(Desktop) Falling Snowflakes

• Download demo project - 5.13 KB
• Download source - 7.79 KB

Introduction

First of all, I have to say that this isn't my idea, it is more a portation of a C++ example to C# using a different way. If you want to get to the original article, click here. (Thanks to Igor Tolmachev for the nice idea.) I changed the way it works (from multiple dialogs to a single form) and added some new features (e.g. Rotation, Scaling, etc.).

Using the Program

Simply run the executable. To close the program, double click on the tray icon representing a snow flake.

Using the Code

The program itself uses a non-bordered form (which is resized to match screen resolution) with a transparent background color for drawing the snow flakes. Instead of using several forms/dialogs (I hate this idea), I just use one form on which I draw using GDI+.

 public MainForm() {
    InitializeComponent();

    //We paint our control ourself 
    //and need a double buffer to prevent flimmering
    SetStyle(
        ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint |
        ControlStyles.DoubleBuffer, true);

    //Resize and relocate form to match Screen settings
    Location = new Point(Screen.PrimaryScreen.Bounds.X, 
                 Screen.PrimaryScreen.Bounds.Y);
    Width = Screen.PrimaryScreen.Bounds.Width;
    Height = Screen.PrimaryScreen.Bounds.Height;
 }

The snowflakes themselves are saved in a List<SnowFlake>. Snowflake is a container class containing the current Data/Positions of the snowflake (X, Y, Rot, Scale) and the Velocities/Changes (XVel, YVel, RotVel)

The main function is the OnTick method, which is divided into several steps:

1. Increasing the tick count (e.g. Adding snow flakes every tick would be a bit too much)
2. Spawning new flakes (If appropriate conditions are given)
3. Moving all flakes (by adding the velocities to the data values)
4. Deleting flakes which are below the screen/taskbar
5. Rendering the flakes

The flakes are drawn by defining a userpaint method MainForm_Paint and calling Refresh() to cause the form to invalidate itself. Refresh() is required, as it supports double buffers, which MainForm_Paint(CreateGraphics()) would not. In this case, I used the Matrix capabilities of GDI+ to rotate and scale the snowflakes.

 foreach (SnowFlake s in SnowFlakes) {
    g.ResetTransform();
    g.TranslateTransform(-16, -16, MatrixOrder.Append); //Align our flakes to the center
    g.ScaleTransform(s.Scale, s.Scale, MatrixOrder.Append); //Scale them..
    g.RotateTransform(s.Rotation, MatrixOrder.Append); //Rotate them..
    //Move them to their appropriate location    
    g.TranslateTransform(s.X, s.Y, MatrixOrder.Append); 
    g.DrawImage(Snow, 0, 0); //draw them
 }

The snowflake image is drawn by using the GDI+ functions and then cached at a 32x32 pixel size for performance reasons. (GDI+ is slow when you draw lots of lines.)

Customize!

You could get some pretty nice results by just increasing the snow flake spawn count/the velocities. But note that GDI+ is not as fast at it may look and it increases CPU usage (especially when using matrices).

History

• 3^rd October, 2007: Initial post