我的选择（Raycast）代码出了什么问题

Question

I am learning Unity and is trying to convert an XCODE game i have.

I have a deck of cards with 61 sprites on top of each other.

...and I am using Raycast to try to capture the first sprite and I am not able to do that?

I also have a drag function to be able to move the sprite around.

I get very strange results:

1. When i click on the top-sprite, the second on top is selected (60 of 61)
2. When i then drag (works) the sprite it is the 51th sprite (51 of 61) that is dragged according to the print

I just do not get my acts together around this "simple" challenge and really need help. I have been spending quite a few hours on this and tested all kinds of stuff but still ends up with the same problem. The current code is just the basic to try to sort this out.

Script attached to an empty GameObject:

void Update() {



if(Input.GetMouseButtonDown(0)) {

        RaycastHit2D hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), Vector2.zero);

        print (hit.collider.tag);

    }

}

The "drag" attached to the sprites:

public class dragTheStuff : MonoBehaviour {



float x;

float y;



void Update() {

    x = Input.mousePosition.x;

    y = Input.mousePosition.y;

}



void OnMouseDrag() {

    // Control the drag of the sprite

    transform.position = Camera.main.ScreenToWorldPoint (new Vector3 (x, y, 1.0f));

    print ("Drag: " + transform.tag);

}

}

When i select the top-sprite manually in the scene the 36th of 61 sprite is selected. See image:

They all have BoxCollider2D.

Answer 1

The 2D Raycast is supposed to be cast along your 2D plane (x,y), but you are trying to get the top element in the Z axis. Switching to the 3D Raycast will not work, because it ignores 2D colliders.

According to MelvMay , a Unity Developer, you should use Physics2D.GetRayIntersection .

I'm not sure why your OnMouseDrag() and manually clicking is not working, but maybe your sprites are not in the correct Z order or don't have one at all. If they all have the same Z position, it would just be random which sprite you will select.

If you are using the Unity default settings for a 2D game, your Z axis will be positive pointing into the game, so that cards at the bottom of the stack should have a higher Z value than the card on top.

In your OnMouseDrag() method you are setting Z to 1 while calling Camera.ScreenToWorldPoint . The Z position is in world units from the camera, so if your camera is at Z = -10 (default value), the resulting Z value will be -10 + 1 = -9 . It would probably be better to ignore the resulting Z value and use only X and Y to update your card.

Answer 2

I think you may have a problem with your raycast. Looking at the documentation , The second parameter is supposed to be direction, but you have Vector2.zero there. So I'm guessing your logic is that since it's a 2D raycast, direction of zero would put it directly towards the 2D plane? I'm thinking that function may be intended to be used for casts along the 2D plane only and doesn't work that way.

You should try Physics2D.GetRayIntersection , it might be more suited for your case. Ray with a direction (0, 0, 1) should work there.

Answer 3

I finally solved this problem. The test project is using this code:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class EGOScript : MonoBehaviour {

public static List<string> cardDeckList = new List<string> {
    "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13",
    "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26",};

public GameObject theGameObject;
float ff = 0f;
public float addIT = 0.2f;
int counter;
public static int zOffset = 0;
public static float zSelect = 26;
public static int zSelectInt = 26;






// Use this for initialization
void Start () {

    counter = 0;
    zOffset = 26;

    print (cardDeckList.Count);

    for (int z = 0; z < 26; z++) {

        theGameObject = Resources.Load(cardDeckList[z]) as GameObject;
        theGameObject.transform.position =  new Vector3(0f + ff, 0f + ff, zOffset);
        theGameObject.renderer.sortingOrder = counter;
        Instantiate(theGameObject);

        ff = ff + addIT;

        counter++;
        zOffset--;
    }
}

// Update is called once per frame
void Update () {
    if(Input.GetMouseButtonDown(0)) {
        //RaycastHit2D hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), Vector2.zero);

        Vector3 worldPoint = Camera.main.ScreenToWorldPoint( Input.mousePosition );
        worldPoint.z = Camera.main.transform.position.z;
        Ray ray = new Ray( worldPoint, new Vector3( 0, 0, 1 ) );
        RaycastHit2D hit = Physics2D.GetRayIntersection( ray );

        zSelect++;
        zSelectInt++;

        if(hit.collider != null) {
            //print (hit.collider.tag);
            //zSelect = hit.collider.transform.position.z;

            Vector3 z3 = hit.collider.transform.position;

            z3.z = zSelect;

            hit.collider.transform.position = z3;
            hit.collider.renderer.sortingOrder = zSelectInt;

            print (hit.collider.transform.position + " + " + zSelectInt);
        }
    }
}
}


using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class DragScript : MonoBehaviour {

float x;
float y;
float z;


// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
    x = Input.mousePosition.x;
    y = Input.mousePosition.y;
}

void OnMouseDrag() {

    // Control the drag of the sprite
    transform.position = Camera.main.ScreenToWorldPoint (new Vector3 (x, y, EGOScript.zSelect));
}
}