Physics library for top-down racer

[Don Kiddick]

Hi,

I'm thinking of writing a top-down racer in the style of micro-machines. I was thinking of using a physics library to help handle things like drag, & collisions and the like. Is this a good plan?

If so what library? Is Phys2d suitable? I know it is 2D like my game however all the demos seem to assume down the screen is down (as opposed to in my case, into the screen).
Any other libraries worth considering?

D.

[kevglass]

Phys2D is probably not suitable I'm afraid.

Kev

[Orangy Tang]

If you want cartoon-y physics rather than realistic ones then I tend to find that doing things manually produces much better results than just throwing a physics engine at it. You can fine tune the different aspects (like grip, torque, acceleration) independently for best gameplay much easier. Micro machines physics shouldn't be too tricky - fundamentally I think it's just simulating each car as a point, plus some variable friction based on the direction of the car.

To save yourself some work you might want to try using just the collision detection code from a physics library, it looks like you could just use the net.phys2d.raw.collide.* stuff directly but I haven't tried it myself.

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[ewjordan]

I don't know of any 2d physics libraries with decent top down support, esp. in Java - Box2d (and once I port the changes, JBox2d) has this planned for a future release, but it's not going to be in for a while.

BorisTheBrave has a controllers framework with a tensor damping controller (see http://www.box2d.org/forum/viewtopic.php?f=8&t=1567&hilit=controllers), which might be useful for some top down stuff, but I haven't ported it to Java yet, and I'm not sure that it would do everything you need.  I still haven't played with it myself.

I agree with Orangy Tang, though - for a racing game, you probably want to really micromanage the car behavior.  You may be able to do this within a physics engine by applying forces and torques, or you may want to write your own mini-engine for it, but you probably don't want to just rely on the default behavior that someone put into an engine, because tuning that stuff for the desired feel is absolutely critical for your game.

Edit: someone put up a Flash demo of something like this using Box2d, see http://www.box2d.org/forum/viewtopic.php?f=8&t=1547&st=0&sk=t&sd=a&start=0

[Eli Delventhal]

Couldn't you just fake it with Phys2D? Have it drawn top-down but factor the physics as if it's going left to right.

i.e. The more left you are on the track, the higher your Y in Phys2D. The more right you are on the track, the lower your Y. The further up the track you are, the higher your X, and the further back you are, the lower your X. Then just turn off gravity for everything and it should probably work all right.

[gholdys]

I would agree with Orangy Tang and ewjordan - making a custom mini-engine seems to be the best solution at this time. You can use Marco Monster's tutorial as a base. This is what I used, when I was writing a car physics engine quite recently. The tutorial can be a little difficult to find. It has disappeared from its original server. I do have a copy however, so I can e-mail it to you, if you want.

Cheers
Grzegorz