Tone Reproduction for Virtual Reality Applications

Tone reproduction (or tone mapping) is the mapping of physical light values to the values which are finally stored in the framebuffer. The operator is comparable to the exposure control in cameras. The challenge is to map the large dynamic range of luminance values in the real world (12 orders of magnitude) to the very restricted dynamic range of image output devices (2 orders of magnitude, in a CAVE with shutter glasses only about one!).

The problems of tone reproduction have been examined for still images since more than ten years. However, the problem has at least the same importance in interactive applications. If users navigate through virtual worlds with high dynamic range, the tone mapping should adapt to the current view, just as a video camera does when for instance moving from a dark to bright room.

We developed a practical way to achieve this adaptation per frame according to the current position and viewing direction of the user. By storing the tone mapping operator in a texture, which can be adapted on-the-fly, the tone reproduction can be adapted with very little overhead.

The following images show an application of that method to a reconstruction of Zeus' temple in Olympia. The model has been created by the Foundation of the Hellenic World in Athens. It is shown to museum visitors in Athens in a CAVE, a room surrounded by projection walls, that gives the audience a convincing impression of full immersion into the reconstructed world. The video shows how the tone mapping adapts when the user moves from the bright environment into the dark temple inside and back.

see the video clip

A paper about this work has been published at EUROGRAPHICS 2000. See also "Tone Reproduction for Interactive Walkthroughs", by A. Scheel, M. Stamminger and H.-P. Seidel.