Tone mapping

Tone mapping takes the wide range of brightness values that a physically based render calculates and fits it into the much narrower range that a monitor or print can display. In the real world, a sunlit window is vastly brighter than a shaded corner of the same room, yet a screen can only show a small part of that difference. Tone mapping decides what detail to keep and how bright areas roll off.

Why tone mapping is needed

If a raw HDR image is sent straight to the screen, bright regions clip hard to white and colors turn oddly saturated as they get brighter. A good tone mapping curve compresses highlights gradually, holds detail in the shadows and lets bright colors fade towards white the way they do on film. Engines offer different curves under names such as filmic or ACES, and each has its own character.

In architectural visualization

Tone mapping is a key tool for balancing a window against the room around it, and for keeping lamp glow from blowing out in night shots. Exposure sets how much light you capture; tone mapping sets how that light is laid out in the final image. When a render looks artificial, the problem is often not the materials at all but these two settings working against each other. For other frequent pitfalls, read common 3D visualization mistakes.