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Thread: random rotation AS2

  1. #1
    Game Player - Developer scheletro's Avatar
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    random rotation AS2

    HI

    Im making a Jigsaw puzzle, I want that every time the game loads the pieces rotate to a random position, but no a range of rotation, I mean, I know how to do that

    Code:
    onClipEvent (load) {
    	this._rotation=random(360)+1; 
    }
    I want my pieces to random select between 4 possible rotations, 0, 90, 180, 270, so the player can rotate the pieces to put them in the right place

    Is the an easy way to do that?


    "I love to make them as I love to play them"

  2. #2
    Senior Member bluemagica's Avatar
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    _rotation = 360 / Math.ceil(Math.random()*4);
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  3. #3
    Funkalicious TOdorus's Avatar
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    Quote Originally Posted by bluemagica View Post
    _rotation = 360 / Math.ceil(Math.random()*4);
    Nice trick blue,; I've got to remember that one. Let's see if I can get that division out of there.

    _rotation = Math.ceil(Math.random()*4) * 360 * .25

  4. #4
    Pumpkin Carving 2008 ImprisonedPride's Avatar
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    Just to be picky, I took a few minutes to read up on random optimization. Truth be told, Math.Random is horridly slow. Not sure it gets much faster than this:

    Code:
    const MAX_RATIO:Number = 1 / uint.MAX_VALUE;
    var r:uint = Math.random() * uint.MAX_VALUE;
    
    function XORandom():Number{
    	r ^= (r << 21);
    	r ^= (r >>> 35);
    	r ^= (r << 4);
    	return (r * MAX_RATIO);
    }
    
    _rotation = int(XORandom()*4) * 90;
    This also stays true to Scheletro's original question of 0,90,180,270 instead of 90,180,270,360, though there's no difference, really. Long live bitwise!

    EDIT: Over one million iterations, calls to XORandom are over 75% faster than calls directly to Math.Random().
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  5. #5
    Pumpkin Carving 2008 ImprisonedPride's Avatar
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    Hmm... just thought about this... Swapping the MAX_VALUE for 4 / uint.MAX_VALUE allows you to completely remove the multiplication by 4 from the call line:

    Code:
    const MAX_RATIO:Number = 4 / uint.MAX_VALUE;
    var r:uint = Math.random() * uint.MAX_VALUE;
    
    function XORandom():Number{
    	r ^= (r << 21);
    	r ^= (r >>> 35);
    	r ^= (r << 4);
    	return (r * MAX_RATIO);
    }
    
    _rotation = int(XORandom()) * 90;
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  6. #6
    Game Player - Developer scheletro's Avatar
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    hi guys, thanks for the help, but I find more issues

    Bluemagica - Some times the pieces appear in an intermediate position like 135, strange

    ImprisionedPride - I have some syntax errors, lol, I dont quite understand your code to fix it


    "I love to make them as I love to play them"

  7. #7
    Senior Member bluemagica's Avatar
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    weird, that shouldn't happen! Try tracing out all the values....

    or you might wanna try
    Code:
    _rotation = (90*Math.floor(Math.random()*4)); //should give 0,90,180,270
    trace your rotation right before and after that step, something else in your code might be modifying the rotation.


    As for IP's code, that is a optimised code for doing randoms, and there shouldn't really be syntax errors, you should give some info about the error. I have been doing bitwise stuff to optimise my own game too, so i kind of understand what is going on there, but you better lay off that unless you really need it. Bitwise operations can really help optimise a lot of stuff, but understanding them can be a pain. It's better to just remember these as snippets, like for example
    Code:
    var i:int = 10;
    i = -i; //-10, normal slow process
    Or
    i = (i ^ -1) + 1;// -10.  about 300% faster than previous one
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  8. #8
    Pumpkin Carving 2008 ImprisonedPride's Avatar
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    You shouldn't any errors even though my code was written for AS3. It's also worth noting that my previous posts' numbers were from the FP10 and AS3; I'm not sure how much overhead you save instead of Math.random() in AS2.
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