Unity游戏开发的数学与物理 2 （ 通过键盘控制物体的运动 ）

using UnityEngine;
using System.Collections;

//通过键盘控制物体的运动
public class KeyControlMotionTest : MonoBehaviour
{
//物体的X位置
float posX = 0;

//物体的Y位置
float posY = 0;

//物体在x方向上的速度
float speedX = 1;

//物体在y方向上的速度
float speedY = 1;

//屏幕的右上像素在世界空间的坐标
Vector3 ScreenRightTopPos;

//屏幕的左下像素在世界空间的坐标
Vector3 ScreenLeftBottomPos;

//box的半宽度
float boxHalfWidth;

readonly float Sqrt2;

public KeyControlMotionTest()
{
//2的开方
Sqrt2 = Mathf.Sqrt(2);
}

void Start()
{
//将屏幕右上的像素转换为世界空间的坐标
ScreenRightTopPos = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height, 0));

//将屏幕右下的像素转换为世界空间的坐标
ScreenLeftBottomPos = Camera.main.ScreenToWorldPoint(new Vector3(0, 0, 0));

//box的半宽度，因为box是正方形
boxHalfWidth = transform.localScale.x * 0.5f;

//初始位置
transform.localPosition = new Vector3(posX, posY, 0);
}

void Update()
{
//按住左键
if (IsLeftKey())
{
//按住左键且按住上键
if (IsUpKey())
{
posX -= speedX / Sqrt2 * Time.deltaTime;
posY += speedY / Sqrt2 * Time.deltaTime;
}
//按住左键且按住下键
else if (IsDownKey())
{
posX -= speedX / Sqrt2 * Time.deltaTime;
posY -= speedY / Sqrt2 * Time.deltaTime;
}
else
{
posX -= speedX * Time.deltaTime;
}
}
//按住右键
else if (IsRightKey())
{
//按住右键且按住上键
if (IsUpKey())
{
posX += speedX / Sqrt2 * Time.deltaTime;
posY += speedY / Sqrt2 * Time.deltaTime;
}
//按住右键且按住下键
else if (IsDownKey())
{
posX += speedX / Sqrt2 * Time.deltaTime;
posY -= speedY / Sqrt2 * Time.deltaTime;
}
else
{
posX += speedX * Time.deltaTime;
}
}
//按住上键
else if (IsUpKey())
{
posY += speedY * Time.deltaTime;
}
//按住下键
else if (IsDownKey())
{
posY -= speedY * Time.deltaTime;
}

//边界检测 右
if (posX + boxHalfWidth >= ScreenRightTopPos.x)
{
posX = ScreenRightTopPos.x - boxHalfWidth;
}

//边界检测 左
if (posX - boxHalfWidth <= ScreenLeftBottomPos.x)
{
posX = ScreenLeftBottomPos.x + boxHalfWidth;
}

//边界检测 上
if (posY + boxHalfWidth >= ScreenRightTopPos.y)
{
posY = ScreenRightTopPos.y - boxHalfWidth;
}

//边界检测 下
if (posY - boxHalfWidth <= ScreenLeftBottomPos.y)
{
posY = ScreenLeftBottomPos.y + boxHalfWidth;
}

//设置当前物体的位置
transform.localPosition = new Vector3(posX, posY, 0);
}

bool IsLeftKey()
{
//按住左键或者a键，都是向左
if (Input.GetKey(KeyCode.LeftArrow)
|| Input.GetKey(KeyCode.A))
{
return true;
}
else
{
return false;
}
}

bool IsUpKey()
{
//按住上键或者w键，都是向上
if (Input.GetKey(KeyCode.UpArrow)
|| Input.GetKey(KeyCode.W))
{
return true;
}
else
{
return false;
}
}

bool IsDownKey()
{
//按住下键或者s键，都是向下
if (Input.GetKey(KeyCode.DownArrow)
|| Input.GetKey(KeyCode.S))
{
return true;
}
else
{
return false;
}
}

bool IsRightKey()
{
//按住右键或者d键，都是向右
if (Input.GetKey(KeyCode.RightArrow)
|| Input.GetKey(KeyCode.D))
{
return true;
}
else
{
return false;
}
}
}