A fast, easy to use, free, and community supported 2D game engine
indy2005
Member
Hi,
Is it possible to give multiple fixtures different positions within a single Box2D body?
I want to make an approximate egg by overlapping 4 or 5 smaller smaller circles (don't laugh) and don't want to use joints as joints can sometimes get distorted.
Regards
i
When you create the circle shape, I believe you can specify it's x and y position... If that doesn't work, I think fixtures also have a "localPoint" that's there position. Either why, what you're asking to do is definitely possible, although there might be a better way to make an egg shape.
indy2005
Member
Hi,
Thanks. Having just looked up egg algorithms...(don't laugh)...it's seems pretty complex (is anything in game development simple)..
I am creating multiple circles with offsets now (I think), but they are overlapping. Is it OK for fixtures to overlap in one body (with our without a collision group being set). I ask because my contact array which stores 128 contact points is now breaching an assertion....and I don't know why (its only 7 circles).
Regards
i
indy2005
Member
just had a chuckle to myself. I wasn't scaling my eggs by the physics ratio, and so was creating godzilla sized eggs which were swallowing every body in the level...hence my contact issue....
How I laughed. I tried to share the joke with my wife but she doesn't get it.
Regards
i
indy2005
Member
...I have something egg like....I am a proud parent. The physics question is therefore how to make it stand up right when at rest...it just lies on its side. I have made the bottom most circle very dense, but that doesn't prevent the top circles from making the egg rest on its side.
I knew I should have studied egg physics at school.
Your approach sounds fine to me (using 2 fixtures). I have something similar, but not an egg (!).
If the eggs just have to stand upright at the start, make sure they're sleeping and upright when created.
Another way would be to add a tiny box fixture at the base, which it can balance on but wouldnt mess much with the physics when its moving around normally?? Anyway, I still would've expected your solution to work, esp if the larger circle is heavier.
Edit - I imagine egg physics in a game would be pretty cool :)
indy2005
Member
Hi,
I created a small, very dense fixture which sits inside and at the base (but just off the base)...I now have the behaviour I want. My issue was around where I was fixing the centre of mass using multiple fixtures. It corrects itself on a flat surface, and rocks gently backwards and forwards....just attached an egg sprite!
Now just need a game idea ;-)
Regards
i
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