>
> I use modulo for rowing too and int() instead of Math.floor() as it's
> faster. ;)
Laurent,
is it, really?
I'm not sure. I recently made similar assumptions about what's faster an
what's slower based on what "made sense", only to be proved wrong by some
actual benchmarking.
Anyway, if the variable is typed as an int, my understanding is that you
don't need to use Math.floor or a cast to int, since the decimal part will
be truncated automatically.
Another option to discard decimals is to use bit shifting ( i >> 0), which
some people say it's faster. But in the end, how do you know that under the
hood, the flash player is not doing exactly the same operation for an int
cast, a Math.floor call and a shift zero ?
Cheers
Juan Pablo Califano
2008/5/25, laurent <[EMAIL PROTECTED]>:
>
> Thanks Jesse for the neat explanation, it all make sense, that's a clever
> trick to get a smooth movement of this type where tweening is not a
> solution.
> That can be applied to other things just to get the right value to change.
> Very good to know that enter Frame and Timer are approximations.
> I use modulo for rowing too and int() instead of Math.floor() as it's
> faster. ;)
>
> L
>
> Jesse Graupmann a écrit :
>
>> @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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>>
>>
>
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