Ironwail is a

A fork of the popular GLQuake descendant QuakeSpasm with a focus on high performance instead of broad compatibility, capable of handling even the most demanding maps at very high framerates by utilizing more modern techniques such as:

• compute-based vis/frustum/backface culling
• compute-based lightmap updates
• better batching through multi-draw indirect rendering, instancing, and bindless textures
• clustered dynamic lighting
• persistent buffer mapping with manual synchronization

To avoid physics issue with high framerates the renderer is decoupled from the server (using code from QSS, via vkQuake). There are also a few other nice-to-have features such as the classic underwater warp effect, slightly higher color/depth buffer precision, reduced heap usage (can play shib1_drake out of the box), slightly faster savefile loading for large maps in complex mods, capped framerate when no map is loaded, and a built-in hackwork-around for the z-fighting issues present in the original levels.