Tonemapping

When an HDR image is transformed to SDR format, tonemapping becomes relevant. It is the translation from undisplayably bright and dark colours to something that makes sense to human eyes on a standard display.

There are many types of tonemapping, all with their own “look”, advantages, and disadvantages. If your goal is photorealism, some are more accurate than others. Otherwise, there is no “correct” way to tonemap an image. It depends on the artstyle you’re going for and it’s technically impossible to 100% accurately map HDR to SDR to begin with.

Read this article by Bruno Opsenica for more accurate and detailed information.

Tonemapping functions

This is a collection of tonemapping functions taken from many different sources. All the Sponza renders are gamma-corrected* and identical apart from the chosen tonemapping function.

* The Unreal 3 tonemapping function has gamma correction built-in, and this is accounted for