koobas.hobune.stream
Can anyone explain this code?
using UnityEngine;
using System.Collections;
public class PerlinNoise
{
const int B = 256;
int[] m_perm = new int[B+B];
public PerlinNoise(int seed)
{
UnityEngine.Random.seed = seed;
int i, j, k;
for (i = 0 ; i < B ; i++)
{
m_perm[i] = i;
}
while (--i != 0)
{
k = m_perm[i];
j = UnityEngine.Random.Range(0, B);
m_perm[i] = m_perm[j];
m_perm[j] = k;
}
for (i = 0 ; i < B; i++)
{
m_perm[B + i] = m_perm[i];
}
}
float FADE(float t) { return t * t * t * ( t * ( t * 6.0f - 15.0f ) + 10.0f ); }
float LERP(float t, float a, float b) { return (a) + (t)*((b)-(a)); }
float GRAD1(int hash, float x )
{
//This method uses the mod operator which is slower
//than bitwise operations but is included out of interest
// int h = hash % 16;
// float grad = 1.0f + (h % 8);
// if((h%8) < 4) grad = -grad;
// return ( grad * x );
int h = hash & 15;
float grad = 1.0f + (h & 7);
if ((h&8) != 0) grad = -grad;
return ( grad * x );
}
float GRAD2(int hash, float x, float y)
{
//This method uses the mod operator which is slower
//than bitwise operations but is included out of interest
// int h = hash % 16;
// float u = h<4 ? x : y;
// float v = h<4 ? y : x;
// int hn = h%2;
// int hm = (h/2)%2;
// return ((hn != 0) ? -u : u) + ((hm != 0) ? -2.0f*v : 2.0f*v);
int h = hash & 7;
float u = h<4 ? x : y;
float v = h<4 ? y : x;
return (((h&1) != 0)? -u : u) + (((h&2) != 0) ? -2.0f*v : 2.0f*v);
}
float GRAD3(int hash, float x, float y , float z)
{
//This method uses the mod operator which is slower
//than bitwise operations but is included out of interest
// int h = hash % 16;
// float u = (h<8) ? x : y;
// float v = (h<4) ? y : (h==12||h==14) ? x : z;
// int hn = h%2;
// int hm = (h/2)%2;
// return ((hn != 0) ? -u : u) + ((hm != 0) ? -v : v);
int h = hash & 15;
float u = h<8 ? x : y;
float v = (h<4) ? y : (h==12 || h==14) ? x : z;
return (((h&1) != 0)? -u : u) + (((h&2) != 0)? -v : v);
}
float Noise1D( float x )
{
//returns a noise value between -0.5 and 0.5
int ix0, ix1;
float fx0, fx1;
float s, n0, n1;
ix0 = (int)Mathf.Floor(x); // Integer part of x
fx0 = x - ix0; // Fractional part of x
fx1 = fx0 - 1.0f;
ix1 = ( ix0+1 ) & 0xff;
ix0 = ix0 & 0xff; // Wrap to 0..255
s = FADE(fx0);
n0 = GRAD1(m_perm[ix0], fx0);
n1 = GRAD1(m_perm[ix1], fx1);
return 0.188f * LERP( s, n0, n1);
}
float Noise2D( float x, float y )
{
//returns a noise value between -0.75 and 0.75
int ix0, iy0, ix1, iy1;
float fx0, fy0, fx1, fy1, s, t, nx0, nx1, n0, n1;
ix0 = (int)Mathf.Floor(x); // Integer part of x
iy0 = (int)Mathf.Floor(y); // Integer part of y
fx0 = x - ix0; // Fractional part of x
fy0 = y - iy0; // Fractional part of y
fx1 = fx0 - 1.0f;
fy1 = fy0 - 1.0f;
ix1 = (ix0 + 1) & 0xff; // Wrap to 0..255
