Silverlight Tip of the Day #5: Timers and the Main Game Loop

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Main Game Loop

[Blog Mirrored from https://silverlight.net/blogs/msnow/default.aspx]

The main game loop is the heart of your game. In this function you will execute the majority of your game related tasks including:

  • Game AI
  • Animations - Updating objects and their positions.
  • Etc...

In this tip I will be demonstrating how to setup the main game loop using the DispatcherTimer. Alternate methods you should look into for your main game loop include:

  1. StoryboardTimer – See Tip of the Day #16
  2. CompositionTarget.Rendering -  See Tip of the Day #50.

My preferred method is using the CompositionTarget.Rendering event as the event is fired before the rendering of each frame.

Couple notes about DispatcherTimer:

  1. You will need to add a using statement: using System.Windows.Threading;
  2. If you set the timer interval to TimeSpan.Zero it will put the rate to be in sync with your monitors refresh rate.

Now, let’s take a look at the code. In the demo below we are simply displaying the number of frames per second our browser is rendering.

Page.xaml.cs:

 using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Net;

 using System.Windows;

 using System.Windows.Controls;

 using System.Windows.Documents;

 using System.Windows.Input;

 using System.Windows.Media;

 using System.Windows.Media.Animation;

 using System.Windows.Shapes;

 using System.Windows.Threading;

  

 namespace SilverlightApplication6

 {

     public partial class Page : UserControl

     {

         private DispatcherTimer _gameLoopTimer;

         private int _fps = 0; 

         private DateTime _lastFPS = DateTime.Now;

  

         public Page()

         {

             _gameLoopTimer = new DispatcherTimer();

             _gameLoopTimer.Interval = TimeSpan.Zero;

             _gameLoopTimer.Tick += new EventHandler(MainGameLoop); 

             _gameLoopTimer.Start();

  

             InitializeComponent();

         }

         void MainGameLoop(object sender, EventArgs e)

         {

             _fps++; 

             if ((DateTime.Now - _lastFPS).Seconds >= 1) 

             { 

                 FPS.Text = _fps.ToString() + " FPS"; 

                 _fps = 0; 

                 _lastFPS = DateTime.Now; 

             }

         }

     }

 }

Page.xaml:

 <UserControl x:Class="SilverlightApplication6.Page"

     xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation" 

     xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml" 

     Width="400" Height="300">

     <Grid x:Name="LayoutRoot" Background="White">

         <TextBlock x:Name="FPS">Current FPS</TextBlock>

     </Grid>

 </UserControl>

Thank you,
--Mike Snow

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