Top Down Shooter: Unity 2d vs Unity 3d

I'm trying out Unity 2D for the first time. My main interest in using it is for the pathfinding, obstacle avoidance, etc. I was looking around for tutorials on creating nav meshes for pathfinding, and came across this forum post:

http://forum.unity3d.com/threads/can-2d-games-use-the-navigation-mesh.211506/

Quoting the post:

> It seems that the navigation mesh is bound to the x-z axis while the new 2d physics and rendering is performed on the x-y axis. Are they completely incompatible?

It seems that Unity 2D can't use nav meshes? That post linked to this request:

http://feedback.unity3d.com/suggestions/make-2d-work-with-navmesh-and-terrain

So:

1. What's the difference between Unity 3D and Unity 2D when creating a top-down shooter?
2. Can I just as easily make my game from scratch in 3D?
3. What are the things that I'd have to account for that I wouldn't have to when using Unity2D?
4. Should I consider XZ the "ground", or XY? Does it actually matter (for things like pathfinding, physics, etc.)?

 

There's no actual "Unity 2D" as such. The 2D physics engine is on the X/Y plane only, so no, it won't work with the built-in navmesh feature, but everything else in Unity is 3D. (Including sprites...you can rotate them so they're aligned with the X/Z plane if you want.) There's nothing that says you're forced to use the built-in navmesh, though, but there's nothing that says you can't use 3D physics with sprites, either.

--Eric

 

Thanks for your reply, Eric.

I'd really like to stick with Unity's built-in features, so it sounds as if I'll be using 3D. My edit was quite recent, but do you know about my fourth question?

 

"Ground" has to be X/Z if you're using navmesh or the terrain, and as mentioned Box2D physics is X/Y only, but other than that it's arbitrary.

--Eric

 

Thanks!