Does this seem weird to anyone else?
http://en.wikipedia.org/wiki/2.5D
Wikipedia's Definition of 2.5D
I use it fairly often, but I was just surprised that they talk mostly about games that I would never consider 2.5DGSZX1337 wrote:I think it's weird that people even consider 2.5D a real word.
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PharmaceuticalCowboy
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lordofduct
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That guy does not know what 2.5D is... it appears as if who ever wrote it just threw together a bunch of math terms to sound right. Kind of like where he brings up gimbal lock in Quake, ermm, what the hell does that have to do with anything? Gimbal lock can occur just about anywhere, its not an actual action, its mathematics that doesn't work out properly... a bad programmer could easily make this mistake in 2.5D (well what this guy is making 2.5D out to be).
A gimbal lock is when you have more then one axis of rotation. If you do not consider each axis independent (usually in math we say n-degrees of freedom) you will get to certain points where one gimbal (gimbal is another word for axis of rotation) is in the same position as another gimbal. As you attempt to rotate around that gimbal you also rotate around the other causing the object to remain in the same place. For instance say you pitched an airplane upward to face the sky, then yawed it to the left, now your pitch and roll are messed up and you will be stuck pointing upward until you break the gimbal lock by returning down the path that got you there in the first place.
oh and this is my fav line ever!
Z-buffer: traditionally in 3D design is used during the process of projecting the 3D scene into a displayable 2D image. See all computer games that are 3D are considered 3D because the math is performed in 3 dimensions and then the resulting image is "projected" into 2D via some Matrix that creates several different camera effects (orthographic, isometric, panoramic, fisheye, and the traditional perspective) the resulting Matrix can now be used to create a 2D image of the scene through the viewpoint of some camera or eye. In most of these camera styles like perspective you have to give a sense of depth.
Well every object still retains a Z value, this Z value defines how far away from the camera it is located. This way objects that are behind another object are placed behind it graphically, and if they fall behind the far plane they can be culled out completely.
height map: this one here is a lot more ambiguous. But still it is a term usually suited for transferring 2D images into a 3D world. Most commonly a heightmap is used to define a terrain map where you draw a 2D image in a texture with powers of 2 (where both width and height a 2^n, like 512X512). The value from 0 to 1 (black being 0 and white being 1) represent a height value... you then select a minimum and maximum height and cycle threw all the pixels of the texture performing and multiplying said value by [(max - min)x + min] to get each vert. You then use polys or triangle strips to draw a terrain with respect to it...
kinda like this:
Heightmap is sometimes also used to describe another 2D or 3D texture that defines the relief, bump, normal, or other shading map of the textures on a 3D model to give more detail to what was a low poly model. This use of the word isn't used as often from what I have noticed.
here is an example of a normal height map:
the word normal does not mean normal as is regular... but normal is a math term that means the vector that points orthogonal to the tangent of a point in some curve. This normal height map uses a u and v value to create a 3D vector to describe the direction it should be receiving light to create a sense of more detail or "height". Like here http://studentpages.scad.edu/~ahilde20/site/toad.html , check the image from beginning to end and see the different maps that give the low poly model much more detail and sense of depth.
Personally I alwasy used 2.5D to describe games that are a cross of 2D gameplay and 3D graphics rendering. For instance games like Contra Shattered Soldier and Viewtiful Joe. Although this doesn't mean this is the ONLY things that 2.5D describes. It is just that usually you give a more specific name for the style of game you are playing and usually most of them rarely get the 2.5D name at all... for instance Isometric 2D games like "LandStalker".
A gimbal lock is when you have more then one axis of rotation. If you do not consider each axis independent (usually in math we say n-degrees of freedom) you will get to certain points where one gimbal (gimbal is another word for axis of rotation) is in the same position as another gimbal. As you attempt to rotate around that gimbal you also rotate around the other causing the object to remain in the same place. For instance say you pitched an airplane upward to face the sky, then yawed it to the left, now your pitch and roll are messed up and you will be stuck pointing upward until you break the gimbal lock by returning down the path that got you there in the first place.
oh and this is my fav line ever!
Excuse me!? That is gibberish.One such method is where a 2D image has an added "depth" channel or Z-buffer which may act like a height map.
Z-buffer: traditionally in 3D design is used during the process of projecting the 3D scene into a displayable 2D image. See all computer games that are 3D are considered 3D because the math is performed in 3 dimensions and then the resulting image is "projected" into 2D via some Matrix that creates several different camera effects (orthographic, isometric, panoramic, fisheye, and the traditional perspective) the resulting Matrix can now be used to create a 2D image of the scene through the viewpoint of some camera or eye. In most of these camera styles like perspective you have to give a sense of depth.
