/// <summary>
/// This is a replacement for the stock API Property "vessel.MOI", which seems buggy when used
/// with "control from here" on parts other than the default control part.
/// <br/>
/// Right now the stock Moment of Inertia Property returns values in inconsistent reference frames that
/// don't make sense when used with "control from here". (It doesn't merely rotate the reference frame, as one
/// would expect "control from here" to do.)
/// </summary>
/// TODO: Check this again after each KSP stock release to see if it's been changed or not.
public Vector3 FindMoI()
{
var tensor = Matrix4x4.zero;
Matrix4x4 partTensor = Matrix4x4.identity;
Matrix4x4 inertiaMatrix = Matrix4x4.identity;
Matrix4x4 productMatrix = Matrix4x4.identity;
foreach (var part in Vessel.Parts)
{
if (part.rb != null)
{
KSPUtil.ToDiagonalMatrix2(part.rb.inertiaTensor, ref partTensor);
Quaternion rot = Quaternion.Inverse(vesselRotation) * part.transform.rotation * part.rb.inertiaTensorRotation;
Quaternion inv = Quaternion.Inverse(rot);
Matrix4x4 rotMatrix = Matrix4x4.TRS(Vector3.zero, rot, Vector3.one);
Matrix4x4 invMatrix = Matrix4x4.TRS(Vector3.zero, inv, Vector3.one);
// add the part inertiaTensor to the ship inertiaTensor
KSPUtil.Add(ref tensor, rotMatrix * partTensor * invMatrix);
Vector3 position = vesselTransform.InverseTransformDirection(part.rb.position - centerOfMass);
// add the part mass to the ship inertiaTensor
KSPUtil.ToDiagonalMatrix2(part.rb.mass * position.sqrMagnitude, ref inertiaMatrix);
KSPUtil.Add(ref tensor, inertiaMatrix);
// add the part distance offset to the ship inertiaTensor
OuterProduct2(position, -part.rb.mass * position, ref productMatrix);
KSPUtil.Add(ref tensor, productMatrix);
}
}
return(KSPUtil.Diag(tensor));
}
