偽三維

等軸測投影和斜向投影

在等軸測投影和斜向投影這兩種投影的形式中，視角被輕微轉動來使得物體的其他面可見，產生一種三維環境的感覺。可以認為一個物體被「傾斜放置「在屏幕前。圖像可以被看作該物體在遊戲平面上以特定角度的投影且不同邊的長度根據投影位置關係被分別調整。
這種效果常用於二維遊戲的相機透視效果。在第四世代遊戲機和掌上遊戲機中較為常見。較新的戰略遊戲和角色扮演遊戲也經常用到。它結合了俯視視角遊戲的角色的操控性和橫版遊戲的角色辨識度。這樣玩家就能夠獲得遊戲世界的一個俯視視角，同時能夠看到角色的身體側面細節，而不是像俯視遊戲一樣只能夠看到角色頭頂和肩部。
等軸測投影有三大類別：等距投影 ，二軸測投影（對稱與不對稱）和三角投影。等距投影在工程繪圖較為常見。這種投影方法旋轉物體使得三條坐標軸投影的夾角均為120度。這樣的好處是物體在三個方向上的縮放長度均相等。在遊戲中，為方便在方形像素顯示器上進行抗鋸齒處理，大部分投影處理選擇2:1的像素長寬比例。
Ultima VII: The Black Gate 和Paperboy 均使用等軸測投影，而SimCity 2000、角色扮演遊戲Diablo 和Baldur's Gate 均使用斜向投影。

看板

在三維場景中，看板技術常常指視野中的一個二維圖像元素。因其效果類似於看板的外觀而得名。這項技術常常被用於1990年早期的遊戲中，因當時設備機能限制，無法很好的渲染全三維的物體。這項技術也同樣被應用於背景中。當一個物體距離相機過遠時，可以將其用二維的精靈圖代替，同時可以使遊戲獲得顯著的性能提升。在遊戲中最為常見的看板技術莫過於粒子（雨滴，煙，火花等）和解析度要求不高的的植被。侏羅紀公園：侵入者 就是經典案例之一。這項技術曾經被大量遊戲應用，如Rome: Total War 將其用於表示戰場上成千上萬的獨立士兵。第一人稱射擊遊戲Duke Nukem 3D 和賽車遊戲馬力歐卡丁車 均有用到此項技術。

天空盒與穹頂

天空盒或穹頂被用於創造一個看起來比實際視野更加廣闊的環境。如果使用的是方形的天空盒，遠到無法觸及的物體如高山和雲等將會以方形貼圖技術表現在四周，創造出一種三維空間遙遠物體的感覺。穹頂則使用球體或半球體。
天空盒或穹頂一般隨著視野位置一起移動，來讓觀察者感到其貼圖上的景物十分遙遠。因為在真實世界中，隨著觀察者移動，遠處的景物看起來也並不會有太大改變。因此，天空盒或穹頂中的景物看起來與觀察者始終保持著無限遠的距離。在背景貼圖中不應包含過多分離的物體或較近的物體，否則將會導致觀察者移動時發現物體仍然靜止，從而產生違和感。

近大遠小

在某些遊戲裡，部分物體的大小會隨著與玩家的遠近不同而改變。世嘉於1986年發布的遊戲Out Run 就是一個典型例子。
在Out Run 中，玩家需駕駛一輛法拉利深入遊戲場景。街道兩側的棕櫚樹雖使用同一個位圖，但被縮放到不同的大小以營造遠近感。大量消耗內存的看板被Out Run 用於渲染即使在最高能見度模式下也看不到邊際的水波和玉米地。
Drakkhen 作為第一個宣稱使用三維場景的角色扮演遊戲值得一提。然而，遊戲並不包含三維引擎，而是使用縮放玩家的算法來營造類似的效果。玩家的隊伍在向量控制的場景內活動，而所有的物體都根據距離進行縮放。 Drakkhen 還帶有動態晝夜交替和開放世界遊戲，均在同時代遊戲中難得一見。此類引擎後來被用於Eternam 遊戲。
某些移動端遊戲，比如Asphalt: Urban GT 2 和Asphalt 3: Street Rules 的移動版，使用這種方法渲染景物和樓房。

