The hardest part of making Doom was not making a Wolfenstein clone.

Quora, the question and answer site that encourages users to take pride in their real names and coherent answers, occasionally features answers from videogame professionals. John Romero recently reflected on the difficulties in developing Doom:

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Each person on the team had a hard time with whichever aspect they were working on. Mine was coming up with the unique abstract level design style, and staying away from the Wolfenstein 3D style of level design. For months Tom and I made very Wolf-like levels.

For John Carmack, it was probably dealing with the new world data structure (no more tile matrix, now it's line segment and sectors), figuring out how to speed up the rendering of the world through BSPs, and implementing multiplayer mode smoothly over serial/modem.

For Adrian and Kevin, it was probably trying out a new way to create our characters. First, Adrian used clay to model the player and Baron of Hell, but when he tried animating them, they tore apart. So he had to switch over to latex models, which we outsourced. We were using a video camera to capture the models on a lazy susan so we could have 8 rotations, then animate the model, and capture all 8 rotations again. Cleaning up all those frames of art was tedious. We were also using a NeXTCUBE to do all the video capture.

The difficulties the design team had in developing Doom remind us of how far technology has come–3D models no longer need physical equivalents, though there's plenty of clean up work with motion capture. However, some obstacles, like coming up with original material, are constant.