Collision Bounce... « cocos2d for iPhone

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Collision Bounce...

(9 posts) (5 voices)

Started 2 years ago by natanavra
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natanavra
Member

Hello,
First off, I'm not using any physics engine as I can't really find tutorials or docs on how to use the ported version.
I have 2 balls, one smaller, one bigger, both are moving in opposite directions (not 180 degrees between vectors) and are bound to collide. Both balls have different velocity values, I have both vectors in CGPoint types, and I know how to find collision between two circles.
The question is how do I find the bounce angle? multiplying velocities by -1.0 won't really work as it won't be realistic at all...
I'm guessing there should be some sort of a vector subtraction but I don't really know how should it work...
An example for a really good collision physics between two balls can be found in this flash game:

http://armorgames.com/play/349/red

Thank in advance for all replies...

Posted 2 years ago #
Cypher
Member

The latest version of Cocos2d includes the Chipmunk and Box2d tests that show a few of the physics with these engines. You could take a look at the source code and adapt the collision used there to your own application.

Posted 2 years ago #
natanavra
Member

Hmm.. You mean by seeing the physics code, the collision code - without using the engine itself?
It's just a bit tough to orientate in this "messy" code... Thanks!

Posted 2 years ago #
coolman
Member

Hi,

Give a lok to Alexandre Gomes tutorial is well done:

http://www.alexandre-gomes.com/articles/chipmunk

Posted 2 years ago #
sunsu
Member

I don't think he means "by seeing the physics code". There are some example demos included in the "tests" folder of Cocos2d-iPhone that show you how to use Chipmunk and Box2d. These were very helpful to me when I first got oriented with Chipmunk. The Chipmunk forums are also a great resource.

-Sunsu

Posted 2 years ago #
natanavra
Member

I was think I shouldn't really mess alot with chipmunk for now, as I have seen the implementation and there are quite a few things I don't know and understand, so I was thinking implementing my own collision and bounce code... As the game is quite simple and that's basically the only collision,bounce calculation done.

Posted 2 years ago #
natanavra
Member

BUMP, been searching the net for a while now and found quite a few things about two circle collision bounce.
I made a hard sketch and started calculating the vectors, from my point of 'physics' although I'm not too god at it.
At collision time I should take the vectors' x and y values and subtract accordingly, If I find the angle between the axis and the vector it would be something like this, when the starting point of the axis would be the big balls center:

meaning if I take the angle between the vector a (small ball) and the y axis. The y value of the vector would be the vectors' length multiplied by cos and the angle, subtracting that from the y value of vector b (big ball).

b*cosA - a*cosB = the y value of the new vector. //A and B are the angles...

Such a mess... I'm kinda confused but I think this should be correct...
Opinions?? Help?!!

Posted 2 years ago #
Codemattic
Moderator

This looks interesting - with code examples:

http://www.gamasutra.com/features/20020118/vandenhuevel_01.htm

Posted 2 years ago #
natanavra
Member

Yeah, I read the tutorial on gamasutra, gonna try again, I missed the collision bounce part - how unfocused am I?
Implementing mass... should I just add it as an object property most likely an integer value?
This will require some trial and error to see what masses fit.. no?

EDIT: Check the flash game I mentioned in the first post, the game has perfect circle to circle collision and bounce physics, at least in my opinion the collision bounce was well made and that's what I'm looking for.

Posted 2 years ago #

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