Benoit Freslon's blog - Game Design, Flash games, ActionScript tutorials ... » ActionScript3 as3

ActionScript: Move an object with keyboard with camera relative control

admin — Tue, 04 Jan 2011 16:22:25 +0000

In this tip I will show you how to move an object with keyboard with camera relative control.

What is a camera relative control?

The direction of your object will be calculated depending the camera position. (Mario 64, Uncharted, GTA 3, etc.).
Eg: If press the right button the character will go on the right.

How to make a camera relative control?

Get the arrow key status (key is up/key is down)
Set the direction vector
Move the object on enter frame with the direction vector

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70

// Assign 4 booleans for the 4 arrow keys
var keyUp = false;
var keyDown = false;
var keyLeft = false;
var keyRight = false;

// Add the keyboard event (KEY_DOWN) on the stage
stage.addEventListener(KeyboardEvent.KEY_DOWN, pressKey);
function pressKey(pEvent) {
// If an arrow key is down, switch the value to true to the assigned variable
if (pEvent.keyCode == 38) {
keyUp = true;
} else if (pEvent.keyCode == 40) {
keyDown = true;
} else if (pEvent.keyCode == 37) {
keyLeft = true;
} else if (pEvent.keyCode == 39) {
keyRight = true;
}
}
// Add the keyboard event (KEY_UP) on the stage
stage.addEventListener(KeyboardEvent.KEY_UP, releaseKey);
function releaseKey(pEvent) {
// If the arrow key is up, switch the value to false to the assigned variable
if (pEvent.keyCode == 38) {
keyUp = false;
} else if (pEvent.keyCode == 40) {
keyDown = false;
} else if (pEvent.keyCode == 37) {
keyLeft = false;
} else if (pEvent.keyCode == 39) {
keyRight = false;
}
}

// Set the velocity of the object
var speed = 6;

// Add an enter frame event on the moving object
myCircle.addEventListener(Event.ENTER_FRAME, circleEnterFrame);
function circleEnterFrame(pEvent) {
// Create a 2D vector in order to get the object direction according the arrow keys
var vector = new Point(0,0);
if (keyUp) {
// If keyUp is true add the -1 value on the y axis
vector.y += -1;
}
if (keyDown) {
// If keyDown is true add the 1 value on the y axis
vector.y += 1;
}
if (keyLeft) {
// If keyLeft is true add the -1 value on the x axis
vector.x += -1;
}
if (keyRight) {
// If keyRight is true add the 1 value on the x axis
vector.x += 1;
}

// Get the radian angle of the direction
var angle = Math.atan2(vector.y,vector.x);

// If vector lenght is not null
if (vector.length > 0) {
// Move the object with the angle and the object speed
pEvent.currentTarget.x += Math.cos(angle) * speed;
pEvent.currentTarget.y += Math.sin(angle) * speed;
}
}

Donwload source: www.benoitfreslon.com-Move-an-objet-with-keyboard-with-camera-relative-control.zip

ActionScript: Move an object to coordinates with smoothing

admin — Mon, 03 Jan 2011 15:53:50 +0000

There is a simple formula to move an object to coordinates with smoothing.
The speed will decrease with smooth during the time.

speed = distance_between_objects / smoothing

The distance will decrease because the distance will decrease too.

If I set values I got:

object.x = 50
targetX = 100

speedX = (targetX – object.x) / 5

On the first frame: speed = 10
object.x += (100 – 50) /5 > 50/5 > 10
> object.x = 50+10 = 60

On the second frame: speed = 8
object.x += (100 – 60) /5 > 40/5 = 8
> object.x = 60 + 8 = 68

On the third frame: speed = 6,4
object.x += (100 – 68) / 5 > 32/5 = 6,4
> object.x = 68 + 6,4 = 74,4

etc.

On the 100th frame: speed = 0
object.x += (100 – 100) / 5 > 0 /5 = 0
> object.x = 100 + 0 = 100

Source:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

// Add a mouse event on the stage
stage.addEventListener(MouseEvent.CLICK, click);
function click(pEvent) {
// On click set the new x and y coordinates
myBall.targetX = stage.mouseX;
myBall.targetY = stage.mouseY;
}

// Set default coordinates
myBall.targetX = 200;
myBall.targetY = 200;

// Add an enter frame event on the ball
myBall.addEventListener(Event.ENTER_FRAME, ballEnterFrame);
function ballEnterFrame(pEvent) {
// On enter frame move the ball to the target coordinates
var b = pEvent.currentTarget;
b.x += (b.targetX - b.x) / 8;
b.y += (b.targetY - b.y) / 8;
}

Exemple:

Download source: www.benoitfreslon.com Move an object to coordinates with smoothing.zip

ActionScript: Launch a function after a delay with setTimeout

admin — Mon, 03 Jan 2011 14:35:38 +0000

There are different ways to launch a function after a delay:

With the enter frame event;
With the Timer class;
With a motion tween;
With the enter frame event and the getTimer() method;
And with the setTimeout function (See setTimeout help on Adobe);

How to master the setTimeout ?

First of all you must create a variable assigned to the setTimeout identifier;

1	var intervalIndentifier

The setTimeout function returns an identifier (uint) when you call this function. Save this identifier into the assigned variable;

1
2
3
4
5

// The hello function will be launched in 2000 ms
intervalIdentifier = setTimeout(hello, 2000)
function hello() {
trace("function launched")
}

This identifier must be clear with the clearTimeout function in order to stop the setTimeout;

1	clearTimeout(intervalIdentifier)

NB:

If you want to launch a setInterval already launched don’t forget to clear the previous setInterval. In witch case the previous setInterval won’t be stopped;
The setTimeout function can’t be paused or resumed;
Assign one variable by one setTimout;
The setTimeout function is based on clock time not on frames time;
When you clear the setTimeout the closure function is not launched;
You don’t have to clear the setTimeout when the setTimeout is already finished;

Add parameters

The setTimeout function can receive one or several arguments. Those arguments are passed to the closure function.
To add arguments just add your arguments after the second parameter into the setTimeout function:
Obviously your closure function must have the same number of arguments.

1
2
3
4

intervalIdentifier = setTimeout(hello, 2000, "world", "www.benoitfreslon.com")
function hello(arg1, arg2) {
trace(arg1, arg2)
}

Exemple:

Download source: www.benoitfreslon.com Launch a function after a delay with setTimeout.zip

Flash CS5 builds Iphone applications

admin — Tue, 06 Oct 2009 09:58:45 +0000

Flash Professional CS5 will enable you to build applications for iPhone and iPod touch using ActionScript 3. These applications can be delivered to iPhone and iPod touch users through the Apple App Store.*

A public beta of Flash Professional CS5 with prerelease support for building applications for iPhone is planned for later this year. Sign up to be notified when the beta starts.

At MAX 2009, Adobe showed a number of applications and games for iPhone that have been built using a prerelease version of Flash Professional CS5. These applications are available now for you to download from the Apple App Store.

Go to the official article on labs.adobe.com: http://labs.adobe.com/technologies/flashcs5/appsfor_iphone/#divider

New game, new gameplay, Roll and Jump

admin — Thu, 03 Sep 2009 16:47:54 +0000

Roll and Jump is a skill game where the goal is to climb as high as possible by jumping from a rolling circle to another.

Clim and do the highest score as possible.
You can do a wall jump, a double jump or activate slow motion!

The game will be released in few days on the web i hope to bring it on iphone as soon as possible.