public static MatrixSingle CreateBillboard(Vector128 <float> objectPosition, Vector128 <float> cameraPosition,
Vector128 <float> cameraUpVector, Vector128 <float> cameraForwardVector)
{
Vector128 <float> z = Vector.Subtract(objectPosition, cameraPosition);
Vector128 <float> norm = LengthSquared3D(z);
z = CompareLessThan(norm, BillboardEpsilon).AnyTrue()
? Vector.Negate(cameraForwardVector)
: Multiply(z, Divide(SingleConstants.AllBitsSet, Sqrt(norm)));
Vector128 <float> x = Normalize3D(Cross3D(cameraUpVector, z));
Vector128 <float> y = Cross3D(z, x);
// We need W to be zero for x, y, and z, and 1.0f for objectPosition. They are currently undefined
x = And(x, SingleConstants.MaskW);
y = And(y, SingleConstants.MaskW);
z = And(z, SingleConstants.MaskW);
// Get objectPosition to be (X, Y, Z, 0) and the mask to be (0, 0, 0, 1.0f) and OR them
Vector128 <float> newObjectPosition = And(objectPosition, SingleConstants.MaskW);
newObjectPosition = Or(newObjectPosition, And(SingleConstants.MaskXYZ, SingleConstants.AllBitsSet));
return(new MatrixSingle(x, y, z, newObjectPosition));
}
public static HwVector2 operator -(HwVector2 vector) => Vector.Negate(vector);