cocos2d/box2d iPhone - 随机圆形路径

Question

I am experimenting with some new ideas in Cocos2D/Box2D on iPhone.

I want to animate a small swarm of fireflies moving on circular (random?) paths... the idea is that the user can capture a firefly with a net..

I have considered using gravity simulations for this but I believe it is over complicating things... my previous experience with using Bezier curves tells me that this isn't the solution either..

Does anyone have any bright insights for me?

Thanks so much.

Answer 1

Do you need the fireflies to collide with each other?

I ask, as if this isn't a requirement, Box2D is probably overkill for your needs. Cocos2d is an excellent choice for this by the sounds of it, but I think you'd be better off looking into flocking algorithms like boids

Even that may be overly complicated. Mix a few sin and cosine terms together with some random scaling factors will likely be enough.

You could have one sin/cosine combination forming an ellipse nearly the size of the screen:

x = halfScreenWidth + cos (t) * halfScreenWidth * randomFactor;
y = halfScreenHeight + sin (t) * halfScreenHeight * randomFactor;

where randomFactor would be something in the realm of 0.6 to 0.9

This will give you broad elliptical motion around the screen, then you could add a smaller sin/cos factor to make them swirl around the point on that ellipse.

By multiplying your time delta (t) by different values (negative and positive) the path of the curve will move in a less geometric way. For example, if you use

x = halfScreenWidth + cos (2*t) * halfScreenWidth * randomFactor;

the ellipse will turn into a figure 8. (i think!)

Hope this helps get you started. Good luck.

Answer 2

One place to look for ideas would be in the domain of artificial life. They have been simulating swarms of entities for a long time. Here is a link for some simple swarm code written in Java that should give you some ideas.

http://www.aridolan.com/ofiles/Download.aspx