Дум это 3д. Просто с ограничением, в нем нельзя свободно двигатся - башка и взгляд зафиксированы параллельно полу, стены 1 высоты.
Это типа как с переломом шеи и ног в гипсе ходить.
И снова ты гугло балабол, иди вопрос изучай.. вниматочно. Они были псевдо 3Д, элементы 3Д в 2Д пространстве, и по оси Z добавлялся физический движок.
Причём про плоские стены уровней написано даже в твой ссылке, и написано почему так делалось.
Ideas from the Deep, now formally established as
id Software, used some of these to prototype ideas for their own games.
[7] Adrian Carmack used them to push his preferred, dark art style, while John Carmack began to experiment with
3D computer graphics, which until then was largely the purview of
flight simulation games such as
Wing Commander (1990). Carmack found that this was largely due to the limitations of
personal computers of the time, which had difficulty displaying a fast
action game in 3D due to the
number of surfaces it needed to calculate, but felt that the increasing computational power of PCs meant that it may be possible.
[6][8] During 1991, he experimented with limiting the possible surfaces the computer needed to display, creating game levels with walls designed only on a flat grid rather than with arbitrary shapes or angles. He also took the unusual approach of creating the displayed graphics through
ray casting, in which only the surfaces visible to the player were calculated rather than the entire area surrounding the player. After six weeks of development, Carmack had created a rudimentary 3D
game engine that used animated 2D
sprites for enemies. Id Software then used the engine for the April 1991 Softdisk game
Hovertank 3D, in which the player drives a tank through a plane of colored walls and shoots nuclear monsters.
[1][6] In the fall of 1991, after the team—sans Wilbur—had relocated to
Madison, Wisconsin, and he had largely finished the engine work for
Commander Keen in Goodbye, Galaxy, Carmack decided to implement a feature from
Ultima Underworld: The Stygian Abyss, a
role-playing game in development by
Blue Sky Productions.
[9] Ultima Underworld was planned to display
texture-mapped 3D graphics without
Hovertank's restrictions of flat walls and simple lighting.
[9][10][11] Deciding that he could add texture mapping without sacrificing the engine's speed or greatly increasing the system requirements as
Underworld was doing, Carmack enhanced the engine over six weeks from
Hovertank 3D for another Softdisk game, the November 1991
Catacomb 3-D.
[1][9] Upon seeing it,
Scott Miller of Apogee began to push the team to make a 3D shareware action game.
[9]
Ниже прочитать не судьба была?
Не, всё, хватит. Эта тупость будет длится вечно.
