unity3d - how to clamp x axis from gameobject transform forward perspective?

Question

i moved object according mouse position with ray cast ,i would like to know how i can clamp in any given position and rotation the object x axis that relative to transform forward of the object? , not generally relative to the world any ideas? , thanks in advance. the code below shows the basic how i implement object movement according the mouse position now i want to clamp it

 Ray ray = mainCamera.ScreenPointToRay(Input.mousePosition);
 
    plane = new Plane(Vector3.up, transform.position);
    float enter;
        if(plane.Raycast(ray,out enter))
        {
            hitPoint = ray.GetPoint(enter);
            transform.position = hitPoint;
        }

Answer 1

If I understand you correctly what you are trying to achieve is to move your object only on its local x-axis.

And do something like this (behold my amazing paint skills)

You can use Vector3.Project to achieve that like e.g.

var ray = mainCamera.ScreenPointToRay(Input.mousePosition);
var plane = new Plane(Vector3.up, transform.position);

if(plane.Raycast(ray, out var enter))
{
    var hitPoint = ray.GetPoint(enter);

    var actualPositionDelta = hitPoint - transform.position;
    var mappedPositionDelta = Vector3.Project(actualPositionDelta, transform.right);

    transform.position += mappedPositionDelta;
}