public override void ComputeSpectrum(Vector3[,] spectrum, float tileSizeMultiplier, int maxResolution, System.Random random)
{
float tileSize = TileSize * tileSizeMultiplier;
float totalAmplitude = amplitude * ComputeWaveAmplitude(windSpeed);
float realSizeInv = 1.0f / tileSize;
int resolution = spectrum.GetLength(0);
int halfResolution = resolution / 2;
float linearWindSpeed = windSpeed;
float L = linearWindSpeed * linearWindSpeed / gravity;
float LPow2 = L * L;
float l = FastMath.Pow2(L / cutoffFactor);
float scale = Mathf.Sqrt(totalAmplitude * Mathf.Pow(100.0f / tileSize, 2.35f) / 2000000.0f);
for (int x = 0; x < resolution; ++x)
{
float kx = 2.0f * Mathf.PI * (x /* + 0.5f*/ - halfResolution) * realSizeInv;
for (int y = 0; y < resolution; ++y)
{
float ky = 2.0f * Mathf.PI * (y /* + 0.5f*/ - halfResolution) * realSizeInv;
float k = Mathf.Sqrt(kx * kx + ky * ky);
float kk = k * k;
float kkkk = kk * kk;
float p = Mathf.Exp(-1.0f / (kk * LPow2) - kk * l) / kkkk;
p = scale * Mathf.Sqrt(p);
float h = FastMath.Gauss01() * p;
float hi = FastMath.Gauss01() * p;
int xCoord = (x + halfResolution) % resolution;
int yCoord = (y + halfResolution) % resolution;
if (x == halfResolution && y == halfResolution)
{
h = 0;
hi = 0;
}
spectrum[xCoord, yCoord] = new Vector3(h, hi, 1.0f);
}
}
}
override public void ComputeSpectrum(Vector3[,] spectrum, float tileSizeMultiplier, int maxResolution, System.Random random)
{
int resolution = spectrum.GetLength(0);
int halfResolution = resolution / 2;
int numRandomSkips = (maxResolution - resolution) / 2;
if (numRandomSkips < 0)
{
numRandomSkips = 0;
}
float frequencyScale = 2.0f * Mathf.PI / (TileSize * tileSizeMultiplier);
float U10 = windSpeed;
//float omegac = 0.84f;
float omegac = 0.84f * Mathf.Pow((float)System.Math.Tanh(Mathf.Pow(fetch / 22000.0f, 0.4f)), -0.75f);
float sqrt10 = Mathf.Sqrt(10.0f);
// short-wave parameters
const float cm = 0.23f;
float km = 2.0f * gravity / (cm * cm);
// long-wave parameters
float kp = gravity * FastMath.Pow2(omegac / U10);
float cp = PhaseSpeed(kp, km);
float omega = U10 / cp;
float alphap = 0.006f * Mathf.Sqrt(omega);
float sigma = 0.08f * (1.0f + 4.0f * Mathf.Pow(omegac, -3.0f));
float z0 = 3.7e-5f * U10 * U10 / gravity * Mathf.Pow(U10 / cp, 0.9f);
float friction = U10 * 0.41f / Mathf.Log(10.0f / z0); // 0.41 is the estimated 'k' from "the law of the wall"
float a0 = Mathf.Log(2.0f) / 4.0f;
float ap = 4.0f;
float am = 0.13f * friction / cm;
float alpham = 0.01f * (friction < cm ? 1.0f + Mathf.Log(friction / cm) : 1.0f + 3.0f * Mathf.Log(friction / cm));
// skip random values that normally would be generated at max resolution
#pragma warning disable 0219
for (int i = 0; i < numRandomSkips; ++i)
{
for (int ii = 0; ii < maxResolution; ++ii)
{
Random.Range(0.000001f, 1.0f);
float t = Random.value;
Random.Range(0.000001f, 1.0f);
t = Random.value;
}
}
for (int x = 0; x < resolution; ++x)
{
float kx = frequencyScale * (x /* + 0.5f*/ - halfResolution);
// skip random values that normally would be generated at max resolution
for (int i = 0; i < numRandomSkips; ++i)
{
Random.Range(0.000001f, 1.0f);
float t = Random.value;
Random.Range(0.000001f, 1.0f);
t = Random.value;
}
for (int y = 0; y < resolution; ++y)
{
float ky = frequencyScale * (y /* + 0.5f*/ - halfResolution);
float k = Mathf.Sqrt(kx * kx + ky * ky);
float c = PhaseSpeed(k, km);
/*
* Long-wave spectrum (bl)
*/
float moskowitz = Mathf.Exp((-5.0f / 4.0f) * FastMath.Pow2(kp / k));
float gamma = omegac <= 1.0f ? 1.7f : 1.7f + 6 * Mathf.Log(omegac);
float r = Mathf.Exp(-FastMath.Pow2(Mathf.Sqrt(k / kp) - 1.0f) / (2.0f * sigma * sigma));
float jonswap = Mathf.Pow(gamma, r);
float fp = moskowitz * jonswap * Mathf.Exp(-(omega / sqrt10) * (Mathf.Sqrt(k / kp) - 1.0f));
float bl = 0.5f * alphap * (cp / c) * fp;
/*
* Short-wave spectrum (bh)
*/
float fm = Mathf.Exp(-0.25f * FastMath.Pow2(k / km - 1.0f));
float bh = 0.5f * alpham * (cm / c) * fm * moskowitz; // equation in paper seems to be wrong (missing moskowitz term) / it's fixed now
/*
* Directionality
*/
float deltak = (float)System.Math.Tanh(a0 + ap * Mathf.Pow(c / cp, 2.5f) + am * Mathf.Pow(cm / c, 2.5f));
//float dp = windSpeed.x * kx / k + windSpeed.y * ky / k;
//float phi = Mathf.Acos(dp);
/*
* Total omni-directional spectrum
*/
float sk = amplitude * (bl + bh) /* (1.0f + deltak * Mathf.Cos(2.0f * phi))*/ / (k * k * k * k * 2.0f * Mathf.PI);
// precision problems may sometimes produce negative values here
if (sk > 0.0f)
{
sk = Mathf.Sqrt(sk) * frequencyScale * 0.5f; // 1.1 added * 0.5 to match empirical wikipedia wave height data
}
else
{
sk = 0.0f;
}
float h = FastMath.Gauss01() * sk;
float hi = FastMath.Gauss01() * sk;
int xCoord = (x + halfResolution) % resolution;
int yCoord = (y + halfResolution) % resolution;
if (x == halfResolution && y == halfResolution)
{
h = 0.0f;
hi = 0.0f;
deltak = 0.0f;
}
spectrum[xCoord, yCoord] = new Vector3(h, hi, deltak);
}
// skip random values that normally would be generated at max resolution
for (int i = 0; i < numRandomSkips; ++i)
{
Random.Range(0.000001f, 1.0f);
float t = Random.value;
Random.Range(0.000001f, 1.0f);
t = Random.value;
}
}
// skip random values that normally would be generated at max resolution
for (int i = 0; i < numRandomSkips; ++i)
{
for (int ii = 0; ii < maxResolution; ++ii)
{
Random.Range(0.000001f, 1.0f);
float t = Random.value;
Random.Range(0.000001f, 1.0f);
t = Random.value;
}
}
#pragma warning restore 0219
}