平行滾動

平行滾動指一組二維精靈圖或圖片層獨立於背景以不同的速度移動來營造景深的效果。  上世紀40年代，傳統動畫所使用的多平面相機衍生出了這項技術。 這種技術最初被用於1982年的街機遊戲Moon Patrol。.Rise of the Triad 的天空，Rygar，刺蝟索尼克，Street Fighter II，Shadow of the Beast，Dracula X Chronicles，超級馬力歐世界 中靠近靠近幻象森林出口的一關和未使用的一關。

Mode 7

Mode 7是電子遊戲機超級任天堂的一種圖形方式，可讓逐掃描線式的背景層支持旋轉與縮放以創造大量不同的三維效果。

射線渲染

使用射線渲染技術的遊戲在相機位置從不同角度射出多條「射線」，當它們碰到牆或物體時，將會在屏幕對應位置渲染圖像。 
早期的第一人稱射擊遊戲使用射線渲染來創造一個類似於三維的效果。即使看上去是三維世界，玩家既不能上下轉動視角，也不能跳躍或蹲下，因為地圖仍是二維的。

凹凸貼圖，法線貼圖和視差貼圖

凹凸貼圖，法線貼圖和視差貼圖是在3D渲染（例如視頻遊戲）中處理紋理的技術，以在不需要渲染額外多邊形的情況下表現出物體表面上的凹凸紋路。經過此類技術處理後，諸如石牆等表面的紋理外觀將具有更明顯的深度，看起來更為真實，對渲染的負載影響也較小。
凹凸貼圖技術根據一張叫做「高度圖」的灰度圖片，在光照計算期間擾動物體的表面法線來實現物體表面凹凸不平的效果。儘管物體的表面形狀實際上沒有改變，視覺上該物體的表面已經變得凹凸不平。凹凸貼圖技術由Blinn於1978年引入。
法線貼圖將陰影點到光源方向的單位矢量與垂直於該表面的單位矢量相乘，得到的數量積即為該表面上的亮度。你無法用多邊形構造一個完美的球體，但通過在你的「球體」上應用一個3通道位圖貼圖，可以加入更精緻的多邊形效果。該位圖中的每個通道對應一個空間維度（XYZ），這些空間維度關聯於某個恆定坐標系來計算基於該對象的物體空間凹凸貼圖，或某個緩慢變化的坐標系（由貼圖材質坐標的位置決定）來計算基於對象切面的切空間凹凸貼圖。與先進的照明技術相結合，法線貼圖可以有效地為你的「球體」表面增加更多細節。
視差貼圖（又被稱為補償貼圖或虛擬位移貼圖）是增強過的凹凸貼圖與法線貼圖技術。該技術通過計算視差角（視線與渲染平面法線構成的角）的正切值函數與視角位置的投影高度來偏移表面上的材質。 在更傾斜的角度，材質會更加偏移，通過透視原理產生隨視角變化的表面「深度」的錯覺。

影視和動畫技術

The term is also used to describe an animation effect commonly used in music videos and, more frequently, title sequences. Brought to wide attention by the motion picture The Kid Stays in the Picture based on the book by film producer Robert Evans, it involves the layering and animating of two-dimensional pictures in three dimensional space. Earlier examples of this technique include Liz Phair's music video Down directed by Rodney Ascher and "A Special Tree" directed by musician Giorgio Moroder.

平面設計

The term also refers to an often-used effect in the design of icons and graphical user interfaces (GUIs), where a slight 3D illusion is created by the presence of a virtual light source to the left (or in some cases right) side, and above a person's computer monitor. The light source itself is always invisible, but its effects are seen in the lighter colors for the top and left side, simulating reflection, and the darker colours to the right and below of such objects, simulating shadow.
An advanced version of this technique can be found in some specialised graphic design software, such as Pixologic's ZBrush. The idea is that the program's canvas represents a normal 2D painting surface, but that the data structure that holds the pixel information is also able to store information with respect to a z-index, as well material settings, specularity, etc. Again, with this data it is thus possible to simulate lighting, shadows, and so forth.

