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Circle Wall
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05-28-2002 17:27

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I have the player and all the enemies duking out inside a circle, and I want to have collision detection for that circle and I think its better to use maths then to use pixel detection.
Could anyone help me?
Oh, and if you need a better explination, just say it.

05-28-2002 17:38

Posted by:
John Treece-Birch

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If you know the position of the centre of the circle and it's radius, then you can work out if something is inside it or not.

x = horizontal distance from the centre of the circle
y = vertical distance from the centre of the circle

if (radius*radius)<(x*x)+(y*y) then it is outside the circle.

Hope this helps,

05-28-2002 19:48

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Ok, thanks.
It works, now anyway...

07-07-2002 14:51

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Mr. Me

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I used this in my game but I want the player to be able to... hmm wait. Lets say that the player goes to the left side of the circle and then pushes down, then I want the player to go down but inside the circle. Understand?
Could anyone help?

08-01-2002 13:08

Posted by:
Mr. Me

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Please, I really need this for my game and I cant get it to work...

08-01-2002 20:07

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Well, I don't know the scpecific math involved off hand, but... What you'll want to do is, instead of not allowing the player to move past the circle, you'll want to bring the player back towards the center of the circle if he leaves the circle instead. What I mean by this is:
If the player leaves the circle, pull him back toward the center of the circle just enough for him to be back inside the circle.. The effect thi swill have is that if you hit, say, the rigth edge of the circle and press down, the player will start moving downward 'on screen' but seem to stick to the edge of the circle while doing so.. well, until he gets to the bottom where he'll simply stay.

08-02-2002 14:47

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Danlab games

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You can use an hidden canvas (canvas 1) with the circle draw on it, and use a pixel color detection...

see ya

08-02-2002 17:46

Posted by:
Mr. ME!

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I tried that, and it was slower then math I could only make it get stuck, not that you could "grind" the wall so to say...

08-08-2002 19:39

Posted by:
James Rhodes

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re: game physics

For those that are interested, there is a new book from O'Reilly called "Physics for Game Developers". Had a look at it and it is pretty good. Buying a copy soon...

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