RayCast not working as expected, help! (Unity 3D) - visual-studio

Question

Okay so I'm making a photography game where when you 'take a photo', Unity sends a few raycasts forward to check if certain tagged items are in the photo (all within the cameras FOV). My problem is, this seems to work intermittently! Sometimes it finds the tagged objects, other times it will be right in front of the view yet it will miss it completely! Can anyone advise about what I'm doing wrong?
public static Transform target;
public static GameObject[] targetName;
public static float length = 250f;
public static Transform thisObject;
// Start is called before the first frame update
void Start()
{
thisObject = GameObject.Find("Main Camera").GetComponent<Transform>();
//target = GameObject.FindGameObjectWithTag("Trees").transform;
}
// Update is called once per frame
void Update()
{
//InFront();
//HasLineOfSight("Trees");
}
public static bool InFront(Transform target1)
{
Vector3 directionToTarget = thisObject.position - target1.position;
float angleOnXAxis = Vector3.Angle(thisObject.right, directionToTarget);
float angleOnYAxis = Vector3.Angle(thisObject.up, directionToTarget);
//Debug.Log(angleOnYAxis);
if (Mathf.Abs(angleOnXAxis) < 130 && Mathf.Abs(angleOnXAxis) > 50
&& Mathf.Abs(angleOnYAxis) < 115 && Mathf.Abs(angleOnYAxis) > 62)
{
//Debug.DrawLine(transform.position, target.position, Color.green);
return true;
}
return false;
}
public static bool HasLineOfSight(string objectTag)
{
RaycastHit hit;
Vector3 direction = target.position - thisObject.position;
//Debug.Log(direction);
if (Physics.Raycast(thisObject.position, direction, out hit, length))
{
if (hit.transform.tag == objectTag)
{
Debug.DrawRay(thisObject.position, direction * 0.96f, Color.red);
return true;
}
else
{
return false;
}
}
else
{
return false;
}
}
public static GameObject SortObjects(string objectTag)
{
targetName = GameObject.FindGameObjectsWithTag(objectTag);
GameObject closestObject = null;
for (int i = 0; i < targetName.Length; i++)
{
if (Vector3.Distance(thisObject.position,
targetName[i].transform.position) <= length)
{
if (InFront(targetName[i].transform))
{
if (closestObject == null)
{
closestObject = targetName[i];
}
else
{
if (Vector3.Distance(targetName[i].transform.position, thisObject.position) <= Vector3.Distance(closestObject.transform.position, thisObject.position))
{
closestObject = targetName[i];
}
}
}
}
}
return closestObject;
}
public static bool ObjectCheck(string objectTag)
{
//Debug.Log(SortObjects(objectTag));
if (SortObjects(objectTag) != null)
{
target = SortObjects(objectTag).transform;
//Debug.Log(target);
if (InFront(target) && HasLineOfSight(objectTag))
{
return true;
}
else
{
return false;
}
}
else
{
return false;
}
}
I'm essentially calling ObjectCheck() with the tag I want to check for to get the closest, visible, object with that tag. What is wrong with this code??

Answer 1

In your script, only the closest object to the main camera gets checked. SortObjects() determines the closest tagged object, and then you only handle that single object in ObjectCheck(). - That object might be obstructed by something else, so the method returns false. And other tagged objects that are actually visible, are not picked up this way...
So, you could rename and change your SortObjects() function to check for both conditions right in the loop (InFront(target) && HasLineOfSight(objectTag)), and filter the objects out right in there, since only those objects are of interest.
Also, your HasLineOfSight() method checks the tag of the hit object, but what you probably wanted to do, is to check if the raycast actually hits that exact object. So it should instead compare the hit's gameObject to the target's gameObject, ignoring the tag, since a correct tag alone isn't enough. (Side note: it would make sense to place all "photographable objects" on a "photo layer", and set the layer mask in the Physics.Raycast() call accordingly, it's more efficient that way in larger scenes.)
The way the angles are calculated in the InFront() method is probably causing issues, because the direction vector to the target is really in 3D. To calculate the angles, you could try to use Vector3.Project() or Vector3.ProjectOnPlane(), but that will also be problematic, because of perspective camera issues.
This check is strongly related to the topic of "frustum culling", a technique usually used for rendering. But it's similar to what you need, to filter out all the (possibly) visible objects in the camera's field of view (frustum culling doesn't handle obstruction, it is just a geometric check to see if a point lies within the camera's frustum space). See:
https://en.wikipedia.org/wiki/Viewing_frustum
https://en.wikipedia.org/wiki/Hidden-surface_determination#Viewing-
http://www.lighthouse3d.com/tutorials/view-frustum-culling/
https://docs.unity3d.com/Manual/UnderstandingFrustum.html
If you want to dig deeper and optimize this, there are a couple of ways this can be done. But luckily, Unity comes with many useful related functions already built into the Camera class. So instead, you could use Camera.WorldToScreenPoint() (or Camera.WorldToViewportPoint()), and compare the resulting screen coordinates to the screen size or viewport, like discussed in Unity forum. (The frustum math is hidden behind these compact functions, but beware that this is probably not the optimal way to do this.)
Instead of calling FindGameObjectsWithTag() every time, you could do it only once in Start(), assuming objects do not get created/destroyed while the game is running.
I've tried to modify your script, since I'm also learning Unity again... The script can be dragged to the main camera, and it should show the "focus object" in the Scene view with the green debug line. I hope this helps:
using UnityEngine;
[RequireComponent(typeof(Camera))]
public class PhotoCast : MonoBehaviour
{
public float maxDistance = 250.0f;
public string objectTag = "photo";
protected GameObject[] objs;
protected GameObject objFocus;
protected Camera cam;
public void Start() {
objs = GameObject.FindGameObjectsWithTag(objectTag);
cam = GetComponent<Camera>();
}
public void Update() {
if (Input.GetButtonDown("Fire1")) {
objFocus = CheckObjects();
if (objFocus) {
Debug.Log("closest object in view: " + objFocus.name);
/* TODO: take actual photo here */
}
}
if (objFocus) {
Debug.DrawLine(transform.position,
objFocus.transform.position, Color.green);
}
}
GameObject CheckObjects() {
GameObject obj_closest = null;
float dist_closest = float.MaxValue;
foreach (GameObject o in objs) {
float dist = Vector3.Distance(
o.transform.position, transform.position);
if (dist < maxDistance && dist < dist_closest
&& InViewport(o.transform.position)
&& HasLineOfSight(o.transform)) {
dist_closest = dist;
obj_closest = o;
}
}
return obj_closest;
}
bool InViewport(Vector3 worldPos) {
Vector3 p = cam.WorldToViewportPoint(worldPos);
return (p.x > 0.0f && p.x <= 1.0f && p.y > 0.0f && p.y <= 1.0f
&& p.z > cam.nearClipPlane);
}
bool HasLineOfSight(Transform target) {
RaycastHit hit;
Vector3 dir = target.position - transform.position;
if (Physics.Raycast(transform.position, dir, out hit, maxDistance)) {
if (hit.collider.gameObject == target.gameObject) {
return true;
}
}
return false;
}
}
Side notes:
Another issue with this technique is, that there can be tagged objects right in front of the camera, but other tagged objects that are closer on the side will be picked up instead of the obvious one. Many small issues to fine-tune until the scripts fits the game, I guess. Instead of only using one Raycast per object, you could use multiple ones, and take the bounding box or the actual collider shape into account.
An improved version of the script could make use of the Physics.Overlap*() or Physics.*Cast*() functions, documented here.