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How to detect when a cube is directly above another cube?

I am using the Unity Engine with C#.
I have a 1x1 cube which moves forward on a grid of 49, 1x1 cubes (screenshot below) - when I press the start button on the controller.
The movement code for the cube is below.
void MovePlayerCube()
{
transform.Translate(direction * moveSpeed * Time.deltaTime);
}
When this cube passes over a cube with an arrow on it, the cube will change direction to where the arrow is pointing (staying on the same Y axis).
I need to detect the exact point at which the cube is directly over the cube with the arrow on it, and run the 'change direction' code at that point.
I'm currently using Vector3.Distance to check if the X and Z coordinates of the 2 cubes are close enough together (if they are less than 0.03f in distance), I can't check if they are equal due to floating point imprecision.
However this is really ineffective as half the time this code doesn't register for probably the same reason, and if I increase the 0.03f to a point where it never misses it becomes really noticeable that the cube isn't aligned with the grid anymore.
There has to be a proper solution to this and hopefully I've clarified the situation enough?
Any advice is appreciated.

You are moving your cube via
transform.Translate(direction * moveSpeed * Time.deltaTime);
which will never be exact an might overshoot your positions.
=> I would rather implement a coroutine for moving the cube exactly one field at a time, ensuring that after each iteration it fully aligns with the grid and run your checks once in that moment.
It doesn't even have to match exactly then, you only need to check if you are somewhere hitting a cube below you.
So something like e.g.
private Vector3Int direction = Vector3Int.left;
private IEnumerator MoveRoutine()
{
// depends on your needs if this runs just forever or certain steps
// or has some exit condition
while(true)
{
// calculate the next position
// optional round it to int => 1x1 grid ensured on arrival
// again depends a bit on your needs
var nextPosition = Vector3Int.RoundToInt(transform.position) + direction;
// move until reaching the target position
// Vector3 == Vector3 uses a precision of 1e-5
while(transform.position != nextPosition)
{
transform.position = Vector3.MoveTowards(transform.position, nextPosition, moveSpeed * Time.deltaTime);
yield return null;
}
// set target position in one frame just to be sure
transform.position = nextPosition;
// run your check here ONCE and adjust direction
}
}
start this routine only ONCE via
StartCoroutine(MoveRoutine());
or if you have certain exit conditions at least only run one routine at a time.
A Corouine is basically just a temporary Update routine with a little bit different writing => of course you could implement the same in Update as well if you prefer that
private Vector3Int direction = Vector3Int.left;
private Vector3 nextPosition;
private void Start()
{
nextPosition = transform.position;
}
private void Update()
{
if(transform.position != nextPosition)
{
transform.position = Vector3.MoveTowards(transform.position, nextPosition, moveSpeed * Time.deltaTime);
}
else
{
transform.position = nextPosition;
// run your check here ONCE and adjust direction
// then set next position
nextPosition = Vector3Int.RoundToInt(transform.position) + direction;
}
}
Then regarding the check you can have a simple raycast since you only run it in a specific moment:
if(Physics.Raycast(transform.position, Vector3.down, out var hit))
{
direction = Vector3Int.RountToInt(hit.transform.forward);
}
assuming of course your targets have colliders attached, your moved cube position (pivot) is above those colliders (assumed it from your image) and your targets forward actually points int the desired new diretcion

