Create

What good is a holiday animation without some snow? That is what I thought until I tried to create a snow animation that looks reasonably realistic. Most tutorials found throughout the net were either too complicated or not realistic enough. With that said, I decided to try my hand at re-creating falling snow. Hopefully, this tutorial will help you to add a cool snow effect to your animations.

	Quick Update
This version of snow is only for Flash MX. A Flash MX 2004 version can be found here: http://www.kirupa.com/developer/mx2004/snow.htm

The following animation is an example of what caffeine and a thrilling re-run of Charlie Brown's Christmas Special can do:

[ it's snowing....in the small box on your screen ]

You will create something similar to the above animation by following the instructions in this tutorial.

Creating Snow:

1. Create a new movie in Flash MX. Set the width and height to anything you want, and make sure you set the frame rate to 25 for smooth playback. You may want to have a darker colored background for the white snow to be visible.
    
2. Now, it is time to draw a particle of snow. Click the Oval tool (the circle icon) from your toolbox. Select a white color from the color palette. Ensure that the circle does not have an outline. Draw your white colored circle anywhere on your stage:

[ draw a white circle without an outline ]

3. Once you have created your snow particle, select it with your mouse pointer and press F8 (Insert | Convert to Symbol). The Convert to Symbol dialog should appear. Select Movie Clip and press OK.

[ convert the snow particle into a movie clip ]

4. Select the movie clip (which you converted in Step iii). Look down towards your Properties panel. Find the text field that says <Instance Name>. Click in that text field and type the word snow:

[ give the movie clip the instance name snow ]

5. Now, let's add some code to create falling snow. Right click on the movie clip and select Actions.
   
   Copy and paste the following code into your Actions dialog box:

onClipEvent (load) { //specifies the size of the movie stage movieWidth = 300; movieHeight = 200; //variables that will modify the falling snow i = 1+Math.random()*2; k = -Math.PI+Math.random()*Math.PI; //giving each snowflake unique characteristics this._xscale = this._yscale=50+Math.random()*100; this._alpha = 75+Math.random()*100; this._x = -10+Math.random()*movieWidth; this._y = -10+Math.random()*movieHeight; } onClipEvent (enterFrame) { //putting it all together rad += (k/180)*Math.PI; this._x -= Math.cos(rad); this._y += i; if (this._y>=movieHeight) { this._y = -5; } if ((this._x>=movieWidth) || (this._x<=0)) { this._x = -10+Math.random()*movieWidth; this._y = -5; } }
 

6. We are still not done adding actions. Right click on the first frame in your movie and select Actions. You will see another Actions dialog box appear - this time for the first frame.
    
   Copy and paste the following code into the Actions dialog box:

for (k=0; k<50; k++) { duplicateMovieClip(this.snow, "snow"+k, k); }
 

7. You are almost done with this tutorial. The remaining sections involve customizing the animation and understanding why the animation works the way it does.

Customizing the Animation
Since the crux of this animation involves ActionScript, you will have to modify some code to customize the animation:

• Adjusting the Range: Width and Height
  Right click on the movie clip and select Actions. Find the commented line that says "specifies the size of the movie stage". Change the values for movieWidth  and movieHeight from 300 x 200 to the width and height of your current movie.
   

• Adjusting number of Snowflakes Displayed
  Right click on the frame you added actions to. Select Actions from the menu that appears. Find the line that says k<50 and change the number 50 to represent the number of snow particles you want displayed at any time.
   
  The larger the number you use instead of 50, the slower the animation will seem to users with slower computers. This animation is fairly CPU intensive, so try to be kind and virtuous by keeping in mind that not all users will be able to see the animation in all its coolness when 300 snow particles are displayed at the same time. It is the Christmas season after all!

You are finished with this tutorial. I highly recommend that you go to the next page and find out how/why the code works the way it does. Not only will you find what each line of code does, you may get a better feel of ActionScript programming so you can create cool effects on your own.

Next Page: Code Explanation