Bug bounds.Intersects returning false positives.

hello! I have a problem where I am instantiating an object, but before I do that I instantiate a version of it called checker, if it detects that the checker collides with another object, it deletes the checker, otherwise, it deletes the checker and instantiates the real object.

however, no matter where I put the object, it comes back as a false positive, even after I decreased the collider size so their borders don't collide.

can anyone help me figure out what is going on?

Video (checkers don't disappear for testing purposes):

Script:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class genericscript : MonoBehaviour
6. {
7.     public List<GameObject> PARTSQUOTA = new List<GameObject>();
8.  
9.     public List<PART_BASE> SCRIPTS = new List<PART_BASE>();
10.  
11.     public LayerMask clickLayerMask;
12.  
13.     public Vector3 here;
14.  
15.     public float gridSize = 1f;
16.     private const float adjustmentOffset = 0.5f;
17.  
18.     private Vector3 LOCATION;
19.  
20.     public GameObject car;
21.  
22.     public GameObject CURRENTPART;
23.  
24.  
25.  
26.     void Start()
27.     {
28.  
29.     }
30.  
31.  
32.  
33.  
34.     void Update()
35.     {
36.         if (Input.GetMouseButtonDown(0))
37.         {
38.             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
39.             if (Physics.Raycast(ray, out RaycastHit hitInfo, Mathf.Infinity, clickLayerMask))
40.             {
41.                 LOCATION = CalculateGridPosition(hitInfo.point - ray.direction * adjustmentOffset);
42.                
43.  
44.                 Vector3 gridPosition = CalculateGridPosition(hitInfo.point);
45.  
46.  
47.                      if (!CheckCollision())
48.                      {
49.                         Instantiate(CURRENTPART, LOCATION, Quaternion.identity, transform);
50.                         PART_BASE CURRENTSCRIPT = CURRENTPART.GetComponent<PART_BASE>();
51.  
52.  
53.  
54.                         if (CURRENTSCRIPT != null)
55.                         {
56.                             SCRIPTS.Add(CURRENTSCRIPT);
57.                         }
58.                        
59.                    
60.                     }
61.  
62.             }
63.         }
64.     }
65.  
66.     void OnDrawGizmos()
67.     {
68.         Gizmos.color = Color.yellow;
69.         Gizmos.DrawCube(LOCATION, here);
70.     }
71.    
72.     private Vector3 CalculateGridPosition(Vector3 position)
73. {
74.     Vector3 localPosition = transform.InverseTransformPoint(position);
75.  
76.     float x = Mathf.Round(localPosition.x / gridSize) * gridSize;
77.     float y = Mathf.Round(localPosition.y / gridSize) * gridSize;
78.     float z = Mathf.Round(localPosition.z / gridSize) * gridSize;
79.  
80.     return transform.TransformPoint(new Vector3(x, y, z));
81. }
82.  
83.  
84. private bool CheckCollision()
85. {
86.     GameObject Checker = Instantiate(CURRENTPART, Vector3.zero, Quaternion.identity, this.transform);
87.     Checker.transform.position = LOCATION;
88.     Checker.name = "checker";
89.  
90.     Collider[] colliders = car.GetComponentsInChildren<Collider>();
91.     Collider[] cursorColliders = Checker.GetComponentsInChildren<Collider>();
92.  
93.     Debug.Log("Number of colliders in car: " + colliders.Length);
94.     Debug.Log("Number of colliders in checker: " + cursorColliders.Length);
95.  
96.     foreach (Collider cursorCollider in cursorColliders)
97.     {
98.  
99.         foreach (Collider collider in colliders)
100.         {
101.                 if (cursorCollider.bounds.Intersects(collider.bounds))
102.                 {
103.                     Destroy(Checker); // Destroy the temporary object
104.                     Debug.Log("Collision detected");
105.                     return true; // Collision detected
106.                 }
107.         }
108.     }
109.  
110.     Destroy(Checker); // Destroy the temporary object
111.     Debug.Log("No collision detected");
112.     return false; // No collision detected
113. }
114.  
115.  
116.  
117.    
118.  
119. }

 

a video showing the colliders a bit better:

 

also it always comes back as not colliding if I remove
this.transform
from
GameObject Checker = Instantiate(CURRENTPART, Vector3.zero, Quaternion.identity, this.transform);

 

A collider's bounds is calculated as an AABB, that is, a big box aligned with the axes in world space, not the box that makes the tightest possible fit nor the local space. This can cause a lot of unexpected false positive "hits" if the objects have any rotation or complex shape.

If you use the Instantiate method like this:

Instantiate(CURRENTPART, Vector3.zero, Quaternion.identity, this.transform);

then the new object becomes a child of

this.gameObject

at the same location (localPosition of Vector3.zero). Colliders automatically don't collide with their parents/children, they're all treated as part of the same complex object. And if you remove the parent argument, it's made at the world origin (position of Vector3.zero) instead.

Instead of trying to instantiate some sort of checker, just use the Physics.CheckBox or Physics.BoxCast methods (or the other primitive shapes) to look for potential conflicts before spawning.

 

that works, but I need it also to work for other shapes, like a T or a C, will bringing the object after it was instantiated not as a child towards all the other ones work?