Cubemap
360-degree environment captured as six faces
Also known as: Reflection cubemap · Environment map
Definition
A cubemap stores a full 360-degree view of an environment as six square faces of a cube, sampled by direction rather than UV. Cubemaps are the data behind reflection probes, sky lighting, and image-based lighting (IBL) in PBR. HDRIs are typically converted to cubemaps at import. When SSR cannot find a reflection on-screen, the engine falls back to the nearest cubemap.
In production
Unreal Engine generates reflection captures as cubemaps baked at each Reflection Capture Actor's position, and artists control resolution per-capture (128 up to 2048 per face) to balance VRAM against reflection sharpness on chrome or wet-surface materials. Marmoset Toolbag and Substance Painter both use a cubemap-based HDRI for their real-time viewport lighting, letting artists preview how a metallic material will pick up environment reflections before it ever touches an engine. When screen-space reflections can't resolve a reflection because the reflected geometry is off-screen, both Unreal and Unity fall back to the nearest baked reflection cubemap, which is why a moving character's SSR reflection sometimes "pops" to a lower-fidelity static reflection at the edge of frame. A common technical-art bug is forgetting to rebuild reflection captures after a lighting change, leaving stale, incorrect reflections baked into the cubemap.
