Why is raycast not ALWAYS working?

Question

I am raycatsing a plane (with collider) 10 times, but for a reason I cannot understand, only a few times a hit is registered and a sphere is generated on that position. I used a Debug.DrawRay to simulate the raycats to amke sure the ray is supposed to hit, but it does not. Is there anyone that can help me?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class WorldGenerator : MonoBehaviour
 {
     public int seed = 11;
     public Material planeMaterial;
     public Material sphereMaterial;
 
     void Start()
     {
         Random.InitState(seed);
         AddPlane();
         AddSpheres(10);
     }
     private void AddSpheres(int maxSpheres)
     {
         for (int i = 0; i < maxSpheres; i++)
         {
             float posX = Random.Range(-14, 14);
             float posZ = Random.Range(-14, 14);
 
             Vector3 rayPos = new Vector3(posX, 50, posZ);
 
             RaycastHit hit;
 
             Debug.DrawRay(rayPos, Vector3.down * 100, Color.yellow, 1000);
 
             if (Physics.Raycast(rayPos, Vector3.down, out hit, 100))
             {
                 Debug.Log(i + ": " + hit.distance);
                 GameObject newSphere = GameObject.CreatePrimitive(PrimitiveType.Sphere); //Instantiate(gameWorld.islandShapes[Random.Range(0, gameWorld.islandShapes.Length)]);
                 newSphere.name = "Sphere_" + i;
                 newSphere.transform.position = new Vector3(posX, 0, posZ);
                 newSphere.transform.localScale = new Vector3(5, 2, 5);
                 newSphere.transform.rotation = Quaternion.identity;
                 newSphere.GetComponent<MeshRenderer>().material = sphereMaterial;
             }
         }
     }
     private void AddPlane()
     {
         GameObject plane = GameObject.CreatePrimitive(PrimitiveType.Plane);
         plane.transform.localPosition = new Vector3(0, 0, 0);
         plane.transform.localScale = new Vector3(3, 1, 3);
         plane.GetComponent<MeshRenderer>().material = planeMaterial;
     }
 }

Answer 1

Answer by SellPet · Feb 13 at 03:49 PM

check if the ray is going where you want

 onDrawGizmos(){
     Gizmos.DrawRay(Paste same ray origin and direction);
     }

you will see the ray in the viewport. if it does go where you want i would recommend changing collider to cube collider. and see if the problem goes

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Answer 2

Answer by edwarddewolf · Feb 13 at 04:12 PM

I added a boxCollider to the plane, and now it works perfectly. Is there a reason why the default meshcollider on a plane would not notice all the raycast hits and a boxcolldier does?

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edwarddewolf · Feb 13 at 06:11 PM 0

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Actually, as far as I understand with my limited knowledge, I found the real reason, I got it working with a default meshcollider now too.

The real issue is that I cam doing this from a start function, which has as a side effect that the physics engine might not have caught up with adding all the objects and colliders.

If I disable Physics.autoSimulation, and add Physics.Simulate(1); in between adding each gameobject , all raycasthits are behaving as expected and will collide with all previously placed objects

Do not forget to enable Physics.autoSimulation afterwards

Why is raycast not ALWAYS working?

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