2.5D 平台遊戲

The term "2.5D" is also applied to 3D games that use polygonal graphics to render the world and/or characters, but whose gameplay is restricted to a 2D plane. Examples include Pandemonium!, Einhänder, Klonoa: Door to Phantomile, Kirby 64: The Crystal Shards (although the scene moves towards and away from the camera), LittleBigPlanet (although it features a playing field three layers thick), Nights into Dreams... and New Super Mario Bros. The Crash Bandicoot series is sometimes referred to as 2.5D because the characters and scenery are rendered in 3D, yet most of its levels are not as free-roaming as "true" 3D platformers.
Some fighting games such as the Super Smash Bros. series, Marvel vs. Capcom 3, Street Fighter IV, Mortal Kombat, BlazBlue, Guilty Gear Xrd and The King of Fighters XIV also utilize 2.5D to showcase 3D backdrops and/or characters while limiting the action to a 2D plane. 2D scrolling shooters are another genre in which 3D graphics are often used in a 2D game, such as in Ikaruga.
In some games, such as Goemon's Great Adventure and Pandemonium!, the area of gameplay can be described as a two-dimensional surface twisting and bending in a three-dimensional space. Inside this surface, the character and physics behave like in a traditional sidescrolling platformer. There are, however, a number of twists that aren't possible with normal sidescroller platformers: it is common in such games to let the two-dimensional plane cross itself or other planes on certain points, thus creating "track switches" in the course. Players can explore different areas of the 3D world that way or can be brought back to previous points seamlessly. Interactions with the "background" (non-accessible points in the 3D landscape) are also used extensively. Other 2.5D games allow the character to interact with objects out of the primare 2D plane; for example in the platformer-shooter Shadow Complex, the player may need to target and fire at enemies that are in the background of the scene.

歷史

The first video games that used pseudo-3D were primarily arcade games, the earliest known examples dating back to the mid-1970s, when they began using microprocessors. In 1975, Taito released Interceptor, an early first-person shooter and combat flight simulator that involved piloting a jet fighter, using an eight-way joystick to aim with a crosshair and shoot at enemy aircraft that move in formations of two and increase/decrease in size depending on their distance to the player. In 1976, Sega released Moto-Cross, an early black-and-white motorbike racing video game, based on the motocross competition, that was most notable for introducing an early three-dimensional third-person perspective. Later that year, Sega-Gremlin re-branded the game as Fonz, as a tie-in for the popular sitcom, Happy Days. Both versions of the game displayed a constantly changing forward-scrolling road and the player's bike in a third-person perspective where objects nearer to the player are larger than those nearer to the horizon, and the aim was to steer the vehicle across the road, racing against the clock, while avoiding any on-coming motorcycles or driving off the road. That same year also saw the release of two arcade games that extended the car driving subgenre into three dimensions with a first-person perspective: Sega's Road Race, which displayed a constantly changing forward-scrolling S-shaped road with two obstacle race cars moving along the road that the player must avoid crashing while racing against the clock, and Atari's Night Driver, which presented a series of posts by the edge of the road though there was no view of the road or the player's car. Games using vector graphics had an advantage in creating pseudo-3D effects. 1979's Speed Freak recreated the perspective of Night Driver in greater detail.
In 1979, Nintendo debuted Radar Scope, a shoot 'em up that introduced a three-dimensional third-person perspective to the genre, imitated years later by shooters such as Konami's Juno First and Activision's Beamrider. In 1980, Atari's Battlezone was a breakthrough for pseudo-3D gaming, recreating a 3D perspective with unprecedented realism, though the gameplay was still planar. It was followed up that same year by Red Baron, which used scaling vector images to create a forward scrolling rail shooter.
Sega's arcade shooter Space Tactics, released in 1980, allowed players to take aim using crosshairs and shoot lasers into the screen at enemies coming towards them, creating an early 3D effect. It was followed by other arcade shooters with a first-person perspective during the early 1980s, including Taito's 1981 release Space Seeker, and Sega's Star Trek in 1982. Sega's SubRoc-3D in 1982 also featured a first-person perspective and introduced the use of stereoscopic 3-D through a special eyepiece. Sega's Astron Belt in 1983 was the first laserdisc video game, using full-motion video to display the graphics from a first-person perspective. Third-person rail shooters were also released in arcades at the time, including Sega's Tac/Scan in 1982, Nippon's Ambush in 1983, Nichibutsu's Tube Panic in 1983, and Sega's 1982 release Buck Rogers: Planet of Zoom, notable for its fast pseudo-3D scaling and detailed sprites.
In 1981, Sega's Turbo was the first racing game to feature a third-person perspective, rear view format. It was also the first racing game to use sprite scaling with full-colour graphics. Pole Position by Namco is one of the first racing games to use the trailing camera effect that is now so familiar.  In this particular example, the effect was produced by linescroll—the practice of scrolling each line