I would do it this way. First I would split the ability of certain objects to be "moving with certain speed" and "moving in a certain direction", this can be done with C# interfaces. Why? Because then your "arrow" cube could affect not only your current moving cube, but anything that implements the interfaces (maybe in the future you'll have some enemy cube, and it will also be affected by the arrow modifier).
IMovingSpeed.cs
public interface IMovementSpeed
{
float MovementSpeed{ get; set; }
}
IMovementDirection3D.cs
public interface IMovementDirection3D
{
Vector3 MovementDirection { get; set; }
}
Then you implement the logic of your cube that moves automatically in a certain direction. Put this component on your player cube.
public class MovingStraight: MonoBehaviour, IMovementSpeed, IMovementDirection3D
{
private float _movementSpeed;
Vector3 MovementSpeed
{
get { return _movementSpeed; }
set { _movementSpeed = value; }
}
private Vector3 _movementDirection;
Vector3 MovementDirection
{
get { return _movementDirection; }
set { _movementDirection= value; }
}
void Update()
{
// use MovementSpeed and MovementDirection to advance the object position
}
}
Now to implement how the arrow cube modifies other objects, I would attach a collision (trigger) component for both moving cube and the arrow cube.
In the component of the arrow cube, you can implement an action when something enters this trigger zone, in our case we check if this object "has direction that we can change", and if so, we change the direction, and make sure that the object will be aligned, by forcing the arrow cube's position and the other object's position to be the same on the grid.
public class DirectionModifier: MonoBehaviour
{
private Vector3 _newDirection;
private void OnTriggerEnter(Collider collider)
{
IMovementDirection3D objectWithDirection = collider as IMovementDirection3D ;
if (objectWithDirection !=null)
{
objectWithDirection.MovementDirection = _newDirection;
// to make sure the object will continue moving exactly
// from where the arrow cube is
collider.transform.position.x = transform.position.x;
collider.transform.position.y = transform.position.y;
}
}
}
If you made your trigger zones too large, however, then the moving cube will "jump" abruptly when it enters the arrow cube's trigger zone. You can fix it by either starting a coroutine as other answers suggested, or you could make the trigger zones pretty small, so that the jump is not noticeable (just make sure not to make them too small, or they may not intersect each other)
You could then similarly create many other modifying blocks, that would change speed or something

I think that it is enough for you to check if the X and Z coordinates are equal, since the movement occurs only along them
Example
if(_player.transfom.position.x == _gameSquare.transfom.position.x && _player.transfom.position.z == _gameSquare.transfom.position.z)
{
Debag.Log("Rotate!")
}

Move Object to the last position or position just outside the collision area

I am using a Player rigid body object and there are walls around the Player. These walls are restricting the Player to go through. The Player gets collided with these walls and then falls. The Player uses teleport function to jump from one area to next. Is there a way to make the Player jump to a position just outside the collision area after the Player is collided with these walls?
That is, Player A gets collided with the wall and does not jump to last position, but the position before the collision happened?
public GameObject Player;
public Vector3 PlayerPos;
public bool RecordPos = true;
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void Update()
{
if(RecordPos == true)
{
PlayerPos = Player.transform.position;
}
}
public void OnTriggerEnter(Collider col)
{
if(col.gameObject.name == "Cube(3)" )
{
RecordPos = false;
Player.transform.position = PlayerPos;
}
}
In this script, the Player moves to last position it teleported from.

The "last" position before colliding is 1 frame before the collision. If you capture this position, the character will probably just fall on the obstacle again. Imagine you have a platform ___...___ and an obstacle. The easiest solution is to have 1 trigger at the left side of the obstacles and 1 trigger at the right side. If the player hasn't overcome the obstacle yet, he will be teleported to a chosen destination by you (before the obstacle) and if he's already overcome the obstacle, he will be teleported at the right side. __S_..._S__ (S stands for save/checkpoint trigger)
You need the following script on the gameobject with the Trigger collider. You also need to create a child object to the gameobject with the trigger:
private void OnTriggerEnter2D(Collider2D collision)
{
SaveManager.Instance.LastCheckpointOnHit = transform.GetChild(0).position;
}
And I suppose you have some sort of a singleton for data persistance. Now you can move the child gameobject whereever you want to teleport the player. And BTW I named the property LastCheckpointOnHit, because I was thinking of Holow Knight where if you get hit by spikes it instantly teleports you.
Then you just move the player: Player.transform.position = SaveManager.Instance.LastCheckpointOnHit;

In general when dealing with Rigidbody you shouldn't apply positions through the Transform component but rather through the Rigidbody.
I could imagine something like if you collide with a wall you get pushed away from the wall a bit in the direction where you came from like e.g.
[SerializeField] private float someDistanceThreshold = 0.01f;
[SerializeField] private Rigidbody _rigidbody;
private void Start()
{
if(!_rigidbody) _rigidbody = Player.GetComponent<Rigidbody>();
}
private void FixedUpdate()
{
PlayerPos = _rigidbody.position;
}
public void OnTriggerEnter(Collider col)
{
// instead of the name I would rather use a tag later to cover all obstacles
if(col.gameObject.name == "Cube(3)")
{
_rigidbody.position -= (_rigidbody.position - PlayerPos).normalized * someDistanceThreshold;
// For stopping the player here
_rigidbody.velocity = Vector3.zero;
}
}

