trying to keep a game object within the screen lef

问题:

I have this code bellow for my gameobject :

private float screenx;
Vector3 playerPosScreen;
 void Start () {
 screenx=Camera.main.pixelWidth-renderer.bounds.size.x ;
 }

 void update(){
  playerPosScreen = Camera.main.WorldToScreenPoint(transform.position);
  if (playerPosScreen.x >= screenx) {
        //playerPosScreen.x=screenx;
        transform.position=new Vector3 (screenx, transform.position.y,transform.position.z);
    }
    //txt.text = playerPosScreen.x.ToString();
    else if(playerPosScreen.x<=renderer.bounds.size.x){
        transform.position=new Vector3 (renderer.bounds.size.x, transform.position.y,transform.position.z);
    }
 }

I'm developing a 2D game with an orthographic camera,my problem is the gameobject is keep on going out of screen , am i missing something here ?

回答1:

After some research i found a solution wish worked excellent with me :

Vector3 playerPosScreen;
Vector3 wrld;
float half_szX;
float half_szY;
void Start () {
    wrld = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width, 0.0f, 0.0f));
    half_szX = renderer.bounds.size.x / 2;
    half_szY = renderer.bounds.size.y /2 ;
}
void Update () {
    playerPosScreen = transform.position;
 if (playerPosScreen.x >=(wrld.x-half_szX) ) {
        playerPosScreen.x=wrld.x-half_szX;
        transform.position=playerPosScreen;
    }
    if(playerPosScreen.x<=-(wrld.x-half_szX)){
        playerPosScreen.x=-(wrld.x-half_szX);
        transform.position=playerPosScreen;
    }
}

回答2:

Firstly your function is never called because there is typo in its name. It should be Update not update.

Secondly the problem with coordinates is that the code is mixing screen coordinates and world coordinates. Screen coordinates go from (0, 0) to (Screen.width, Screen.height). Coordinates can be changed from world coordinates to screen coordinates with WorldToScreenPoint and back with ScreenToWorldPoint, in which the Z value is the distance of the converted point from camera.

Here is a complete code example, which can be used after changing the player's position to make sure that it is inside the screen area:

    Vector2 playerPosScreen = Camera.main.WorldToScreenPoint(transform.position);
    if (playerPosScreen.x > Screen.width)
    {
        transform.position = 
            Camera.main.ScreenToWorldPoint(
                new Vector3(Screen.width, 
                            playerPosScreen.y, 
                            transform.position.z - Camera.main.transform.position.z));
    }
    else if (playerPosScreen.x < 0.0f)
    {
        transform.position = 
            Camera.main.ScreenToWorldPoint(
                new Vector3(0.0f, 
                            playerPosScreen.y, 
                            transform.position.z - Camera.main.transform.position.z));
    }