Raycast "Object reference not set to an instance of an object"

Hey all - I'm new to Unity and I'm poring over old threads but I still can't figure out my problem! Could someone help me out? I know the error is on line 35, and I've looked over the documentation - but I'm not sure what I'm missing. What object isn't being referenced?

Using: Unity 2018.3.8
Error: NullReferenceException: Object reference not set to an instance of an object
clickMoveDropScript.Update () (at Assets/Scripts/clickMoveDropScript.cs:35)

Script:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class clickMoveDropScript : MonoBehaviour
6. {
7.  
8.     public bool moveableObjectGrabbed = false;
9.  
10.     Ray moRay;
11.     public Transform moTransform;
12.     public LayerMask whatIsMoveableObject;
13.     RaycastHit moHit;
14.  
15.     public LayerMask whatIsGround;
16.     public Transform ground;
17.     RaycastHit groundHit;
18.  
19.     public Transform mousePosMarker;
20.     RaycastHit mousePosHit;
21.     public float moYOffsetFromGround = 0f;
22.     public float mousePosYOffsetFromGround = 0f;
23.     public Vector3 mousePosRelToGround;
24.  
25.     // Start is called before the first frame update
26.    void Start() {
27.         moHit = new RaycastHit();
28.         groundHit = new RaycastHit();
29.         mousePosMarker.gameObject.SetActive(false);
30.     }
31.  
32.     // Update is called once per frame
33.     void Update() {
34.  
35.         moRay = Camera.main.ScreenPointToRay(Input.mousePosition);
36.  
37.         if (Input.GetMouseButtonDown(0))
38.     {
39.         FindAndGrabMoveableObject();
40.     }
41.         if (Input.GetMouseButtonUp(0))
42.         {
43.             DropMoveableObject();
44.         }
45.  
46.         moveableObjectGrabbed = moTransform != null;
47.         mousePosMarker.gameObject.SetActive(moveableObjectGrabbed);
48.  
49.         if (moveableObjectGrabbed)
50.         {
51.             TraceMousePosRelToGround();
52.         }
53.  
54. }
55.  
56.     //Find And Grab
57.     void FindAndGrabMoveableObject() {
58.         if (Physics.Raycast(
59.             moRay,
60.             out moHit,
61.             Mathf.Infinity,
62.             whatIsMoveableObject))
63.         {
64.         moTransform = moHit.transform;
65.         moTransform.GetComponent<Rigidbody>().isKinematic = true;
66.         FindGroundBelowMoveableObject();
67.         }
68.     }
69.  
70.     //Find ground
71.    void FindGroundBelowMoveableObject() {
72.         if(Physics.Raycast(
73.             moTransform.position,
74.             Vector3.down,
75.             out groundHit,
76.             Mathf.Infinity,
77.             whatIsGround))
78.  
79.         {
80.         ground = groundHit.transform;
81.         }
82.     }
83.  
84.     //Trace Position Relative to ground
85.    void TraceMousePosRelToGround () {
86.     if(Physics.Raycast(
87.             moRay,
88.             out mousePosHit,
89.             Mathf.Infinity,
90.             whatIsGround))
91.         {
92.         mousePosRelToGround = mousePosHit.point;
93.         moTransform.position = new Vector3(
94.             mousePosRelToGround.x,
95.             mousePosRelToGround.y + moYOffsetFromGround,
96.             mousePosRelToGround.z);
97.  
98.         mousePosMarker.position = new Vector3(
99.             mousePosRelToGround.x,
100.             mousePosRelToGround.y + mousePosYOffsetFromGround,
101.             mousePosRelToGround.z);
102.         }
103.  
104. }
105.  
106.     //DropMoveableObject
107.     void DropMoveableObject () {
108.     if (moTransform != null)
109.         moTransform.GetComponent<Rigidbody>().isKinematic = false;
110.         moTransform = null;
111.         ground = null;
112.     }
113. }

 

Camera.main requires a camera in your scene to be tagged as MainCamera, so it should be null if it can't find it.

That being said, also look at Unity's doc about caching Camera.main
https://docs.unity3d.com/ScriptReference/Camera-main.html

 

That was the issue!! Thankfully just a minor fix. Thanks so much, everything is working great now