Specifically for a platformer. For reference, I've been inspired mainly by games such as "Kirby's Return to Dreamland" and the "New Super Mario Bros" series, where everything is rendered in 3D but the game plays on a 2D plane. While you do have your "true 3D" engines such as Unity, and the 2D dedicated like LÖVE, I haven't really found one specialised for handling this sort of game, can anyone give me any recommendations? If there aren't really any good picks that are specialised towards this 2.5D design, are there any 3D engines I could achieve this effect with and how would I go about doing it?

Thanks in advance for any responses.

Trivial, just position the camera correctly, and the 3D renderer will do the rest. Don't remember the angles exactly, but wikipedia does: https://en.wikipedia.org/wiki/Isometric_graphics_in_video_games_and_pixel_art

Like Alberth says, you can just use a normal 3D engine and position the camera where you want it.

You might also want to make the camera orthographic, which disables perspective. In Unity3D, this is just a setting on the camera component.

"2.5D" definition shouldn't even exist if you ask me, it confuses begginners and is useless to professionals (I would guess)  

A better name can be found I thinkm like "3D Side Scroller"

8 hours ago, MarcusAseth said:

"2.5D" definition shouldn't even exist if you ask me, it confuses begginners and is useless to professionals (I would guess)

It serves nicely as a unique name for a way to show the world, and as such, is a term to express you mean such a view.

It is not different from having names like the Visitor Pattern, which expresses a way to walk over a tree. Name works much better than having to draw several classes with arrows between them.

8 hours ago, MarcusAseth said:

A better name can be found I thinkm like "3D Side Scroller"

Hmm, but it's not actually a side-ways view. It's a sort-of 45 degrees view. Another common name is Isometric view, although that is technically also not entirely correct, since that covers all forms of such views, while 2.5D implies one very specific form.

Besides, "3D side scroller" sounds like having many more possibilities to me, I once saw a video here with a side-scroller, but at the end of the wall, the camera rotated 90 degrees (in about one second), and there was another wall for side-way scrolling. That is, you got a glimpse of the 3D world around the walls for a moment. It looked very cool. Similarly, you could switch between sideways and top-down in much the same way, all "sideways" but not really

Unreal Engine has pretty much just what you're looking for built in.  It's the template they call "Side Scroller".  Then it has 2D Side Scroller which is more like the traditional pixel Mario.

On 19/7/2017 at 5:13 PM, Alberth said:

Trivial, just position the camera correctly, and the 3D renderer will do the rest. Don't remember the angles exactly, but wikipedia does: https://en.wikipedia.org/wiki/Isometric_graphics_in_video_games_and_pixel_art

It is also possible to achieve the same result without a 3D engine? I looked at SNES mode7 and old games that "simulate" a 3D view with only perspective projection. Do you now if there are some examples that I can study?

Ha, sure. In the retro games (ie 80s and 90s games), there are lots of these games.

Basically what happens is that you have weirdly shaped images that fake depth. You plot them from back to front, et voila one 2.5D game. (Well, graphically, at least )

Examples are Theme Hospital, RollerCoaster Tycoon I and II, and Transport Tycoon Deluxe. There are many more though, look for "isometric game".

For the above games, open source versions are CorsixTH, OpenRct and FreeRct, and OpenTTD. The first and second use the old commercial graphics afaik, the 3rd and 4th have gpl-licensed graphics, which should be easy to find / look at.

(OpenGFX baset graphics are at http://dev.openttdcoop.org/projects/opengfx)
 

My opinion, this is the best definition for 2.5d game

 "2.5D definition shouldn't even exist if you ask me, it confuses beginners and is useless to professionals"-MarcusAseth

2.5D is perfect sayd, i needed to read this topic because i instantly understanded what it is.

Professional dont cry that it exists now, you only making 3D for money, the gameplay sucks, here is why :

a joystick / gamepad is 2D.

You need to make your own engine, is way better, without all the stuff you dont need + extra stuff you need.

By example look at Mighty n0 9, made with unreal engine, its a realy crap made game because of wrong engine.

If you made yourself you could limit the timer to a certain framerate, will cause slowdown instead of huge steps.

In 3D you dont see shocks very much, and all threads working slower and faster then eachother.

You know : you ride your car in a wall, after a while you get set back, we cant have that in a 2D game, its bad.

3D has many of these things that are impossible to have in a 2D game, they dont mind, they just look at the money.

Many things are not made for the performance and stability you need for a good shooter.

You cannot play online a shootemup, impossible, all bullet counts as 1 player, you need 0 ping.

Ok in new unreal tournament they have lots of bullets on screen, i dont know what trick they use to have all that.