試圖射擊子彈

Question

所以，我正在做我自己的小行星遊戲，我有點卡住了。當我按下按鍵Z時，我有一顆子彈從船上發射出去。但子彈總是以相同的方向發射，我不知道如何改變它？我希望它能夠朝着船所面臨的方向發射。此外，如果我快速推Z（發射許多子彈），一顆子彈似乎不斷重置。我如何解決這些問題？這裏是我的代碼：

class SpaceShip 
{ 
    private Vector2 pos; //Our position in 2D. 
    private Texture2D tex; //Our texture 
    private float speed = 8; //The speed to move. 
    private float angleOfRotation = 0; 
    Sprite tempSprite; 


    public SpaceShip(Vector2 pos, Texture2D tex, Texture2D bulletsToAdd) 
    { 
     this.pos = pos; //Our starting position 
     this.tex = tex; //Our texture 
     tempSprite = new Sprite(bulletsToAdd); 
    } 



    private void WorldWrap(int worldWidth, int worldHeight) 
    { 

     if (this.pos.X < 0) 
     { 
      //If we've past the left side of the window, set on other side of the world. 
      this.pos.X = worldWidth; 
     } 
     if (this.pos.X > worldWidth) 
     { 
      //If we've past the right side of the window, set on other side of the world. 
      this.pos.X = this.tex.Width; 
     } 
     if (this.pos.Y < 0) 
     { 
      //If we've passed the top side of the window, set on other side of the world. 
      this.pos.Y = worldHeight; 
     } 
     if (this.pos.Y > worldHeight) 
     { 
      //If we've passed the bottom side of the window, set on other side of the world. 
      this.pos.Y = this.tex.Height; 
     } 
    } 

    public void CreateBullets(Texture2D bulletsToAdd) 
    { 

     tempSprite.Position = new Vector2((pos.X),(pos.Y)); 
     tempSprite.Velocity = new Vector2((float)7, 7); 
     //tempSprite.Rotation = angleOfRotation; 
    } 


    public void Update(int WorldWidth, int WorldHeight, Texture2D bulletsToAdd) 
    { 
     KeyboardState keys = Keyboard.GetState(); 
     if (keys.IsKeyDown(Keys.A)) 
     { 
      //We want to turn the ship LEFT 
      this.angleOfRotation -= 2f; 

     } 
     if (keys.IsKeyDown(Keys.D)) 
     { 
      //We want to turn the ship RIGHT 
      this.angleOfRotation += 2f; 

     } 
     if (keys.IsKeyDown(Keys.W)) 
     { 
      //We're pressing the up key (W) so go Forwards! 
      this.pos.X += (float)(Math.Cos(this.angleOfRotation * Math.PI/180) * this.speed); 
      this.pos.Y += (float)(Math.Sin(this.angleOfRotation * Math.PI/180) * this.speed); 

     } 
     if (keys.IsKeyDown(Keys.S)) 
     { 
      //We're pressing the down key (S) so go Backwards! 
      this.pos.X -= (float)(Math.Cos(this.angleOfRotation * Math.PI/180) * this.speed); 
      this.pos.Y -= (float)(Math.Sin(this.angleOfRotation * Math.PI/180) * this.speed); 

     } 
     if (keys.IsKeyDown(Keys.Right)) 
     { 
      //We're pressing the up key (W) so go Forwards! 
      this.pos.X += (float)(Math.Cos(this.angleOfRotation * Math.PI/180) * this.speed); 
      this.pos.Y += (float)(Math.Sin(this.angleOfRotation * Math.PI/180) * this.speed); 

     } 
     if (keys.IsKeyDown(Keys.Left)) 
     { 
      //We're pressing the down key (S) so go Backwards! 
      this.pos.X -= (float)(Math.Cos(this.angleOfRotation * Math.PI/180) * this.speed); 
      this.pos.Y -= (float)(Math.Sin(this.angleOfRotation * Math.PI/180) * this.speed); 

     } 

     if (keys.IsKeyDown(Keys.Up)) 
     { 
      //We want to turn the ship LEFT. Rotate it counter-clockwise 
      this.angleOfRotation -= 2f; 

     } 
     if (keys.IsKeyDown(Keys.Down)) 
     { 
      //We want to turn the ship RIGHT. Rotate it clockwise 
      this.angleOfRotation += 2f; 

     } 
     if (keys.IsKeyDown(Keys.Z)) 
     { 

      CreateBullets(bulletsToAdd); 
     } 


     tempSprite.Position += tempSprite.Velocity; 

     //check if we need to move the ship. 
     WorldWrap(WorldWidth, WorldHeight); 

    } 

    public void Draw(SpriteBatch batch) 
    { 
     batch.Draw(this.tex, //Texture to use. 
     this.pos, //Position to draw at 
     new Rectangle(0, 0, this.tex.Width, this.tex.Height),Color.White, (float)((this.angleOfRotation + 90) * Math.PI/180), new Vector2(this.tex.Width/2, this.tex.Height/2), 1.0f, SpriteEffects.None, 0.0f); 

     batch.Draw(tempSprite.Texture, tempSprite.Position, null, Color.White, tempSprite.Rotation, tempSprite.Center, tempSprite.Scale, SpriteEffects.None, 1.0f); 
    } //End Draw function 

Answer 1

首先，你只有一顆子彈 - tempSprite。您可能要創建一個單獨的Bullet類和一個List<Bullet>某處，您可以添加項目符號。

所有你需要的是一個小三角。現在你的速度矢量是一個常數< 7,7>。你想要做的就是讓這個矢量朝着太空船指向的方向前進。因此，假設您的角度是弧度而不是度（如果它們的角度是度數，則需要將它們更改爲弧度），我們可以使用Math.Sin()和Math.Cos()來獲取速度矢量的各個X和Y分量，如下所示：

bulletSpeed = 7; 
tempSprite.Velocity = new Vector2((float)Math.Cos(angleOfRotation) * bulletSpeed, (float)Math.Sin(angleOfRotation) * bulletSpeed);