unity3D 在屏幕边框创建碰撞框

private static GameObject s_aroundCols;
public static void CreateAroundColliders()
{
if(s_aroundCols != null) return;
s_aroundCols = new GameObject("aroundCols");
s_aroundCols.transform.position = Vector3.zero;
s_aroundCols.transform.localScale = Vector3.one;
s_aroundCols.transform.localEulerAngles = Vector3.zero;

Vector3 top = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width / 2f, Screen.height, 3f));
Vector3 bottom = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width / 2f, 0f, 3f));
Vector3 left = Camera.main.ScreenToWorldPoint(new Vector3(0f, Screen.height/2f, 3f));
Vector3 right = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height/2f, 3f));
float width = Vector3.Distance(left, right);
float height = Vector3.Distance(bottom, top);

PhysicMaterial pmat = new PhysicMaterial();
pmat.dynamicFriction = 0f;      //动摩擦力//
pmat.staticFriction = 0f;       //静摩擦力//
pmat.bounciness = 1f;       //弹力//
pmat.frictionCombine = PhysicMaterialCombine.Maximum;       //接触物体之间的摩擦力计算//
pmat.bounceCombine = PhysicMaterialCombine.Maximum;         //接触物体之间的弹力计算//

createOnCollider("top", s_aroundCols.transform, Vector3.zero, top, new Vector3(width, 0.05f, 0.05f), pmat);
createOnCollider("bottom", s_aroundCols.transform, Vector3.zero, bottom, new Vector3(width, 0.05f, 0.05f), pmat);
createOnCollider("left", s_aroundCols.transform, Vector3.zero, left, new Vector3(0.05f, height, 0.05f), pmat);
createOnCollider("right", s_aroundCols.transform, Vector3.zero, right, new Vector3(0.05f, height, 0.05f), pmat);
}

private static void createOnCollider(string name, Transform parent, Vector3 pos, Vector3 center, Vector3 size, PhysicMaterial mat)
{
GameObject col = new GameObject(name);
col.transform.position = pos;
col.transform.parent = parent;
BoxCollider box = col.AddComponent<BoxCollider>();
box.center = center;
box.size = size;
box.material = mat;
}