float "angle" should be a variable, not a object.

Questions & Answers
1

If float “angle” should be a variable. why is it Debug.Log(); as a object that I can not
use.
The script should take the vector3s and return the angle of the 2 objects. Then round to nearest hole number and display it on screen, It failed. To remove
public float angle =0; gives multiple errors.To use the script as is: Dose nothing. some times it said the angle is populated but value is never used.

using UnityEngine;
using System.Collections;

public class Target_Indicator : MonoBehaviour
{
    public Transform target; //values that will be set in the Inspector.
    public float angle = 0; //Create sting, Now we can see it in the inspector.
	
	void Update()
	{
		 Vector3 targetDir = target.position - transform.position;
         Vector3 forward = transform.forward;
         float angle = Vector3.Angle(targetDir, forward);
	}
		
		void OnGUI()		
     	{
			float displayValue = Mathf.Round(angle);//Change decimal to hole numbers.
			
			//Make a GUI label - position on sccreen - add "angle:" - display the value.
			GUI.Label(new Rect(30, 475, 150, 50), "angle: " + displayValue.ToString());
   		}    
}

So what is going on with the value “angle” that I can not use it to display in the inspector or on screen.

2

You’re storing the angle calculated in Update in a temporary variable angle - the variable angle you’ve defined at the beginning isn’t ever affected. Temporary variables are those declared inside a function: they exist only while the function is running, and are destroyed upon return.

To solve the problem, just remove the float declaration before angle in Update:

void Update()
{
    Vector3 targetDir = target.position - transform.position;
    Vector3 forward = transform.forward;
    angle = Vector3.Angle(targetDir, forward); // no float declaration here!
}

EDITED: If you’re using planes for the indicator and compass, set the indicator Y angle to the angle found. You should also remove height differences from the direction vector to keep it strictly horizontal, like below:

public Transform indicatorPlane; // drag the indicator here

void Update()
{
     Vector3 targetDir = target.position - transform.position;
     Vector3 forward = transform.forward;
     targetDir.y = 0; // remove any height difference
     angle = Vector3.Angle(targetDir, forward);
     indicatorPlane.eulerAngles = Vector3(0, angle, 0);
}

But this isn’t the best way to display an on-screen compass - usually this is done in OnGUI: draw the compass texture, rotate the gui matrix with GUIUtility.RotateAroundPivot, draw the indicator texture, then restore the gui matrix - something like this:

public Rect rCompass = new Rect(30, 400, 80, 80); // compass position/size
public Texture2D compass;
public Texture2D indicator;

void Update()
{
    Vector3 targetDir = target.position - transform.position;
    Vector3 forward = transform.forward;
    targetDir.y = 0; // remove any height difference
    angle = Vector3.Angle(targetDir, forward);
}

void OnGUI(){
    GUI.DrawTexture(rCompass, compass); // draw the compass
    Matrix4x4 curMatrix = GUI.matrix; // save cur matrix
    GUIUtility.RotateAroundPivot(angle, rCompass.center); // rotate gui matrix
    GUI.DrawTexture(rCompass, indicator); // draw indicator
    GUI.matrix = curMatrix; // restore matrix (no rotation)
}