Problems of the DOOM: The Dark Ages engine led developers to ray tracing to reduce the game's size

Developers from id Software revealed some behind‑the‑scenes technical details about the making of DOOM: The Dark Ages. According to them, switching to a modern real‑time lighting pipeline wasn’t a stylistic choice — the engine basically forced their hand.

The reason is storage: baking global lights into static data would have blown up the game’s size because those lightmaps are huge. Baked lighting alone was estimated to “weigh” about 110 GB. By contrast, the lighting computed via ray tracing doesn’t add bulky files (i.e., most of it exists at runtime), and the final game — even without an open‑world structure — still tops out at more than 80 GB.

This extreme footprint seems tied to idTech’s particular implementation rather than to baked lighting as a technique. Other engines that use baked lighting for large worlds (e.g., some open‑world titles) usually don’t demand that kind of SSD space for the whole install.