Chapter 3.3Macromedia Flash
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Overview
Flash is one of the leading web game development platforms
Flash MX 2004 ActionScript has all the power and strength of most professional (non-web) programming languages
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Advantages of Flash
Wide Audience 98% of web viewers have the Flash player
Rapid Development Self-contained graphic and code
development Easy Deployment
Flash automatically creates web pages
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Advantages of Flash
Fast Learning Curve Programmers and artists alike can learn
Flash ActionScript in very little time Easily Applicable to Designers and
Programmers ActionScript is similar to other ECMA
languages Drawing tools are identical to most other
graphics applications
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How Flash Works
Timeline Based Flash uses a timeline of frames, causing
the game to run at a fixed frame rate
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How Flash Works
Timeline Based Code is placed on frames of the timeline Designers and artists will be more likely to make
use of this timeline to draw and animate character animations, motion graphics, etc
Programmers, on the other hand will tend to place all of their ActionScript on one single frame, and keep their timeline only one frame long
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How Flash Works
Vector Engine The base graphics engine behind Flash is a vector
engine All graphics and shapes are defined in terms of
mathematical shapes like lines, spline curves, vertices, circles and stroke / fill information
Advantage of using a vector engine is that a game can be scaled to any size, and its graphics will continue to look sharp and crisp
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How Flash Works
Vector Engine Shapes can be filled with solid colors, radial
gradients, linear gradients and even a tiled bitmap
The more complex the vector, the slower it will be rendered in Flash, and the more it will be likely to slow down the game performance
Once a shape is defined, it can then be converted into a movie clip
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How Flash Works
Vector Engine Movie Clips are the base item of all game
interaction Movie Clips can be moved, rotated, scaled
and faded (made transparent) with ActionScript code
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How Flash Works
Audio Engine We can easily create sound effects,
music or voice-overs in an audio application, and then import these sounds into Flash
We can create an instance of the Sound object in ActionScript, and then trigger a sound any time we need it
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How Flash Works
Audio Engine Sound can be compressed as raw,
ADPCM or MP3 Music loops can be used to create a
seamless soundtrack
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The Scripting Environment
ActionScript All coding and scripting is done in Flash in
a language known as ActionScript Curly Braces for Code Blocks { } Semicolon for Statement Line Endings; if Logic conditions
if (condition) doSomething(); Loops
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The Scripting Environment
ActionScript Loops. Loops accomplished with standard
for, do or while. for (j = 0; j < 100; j++)
{ do something 100 times;}
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The Scripting Environment
ActionScript Variable Types
Standards Number String Array Boolean
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The Scripting Environment
ActionScript Variable Types
Flash Specific Object MovieClip Color Date Camera Microphone Sound TextField
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The Scripting Environment
ActionScript Classes
In Flash MX 2004, Macromedia introduced ActionScript 2.0
ActionScript 2.0 introduced the ability to create true classes with all of the standard class elements available to other OOP ECMA languages
Created in their own files called class files, with the format “classname.as”
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The Scripting Environment
ActionScript The Draw API
Flash has a series of ActionScript commands that are available to use at runtime called the Draw API
The Draw API allows us to draw shapes and graphics at runtime by using a few routines
moveTo, lineTo, lineStyle, beginFill, endFill
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Integrating Graphics and Code
The Main Timeline This is where we have several movie clips on
the stage, and we place ActionScript on frame one of the main timeline
All movie clips on the stage can be referred to in this frame by simply addressing their instance names
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Integrating Graphics and Code
The Main Timeline code example beachball._alpha = 10;
beachball._rotation = 90;beachball._x = 214;beachball._y = 12;beachball._xscale = 50;beachball._yscale = 50;beachball.onPress = function(){ this._y++;}
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Integrating Graphics and Code
The Main Timeline code example All of this code would apply to the movie clip
beachball It would set the _alpha transparency to 10 percent,
making the beachball almost invisible Then it would set its _rotation to 90 degrees, its _x
position to 214, _y position to 12, and then set its scale to 50 percent by adjusting _xscale and _yscale to 50
Would create an onPress function on the beachball, which would be triggered whenever the user clicked the mouse on the beachball
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Integrating Graphics and Code
The Movie Clip timeline Its also possible to place code on the first
frame of a movie clip itself We can go into its timeline and place code
on any one of its frames, just like the main movie
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Integrating Graphics and Code
The Movie Clip timeline code example this._alpha = 10;
this._rotation = 90;this._x = 214;this._y = 12;this._xscale = 50;this._yscale = 50;this.onPress = function(){ this._y++;}
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Backend and Server Connectivity Other powerful feature of Flash is its ability to
load external files and resources at runtime, from a URL
Can be used to load data from a server through ASP, JSP, PHP or any other scripting language
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Backend and Server Connectivity
loadMovie The design of Flash is so modular that we
can actually load other SWF movies into other SWF movies
The loadMovie method can also be used to load JPEG images at runtime
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Backend and Server Connectivity getURL
We can use the getURL command to open up a link in a browser. For example, we can have a movie clip that displays the text “Click here to open somenewsite.com”
getURL("http://www.somenewsite.com", "_blank");
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Backend and Server Connectivity LoadVars
The loadVars object is an ActionScript object that is capable of sending and receiving data to and from a URL. The URL would normally contain an ASP, JSP or PHP script that we had written.
We can use the loadVars object to send and load variables to and from a backend script. We could use this to load game data like a list of online users, or a list of high-scores.
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Where Flash Struggles
Flash does not have the ability to do serious real-time 3D graphics
Flash also struggles when we have too many things going on at once When we have hundreds of movie clips, all
running their own onEnterFrame code, with user interaction and sound, Flash will have difficulty keeping all of this going, and still maintaining our desired frame rate
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Where Flash Struggles
Flash doesn’t actually compile the ActionScript to a low-level machine language form Instead Flash converts the ActionScript into
codes that are several bytes in size (bytecode), and then parses them at runtime
In essence, a SWF file still contains scripted code, even though it has been compressed
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Where Flash Excels
Physics and Motion Given the x, y grid-based design of the
Flash stage We can apply all sorts of standard physics
concepts to Flash games We can easily do things like translation
(movement), collision, gravity, bounce and friction
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Where Flash Excels
Bitmap-based Tile Games With a few careful tricks, Flash can be
used to recreate all of the bitmap games of the 1980s and early 1990s
Re-creating a Super Mario Brothers type of platform game is relatively easy using bitmap tiles and it will run very, very fast
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Where Flash Excels
“Old School” games We can use Flash to easily recreate all
of the games of the early 1980’s, like Pac Man, Galaga, Asteroids, etc
Popular Puzzle Games Flash excels at puzzle games, like the
ones found online at shockwave.com
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Where Flash Excels
Games for Devices Flash player is available on dozens of
platforms, so we can technically create games that work on all of these platforms
Can create games that play on devices like the Pocket PC, cell phones and watches
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Macromedia Flash:Summary Flash games
Have an instant potential audience of millions Can be rapidly and easily developed Can be deployed easily and quickly
Both programmers and artists can learn flash quickly and easily
Flash moves along based on a timeline that proceeds at a specified frame rate
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Macromedia Flash:Summary Flash is a vector-based graphics engine
Supports lines, fills, gradients and bitmaps Flash has strong support for audio
MP3, ADPCM and RAW compression Flash uses a powerful scripting language called ActionScript to
program the game ActionScript 2.0 has a powerful class structure Graphics and code are integrated into one unit in the Flash IDE The Draw API can be used to create graphics at runtime Flash can communicate with external servers to retrieve files
and data