Ray Tracing is a Necessity According to DOOM: The Dark Ages Developers

DOOM: The Dark Ages

marks a significant technical change for id Software, which during SIGGRAPH 2025 illustrated with concrete data why the switch to Ray-Traced Global Illumination (RTGI) has become necessary for the future of the series.

According to what the studio presented, adopting the previous global illumination system based on baked GI, used in the idTech 7 era, would have led to extremely high production costs in order to achieve comparable results in the current project. The team would have had to handle up to 110GB of data solely dedicated to lighting, with offline processing times reaching up to 68 days.

The baked GI relies on a pre-computation process of lighting before the game is published or the maps are finalized. In practice, developers offline simulate the behavior of light on walls, floors, and objects, then store the result. This method lightens the load during execution but imposes heavy limitations when modifying environments or game structures, as any significant intervention requires a complete recalculation.

In contrast, with RTGI, DOOM: The Dark Ages calculates much of the light behavior in real-time through ray tracing. This system improves the handling of indirect lighting, deeper shadows, chromatic bounces between surfaces, and interaction with dynamic elements. The result is not only a visual quality enhancement but also a more flexible development pipeline.

Global illumination indeed represents all the indirect light that bounces in the environment after hitting different surfaces for superior realism and depth. The main difference between baked GI and RTGI lies precisely in the calculation method: the former stores predefined data, while the latter generates it during gameplay, adapting more effectively to scene changes.

For id Software, this transition is not just about graphical enhancement but a precise necessity: to drastically reduce production times and the amount of data without sacrificing a higher qualitative level. DOOM: The Dark Ages hence demonstrates how ray tracing can represent a concrete answer to the complexities of modern development, beyond just aesthetic impact.