iy1 = (iy0 + 1) & 0xff;
ix0 = ix0 & 0xff;
iy0 = iy0 & 0xff;
t = FADE( fy0 );
s = FADE( fx0 );
nx0 = GRAD2(m_perm[ix0 + m_perm[iy0]], fx0, fy0);
nx1 = GRAD2(m_perm[ix0 + m_perm[iy1]], fx0, fy1);
n0 = LERP( t, nx0, nx1 );
nx0 = GRAD2(m_perm[ix1 + m_perm[iy0]], fx1, fy0);
nx1 = GRAD2(m_perm[ix1 + m_perm[iy1]], fx1, fy1);
n1 = LERP(t, nx0, nx1);
return 0.507f * LERP( s, n0, n1 );
}
float Noise3D( float x, float y, float z )
{
//returns a noise value between -1.5 and 1.5
int ix0, iy0, ix1, iy1, iz0, iz1;
float fx0, fy0, fz0, fx1, fy1, fz1;
float s, t, r;
float nxy0, nxy1, nx0, nx1, n0, n1;
ix0 = (int)Mathf.Floor( x ); // Integer part of x
iy0 = (int)Mathf.Floor( y ); // Integer part of y
iz0 = (int)Mathf.Floor( z ); // Integer part of z
fx0 = x - ix0; // Fractional part of x
fy0 = y - iy0; // Fractional part of y
fz0 = z - iz0; // Fractional part of z
fx1 = fx0 - 1.0f;
fy1 = fy0 - 1.0f;
fz1 = fz0 - 1.0f;
ix1 = ( ix0 + 1 ) & 0xff; // Wrap to 0..255
iy1 = ( iy0 + 1 ) & 0xff;
iz1 = ( iz0 + 1 ) & 0xff;
ix0 = ix0 & 0xff;
iy0 = iy0 & 0xff;
iz0 = iz0 & 0xff;
r = FADE( fz0 );
t = FADE( fy0 );
s = FADE( fx0 );
nxy0 = GRAD3(m_perm[ix0 + m_perm[iy0 + m_perm[iz0]]], fx0, fy0, fz0);
nxy1 = GRAD3(m_perm[ix0 + m_perm[iy0 + m_perm[iz1]]], fx0, fy0, fz1);
nx0 = LERP( r, nxy0, nxy1 );
nxy0 = GRAD3(m_perm[ix0 + m_perm[iy1 + m_perm[iz0]]], fx0, fy1, fz0);
nxy1 = GRAD3(m_perm[ix0 + m_perm[iy1 + m_perm[iz1]]], fx0, fy1, fz1);
nx1 = LERP( r, nxy0, nxy1 );
n0 = LERP( t, nx0, nx1 );
nxy0 = GRAD3(m_perm[ix1 + m_perm[iy0 + m_perm[iz0]]], fx1, fy0, fz0);
nxy1 = GRAD3(m_perm[ix1 + m_perm[iy0 + m_perm[iz1]]], fx1, fy0, fz1);
nx0 = LERP( r, nxy0, nxy1 );
nxy0 = GRAD3(m_perm[ix1 + m_perm[iy1 + m_perm[iz0]]], fx1, fy1, fz0);
nxy1 = GRAD3(m_perm[ix1 + m_perm[iy1 + m_perm[iz1]]], fx1, fy1, fz1);
nx1 = LERP( r, nxy0, nxy1 );
n1 = LERP( t, nx0, nx1 );
return 0.936f * LERP( s, n0, n1 );
}
public float FractalNoise1D(float x, int octNum, float frq, float amp)
{
float gain = 1.0f;
float sum = 0.0f;
for(int i = 0; i < octNum; i++)
{
sum += Noise1D(x*gain/frq) * amp/gain;
gain *= 2.0f;
}
return sum;
}
public float FractalNoise2D(float x, float y, int octNum, float frq, float amp)
{
float gain = 1.0f;
float sum = 0.0f;
for(int i = 0; i < octNum; i++)
{
sum += Noise2D(x*gain/frq, y*gain/frq) * amp/gain;
gain *= 2.0f;
}
return sum;
}
public float FractalNoise3D(float x, float y, float z, int octNum, float frq, float amp)
{
float gain = 1.0f;
float sum = 0.0f;
for(int i = 0; i < octNum; i++)
{
sum += Noise3D(x*gain/frq, y*gain/frq, z*gain/frq) * amp/gain;
gain *= 2.0f;
}
return sum;
}
}
I found this while looking up tutorials for procedural terrain generation, but it comes with no explanation . Can someone please explain how this script works?
