,B> (DEFAULT_OCTAVES,
DEFAULT_H,
DEFAULT_FREQUENCY,
DEFAULT_LACUNARITY,
DEFAULT_AMPLITUDE,
@ -63,13 +68,13 @@ namespace util { namespace noise { namespace fractal {
{
T total = 0;
T f = frequency;
T a = amplitude;
T a = invAH;
for (size_t i = 0; i < octaves; ++i) {
total += basis (p * f) * a;
f *= lacunarity;
a *= gain;
a *= invGH;
}
return total;

4
noise/fractal/hetero.hpp
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@ -45,6 +45,10 @@ namespace util { namespace noise { namespace fractal {
B basis;
constexpr T operator() (util::point<2,T>) const;
private:
T invAH;
T invGH;
};
} } }

21
noise/fractal/hetero.ipp
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@ -29,7 +29,9 @@ namespace util { namespace noise { namespace fractal {
lacunarity (2),
offset (0.7f),
amplitude (1),
gain (1)
gain (1/lacunarity),
invAH (std::pow (amplitude, -H)),
invGH (std::pow (gain, H))
{ ; }
@ -38,20 +40,19 @@ namespace util { namespace noise { namespace fractal {
constexpr T
hetero<T,B>::operator() (util::point<2,T> p) const
{
T exponents[octaves];
for (size_t i = 0; i < octaves; ++i)
exponents[i] = std::pow (std::pow (lacunarity, float (i)), -H);
T result = 0;
T increment = 0;
T scale = invAH;
p *= frequency;
result = basis (p) + offset;
T result = (basis (p) + offset) * scale;
p *= lacunarity;
for (size_t i = 0; i < octaves; ++i) {
T increment = 0;
for (size_t i = 1; i < octaves; ++i) {
scale *= invGH;
increment = basis (p) + offset;
increment *= exponents[i];
increment *= scale;
increment *= result;
result += increment;

7
noise/fractal/hmf.hpp
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@ -23,6 +23,7 @@
namespace util { namespace noise { namespace fractal {
///////////////////////////////////////////////////////////////////////
/// Musgrave's "Hybrid MultiFractal"
template <typename T, typename B>
struct hmf {
using seed_t = uint64_t;
@ -44,7 +45,11 @@ namespace util { namespace noise { namespace fractal {
B basis;
constexpr T operator() (util::point<2,T>) const;
constexpr T operator() (point<2,T>) const;
private:
T invAH;
T invGH;
};
} } }

19
noise/fractal/hmf.ipp
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@ -22,6 +22,7 @@
namespace util { namespace noise { namespace fractal {
//-------------------------------------------------------------------------
// H should be fairly low due to the decreasing weight parameter in eval
template <typename T, typename B>
hmf<T,B>::hmf ():
H (0.25f),
@ -30,7 +31,9 @@ namespace util { namespace noise { namespace fractal {
lacunarity (2),
offset (0.7f),
amplitude (1),
gain (1)
gain (1 / lacunarity),
invAH (std::pow (amplitude, -H)),
invGH (std::pow (gain, H))
{ ; }
@ -39,9 +42,7 @@ namespace util { namespace noise { namespace fractal {
constexpr T
hmf<T,B>::operator() (util::point<2,T> p) const
{
T exponents[octaves];
for (size_t i = 0; i < octaves; ++i)
exponents[i] = std::pow (std::pow (lacunarity, float (i)), -H);
T scale = invAH;
T result = 0;
T signal = 0;
@ -50,13 +51,13 @@ namespace util { namespace noise { namespace fractal {
p *= frequency;
for (size_t i = 0; i < octaves; ++i) {
signal = (basis (p) + offset) * exponents[i];
result += weight * signal;
signal = (basis (p) + offset) * scale;
result += signal * weight;
weight *= gain * signal;
if (weight > 1)
weight = 1;
weight *= signal;
weight = min (weight, T{1});
scale *= invGH;
p *= lacunarity;
}

