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I have read several posts stating what seems like a "standard" in how to chose your 2d axises in a 3d engine. It is often Y up on screen and X right on screen. However, in these examples I often see that it's a scene set up like a platformer, where the player sees the world from the side.

I'm developing a top down 2.5D (locking depth axis but keeping perspective on camera) game and I have it setup so that Z is up on the screen and X is right on the screen. To me it makes sense as Y is height in the world and thus would approach the camera. I will make use of the 3d world at certain times and I feel that it would be confusing to not have the standard axises then...

Is there something I'm not thinking about here?

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  • \$\begingroup\$ Typically in 2.5D games I've done I've kept Z consistently at 0, and have it essentially control depth. For the Player object I have Z position frozen, and X/Y rotation frozen. However keep in mind in my 2.5D games, they are side scrollers. Since yours is top down, the freeze constraints would change. However the coordinate system like Sean answered below is relative to you! For clarity sake, you may want to adhere to some standard. \$\endgroup\$ – Apollo SOFTWARE Jul 17 '13 at 14:17
  • \$\begingroup\$ Yes, that's why I asked, to see if there's any general standard I could adhere to. In context of my development though, the coordinate system I mentioned in my question (Z up on screen, X right on screen) is enforced. \$\endgroup\$ – Phil Jul 17 '13 at 14:21
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No. You can choose whichever coordinate system you want. The only thing to maybe consider is what coordinate systems your tools and models are in; converting is no biggie but there's only headaches to be found in being too different.

There's a lot of opinion about coordinate. I've been witness to some rather heated debates about whether it makes "more sense" to use a left-handed coordinate system or a right-handed one, for instance. In the end, it just doesn't matter.

If the coordinate system makes sense to you and your content folks, you are good.

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  • \$\begingroup\$ the reason I'm asking is that some of my sprites got flipped because of settings. So yeah, as long as we control and conquer the pipeline it shouldn't be a technical problem. Thanks \$\endgroup\$ – Phil Jul 17 '13 at 7:41
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I would consider using the standard axis (which I believe are (x y) for a 2d plateformer and (x z) for a top-down view).

  • It will be easier after to associate the Vector3 (up, forward, left) to their respective axis.
  • It will also prevent you from having trouble with built in functionalities like gravity or particle effects
  • and any asset you make for this game will be easily reusable in any other kind of game.

It sure can take some time to get used that your playground is defined by x and z axis, but I guaranty you will save time in the end.

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