Need to instantiate prefab at mouse position

So, I am dragging 2D sprites from the canvas and instantiating a 3D object. But the issue is prefabs are spawning at their default location.This is the code. Removed all the things I tried for spawning

You are trying to instatiate a prefab without specifying the position to instantiate. Try something like this.
public void OnEndDrag(PointerEventData eventData)
{
Instantiate(prefab,eventData.position);
}
Reference:
https://docs.unity3d.com/ScriptReference/Object.Instantiate.html
https://docs.unity3d.com/2017.3/Documentation/ScriptReference/EventSystems.PointerEventData-position.html

You don't do anything with the objects position so it will spawn at the origin.
Without seeing your project it's hard to guess what you game requires for placing behavior, I'm assuming you have some an environment you want to place it on and that can easily be done with a Physics.Raycast(). But if you're not over any environment then you can fire a ray from your mouse position & project it an arbitrary amount forwards from the camera and place the object there for a good effect.
This snippet should be enough for that:
public float raycastDistance = 10f;
public float projectDistance = 4f;
public void OnEndDrag(PointerEventData eventData)
{
var spawned = Instantiate(prefab);
var ray = Camera.main.ScreenPointToRay(eventData.position);
if (Physics.Raycast(ray, out RaycastHit hit, raycastDistance)
{
spawned.transform.position = hit.point;
}
else
{
spawned.transform.position = Camera.main.transform.position + (ray * projectDistance);
}
}
If you prefer you can update the position of the spawned object in OnDrag() instead of just setting it in OnDragEnd() which can look quite nice if you interpolate the position of the object slightly as the mouse moves.

2D Raycast does not correctly detect overlapping colliders and ignores Sorting Layer

I want to be able to interact with my gameobjects while organising my sprites with Sorting Layer.
Right now, Sorting Layer do not affect my Raycast/collider situation and only change the visual appearance of my order.
In my Test scene I have two sprites: a Background and one Object.
Both have a 2D Box Collider component.
My Raycast script is suppose to detect on which Object my mouse is hovering on; either the Background (BG) or the Object, which lays on top of the BG.
As long as the BG collider is enabled in the inspector, my script will ONLY recognize the BG, even if the other object lays on top of my BG (visually and according to the Sorting Layer) (both Z-positions = 0, Sorting Layer Default (BG: 0, Object 1)).
The collider have the correct size and if I disable or remove the Collider from the BG, my script will detect the other Object just fine.
The only way to make sure that my Object gets detected, while my BG collider is activated is by changing the Objects Z position to a position between my BG and my Camera (between smaller 0 and greater -10)
I tried to:
this is a fresh 2D project, so my cameras Projection is set to Orthograph, my BG and Object use Sprite Renderer and is use 2D collider
change the "Order in Layer", back and forth, including negative numbers.
add a Foreground (and Background) "Sorting Layer"
(both options only had a visual effect and did not affect the Raycast output)
change the positions in the hierarchy.
removing and re-adding the colliders. (!) I observed that the 2D Box collider I added last, will always be behind every other colliders. This is something I can work with for now. But will become a problem later in the future, when the project gets bigger.
I want to be able to interact with items and doors etc. (clicks and reactions to mouse hovering) in my 2D click adventure. If 2D Raycast is not the way to go to archive this, I would be glad to know about the proper technique to use in this situation.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class RayCast : MonoBehaviour
{
[SerializeField] private Vector2 mousePosWorld2D;
RaycastHit2D hit;
void Update()
{
mousePosWorld2D = (Vector2)Camera.main.ScreenToWorldPoint(Input.mousePosition);
hit = Physics2D.Raycast(mousePosWorld2D, Vector2.zero);
if (hit.collider)
{
Debug.Log("Found collider: " + hit.collider.name);
}
else
{
Debug.Log("No collider found.");
}
}
}
I expected the "Sorting Layer" or "Order in Layer" to have an impact on my Raycast, while changing the Z position does nothing. But it is the other way around. Sorting Layer only have a visual effect and moving my Object closer to the camera (Z position) helps to detect the right collider.
How do I solve the problem?