independently in order to warp an image.  In this case, the warping would simulate curves and steering.  To make the road
appear to move towards the player, per-line color changes were used, though many console versions opted for palette
animation instead.
Zaxxon, a shooter introduced by Sega in 1982, was the first game to use isometric axonometric projection, from which its name is derived. Though Zaxxon's playing field is semantically 3D, the game has many constraints which classify it as 2.5D: a fixed point of view, scene composition from sprites, and movements such as bullet shots restricted to straight lines along the axes. It was also one of the first video games to display shadows. The following year, Sega released the first pseudo-3D isometric platformer, Congo Bongo. Another early pseudo-3D platform game released that year was Konami's Antarctic Adventure, where the player controls a penguin in a forward-scrolling third-person perspective while having to jump over pits and obstacles. It was one of the earliest pseudo-3D games available on a computer, released for the MSX in 1983. That same year, Irem's Moon Patrol was a side-scrolling run & gun platform-shooter that introduced the use of layered parallax scrolling to give a pseudo-3D effect. In 1985, Space Harrier introduced Sega's "Super Scaler" technology that allowed pseudo-3D sprite-scaling at high frame rates, with the ability to scale 32,000 sprites and fill a moving landscape with them.
The first original home console game to use pseudo-3D, and also the first to use multiple camera angles mirrored on television sports broadcasts, was Intellivision World Series Baseball (1983) by Don Daglow and Eddie Dombrower, published by Mattel. Its television sports style of display was later adopted by 3D sports games and is now used by virtually all major team sports titles. In 1984, Sega ported several pseudo-3D arcade games to the Sega SG-1000 console, including a smooth conversion of the third-person pseudo-3D rail shooter Buck Rogers: Planet of Zoom.
With the advent of consoles and computer systems that were able to handle several thousands of polygons (the most basic element of 3D computer graphics) per second and the usage of 3D specialized graphics processing unit, pseudo 3D became obsolete. But even today, there are computer systems in production, such as cellphones, which are often not powerful enough to display true 3D graphics, and therefore use pseudo-3D for that purpose. Interestingly, many games from the 1980s' pseudo-3D arcade era and 16-bit console era are ported to these systems, giving the manufactures the possibility to earn revenues from games that are now nearly twenty years old.
By 1989, 2.5D representations were surfaces drawn with depth cues and a part of graphic libraries like GINO. 2.5D was also used in terrain modeling with software packages such as ISM from Dynamic Graphics, GEOPAK from Uniras and the Intergraph DTM system. 2.5D surface techniques gained popularity within the geography community because of its ability to visualize the normal thickness to area ratio used in many geographic models; this ratio was very small and reflected the thinness of the object in relation to its width, which made it the object realistic in a specific plane. These representations were axiomatic in that the entire subsurface domain was not used or the entire domain could not be reconstructed; therefore, it used only a surface and a surface is one aspect not the full 3D identity.
The resurgence of 2.5D or visual analysis, in natural and earth science, has increased the role of computer systems in the creation of spatial information in mapping. GVIS has made real the search for unknowns, real-time interaction with spatial data, and control over map display and has paid particular attention to three-dimensional representations. Efforts in GVIS have attempted to expand higher dimensions and make them more visible; most efforts have focused on "tricking" vision into seeing three dimensions in a 2D plane. Much like 2.5D displays where the surface of a three dimensional object is represented but locations within the solid are distorted or not accessible.

Technical aspects and generalizations

The reason for using pseudo-3D instead of "real" 3D computer graphics is that the system that has to simulate a three dimensional-looking graphic is not powerful enough to handle the calculation-intensive routines of 3D computer graphics, yet is capable of using tricks of modifying 2D graphics like bitmaps. One of these tricks is to stretch a bitmap more and more, therefore making it larger with each step, as to give the effect of an object coming closer and closer towards the player.
Even simple shading and size of an image could be considered pseudo-3D, as shading makes it look more realistic. If the light in a 2D game were 2D, it would only be visible on the outline, and because outlines are often dark, they would not be very clearly visible. However, any visible shading would indicate the usage of pseudo-3D lighting and that the image uses pseudo-3D graphics. Changing the size of an image can cause the image to appear to be moving closer or further away, which could be considered simulating a third dimension.
Dimensions are the variables of the data and can be mapped to specific locations in space; 2D data can be given 3D volume by adding a value to the x, y, or z plane. "Assigning height to 2D regions of a topographic map" associating every 2D location with a height/elevation value creates a 2.5D projection; this is not considered a "true 3D representation", however is used like 3D visual representation to "simplify visual processing of imagery and the resulting spatial cognition".