First Person Mouse Aiming

Question

For one segment of my game, the player is in a fixed position (no movement) and has to aim and shoot at enemies in a first person 3D perspective using the Mouse. The player is holding a wand that shoots projectiles (which I have working) and I need it to rotate and aim towards the cursor as an aiming reticle. I also want to limit how much the player can rotate, so they can look around, but can't turn more than 180 degrees (sort of like this). However, I'm a designer and am having trouble programming this myself. I haven't been able to find a proper solution.

So far, I've been able to cobble the following code together, but the aiming is super wonky and doesn't properly point to the mouse position, making it impossible to actually aim at anything. I would really appreciate some help with figuring this out.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerShoot : MonoBehaviour {

public float magnifier = 0.5f;
public Rigidbody shotPrefab;
public Transform barrelEnd;
public float shotSpeed = 500;
public Rigidbody sparkPrefab;


// Update is called once per frame
void Update () {

    Ray mouseRay = Camera.main.ScreenPointToRay (Input.mousePosition);
    float midPoint = (transform.position - Camera.main.transform.position).magnitude * magnifier;

    transform.LookAt (mouseRay.origin + mouseRay.direction * midPoint*magnifier);

    if (Input.GetButtonDown("Fire1"))
    {
        Rigidbody shotInstance;
        shotInstance = Instantiate(shotPrefab, barrelEnd.position, barrelEnd.rotation) as Rigidbody;
        shotInstance.AddForce(barrelEnd.forward * shotSpeed);
        sparkBlast();

    }
}
// Particle recoil effect
void sparkBlast () {
    Rigidbody shotSparks;
    shotSparks = Instantiate(sparkPrefab, barrelEnd.position, barrelEnd.rotation) as Rigidbody;
    Destroy (shotSparks,0.5f);
}

}

Answer 1

Usually for an FPS style interface, we'd want to hide and lock the mouse cursor to the middle of the screen, so the player isn't distracted by the cursor zipping around disconnected from their aiming reticle, and doesn't accidentally click outside the window and interrupt the game.

We can do that something like this:

public class SimpleTurretCamera : MonoBehaviour {

    [Tooltip("Speed multiplier for horizontal & vertical rotation.")]
    public Vector2 turnSpeed = new Vector2(1, 1);

    [Tooltip("Maximum rotation from the initial orientation.")]
    public Vector2 degreeClamp = new Vector2(90, 80);

    [Tooltip("Check this box if you want forward input to look downward.")]
    public bool invertY;

    // Orientation state.
    Quaternion _initialOrientation;
    Vector2 _currentAngles;   

    // Cached cursor state.
    CursorLockMode _previousLockState;
    bool _wasCursorVisible;

    void OnEnable () {
        // Cache our starting orientation as our center point.
        _initialOrientation = transform.localRotation;

        // Cache the previous cursor state so we can restore it later.
        _previousLockState = Cursor.lockState;
        _wasCursorVisible = Cursor.visible;

        // Hide & lock the cursor for that FPS experience
        // and to avoid distractions / accidental clicks
        // from the mouse cursor moving around.
        Cursor.lockState = CursorLockMode.Locked;
        Cursor.visible = false;
    }

    void Update () {
        // Collect relative motion of mouse since last frame.
        Vector2 motion = new Vector2(
                            Input.GetAxis("Mouse X"), 
                            Input.GetAxis("Mouse Y"));

        // Scale it by the turn speed, add it to our current angle, and clamp.
        motion = Vector2.Scale(motion, turnSpeed);
        _currentAngles += motion;
        _currentAngles = Vector2.Min(_currentAngles, degreeClamp);
        _currentAngles = Vector2.Max(_currentAngles, -degreeClamp);

        // Rotate to look in this direction, relative to our initial orientation.
        Quaternion look = Quaternion.Euler(
                            -_currentAngles.y,                       // Yaw
                            (invertY ? -1f : 1f) * _currentAngles.x, // Pitch
                            0);                                      // Roll

        transform.localRotation = _initialOrientation * look;
    }

    void OnDisable () {
        // When switched off, put everything back the way we found it.
        Cursor.visible = _wasCursorVisible;
        Cursor.lockState = _previousLockState;
        transform.localRotation = _initialOrientation;
    }
}

Answer 2

Okay, so I got a bit of help elsewhere and mostly solved the issue. I'll post my code here for people to see in case someone else has the same issue, but surprisingly it had a lot to do with changing transform.forward into transform.up.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerShoot : MonoBehaviour {

public float magnifier = 0.5f;
public Rigidbody shotPrefab;
public Transform barrelEnd;
public float shotSpeed = 500;
public Rigidbody sparkPrefab;
public Rigidbody sparkBurst;

public Texture2D reticle;
public CursorMode cursorMode = CursorMode.Auto;
public Vector2 hotSpot = Vector2.zero;

public int RayLength = 100;

// Update is called once per frame
void Update () 
{
          // Aiming Mechanic
    var vMousePosition = Input.mousePosition;
    vMousePosition.z = Camera.main.nearClipPlane;

    var vPosition = Camera.main.ScreenToWorldPoint(vMousePosition);

    var vForward = (vPosition-Camera.main.transform.position).normalized;
    var ray = new Ray(Camera.main.transform.position, vForward);

    var targetPosition = ray.origin + (ray.direction * RayLength); // 100 is arbitary, but should be roughly equal to wand length

    transform.up = (targetPosition - transform.position).normalized;

    //Firing
            if (Input.GetButtonDown("Fire1"))
    {
        Rigidbody shotInstance;
        shotInstance = Instantiate(shotPrefab, barrelEnd.position, barrelEnd.rotation) as Rigidbody;
        shotInstance.AddForce(barrelEnd.forward * shotSpeed);
        sparkBlast();

    }
}
// Particle recoil effect
void sparkBlast () {
    Rigidbody shotSparks;
    Rigidbody shotBurst;
    shotSparks = Instantiate(sparkPrefab, barrelEnd.position, barrelEnd.rotation) as Rigidbody;
    shotBurst = Instantiate(sparkPrefab, barrelEnd.position, barrelEnd.rotation) as Rigidbody;
    Destroy (shotSparks,0.5f);
}

}