24
noise/fractal/rmf.hpp
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@ -25,19 +25,27 @@ namespace util { namespace noise { namespace fractal {
/// Rigid Multifractal summation, based on Musgrave's algorithm
///
/// octaves: count of layers to be summed
/// H: hurst parameter (~roughness)
/// offset: TODO
/// frequency: point scaling factor for the base octave
/// lacunarity: per octave frequency scaling factor
/// lacunarity: incremental octave frequency scaling factor
/// amplitude: value scaling factor for the base octave
/// gain: incremental octave value scaling factor
template <typename T, typename B>
struct rmf {
using seed_t = uint64_t;
static constexpr unsigned DEFAULT_OCTAVES = 5;
static constexpr T DEFAULT_FREQUENCY = T(1);
static constexpr T DEFAULT_H = 1;
static constexpr T DEFAULT_OFFSET = 1;
static constexpr T DEFAULT_FREQUENCY = 1;
static constexpr T DEFAULT_LACUNARITY = 2;
static constexpr T DEFAULT_AMPLITUDE = 1;
static constexpr T DEFAULT_GAIN = 2;
static constexpr T DEFAULT_AMPLITUDE = 2;
static constexpr T DEFAULT_GAIN = 1 / DEFAULT_LACUNARITY;
rmf (unsigned octaves,
T H,
T offset,
T frequency,
T lacunarity,
T amplitude,
@ -46,7 +54,10 @@ namespace util { namespace noise { namespace fractal {
rmf ();
seed_t seed;
unsigned octaves;
T H;
T offset;
T frequency;
T lacunarity;
@ -55,7 +66,12 @@ namespace util { namespace noise { namespace fractal {
T gain;
B basis;
constexpr T operator() (util::point<2,T>) const;
private:
T invAH;
T invGH;
};
} } }

24
noise/fractal/rmf.ipp
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@ -24,6 +24,8 @@ namespace util { namespace noise { namespace fractal {
///////////////////////////////////////////////////////////////////////////
template <typename T, typename B>
rmf<T,B>::rmf (unsigned _octaves,
T _H,
T _offset,
T _frequency,
T _lacunarity,
T _amplitude,
@ -31,11 +33,15 @@ namespace util { namespace noise { namespace fractal {
seed_t _seed):
seed (_seed),
octaves (_octaves),
H (_H),
offset (_offset),
frequency (_frequency),
lacunarity (_lacunarity),
amplitude (_amplitude),
gain (_gain),
basis (_seed)
basis (_seed),
invAH (std::pow (amplitude, -H)),
invGH (std::pow (gain, H))
{ ; }
@ -43,6 +49,8 @@ namespace util { namespace noise { namespace fractal {
template <typename T, typename B>
rmf<T,B>::rmf ():
rmf<T,B> (DEFAULT_OCTAVES,
DEFAULT_H,
DEFAULT_OFFSET,
DEFAULT_FREQUENCY,
DEFAULT_LACUNARITY,
DEFAULT_AMPLITUDE,
@ -52,16 +60,13 @@ namespace util { namespace noise { namespace fractal {
//-------------------------------------------------------------------------
// we use the name 'amplitude' instead of musgrave's 'gain'.
// assumes basis distribution [-1,1] and offset ~= 1
template <typename T, typename B>
constexpr T
rmf<T,B>::operator() (util::point<2,T> p) const
{
const T offset = 1;
const T H = 1.f;
T exponents[octaves];
for (size_t i = 0; i < octaves; ++i)
exponents[i] = std::pow (std::pow (lacunarity, float (i)), -H);
T scale = invAH;
T signal = 0;
T result = 0;
@ -82,12 +87,13 @@ namespace util { namespace noise { namespace fractal {
signal *= weight;
// contribute to the weight
weight = signal * gain;
weight = signal * amplitude;
weight = limit (weight, 0, 1);
// record and continue
result += signal * exponents[i];
result += signal * scale;
scale *= invGH;
p *= lacunarity;
}