What gets hit first from a Ray has only to do with how close the collider is to the camera, and nothing with the order in the Hierarchy or the SortinLayers.
To find the "highest" RaycastTarget based on the SortingLayer, I created the Script below.
We fire a Raycast and iterate over all the Colliders that we hit, by using a foreach-loop. Then the function will return the GameObject with the highest SortingLayer. Note: If there is more than one GameObject with the highest SortingLayer, the function will return the last one it found.
using UnityEngine;
public class Raycast : MonoBehaviour
{
// The name of the relevant Layer
[SerializeField] string layerToCheck = "Default";
void Update()
{
Vector2 mousePosWorld2D = (Vector2)Camera.main.ScreenToWorldPoint(Input.mousePosition);
GameObject result = GetHighestRaycastTarget(mousePosWorld2D);
// Do Stuff example:
Debug.Log($"Highest Layer: {result}");
if (Input.GetMouseButtonDown(0)
&& result != null)
{
Destroy(result);
}
}
// Get highest RaycastTarget based on the Sortinglayer
// Note: If multiple Objects have the same SortingLayer (e.g. 42) and this is also the highest SortingLayer, then the Function will return the last one it found
private GameObject GetHighestRaycastTarget(Vector2 mousePos)
{
GameObject topLayer = null;
RaycastHit2D[] hit = Physics2D.RaycastAll(mousePos, Vector2.zero);
foreach (RaycastHit2D ray in hit)
{
SpriteRenderer spriteRenderer = ray.transform.GetComponent<SpriteRenderer>();
// Check if RaycastTarget has a SpriteRenderer and
// Check if the found SpriteRenderer uses the relevant SortingLayer
if (spriteRenderer != null
&& spriteRenderer.sortingLayerName == layerToCheck)
{
if (topLayer == null)
{
topLayer = spriteRenderer.transform.gameObject;
}
if (spriteRenderer.sortingOrder >= topLayer.GetComponent<SpriteRenderer>().sortingOrder)
{
topLayer = ray.transform.gameObject;
}
}
}
return topLayer;
}
}

Have you tried with the script that it's in the Unity official documentation?
https://docs.unity3d.com/ScriptReference/Physics.Raycast.html
using UnityEngine;
// C# example.
public class ExampleClass : MonoBehaviour
{
void Update()
{
// Bit shift the index of the layer (8) to get a bit mask
int layerMask = 1 << 8;
// This would cast rays only against colliders in layer 8.
// But instead we want to collide against everything except layer 8. The ~ operator does this, it inverts a bitmask.
layerMask = ~layerMask;
RaycastHit hit;
// Does the ray intersect any objects excluding the player layer
if (Physics.Raycast(transform.position, transform.TransformDirection(Vector3.forward), out hit, Mathf.Infinity, layerMask))
{
Debug.DrawRay(transform.position, transform.TransformDirection(Vector3.forward) * hit.distance, Color.yellow);
Debug.Log("Did Hit");
}
else
{
Debug.DrawRay(transform.position, transform.TransformDirection(Vector3.forward) * 1000, Color.white);
Debug.Log("Did not Hit");
}
}
}

Air hockey game - Player bat goes through puck if moved too fast

Im currently developing an Air hockey game in Unity3d. The issue I'm having is that when the player attempts to hit the puck too quickly, the player ends up going through the puck and therefore there is no collision. The game works perfectly as expected if the player stays still and the puck hits the player or if the player hits the puck at a slow pace.
The player has a rigidbody using continuous collision detection using a capsule collider. The puck also has rigidbody with continuous dynamic collision detection and a mesh collider with convex.
I tried setting the fixed timestep to 0.01 but that didn't have an effect. Here is the script for the player movement:
void ObjectFollowCursor()
{
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
Vector3 point = ray.origin + (ray.direction * distance);
Vector3 temp = point;
temp.y = 0.2f; // limits player on y axis
cursorObject.position = temp;
}
and here is the code for the puck when it collides with the player:
// If puck hits player
if(collision.gameObject.tag == "Player")
{
Vector3 forceVec = this.GetComponent<Rigidbody>().velocity.normalized * hitForce;
rb.AddForce(forceVec, ForceMode.Impulse);
Debug.Log ("Player Hit");
}
Any help would be much appreciated. Thanks.

