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fixed MOI calculation to match stock values #3201

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fixed MOI calculation to match stock values #3201

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8a3b26d
fixed MOI calculation to match stock values
ChrisInBed Jul 28, 2026
23a040c
switch to stock MOI API
ChrisInBed Aug 17, 2026
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9 changes: 6 additions & 3 deletions src/kOS/Control/SteeringManager.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -591,8 +591,9 @@ public void UpdateStateVectors()

// TODO: If stock vessel.MOI stops being so weird, we might be able to change the following line
// into this instead. (See the comment on FindMOI()'s header):
// momentOfInertia = shared.Vessel.MOI;
momentOfInertia = FindMoI();
// 20260817: According to Lamont, this issue has long been fixed, so we switch to stock vessel.MOI
momentOfInertia = shared.Vessel.MOI;
// momentOfInertia = FindMoI();

adjustTorque = Vector3d.zero;
measuredTorque = Vector3d.Scale(momentOfInertia, angularAcceleration);
Expand Down Expand Up @@ -788,7 +789,9 @@ public Vector3 FindMoI()
{
KSPUtil.ToDiagonalMatrix2(part.rb.inertiaTensor, ref partTensor);

Quaternion rot = Quaternion.Inverse(vesselRotation) * part.transform.rotation * part.rb.inertiaTensorRotation;
// Quaternion.Euler(90, 0, 0) is to recover vesselRotation from kOS reference frame to Unity frame.
// To keep concensus with shared.Vessel.MOI
Quaternion rot = Quaternion.Inverse(vesselRotation * Quaternion.Euler(90, 0, 0)) * part.transform.rotation * part.rb.inertiaTensorRotation;
Quaternion inv = Quaternion.Inverse(rot);

Matrix4x4 rotMatrix = Matrix4x4.TRS(Vector3.zero, rot, Vector3.one);
Expand Down