"The most valuable part of the GCS has got to be the 3D game engine. A game engine is the software that runs when the user is playing the 3D game. When you are running down a corridor, blasting a mutant creature to death with a shotgun, the 3D engine is doing a variety of complicated tasks. Each pixel on the screen has to be read from some stored image and placed in exactly the right spot on the screen. A typical screen has 20,000 to 64,000 pixels on it, which is a lot of 3D calculations! But that is only part of what a 3D engine does. It also must decide which parts of the virtual world are visible and which parts are hidden behind other walls or objects. It must make sure that the player and the enemies can't walk through walls. It must keep track of all the gunshots or other weapons, check 3D aim, and determine if any objects are blocking the path between weapon and target. It must control all the moving objects in the game, including animations, opening doors, and artificially intelligent enemy characters."
Power 3D (stylized as POWER 3D) is the underlying 2.5D first person graphics engine written by Kevin Stokes and used by Lethal Tender (1993), Terminal Terror (1994) and the 3D Game Creation System (1995, 1998, 2001) and associated games. It was also going to be used in a later cancelled German FPS in development by Pie in the Sky Software.
Originally inspired by Wolfenstien 3D by id Software, it featured several features beyond it including diagonal walls, multiple wall heights, stairs and height blocks. It also featured several then singular gameplay features for first-person shooters such as an inventory system, the ability to pick up written notes, a distinctive implementation of jumping, and more.
It remained however grid-based, unlike the sector-based designs of the Doom, Build and Jedi engines. In this sense, it was somewhat similar the early grid-based draft of Build created by Ken Silverman pre-June 1993 or the highly modified Wolfenstein 3D engine used in Rise of the Triad.
Version 2.x of the GCS, also known as the Win95 GCS Replacement Engine, was released in December 1998 and converted it to DirectX and made it true-3D, featuring the ability to look up and down. The final version 3.x was released in 2001 and upgraded it with more 3D geometry, MD2 models from id Tech 2 and better lighting and post effects.
"On May 5, 1992, Id Software released a shareware game called Castle Wolfenstein. The game featured texture-mapped 3D graphics, and first person game play. This took the shareware game market by storm. The graphics engine could only draw vertically oriented cubes, and vertical sprites which always turned to face you. The floor and ceilings were just solid color and always were at the same height. In fact, the floor and ceiling didn't have to be drawn at all, since it was just a solid color fill in the window, with the walls and sprites drawn on top of it. After having written the Corncob 3D game engine, which could handle polygons of any number of sides at any angle, I realized how simple it was. And yet they managed to absolutely maximize the potential of such a simple engine. The natural thought was, 'Hey I could do that too!' And the P3d game engine was born."
--A History of Pie in the Sky Software's Products
"The Pie in the Sky engine was primarily the work of programmer Kevin Stokes, who used it for first-person shooters like Lethal Tender and Terminal Terror. They would then sell the tool at retail as the 3D Game Creation System, which was bought and used by a number of small teams that created games like Red Babe and the surreal hand-drawn Pencil Whipped."
--The Complete History Of First Person Shooters, Geek.Com, October 11, 2017