unity 2d 与3d坐标互相转换

// 根据3d的主角坐标，得到主角血条的坐标 (经过视窗坐标转换)web

Vector3 pos = cam.WorldToViewportPoint(Boy.position); // 将主角的3d坐标转换成对象屏幕的视窗坐标
 UI.transform.position = UIcam.ViewportToWorldPoint(pos); // 根据视窗坐标得到UI血条在3d的位置

// 根据3d的主角坐标，得到主角血条的坐标 (经过屏幕坐标转换)svg

screenpos = _cameraScene.WorldToScreenPoint (target);
        viewpos = _cameraUI.ScreenToWorldPoint (new Vector3 (screenpos.x,screenpos.y,_cameraUI.nearClipPlane));
        viewpos.z = 0;

// 经过2d的坐标加上z轴的深度，得到该2d坐标在3d上的位置

public static Vector3 PointVec2ToVec3(Vector2 vec2, float z){
        Vector3 world = new Vector3 (vec2.x / Screen.width, vec2.y / Screen.height, z);
        Vector3 world1 = Camera.main.ViewportToWorldPoint (new Vector3(world.x, world.y, world.z)); // 屏幕坐标转换成场景坐标
        return world1;
    }