Valve's High Dynamic Range Explored

Introduction

Now is an interesting time for PC gaming. With the release of NVIDIA's 7800 series as well as the upcoming ATI x1000 series graphics cards, the potential for graphics in games is only just starting to be realized. Games like F.E.A.R, Call of Duty 2, and Age of Empires 3 promise to take PC gaming to a new level graphically, and frankly, we couldn't be happier about it. We seem to have a similar situation right now of when ATI's RADEON 9700 series launched, and the new hardware allowed game developers the freedom to experiment with new ideas; therefore, creating a new generation of games. One particular graphics engine that has had an important impact for developers lately is Half life 2's Source engine, and though it has been around for a while now, the developers have recently decided to give the engine a bit of a face-lift, metaphorically speaking.

That's right, Valve has updated their source engine to enable something called High Dynamic Range, and the first two applications to implement this are Day of Defeat (a popular Half life 2 mod) and the upcoming new level for Half life 2: the Lost Coast. High dynamic range is basically a more realistic way to implement lighting in a three-dimensional world. With HDR, light sources will appear brighter, and other effects like blooming are possible. HDR, along with other things like auto-exposure, take lighting to a new level, further enhancing the realism of a virtual world. To give you a better idea of the concept behind HDR, here is a quote from Paul Debevec:

"The 'dynamic range' of a scene is the contrast ratio between its brightest and darkest parts. A plate of evenly-lit mashed potatoes outside on a cloudy day is low-dynamic range. The interior of an ornate cathedral with light streaming in through its stained-glass windows is high dynamic range. In fact, any scene in which the light sources can be seen directly is high dynamic range."

Obviously, one of the first things that we were concerned about regarding this upgrade was how this would affect performance. We weren't sure quite what to expect, but we did some testing on multiple ATI and NVIDIA graphics cards, and we'll take a look at the results later on. First, let's go a bit more in-depth into the technology.