Well every object still retains a Z value, this Z value defines how far away from the camera it is located. This way objects that are behind another object are placed behind it graphically, and if they fall behind the far plane they can be culled out completely.
height map: this one here is a lot more ambiguous. But still it is a term usually suited for transferring 2D images into a 3D world. Most commonly a heightmap is used to define a terrain map where you draw a 2D image in a texture with powers of 2 (where both width and height a 2^n, like 512X512). The value from 0 to 1 (black being 0 and white being 1) represent a height value... you then select a minimum and maximum height and cycle threw all the pixels of the texture performing and multiplying said value by [(max - min)x + min] to get each vert. You then use polys or triangle strips to draw a terrain with respect to it...
kinda like this:
Heightmap is sometimes also used to describe another 2D or 3D texture that defines the relief, bump, normal, or other shading map of the textures on a 3D model to give more detail to what was a low poly model. This use of the word isn't used as often from what I have noticed.
here is an example of a normal height map:
the word normal does not mean normal as is regular... but normal is a math term that means the vector that points orthogonal to the tangent of a point in some curve. This normal height map uses a u and v value to create a 3D vector to describe the direction it should be receiving light to create a sense of more detail or "height". Like here http://studentpages.scad.edu/~ahilde20/site/toad.html , check the image from beginning to end and see the different maps that give the low poly model much more detail and sense of depth.
Personally I alwasy used 2.5D to describe games that are a cross of 2D gameplay and 3D graphics rendering. For instance games like Contra Shattered Soldier and Viewtiful Joe. Although this doesn't mean this is the ONLY things that 2.5D describes. It is just that usually you give a more specific name for the style of game you are playing and usually most of them rarely get the 2.5D name at all... for instance Isometric 2D games like "LandStalker".
@lordofduct
Well...you could edit the page to fix those errors. I mean that is the whole point of Wikipedia after all, and you obviously seem to know what you're talking about.
As for what 2.5D is, it's obvious from this thread that there are many different views. While there are many things wrong with that article, it did get at least one thing right in my opinion, and that is the "generalization" section, which should be expanded. The general point to get across is that there is no set consensus on what should be considered 2.5D and what should not. It really is an inexact term... They might even consider deleting it entirely.
Well...you could edit the page to fix those errors. I mean that is the whole point of Wikipedia after all, and you obviously seem to know what you're talking about.
As for what 2.5D is, it's obvious from this thread that there are many different views. While there are many things wrong with that article, it did get at least one thing right in my opinion, and that is the "generalization" section, which should be expanded. The general point to get across is that there is no set consensus on what should be considered 2.5D and what should not. It really is an inexact term... They might even consider deleting it entirely.
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lordofduct
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That is why I won't edit it... you can't define 2.5D properly because it is more slang then anything else. Everyone has their own definition for it. I just know what it isn't, and it isn't Z-buffering heightmaps... lol.Abras wrote:@lordofduct
Well...you could edit the page to fix those errors. I mean that is the whole point of Wikipedia after all, and you obviously seem to know what you're talking about.
As for what 2.5D is, it's obvious from this thread that there are many different views. While there are many things wrong with that article, it did get at least one thing right in my opinion, and that is the "generalization" section, which should be expanded. The general point to get across is that there is no set consensus on what should be considered 2.5D and what should not. It really is an inexact term... They might even consider deleting it entirely.
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lordofduct
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If you're going to allow Mode7 off the SNES, then why not allow things like sprite depth scaling like that of Out Run, Space Harrier, or Sonic 2 special stage, or even more prevalent is Panorama Cotton. These are all psuedo-3D techniques. And how about Doom or Wolfenstein.opethfan wrote:I'd say there are 2 types of 2.5D: Mode 7 (a la F-Zero) and 2D gameplay with 3D graphics (a la Klona and Nights).
One is 2D graphics making 3D gameplay and the other is 3D graphics making 2D gameplay.
All these games fake 3D via some "trick".
Keep in mind Mode 7 is a term used for only the SNES, and was also adopted for the background modes on the GBA. It was a reference to 1 of the 8 (0-7) background modes that could be implemented on background sprites with the SNES. It took a depth scale of how high up the screen the texture wanted to go, rotated it with a 3X3 matrix and scaled each scanline from the bottom to up creating a perspective view out of an immovable camera.
That is the issue with the article about what can one consider 2.5D... is it faking 3D? Is it rendering 3D but billboarding all your objects onto a 2D coordinate system? Is it hardware only (Mode7) or software accepted (Sonic 2 special stage)? Is it specific to if rotation can occur (Mode7) or to just depth (any isometric view like Sim City or Landstalker).
That's a very hard choice to make when debating the definition of an informal word that has no real definition because it isn't an actual technical term used in the industry, but that of by the consumers of the products produced by the industry.
Hence why I think the wikipedia article should be stripped and rewritten as saying that 2.5D is a non-technical term used by many different people to describe a number of different effects performed in the 2D world, or restrictions put on a 3D game world. Keeping in mind that 3D denotes only games that utilize 3 dimensional mathematics for lighting positioning and transformation.