The problem you are having its called "tunneling".
This happens because your object is moving at a high speed and in that specific frame the collision is not detected. In frame n the ball is just in front of the bat, but when frame n+1 is calculated the ball has moved behind the bat, thus "missing" the collision completely.
It is a common problem but there are solutions.
I recommend you study this script and try to implement on your game.
This is not my code:
SOURCE: http://wiki.unity3d.com/index.php?title=DontGoThroughThings
using UnityEngine;
using System.Collections;
public class DontGoThroughThings : MonoBehaviour
{
// Careful when setting this to true - it might cause double
// events to be fired - but it won't pass through the trigger
public bool sendTriggerMessage = false;
public LayerMask layerMask = -1; //make sure we aren't in this layer
public float skinWidth = 0.1f; //probably doesn't need to be changed
private float minimumExtent;
private float partialExtent;
private float sqrMinimumExtent;
private Vector3 previousPosition;
private Rigidbody myRigidbody;
private Collider myCollider;
//initialize values
void Start()
{
myRigidbody = GetComponent<Rigidbody>();
myCollider = GetComponent<Collider>();
previousPosition = myRigidbody.position;
minimumExtent = Mathf.Min(Mathf.Min(myCollider.bounds.extents.x, myCollider.bounds.extents.y), myCollider.bounds.extents.z);
partialExtent = minimumExtent * (1.0f - skinWidth);
sqrMinimumExtent = minimumExtent * minimumExtent;
}
void FixedUpdate()
{
//have we moved more than our minimum extent?
Vector3 movementThisStep = myRigidbody.position - previousPosition;
float movementSqrMagnitude = movementThisStep.sqrMagnitude;
if (movementSqrMagnitude > sqrMinimumExtent)
{
float movementMagnitude = Mathf.Sqrt(movementSqrMagnitude);
RaycastHit hitInfo;
//check for obstructions we might have missed
if (Physics.Raycast(previousPosition, movementThisStep, out hitInfo, movementMagnitude, layerMask.value))
{
if (!hitInfo.collider)
return;
if (hitInfo.collider.isTrigger)
hitInfo.collider.SendMessage("OnTriggerEnter", myCollider);
if (!hitInfo.collider.isTrigger)
myRigidbody.position = hitInfo.point - (movementThisStep / movementMagnitude) * partialExtent;
}
}
previousPosition = myRigidbody.position;
}
}

You were right to try continuous collision detection (CCD). There are some constraints (especially in this case where you want to use CCD with two moving objects rather than one moving object and one static object), but it is designed for this kind of scenario. The Rigidbody documentation goes into these constraints:
Set the collision detection mode to Continuous to prevent the
rigidbody from passing through any static (ie, non-rigidbody)
MeshColliders. Set it to Continuous Dynamic to also prevent the
rigidbody from passing through any other supported rigidbodies with
collision detection mode set to Continuous or Continuous Dynamic.
Continuous collision detection is supported for Box-, Sphere- and
CapsuleColliders.
To sum up, both puck and paddle need to be set to Continuous Dynamic, and both need to be Box-, Sphere-, or Capsule Colliders. If you can make these constraints work for your game you should be able to get continuous collision detection without writing it yourself.
A note about Unity's CCD that bears repeating:
Note that continuous collision detection is intended as a safety net
to catch collisions in cases where objects would otherwise pass
through each other, but will not deliver physically accurate collision
results, so you might still consider decreasing the fixed Time step
value in the TimeManager inspector to make the simulation more
precise, if you run into problems with fast moving objects.
But since you are manually specifying the collision reaction, that might not be an issue.