Passing class' own method using Func<> in C#

Question

I'm doing a project in Unity engine and have 3 functions in a C# class, which are structured the following way:

public Vector3 FunctionOne(Vector3 point) 
{
    // do some vector operations and return it as var a
    return a;
}

public Vector3 Sample(System.Func<Vector3, Vector3> funcOne, Vector3 samplePoint)
{
    // sample the resulting vector field from funcOne and return as var b
    return b;
}

public Vector3 Trace(Vector3 point)
{
    // Even more vector operations, as follows
    Vector3 k1 = Sample(FunctionOne(point), point);
    // (...)
    return k1;
}

Basically I need the Trace() function to call the Sample() function on some variable, but also need the Sample() function to take in different functions as a variable, such as for instance FunctionOne(). I get the following error inside Trace() when doing it like above:

Argument 1: cannot convert from 'UnityEngine.Vector3' to 'System.Func<UnityEngine.Vector3, UnityEngine.Vector3>'

How would I deal with this properly? As far as I can see, the Sample() function both takes in and returns a Vector3, I specify what function for it to take in as well so why doesn't this work? Do I need to pass FunctionOne() to Trace() as well, even though it's within the same class?

I left out most of the meat of the functions as it's really just vector operations and kind of irrelevant to the question.

Answer 1

This?

public Vector3 Sample(System.Func<Vector3, Vector3> funcOne, Vector3 samplePoint)
{
    var b = funcOne(samplePoint);
    return b;
}

public Vector3 Trace(Vector3 point)
{
    // Even more vector operations, as follows
    Vector3 k1 = Sample(FunctionOne, point);
    // (...)
    return k1;
}