/// <summary>
/// Generate a spherical harmonic from the faces of a cubemap, treating each pixel as a light source and averaging the result.
/// </summary>
public static SphericalHarmonicL1RGB GenerateSphericalHarmonicFromCubeMap(
Vector3[] colourDataPositiveX,
Vector3[] colourDataNegativeX,
Vector3[] colourDataPositiveY,
Vector3[] colourDataNegativeY,
Vector3[] colourDataPositiveZ,
Vector3[] colourDataNegativeZ)
{
if (colourDataPositiveX == null ||
colourDataNegativeX == null ||
colourDataPositiveY == null ||
colourDataNegativeY == null ||
colourDataPositiveZ == null ||
colourDataNegativeZ == null)
throw new ArgumentNullException();
SphericalHarmonicL1RGB sh = new SphericalHarmonicL1RGB();
Vector3[][] source = {
colourDataPositiveX,
colourDataNegativeX,
colourDataPositiveY,
colourDataNegativeY,
colourDataPositiveZ,
colourDataNegativeZ,
};
//extract the 6 faces of the cubemap.
for (int face = 0; face < 6; face++)
{
int size = (int)(Math.Sqrt(source[face].Length) + 0.5);
if (size * size != source[face].Length)
throw new ArgumentException("Cubemap face is an unexpected (non square) size");
Microsoft.Xna.Framework.Graphics.CubeMapFace faceId = (Microsoft.Xna.Framework.Graphics.CubeMapFace)face;
//get the transformation for this face,
Matrix cubeFaceMatrix;
Xen.Graphics.DrawTargetTextureCube.GetCubeMapFaceMatrix(faceId, out cubeFaceMatrix);
//extract the spherical harmonic for this face and accumulate it.
sh += ExtractSphericalHarmonicForCubeFace(cubeFaceMatrix, source[face], size);
}
//average out over the sphere. account for cosine weighting which doubles the output - but it's also over a full sphere not a hemisphere
return sh / 3;
}
/// <summary>
/// Multiply a spherical harmonic by a constant scale factor
/// </summary>
public static SphericalHarmonicL1RGB operator *(SphericalHarmonicL1RGB x, float scale)
{
SphericalHarmonicL1RGB o = new SphericalHarmonicL1RGB();
o.Red.X = x.Red.X * scale; o.Red.Y = x.Red.Y * scale; o.Red.Z = x.Red.Z * scale;
o.Blue.X = x.Blue.X * scale; o.Blue.Y = x.Blue.Y * scale; o.Blue.Z = x.Blue.Z * scale;
o.Green.X = x.Green.X * scale; o.Green.Y = x.Green.Y * scale; o.Green.Z = x.Green.Z * scale;
return o;
}
/// <summary>
/// Divide a spherical harmonic by a constant factor
/// </summary>
public static SphericalHarmonicL1RGB operator /(SphericalHarmonicL1RGB x, float divider)
{
SphericalHarmonicL1RGB o = new SphericalHarmonicL1RGB();
float scale = 1.0f / divider;
o.Red.X = x.Red.X * scale; o.Red.Y = x.Red.Y * scale; o.Red.Z = x.Red.Z * scale;
o.Blue.X = x.Blue.X * scale; o.Blue.Y = x.Blue.Y * scale; o.Blue.Z = x.Blue.Z * scale;
o.Green.X = x.Green.X * scale; o.Green.Y = x.Green.Y * scale; o.Green.Z = x.Green.Z * scale;
return o;
}
/// <summary>
/// Add two spherical harmonics together
/// </summary>
public static SphericalHarmonicL1RGB operator +(SphericalHarmonicL1RGB x, SphericalHarmonicL1RGB y)
{
SphericalHarmonicL1RGB o = new SphericalHarmonicL1RGB();
o.Red.X = x.Red.X + y.Red.X; o.Red.Y = x.Red.Y + y.Red.Y; o.Red.Z = x.Red.Z + y.Red.Z;
