無法讓我的視口在XNA遊戲中工作

Question

我正在嘗試學習C＃和XNA，同時製作一個簡單的平臺遊戲（馬里奧式遊戲）。 我試圖用viewport實現滾動背景，我借用並調整了一個準備好的工作示例中的一些位代碼，但出於奇怪的原因，它陷入了一個點。 我認爲問題在於我指向視口中心的方式。你能幫我個忙嗎？

這就是我的等級類

using System; 
using Microsoft.Xna.Framework; 
using Microsoft.Xna.Framework.Content; 
using Microsoft.Xna.Framework.Graphics; 


namespace JumpMan 
{ 
    public class Level 
    { 
     //game content manager 
     private ContentManager content; 
     public ContentManager Content 
      { 
       get { return content; } 
      } 

      // level of the ground in the game 
      private int groundLevel = 192; 
      public int GroundLevel 
      { 
       get { return groundLevel; } 
      } 

      //Gravitation in the game - pulling JumpMan down 
      private float gravitation = 1.4f; 
     public float Gravitation 
     { 
      get { return gravitation; } 
     } 

     //Current game to which this level belongs 
     private Game1 game; 

     // Player 
     private JumpMan jumpMan; 
     //Amount of lives 
     public int Live; 

     /background texture for this level 
     private Texture2D backgroundTexture; 
     public Texture2D BackgroundTexture 
     { 
      get { return backgroundTexture; } 
     } 

     //viewport size and centre 
     Vector2 viewPortCentre; 
     Vector2 viewPortSize; 

     //Prepare the level 
     public Level(Game1 game) 
     { 
      //store the game referance 
      this.game = game; 
      content = game.Content; 


      //build the level 
      LoadContent(); 
      Initialize(); 

     } 

     //Load game level content 
     private void LoadContent() 
     { 
      backgroundTexture = Content.Load<Texture2D>(@"Background"); 


     } 

     //Initialise level 
     private void Initialize() 
     { 
      // Resize the back buffer to match the loaded level size 
      game.Graphics.PreferredBackBufferWidth = backgroundTexture.Width; 
      game.Graphics.PreferredBackBufferHeight = backgroundTexture.Height; 
      game.Graphics.ApplyChanges(); 


      viewPortSize = new Vector2(
       game.Graphics.GraphicsDevice.Viewport.Width, 
       game.Graphics.GraphicsDevice.Viewport.Height); 
      viewPortCentre = new Vector2(0.0f, viewPortSize.Y/2.0f); 


      //Set Jumpmans number of lives 
      Live = 3; 
      //Initialise the JumpMan class (create JumpMan) 
      jumpMan = new JumpMan(this); 


     } 

     //Update game level 


     /// Update the game level 
     public void Update(GameTime gameTime) 
     { 
      //Update JumpMan 
      jumpMan.Update(gameTime); 
     } 


     //Draw the level 
     public void Draw(GameTime gameTime) 
     { 

      //Determine the width of the viewport 
      // int viewPortSize = game.Graphics.GraphicsDevice.Viewport.Width; 

      // Draw level textures 
      SpriteBatch spriteBatch = game.SpriteBatch; 
      spriteBatch.Begin(); 

      viewPortCentre.X = jumpMan.JumpManPosition.X; 
      if (viewPortCentre.X < viewPortSize.X/2) 
       viewPortCentre.X = viewPortSize.X/2; 

      // Determine the start location of the background relative to the viewport 
      int backgroundStartX = (int)(viewPortSize.X - viewPortSize.X/2.0f) % backgroundTexture.Width; 

      // Draw out the first slices 
      //spriteBatch.Draw(backgroundTexture, new Vector2(-backgroundStartX, 0.0f), Color.White); 

      // If needed draw out a second slice 
      if (backgroundTexture.Width - backgroundStartX < viewPortSize.X) 
       spriteBatch.Draw(backgroundTexture, new Vector2(backgroundTexture.Width - backgroundStartX, 0.0f), Color.White); 

      // Draw JumpMan by calling JumpMan class 
      jumpMan.Draw(spriteBatch, viewPortSize, viewPortCentre, gameTime); 

      spriteBatch.End(); 
     } 
    } 
} 

Answer 1

當你viewPortCenter.X爲負，會發生什麼？假設您的viewPortSize.X等於800，並且您的viewPortCenter.X是-1000。 if if語句將評估爲真：

if (viewPortCentre.X < viewPortSize.X/2) 
    viewPortCentre.X = viewPortSize.X/2; 

所以，如果你走得足夠遠，你會最終看到你的背景「棒」。

，可以快速使用解決這個問題：

if (Math.Abs(viewPortCenter.X) < viewPortSize.X/2) 
    viewPortCentre.X = viewPortSize.X/2;