Physics.Raycast() inconsistent behavior

Questions & Answers
1

I’ve the following code snippets:

void Update()
{
    if (Input.GetMouseButtonDown(0))       // Make sure the user pressed the mouse down
    {
        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        RaycastHit hit;
        bool intersect = Physics.Raycast(ray, out hit);

        if (intersect)
        {
            if (!hit.rigidbody)
            {
                Utility.Log(typeof(Fpc), "Not RigidBody");
                return;
            }

            if (hit.rigidbody.isKinematic) 
            {
                Utility.Log(typeof(Fpc), "Kinematic");
                return;
            }

            Utility.Log(typeof(Fpc), "current=" + gameObject.name + " " + hit.ToString() + " hit=" + hit.rigidbody.name);
        }
        else
        {
            Utility.Log(typeof(Fpc), "No Hit");
        }

    } // if

} // Update

I have a cube with attached RigidBody on top of a plane/ground.
It occasionally behaves as expected. I use the Standard Assets First Person Controller (FPC) and attach the above script to the FPC.

However, it sometimes keeps telling me that there is no hit even I hit the cube at the center.

What did I do wrong?

Thanks in advance for your help.

MORE INFO:
I added a few more log statements as the following:

    Vector3 mousePosition = Input.mousePosition;
    Ray ray = theCamera.ScreenPointToRay(mousePosition);
    Utility.Log(typeof(Fpc), mousePosition.ToString());
    Utility.Log(typeof(Fpc), ray.ToString());

I got the following output:

Fpc.(490.0, 240.0, 0.0)
UnityEngine.Debug:Log(Object)

Fpc.Origin: (0.0, 1.0, -4.7), Dir: (0.0, -0.1, 1.0)
UnityEngine.Debug:Log(Object)

Fpc.(490.0, 240.0, 0.0)
UnityEngine.Debug:Log(Object)

Fpc.Origin: (0.0, -12.4, -4.7), Dir: (0.0, -0.1, 1.0)
UnityEngine.Debug:Log(Object)

Notice the same mousePosition (490.0, 24.0, 0.0) produce different Ray origin: (0.0, 1.0, -4.7) vs (0.0, -12.4, -4.7)

Why is that?

EVEN MORE INFO:

I added

Debug.Log(“Camera.main.transform.position” + Camera.transform.position.ToString());

I notice that the Camera.main.transform.position keeps changing specifically the y position keeps going down negative.

Why is that?

2

I think I found the problem.

It turns out that I attached a RigidBody to my FPC.
After removing it, everything is fine.

Thanks for everyone’s help.