Thursday, 21 January 2016


Sometimes how specific terminology has come to stay make me furious. It shouldn't matter since it doesn't affect my life. But strolling through gaming or tech forums, I might end ranting to the air, search for other people hating the same terms, rejoicing in the thought that I am not alone.

Today it was 2.5D. I don't know how I have come here, maybe from articles defining raycasting, raytracing, raymarching, sphere tracing, remembering all those terms that are so intermixed with each other, sometimes even in graphics articles or papers. Later, on wikipedia talks about raycasting, people mistakenly calling Doom or Duke 3D raycaster based, also named it 2.5D. Although does it matter? What if we use the terms but then if misunderstood, describe in more words what we exactly mean?

2.5D. That's the problem with this term even between those who use it, which is used to describe various different cases of rendering and gameplay. They might be meaning 2d gameplay in a 3d environement (Trine series), 3d gameplay in 2d rendering (oldschool isometric games where you could still climb over objects and above enemies, e.g. Knight Lore), or games with 2D maps but 3d gameplay like Doom (about which, there are many misconceptions I'd like to discuss another day). And there is even misunderstanding of what they mean, for example some consider the new Mario World 3D on the Wii U to be 2.5D because sometimes the level design forces you to move through one axis. What they want to define is so diverse, that it's better to describe both it's gameplay and rendering in more detail than shoehorning it into one category.

I personally hate the term at all. It's meaningless. I read it was used as a derogatory term to differentiate classic first person shooters from later 3d polygon games. And sometimes I like to joke about it, talking about fractal dimensions and especially 3d quadratic koch surfaces (exactly 2.5D by Hausdorff dimension :).

It's isometric, so it must be 2.5D, right? :)

In fact, come to think, even the most modern 3D polygon games, what they really are, is projections onto the 2D screen. That's another way I like to mock this term. Your nextgen 3D games are 2D. Not even a half more :P

p.s. I read so much misconceptions about Doom that I will briefly mention. First, it's not a raycaster, no rays are cast to determine the wall rendering, not everywhere in the code. But the walls are still rendered with stretched column rendering just like wolfenstein. Then, people said you don't have control on the vertical axis. That's not true. While the maps have sections called sector made only by 2d vertices and having information for floor/ceiling height, all the things (player, enemies, items) have three dimensions. You can walk from a ledge and fall or climb stairs. They could easilly have added jump function in the game. Someone said there is autoaim when you shoot, which shows the limitations of the engine. It's not because of limitation. They could have done it. They just didn't have look up or down to aim the crosshair in one axis at the time because it would be harder for the gameplay. Also, there is an effect where you shoot a bazooka that hits a wall below a monster on a ledge but the explosion radius damages it. Just lazy coding. Monster has x,y,z. Your projectile too. Could do 3d distance or 2d distance like it does and another 1D distance check between heights of projectile and enemy. When imps throw fireballs at you from higher ground, the fireballs really move on a 3d linear path. Cacodemons fly above and below. If you shoot a bazooka on a higher place and later another monster crosses the trajectory below, it's not hitting it because it's above. At least, there is true 3d gameplay, things move in three axes and the 3rd axis matters.

p.p.s. Come to think, that's the best thing 3d graphics technology (no matter if real polygons or projections of 2d walls) has given us. Not more brilliant visuals, but an expansion of the gameplay space. Suddenly you don't scroll in front of a background, but you can discover things behind it, find hidden rooms from the other side, hide above or below, reach and attack from other paths, new views of the same data. Think Deus Ex. So many unique paths to infiltrate the same place. One could argue that you could have some of these things in 2d games but this has expanded a lot in the 3d space. That's another reason why it makes me mad to see another linear on-rails FPS with "brilliant" graphics but very restrictive paths. I could joke another time and mock modern FPS games by saying they take the 3D and restrict it in 2.5D. If we wanna play like this, Doom, naively called 2.5D, has more exploration and expansion of your 3D senses in terms of gameplay than your average modern FPS.

p.p.p.s. Yeah, I am ranting. I could be writing more if I didn't stop now..