Doom (1993 video game)
The ability for others to create custom levels and otherwise modify the game using WAD files turned out to be a popular aspect of "Doom". Gaining the first large mod-making community, "Doom" affected the culture surrounding first-person shooters, and also the industry. Several future professional game designers started their careers making "Doom" WADs as a hobby, among them Tim Willits, who later became the lead designer at id Software.
Doom 3
Chris Vrenna and Clint Walsh, known together as Tweaker, were hired to work on the theme music for "Doom 3". Walsh was credited as composer while Vrenna was credited as producer.
According to John Carmack, the lead graphics engine developer at id Software, the technology of "Doom 3" was supported by three primary features: unified lighting and shadowing, complex animations and scripting that showed real-time with fully dynamic per-pixel lighting and stencil shadowing, and GUI surfaces that add extra interactivity to the game. The key advance of the id Tech 4 graphics engine developed for "Doom 3" is the unified lighting and shadowing. Rather than computing or rendering lightmaps during map creation and saving that information in the map data, most light sources are computed in real-time. This allows lights to cast shadows even on non-static objects such as monsters and machinery, which was impossible with static non-directional lightmaps. A shortcoming of this approach is the engine's inability to render soft shadows and global illumination.