如何在旋转后沿它所面对的方向移动精灵？

Question

我可以让小船精灵上下左右移动，也可以旋转它。但是，当按下 'up' 键时，船不是总是向上移动，而是希望船向船头的方向移动。我在想我可以在更新方法中的某处放置一个 vector2 变量，它始终指向精灵的尖端，但我无法思考如何 "hardcode" 精灵上的坐标。

我会 post 我的船 class 下面，我觉得事情有点乱，也欢迎任何关于清理代码的建议。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;


//width = 62 pixels
//height = 179 pixels

namespace my_first_game
{
class Ship
{

    private Vector2 position = new Vector2(300, 300);
    private int radius = 50;
    private bool ismoving = false;
    private Dir direction = Dir.down;
    private int health = 3;
    private float speed = 100;
    public float angle = 0;
    public double turntime = .5d;

    private float velocity = 10f;
    private float drifttime = 0f;

   // Constructor for the ship class
   public Ship(int shiphealth)
    {
        shiphealth = health;
    }

    //getter/setter for angle
     public float Get_angle
     {
         get { return angle; }
        set { value = angle; }

     }         

    //get and set health
    public int Health
    {
        get { return health; }
        set { value = health; }
    }

    // get and set the ship's position
    public Vector2 Position
    {
        get{ return position; }
        set { value = position; }
    }

    public void SetAngle (float f)
    {
        angle = MathHelper.ToDegrees(f);
    }

    //update loop for the ship's state
    public void update_ship(GameTime gameTime)
    {
        KeyboardState kstate = Keyboard.GetState();
        float dt = (float)gameTime.ElapsedGameTime.TotalSeconds;

        float rotation = 0.02f;

        //Vector2 Direction = new Vector2((float)Math.Cos(angle + 45), (float)Math.Sin(angle));
        //Direction.Normalize();           

        //if keys are pressed, the ship moves until the keys are unpressed

        if (kstate.IsKeyDown(Keys.W))
        {
            direction = Dir.up;
            ismoving = true;
        }
        if (kstate.IsKeyDown(Keys.A))
        {
            direction = Dir.left;
            ismoving = true;
        }
        if (kstate.IsKeyDown(Keys.D))
        {
            direction = Dir.right;
            ismoving = true;
        }
        if (kstate.IsKeyDown(Keys.S))
        {
            direction = Dir.down;
            ismoving = true;
        }
        if(kstate.IsKeyDown(Keys.W) && kstate.IsKeyDown(Keys.D))
        { direction = Dir.up_right;
            ismoving = true;
        }
        if(kstate.IsKeyDown(Keys.W) && kstate.IsKeyDown(Keys.A))
        {
            direction = Dir.up_left;
            ismoving = true;
        }
        if (kstate.IsKeyDown(Keys.S) && kstate.IsKeyDown(Keys.D))
        { direction = Dir.down_right;
            ismoving = true;
        }
        if (kstate.IsKeyDown(Keys.S) && kstate.IsKeyDown(Keys.A))
        {
            direction = Dir.down_left;
            ismoving = true;
        }

            //"ismoving" is used as a flag to move the ship if keys are held
            //angle also rotates the boat when "A" and "D" are pressed
            if (ismoving) {

            switch (direction)
            {
                case Dir.up:
                    position.Y -= speed * dt;
                    ismoving = false;
                    break;

                case Dir.down:

                    position.Y += speed * dt;
                    ismoving = false;
                    break;

                case Dir.left:

                    angle -= rotation;
                    ismoving = false;
                    break;

                case Dir.right:
                    angle += rotation;
                    ismoving = false;
                    break;

                case Dir.up_right:
                    position.Y -= speed * dt;
                    position.X += speed * (float)turntime * dt;
                    angle += rotation;
                    ismoving = false;
                    break;

                case Dir.up_left:
                    position.Y -= speed * dt;
                    position.X -= speed * (float)turntime * dt;
                    angle -= rotation;
                    ismoving = false;
                    break;
                case Dir.down_right:
                    position.Y += speed * dt;
                    position.X += speed * (float)turntime * dt;
                    angle += rotation;
                    ismoving = false;
                    break;
                case Dir.down_left:
                    position.Y += speed * dt;
                    position.X -= speed * (float)turntime * dt;
                    angle -= rotation;
                    ismoving = false;
                    break;

                default: break;
            }
            }   
        }
    }
}

这是我的船的相关绘制方法：

//create a new rectangle around the ship_sprite
        Rectangle ship_rectangle = new Rectangle(0, 0, ship_sprite.Width, 
ship_sprite.Height);

        Vector2 origin = new Vector2(31, 160);


        spriteBatch.Draw(ship_sprite, ship.Position, ship_rectangle, 
Color.White, ship.angle, origin, 1.0f, SpriteEffects.None, 1);

Answer 1

我怀疑这个问题只有一个 "Right" 答案，但我会做的是使用你的 "angle" 属性来确定按下向上按钮时的移动。

我在沿着三角线思考 - 你的半径就是船速。然后你会按照（伪代码！）的方式做一些事情：

x += (cos(angle) * speed);
y += (sin(angle) * speed);

这假设角度 = 0 对应于法线平面图上 0 度的标准解释（因此面向右侧）。如果不是这种情况，您需要相应地进行调整。

警告：我自己没有编写过这样的代码，所以这只是我对实现方式的估计。我鼓励您进行实验，看看不同的方法是如何工作的。

Answer 2

经过一番修改后，我找到了适合我的解决方案。

Vector2 direction = new Vector2((float)Math.Cos(angle + 30), 
(float)Math.Sin(angle + 30));

然后当按下'up'键时，您可以简单地将船的位置设置为其当前位置加上船的角度。这两者的总和可以乘以增量时间和船速。

if(kstate.IsKeyDown(Keys.W))
{
  position = position + direction * dt * speed;   
}

如何在旋转后沿它所面对的方向移动精灵？

How do I move a sprite in the direction it is facing after being rotated?

c#

monogame