About features

[TomCatFort]

I need to know before choosing a physics engine for my projects that
what features are they have.
I need to know that Physics2D could do these thing or not:
- Making objects non rotatable
- Collision callbacks (to know that the player was hit by a bullet)?
- In collision callbacks can i tell the engine to not collide with
each other. (bullet can go trough the after it hit him)
- Can i set friction coefficients? (Objects slide on ice more than on
a wooden floor)?

[Bobby5808]

Yup it does all that. In fact I think most physics engines will do all
that.

Here are some other things to look for in a physics engine from my
experience:

If you are developing for a platform other than PC make sure you look
for a physics engine that is optimized for that platform. Lots of
physics engines really battle on XBOX because it uses different
numbers or something, but an engine optimised for XBOX runs just fine.
Farseer is an example for XBOX.

If you are going to have small objects moving really fast in respect
to the other objects use an engine that has Continuous Collision
Detection(CCD) so they dont go through each other. BOX2D allows you to
set which objects use CCD, but if you use it on a lot of objects its
really CPU expensive.

Some engines like BOX2D are faster and you don't have to worry about
grid-spacing, but they only support convex shapes. You can get around
this though using convex decomposition, but its up to you to decide
what you're going to need.

Thats about all I can think of, other than that an open source project
is probably better, because you can see everything that is going on
and make any changes you want.

Physics2D has been good for me, the only major problem I have is that
it uses a distance-grid, which has to be recalculated each time I
change a shape.

Anyway I hope I helped, Cheers!

[TomCatFort]

Thank you very much. I checked out BOX2D but it does not have object
in fluid simulation like Physics2D. And I want to add floating
platforms and underwater objects.
My target platforms are Windows and maybe Linux.

[Bobby5808]

Farseer physics has a nice Wave simulator that goes with their Fluid
Simulator that I converted it to Physics2D.Net, I wrote about it
somewhere in these discussions. I dont know much about which physics
engines have fluid simulation, but I do remember reading that someone
made a fluid simulator for BOX2D. It'l be in their forums somewhere, I
can't remember what functionalities it had offhand.