@Laurent
So modulus is great and slow from what I've read. I tend to use it in row/
column calculation rather than wrapping a MovieClip position.
var num:int = 6;
var cols:int = 3;
for ( var i:int = 0; i < num; i++ ) {
var row:int = Math.floor( i / cols );
var col:int = i % cols;
trace ( "i: " + i + "\trow:" + row + "\tcol:" + col );
}
i: 0 row:0 col:0
i: 1 row:0 col:1
i: 2 row:0 col:2
i: 3 row:1 col:0
i: 4 row:1 col:1
i: 5 row:1 col:2
In the previous post I'm moving a MovieClip to the right X.X pixels and
when
its position is off the screen I reset it back to 0. If I used the modulus
method, the movement would always be rounded numbers and appear jerkier
than
this experiment requires. I'm actually hoping to round to the nearest
twip.
As for the examples themselves....
#1
onT is a timer tick. So about every 30ms it will move the MovieClip X
pixels
based on speed. Because Timers are never accurate to what you expect (
they
only get as close as they can - see below ) onT will always be dragging
behind the other two methods and moving at varied speeds.
// Elapsed time from a tick on var t:Timer = new Timer(30);
47,38,36,36,36,36,36,38,36,35,35,36,36,34,36,42,36,35,35,36,35,37,40,36,36,3
6,36,36,54,36,37,35,34,36,38,38,36,36,36,36,69,39,35,36,35,36,36,42,44,36,36
,35,36,35,63,37,33,36,35,37,40,30,35,34,36,92,55,66,35,36,34,36,46,36,36,36,
36,97,50,34,35,35,36,36,34,33,218,142,49,121,59,110,84,102,65,106,66,58,55,6
5,34,36,35,36,64,33,35,36,35,37,31,48,34,36,35,35,36,77,34,34,36,36,36,70,36
,35,37,35,37,74,54,35,36,71,65,35,36,36,35,35,73,37,36,36,34,43,66,35,38,36,
35,34,73,36,34,50,59,67,37,36,36,36,56,47,37,36,36,34,36,30,46,35,36,36,36,5
9,46,35,36,36,36,59,45,35,36,36,34,36,32,48,37,37,35,38,56,48,34,36,36,36,58
,47,34,37,36,36,57,72,45,36,50,55,45,35,35,35,36,61,45,36,35,35,36,66,45,131
,39,45,33,37,34,37,34,45,51,36,51,49,38,67,35,36,36,34,43,47,38,50,35,34
// Difference from expected 30ms
17,8,6,6,6,6,6,8,6,5,5,6,6,4,6,12,6,5,5,6,5,7,10,6,6,6,6,6,24,6,7,5,4,6,8,8,
6,6,6,6,39,9,5,6,5,6,6,12,14,6,6,5,6,5,33,7,3,6,5,7,10,0,5,4,6,62,25,36,5,6,
4,6,16,6,6,6,6,67,20,4,5,5,6,6,4,3,188,112,19,91,29,80,54,72,35,76,36,28,25,
35,4,6,5,6,34,3,5,6,5,7,1,18,4,6,5,5,6,47,4,4,6,6,6,40,6,5,7,5,7,44,24,5,6,4
1,35,5,6,6,5,5,43,7,6,6,4,13,36,5,8,6,5,4,43,6,4,20,29,37,7,6,6,6,26,17,7,6,
6,4,6,0,16,5,6,6,6,29,16,5,6,6,6,29,15,5,6,6,4,6,2,18,7,7,5,8,26,18,4,6,6,6,
28,17,4,7,6,6,27,42,15,6,20,25,15,5,5,5,6,31,15,6,5,5,6,36,15,101,9,15,3,7,4
,7,4,15,21,6,21,19,8,37,5,6,6,4,13,17,8,20,5,4
#2
onT2 - To compensate for the difference, I decide that for every 30ms that
have passed the MovieClip should increment the correct amount ( 1 pixel ).
When the tick occurs, I subtract the stored time (lastTick2) from the
current time giving me the most accurate elapsed time. Dividing by the
tick
time gives me a percentage of my expected elapsed time. Multiplying that
value by the speed produces the most accurate change over time.
#3
onT3 - Because I can assume speed based on elapsed time is the most
accurate, it won't matter when I call the function as long as it happens
once per frame. So onT3 just uses the ENTER_FRAME event to calculate speed
based on elapsed time using lastTick3.
Here is another example that is commented a bit better and should make all
this very apparent.
stage.align = "TL";
stage.scaleMode = "noScale";
stage.addEventListener ( Event.ENTER_FRAME, onFrame );
// for every (stepTime)ms move (stepRate)pixels
var stepTime:int = 30; var stepRate:int = 1;
var time:int = getTimer();
function onFrame ( e:Event ):void {
// time since last frame
var elapsedTime:int = getTimer() - time;
// store current time for the next check
time = getTimer();
// percentage of expected time
var timePercentage:Number = elapsedTime / stepTime;
// rate compensation
var movement:Number = timePercentage * stepRate;
// move mc
mc.x += movement;
// wrap if off the stage
if ( mc.x > stage.stageWidth ) mc.x = 0;
}
Hasta!
Jesse
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of laurent
Sent: Saturday, May 24, 2008 2:13 AM
To: Flash Coders List
Subject: Re: [Flashcoders] Tweening text more smoothly - AS3
:) I just read about wraping using modulus on Grant Skinner's blog:
sprite.x = (sprite.x + 5) % stage.stageWidth;
And then get where was that checkWrap methods :]
Still I'm interested in the onT methods...I don't think I will get them
before Grant's next post.
the article about using modulus:
http://www.gskinner.com/blog/archives/2008/05/core_as3_modulu.html
L
Jesse Graupmann a écrit :
Maybe converting the actual time elapsed to a constant rate of motion
could
help... who knows?
stage.align = "TL";
stage.scaleMode = "noScale";
function checkWrap ( o:DisplayObject ):void
{
if ( o.x > stage.stageWidth ) o.x = 0;
}
var speed:Number = 1;
var tick:Number = 30;
var lastTick2:Number = getTimer();
var lastTick3:Number = getTimer();
var t:Timer = new Timer(tick);
var t2:Timer = new Timer(tick);
t.addEventListener( TimerEvent.TIMER, onT );
t2.addEventListener( TimerEvent.TIMER, onT2 );
stage.addEventListener( Event.ENTER_FRAME, onT3 );
t.start();
t2.start();
function onT( e:TimerEvent ):void
{
// timer
mc.x += speed;
checkWrap ( mc );
}
function onT2( e:TimerEvent ):void
{
// timer + speed
mc2.x += (( getTimer() - lastTick2 ) / tick ) * speed;
lastTick2 = getTimer();
checkWrap ( mc2 );
}
function onT3( e:Event ):void
{
// enter frame + speed
mc3.x += (( getTimer() - lastTick3 ) / tick ) * speed;
lastTick3 = getTimer();
checkWrap ( mc3 );
}
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