Half-Life 2: Lost Coast

Half-Life 2: Lost Coast Introduction to HDR

"Hi. This is Gabe Newell and welcome to The Lost Coast. In this tour, we're going to be talking about a new graphics technology we've been developing called High Dynamic Range, or HDR. We'll also be giving you some insight into the design and production challenges we faced during the construction of The Lost Coast."

Thus begins Half-Life 2: Lost Coast, as introduced by Valve founder and Managing Director, industry legend Gabe Newell. At the kind invitation of Valve, we flew to Seattle to meet the development team behind Lost Coast and talk about HDR, performance, image quality, as well as their up-coming release of Day of Defeat: Source. We also had the opportunity to play through the Lost Coast and performance test it.

In this article, we're going to be looking at the technology Valve have built (Pages 1 and 2), as well as taking you through the story of the level (Pages 3 and 4) and answering some basic questions and giving you our thoughts, as well as a quick look at Valve's office (Page 5). In our next article, we'll show you performance figures for different graphics boards ahead of the level's public release. For now, read on...

Dare to dream

Half-Life 2: Lost Coast is Valve's reply to a series of What If questions: what if there were no limits? What if we didn't have to make sure people with mid-range systems could enjoy our games? What if the system requirements knew no bounds?

Following the release of Half-Life 2 worldwide on 16th November 2004, a group of programmers and artists at Valve sat down to create the ultimate level, incorporating ultra high resolution textures, models and adding High Dynamic Range Rendering (HDR) to the Source engine. Their aim was to create a technology showcase: a no-holds barred level that would set new standards in image quality and realism; something to really push even the highest of today's high-end systems.

Let's be clear: Lost Coast isn't just about HDR. It's also about those other things - the amazing textures and the high quality models.

High Dynamic what now?

HDR represents the greatest leap in in-game image quality since the advent of Anti-Aliasing. It adds depth and character to a game such that once you have played with HDR enabled for a period of time, switching it off reveals a flat, dull scenery and lifeless characters. So what exactly is HDR and what does it mean? Paul Debevec, a graphics researcher from the University of Southern California, is seen as the Father of HDR, and world expert in the field.

"The 'dynamic range' of a scene is the contrast ratio between its brightest and darkest parts," he told us. "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."

A High-Dynamic Range image is an image that has a greater contrast range than can be shown on a standard display device, or that can be captured with a standard camera with just a single exposure.

Current TFT monitors have a typical contrast ratio of 400:1, and even the most expensive models can only boast 1000:1. This means that in any given scene, the colour value or brightness of the darkest pixel can only be one thousandth of the value of the brightest pixel. This may sound like a lot, but in the real world, the dynamic range of the human eye is measured not in the hundreds, but in hundreds of thousands or more.

Half-Life 2: Lost Coast Introduction to HDR
Here you can see a photo of the sun taken with a digital camera. Even with a very short exposure time on the far left, the sun is grossly over-exposed, while the rest of the image is under-exposed. As you increase the exposure time to compensate, you end up with an over-saturated image (far right).

Half-Life 2: Lost Coast Introduction to HDR
To put this theory into context, here is an example from Lost Coast. Chris Green, one of Valve's Software Engineers, explains: "You can see that none of those exposure values captures all the detail in this scene," he said. "You either have blown out highlights on the exterior, or you have stuff inside the alcove that is too dark to make out the detail. No one exposure can draw that scene [as the human eye would see it]."

To see this effect in full, check out our exclusive Half-Life 2: Lost Coast video trailer.

What this all means to the game developers is that while they strive for greater realism in their graphics, they are constantly handicapped by the standard dynamic range. By adding HDR to the Source engine codebase, Valve have much greater freedom in how the represent the game world, and in the realism of the lighting. By using clever methods, they can also get around the fairly average range of today's display devices.