o.Blue.X = x.Blue.X + y.Blue.X; o.Blue.Y = x.Blue.Y + y.Blue.Y; o.Blue.Z = x.Blue.Z + y.Blue.Z;
o.Green.X = x.Green.X + y.Green.X; o.Green.Y = x.Green.Y + y.Green.Y; o.Green.Z = x.Green.Z + y.Green.Z;
return o;
}
/// <summary>
/// Linear interpolate (Lerp) between two spherical harmonics based on a interpolation factor
/// </summary>
/// <param name="factor">Determines the interpolation point. When factor is 1.0, the output will be <paramref name="x"/>, when factor is 0.0, the output will be <paramref name="y"/></param>
/// <param name="result"></param>
/// <param name="x"></param>
/// <param name="y"></param>
public static void Lerp(ref SphericalHarmonicL1RGB x, ref SphericalHarmonicL1RGB y, float factor, out SphericalHarmonicL1RGB result)
{
result = new SphericalHarmonicL1RGB();
float xs = factor;
float ys = 1.0f - factor;
result.Red.X = xs * x.Red.X + ys * y.Red.X; result.Red.Y = xs * x.Red.Y + ys * y.Red.Y; result.Red.Z = xs * x.Red.Z + ys * y.Red.Z;
result.Blue.X = xs * x.Blue.X + ys * y.Blue.X; result.Blue.Y = xs * x.Blue.Y + ys * y.Blue.Y; result.Blue.Z = xs * x.Blue.Z + ys * y.Blue.Z;
result.Green.X = xs * x.Green.X + ys * y.Green.X; result.Green.Y = xs * x.Green.Y + ys * y.Green.Y; result.Green.Z = xs * x.Green.Z + ys * y.Green.Z;
}
/// <summary>
/// Divide a spherical harmonic by a constant factor
/// </summary>
public static void Divide(ref SphericalHarmonicL1RGB x, float divider, out SphericalHarmonicL1RGB result)
{
result = new SphericalHarmonicL1RGB();
float scale = 1.0f / divider;
result.Red.X = x.Red.X * scale; result.Red.Y = x.Red.Y * scale; result.Red.Z = x.Red.Z * scale;
result.Blue.X = x.Blue.X * scale; result.Blue.Y = x.Blue.Y * scale; result.Blue.Z = x.Blue.Z * scale;
result.Green.X = x.Green.X * scale; result.Green.Y = x.Green.Y * scale; result.Green.Z = x.Green.Z * scale;
}
/// <summary>
/// Multiply a spherical harmonic by a constant scale factor
/// </summary>
public static void Multiply(ref SphericalHarmonicL1RGB x, float scale, out SphericalHarmonicL1RGB result)
{
result = new SphericalHarmonicL1RGB();
result.Red.X = x.Red.X * scale; result.Red.Y = x.Red.Y * scale; result.Red.Z = x.Red.Z * scale;
result.Blue.X = x.Blue.X * scale; result.Blue.Y = x.Blue.Y * scale; result.Blue.Z = x.Blue.Z * scale;
result.Green.X = x.Green.X * scale; result.Green.Y = x.Green.Y * scale; result.Green.Z = x.Green.Z * scale;
}
/// <summary>
/// Add two spherical harmonics together
/// </summary>
public static void Add(ref SphericalHarmonicL1RGB x, ref SphericalHarmonicL1RGB y, out SphericalHarmonicL1RGB result)
{
result = new SphericalHarmonicL1RGB();
result.Red.X = x.Red.X + y.Red.X; result.Red.Y = x.Red.Y + y.Red.Y; result.Red.Z = x.Red.Z + y.Red.Z;
result.Blue.X = x.Blue.X + y.Blue.X; result.Blue.Y = x.Blue.Y + y.Blue.Y; result.Blue.Z = x.Blue.Z + y.Blue.Z;
result.Green.X = x.Green.X + y.Green.X; result.Green.Y = x.Green.Y + y.Green.Y; result.Green.Z = x.Green.Z + y.Green.Z;
}
