public float[] coeffs; // Must have the size of 3
public static ZonalHarmonicsL2 GetHenyeyGreensteinPhaseFunction(float asymmetry)
{
float g = asymmetry;
var zh = new ZonalHarmonicsL2();
zh.coeffs = new float[3];
zh.coeffs[0] = 0.5f * Mathf.Sqrt(1.0f / Mathf.PI);
zh.coeffs[1] = 0.5f * Mathf.Sqrt(3.0f / Mathf.PI) * g;
zh.coeffs[2] = 0.5f * Mathf.Sqrt(5.0f / Mathf.PI) * g * g;
return(zh);
}
public static ZonalHarmonicsL2 GetCornetteShanksPhaseFunction(float asymmetry)
{
float g = asymmetry;
var zh = new ZonalHarmonicsL2();
zh.coeffs = new float[3];
zh.coeffs[0] = 0.282095f;
zh.coeffs[1] = 0.293162f * g * (4.0f + (g * g)) / (2.0f + (g * g));
zh.coeffs[2] = (0.126157f + 1.44179f * (g * g) + 0.324403f * (g * g) * (g * g)) / (2.0f + (g * g));
return(zh);
}
// Ref: "Stupid Spherical Harmonics Tricks", p. 6.
public static SphericalHarmonicsL2 Convolve(SphericalHarmonicsL2 sh, ZonalHarmonicsL2 zh)
{
for (int l = 0; l <= 2; l++)
{
float n = Mathf.Sqrt((4.0f * Mathf.PI) / (2 * l + 1));
float k = zh.coeffs[l];
float p = n * k;
for (int m = -l; m <= l; m++)
{
int i = l * (l + 1) + m;
for (int c = 0; c < 3; c++)
{
sh[c, i] *= p;
}
}
}
return(sh);
}
