Half-Life 2: Lost Coast
- Platform: PC
- Published by: Valve
- Developed by: Valve
- Release Date: Fall 2005
- Genre: Action
- Multiplayer: No
- Online: No
A Day at Valve
-- September 15, 2005 by: Chris Remo
Only a couple weeks after Day of Defeat: Source launches, gamers will be able to get their hands on the short single-player HDR showcase Lost Coast. Somewhere down the line, probably in November and definitely by the end of the year, Valve will also release Aftermath, the first full-on single-player expansion for Half-Life 2. There's also the Xbox version of Half-Life 2, which Valve mainly sees as a way to get the game into the hands of those who haven't yet gotten a chance to play it on a PC. Beyond that, it's anybody's guess. The team has its hands more than full at the moment, so we'll just have to sit it out for news of what's coming next.
Valve and HDR
So what is HDR? It proved so difficult to implement that Valve had to cancel its inclusion in the original Half-Life 2 game, but why? Succinctly, HDR is probably best explained by Paul Debevec, the man who was pioneering HDR research long before it was the type of thing even being considered in video games.
"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."
HDR rendering attempts to compensate for the relatively limited contrast range of display devices--such as computer monitors--through various means. The first is blooming, which has become a fairly commonly used visual technique in games recently, though it is only one part of what Valve considers a more complete HDR solution. In order to simulate the overexposure of a camera or the eye due to very bright light, the brightly lit portions of the scene are blurred, giving that familiar effect from games such as Far Cry.
Next, there's the use of an HDR skybox. Multiple versions of the sky texture at different exposure levels are painted, so that the game can adjust the exposure in real time depending on a variety of factors. This is an impressive feature that allows for the entire scene to be dynamically relit based only on changing the exposure levels. A very impressive part of Lost Coast is that there is literally only one source of light in the entire level: the sun (well, and your flashlight and gunfire). Thus, when its exposure is adjusted, it affects the lighting everywhere. One thing that causes exposure adjustment, just as in real life, is moving from a very dark area to a very bright area, or vice versa. When your eye experiences a drastic change in perceived brightness, there is a moment during which the iris adjusts. The game too has that auto-exposure affect. In fact, Valve is hoping that the mod community will find interesting ways to manipulate exposure as a gameplay element. Perhaps it would be a key feature in stealth games where light and dark make all the difference. There were even suggestions such as binding exposure adjustment to the mousewheel. For what purpose? Valve has no idea, but they hope somebody else will.
One of the most visually impressive parts of HDR is that it allows higher light values than would normally be allowed in a game engine for surfaces that aren't very reflective. For example, consider sand on a beach that is in general 20% reflective. Without HDR, that sand would only be able to use 20% of your monitor's maximum brightness, leading to a fairly low contrast range. However, in reality, the sun is such an incredibly powerful source of light that on a bright clear day, it will still cause quite a lot of light to reflect off of the beach, and can have a blown out white effect; this is represented in the game. The same goes for water; if the sky is very bright, the water will reflect it as such.
All in all, it's a very impressive technology to which Valve has really dedicated a lot of time and effort. One testament to the artistry with which the company is implementing HDR is that, with the exception of fairly obvious effects such as blooming, many of the improvements to normal lighting are almost transparent. There were several moments when I didn't realize how much of a difference the techniques made until they were put side to side with traditional low dynamic range screenshots, simply because the HDR scenes looked more "right". As gamers we are often used to measuring graphical improvements in terms of higher polygon counts and visual pyrotechnics, and while some elements of HDR definitely provide a lot of showy effects, much of it is very subtle and fundamental.
Continue to the next page for my impressions of Lost Coast and Day of Defeat: Source, as well as more on Valve.