Tonemapping
HDR → display-range remapping
Also known as: Tone mapping
Definition
Tonemapping is the final stage of the render pipeline that compresses the engine's internal high-dynamic-range (HDR) lighting calculations into the 0-1 colour range a display can actually show. Without tonemapping, bright lights would clip to pure white and dark areas to pure black. Different tonemappers (ACES, Reinhard, Filmic, AgX) produce different cinematic looks — choosing one is as much an art-direction call as a technical one.
In production
Unreal Engine 5 uses ACES by default and exposes a colour-grading panel (white balance, shadows/midtones/highlights wheels, and a tone curve) for fine-tuning inside the Post Process Volume. Blender 4.x ships with AgX as the default view transform, which preserves chroma better in highlights than the older Filmic tonemapper — a bright red light source stays visibly red instead of blowing out to white. Unity's HDRP offers both ACES and a custom "Neutral" tonemapper, and switching between them mid-project can shift every material's apparent value, which is why art directors lock the tonemapper choice early. Tonemapping also interacts with exposure: auto-exposure systems that adapt to scene brightness can cause visible "pumping" as the camera pans between a dark interior and a bright exterior, which some tonemapping setups mitigate with eye-adaptation speed curves.