What is Vector3d.Exclude()?

[Xavier513]

Edit:

OK, this should be the answer: https://github.com/sldsmkd/vector3d/blob/master/Vector3d.cs#L325

Please correct me if I'm wrong.

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I understand vector calculations such as "Cross" and "Dot", but what does "Vector3d.Exclude()" means?

public static Vector3d Exclude(Vector3d excludeThis, Vector3d fromThat);

I'm trying to understand following code from KRPC :

        /// Returns the up vector for the reference frame in world coordinates.
        /// The direction in which the y-axis points.
        /// The vector is not normalized.
        Vector3d UpNotNormalized {
            get {
                switch (type) {
                .......
                case ReferenceFrameType.VesselSurface:
                    {
                        var right = vessel.CoM - vessel.mainBody.position;
                        return Vector3d.Exclude (right, ToNorthPole (vessel).normalized);
                    }
		......
                }
            }
        }

        /// Vector from given vessel to north pole of body being orbited, in world space.
        static Vector3d ToNorthPole (global::Vessel vessel)
        {
            var parent = vessel.mainBody;
            return parent.position + ((Vector3d)parent.transform.up) * parent.Radius - (vessel.CoM);
        }

It returns a vector in UP direction in "VesselSurface" reference frame, and I don't understand what "Exclude" means in math.

Help please! Thanks!

Edited July 21, 2019 by Xavier513

[Xavier513]

I find another "Exclude()" method at https://github.com/sldsmkd/vector3d/blob/master/Vector3d.cs#L325

public static Vector3d Exclude(Vector3d excludeThis, Vector3d fromThat) {
	return fromThat - Vector3d.Project(fromThat, excludeThis);
}

Is it the same with the one in KSP?

Edited July 21, 2019 by Xavier513

[Shadowmage]

On 7/21/2019 at 3:39 AM, Xavier513 said:

Is it the same with the one in KSP?

Likely yes.

I had to use this exact function for something recently, but can't for the life of me remember what it was for (or even what project it was in).  Projection of something onto something...  IIRC I was doing orbital mechanics work at the time, so I was likely trying to find something relative to the ecliptic.

https://answers.unity.com/questions/25110/what-is-vector3exclude-for.html

https://docs.unity3d.com/ScriptReference/Vector3.ProjectOnPlane.html

[Xavier513]

@Shadowmage

I think this is what "Exclude()" does:

for example,

Exclude(a, b) = b - Project(b, a)

 

Edited July 23, 2019 by Xavier513

[sarbian]

Yes, it s a projection on the plane with the excluded vector as the plane normal.