如何在Unity中实例化对象？

Question

我正在Unity中制作自顶向下的游戏，如何从Unity中摄像机视图顶部的玩家当前位置实例化对象？

到目前为止，我已经尝试过：

Instantiate(prefab, player.transform.position * 2 * Space.World)

但这没用。这只是从相机中心产生物体。

Answer 1

Space只是一个枚举，与您尝试的内容无关！（它的目的是定义用于例如相对变换空间Transform.Rotate或Transform.Translate）

在那个枚举中

• Space.World 只是具有int值 0
• Space.Self 具有int值 1

所以你实际要做的是

Instantiate(prefab, player.transform.position * 2 * 0);

等于

Instantiate(prefab, Vector3.zero);

这意味着该对象在World位置实例化0,0,0。

也使用

Instantiate(prefab, player.transform.position * 2);

看起来有点奇怪。您确定要复制的实际position值player吗？这意味着生成的对象始终与玩家和世界在一条直线上，0,0,0并且始终是玩家中心的两倍。

对我来说，听起来更像是您想在玩家面前生成一些东西……取决于玩家的观看方向（通常是在自上而下的游戏中player.transform.up或player.transform.right），所以我想您想做的是

Instantiate(prefab, player.transform.position + player.transform.forward * 2);

而是2在播放器对象前面生成对象Unity单位

您的评论后，它听起来像，而不是你想对球员位置产卵的对象X-axis，但“在它”在Y-axis这样

Instantiate(prefab, player.transform.position + Vector3.Up * 2);

也许您必须2根据播放器的移动方式以及“屏幕外”的移动距离来调整。另外，您也可以使用更复杂的方法Camera.ScreenToWorldPoint

// get players position
var playerPos = player.transform.position;

// get camera's position
var cameraPos = Camera.main.transform.position;

// get difference on Z-axis
var cameraDistance = cameraPos.z - playerPos.z;

// Get the world 3d point for the upper camera border
// don't care about the X value
// and as distance we use the z-distance to the player
var cameraTopPoint = Camera.main.ScreenToWorldPoint(new Vector3(0, Camera.main.pixelHeight, cameraDistance);

// use the players X-axis position
cameraTopPoint.x = player.transform.x;

// to spawn it exactly on the Screen border above the player
Instantiate(prefab, cameraTopPoint);

// or to spawn it a bit higher
Instantiate(prefab, cameraTopPoint + Vector3.Up * 1);

更新资料

您说过要在X轴上播放器位置的“对面”生成预制体。

如果您的相机在x = 0的世界上是静态的，那么这实际上很简单：

cameraTopPoint.x = -player.transform.x;

如果您的相机是否在x = 0上移动，那么我们必须已经在屏幕位置级别上对其进行了计算：

// get players position
var playerPos = player.transform.position;

// additionally convert the player position to screen space
var playerScreenPos = Camera.main.WorldToScreenPoint(playerPos);

var centerX = Camera.main.pixelWidth / 2.0f;

// get the difference between camera an player X (in screen space)
var differenceX = Mathf.Abs(playerScreenPos.x - centerX);

// here calculate the opposide side
var targetX = centerX + differenceX * (playerScreenPos.x < centerX ? 1 : -1);
// or alternatively if you want e.g. that the prefab always
// spawn with a bit of distance to the player even though he is very close
// to the center of the screen you could do something like
//var targetX = centerX + centerX / 2 * (playerScreenPos.x < centerX ? 1 : -1);

// Get the world 3d point for the upper camera border
// with the calculated X value
// and as distance we use the z-distance to the player
var cameraTopPoint = Camera.main.ScreenToWorldPoint(new Vector3(targetX, Camera.main.pixelHeight, playerScreenPos.z);

// to spawn it exactly on the Screen border above the player
Instantiate(prefab, cameraTopPoint);

// or to spawn it a bit higher
Instantiate(prefab, cameraTopPoint + Vector3.Up * 1);

其他更新

好的，所以您希望预制件始终在玩家附近一定距离处生成。侧面取决于播放器在屏幕的哪一侧，因此您实际上可以再次使用第一种方法，而只需添加所需的距离即可：

// Adjust this is the Inspector (in Unity units)
public float spawnDistanceToPlayer;

...

// get players position
var playerPos = player.transform.position;

// additionally convert the player position to screen space
var playerScreenPos = Camera.main.WorldToScreenPoint(playerPos);

var centerX = Camera.main.pixelWidth / 2.0f;

// Get the world 3d point for the upper camera border
// with the calculated X value
// and as distance we use the z-distance to the player
var cameraTopPoint = Camera.main.ScreenToWorldPoint(new Vector3(playerScreenPos.x, Camera.main.pixelHeight, playerScreenPos.z);

// now add or reduce spawnDistanceToPlayer 
// depending on which side of the screen he is
cameraTopPoint.x += spawnDistanceToPlayer * (playerScreenPos.x < centerX ? 1 : -1);

// OR if your camera sits static on X=0 anyway you also could compare
// the player position directly without calculating in screenspace:
cameraTopPoint.x += spawnDistanceToPlayer * (playerPos.x < 0 ? 1 : -1);

// to spawn it exactly on the Screen border above the player
Instantiate(prefab, cameraTopPoint);

// or to spawn it a bit higher
Instantiate(prefab, cameraTopPoint + Vector3.Up * 1);

在智能手机上输入，因此可能无法“复制粘贴”;）