High-dynamic-range rendering

High dynamic range (HDR) rendering is the rendering 3D computer graphics scenes in a high dynamic range, often used in video games. A recent effect that got a lot of attention when Valve Software released a video of their Source engine rendering a scene from the game Half-Life 2 in HDR. At a first glance when HDR rendering was used elsewhere, it was confused for a combination of overbrightening certain areas of light, exaggerating bloom effects, and the usage of halo effects. ILM's OpenEXR technology has been the standard to use when putting HDR in games

What HDR rendering really does is that it helps hardware render realistic images from environments with a HDR. Before Shader Model 3.0 came out, which enabled HDR to be possible, dynamic ranges were limited to a maximum of 256:1. After Shader Model 3.0 was released, the dynamic range inceased to a maximum of 65536:1.

So what exactly does HDR rendering do on an image versus the same scene in low dynamic range (LDR)?

This is an example:

Say you're in a dark room, but your eyes have adjusted so you can see clearly. If you were to render this scene in either HDR or LDR, there wouldn't be much of a difference because the dynamic range is low. But say you're now in front of your computer monitor (this works best because a monitor usually increase the dynamic range greatly, but make sure it's displaying something bright, such as this website), move an object that has a fair amount of detail (such as a dollar bill for example) and place it between you and the monitor. Focus on the bill, you should be able to see a good amount of detail on the bill and the text on this webpage. If you try to take a picture of this using a digital camera which usually has a low dynamic range, chances are, the bill will appear no more than a black rectange blocking the detail on the monitor. Even if you change the camera's exposure, you won't be able to see the detail on the monitor and it will appear as a white background behind a detailed dollar.

Currently only nVidia's GeForce 6 and GeForce 7series videocards support Shader Model 3.0 to utilize HDR rendering. ATi has a videocard that will be released approximately in September, 2005 that supports Shader Model 3.0.