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AppGameKit Classic Chat / fastest way to calculate distance in 2d ?

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haliop
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Posted: 26th Jul 2013 20:40
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i think i rad somewhere that
sqrt((x1-x2) * (y1-y2) is kinda slow is there a faster way then that?



http://forum.thegamecreators.com/?m=forum_view&t=198467&b=22
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kamac
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Posted: 26th Jul 2013 21:09
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I don't think there is any other method than that.

Also, "kinda slow" - unless you're going to have lots of such checks, it doesn't really matter.

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haliop
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Posted: 26th Jul 2013 21:21
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i have about from 100 to 500 per cycle..



http://forum.thegamecreators.com/?m=forum_view&t=198467&b=22
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Matty H
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Posted: 26th Jul 2013 21:21 Edited at: 26th Jul 2013 21:21
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If you are comparing two distances you can leave out the square root and the result will be equivalent.

If you already have the distance of one then square that one before you compare to the other.

Other than that you can look at some fast square root algorithms which lose accuracy but may be fine for your needs.

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Marl
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Posted: 26th Jul 2013 21:22
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Quote: "sqrt((x1-x2) * (y1-y2)"

Don't you mean

sqrt( (x1-x2)^2 + (y1-y2)^2 ) ?

Anyway, it's not really a question of if there is a faster way, it's a question of do I need it ?

for movement between two points, you can often work with X and Y without needing to combine them - if you wanted a bullet to hit an enemy, you could just set the vx and vy of the bullet, based on the ratio of (x1-x2) to (y1-y2).

So if the enemy was +100, -500 distance, a speed of +1,-5 would be going the right way to hit it, without needing the extra maths.
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Markus
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Posted: 26th Jul 2013 21:33
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what are you doing with this distances?
maybe there exists a other solution.
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haliop
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Posted: 26th Jul 2013 22:35
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ok got it .. this was kinda stupid never even had to used it , i use it for "line sprites" and i didnt even had to use it since i already have a var for Length... so .. that was just me not noticing and trying to overcome an obstacle which wasnt even there..

thank you for your awesome quick respones.

so now instead of using the calculation i just use a value.... idiotic me..



http://forum.thegamecreators.com/?m=forum_view&t=198467&b=22
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baxslash
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Posted: 27th Jul 2013 11:31
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I always do it this way as I was told that using powers is slower than multiplication:

Although I haven't actually checked it for speed I haven't had to use it more than a hundred times per loop...


this.mess = abs(sin(times#))
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