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Rage: The Tech Behind Id Tech 5
Date: Aug 16, 2011
Author: Joel Hruska
id Software's long-awaited FPS Rage is set to ship in October. When it launches, it'll be the first game to feature id's newest graphics engine, dubbed id Tech 5. With expectations running high in the wake of the latest game trailer shown at QuakeCon last week, we've put together an article to examine the merits of both the game and the technology behind it.

Note:  Some of the big images in this article are quite large. This was done to make certain texture detail and rendering quality weren't adversely affected by JPEG compression.

The Game

Vehicular combat is a major part of Rage. The engine doesn't support tessellation, but character detail is good without it

Rage takes place in an alternate future in which the asteroid 99942 Apophis struck the Earth in 2029. Prior to the impact, governments created underground storage facilities to house the best and brightest of humanity and to safeguard technology that might be needed in the future. The Ark inhabitants were put into cryo-sleep, but the process didn't work as planned. When the player character awakens, he finds himself to be the only member of his Ark to have survived the process.

Rage shares certain thematic similarities with Bethesda's well-received Fallout 3 and Fallout: New Vegas, but approaches the post-apocalyptic wasteland from its own unique angle.

When the company built Rage, id eschewed the fairly common 30 fps standard for modern console games and went with a 60 fps target. Watch any Rage demo, or listen to id executives talk about the game, and you'll most likely hear 60 fps mentioned within minutes.

Rage is meant to be experienced one way—fast. It's refreshing to hear id talk about speed after Doom 3's somewhat slow pace and the ridiculous lack of light. This time around, neither issue is a problem; when company executives aren't talking about the game's speed, they're talking about its visuals. Screenshots of players and terrain both, bear out the company's claims.

In the wake of the Apophis impact, humanity finally develops flying cars

One caveat we will note is that previews and controlled game sessions don't always give an accurate impression of how much fun a game is (or isn't). We're willing to believe the hype when it comes to Rage's visuals and its speed--Carmack and the crew at id have decades of experience in 3D graphical design.  The company has also released a fair bit of information on how it optimized the game for different platforms in order to ensure it would run at 60 fps across the board. Even if the game's plot isn't Oscar-worthy, it'd scarcely be the first title where a paper-thin plot is cemented together with rock-solid gameplay and stunning visuals.

id Tech 5
id Tech 5: MegaTexturing and Other Key Techniques -

When id first announced Rage back in 2007, much of the discussion focused on Carmack's then-new MegaTexture technology, which first debuted in Splash Damage's Enemy Territory: Quake Wars. id Tech 5 has evolved considerably since the company started talking about it four years ago, however. While it contains a number of additional features, MegaTexturing remains one of the game's most visible advances and remains a good jumping-off point for any discussion.

The vast majority of games use a technique known as texture tiling when rendering a game environment. Texture tiling uses a  small number of texture tiles to create a large environment. The advantage to creating an environment this way is that it dramatically reduces RAM storage requirements and memory bandwidth overhead. The downside is that it creates extremely repetitive patterns, as shown in the left-hand image below.

Screenshots from WoW's DX11 mode. The only difference is the amount of ground clutter--"Low" on the left, "Ultra" on the right.

The traditional solution to this problem is to introduce additional environmental objects, shadows, and what WoW helpfully calls 'ground clutter.'  Turning that option all the way to 'Ultra' produces the upper right-hand image. Adding ground clutter makes the texture repetition less obvious, but doesn't resolve the underlying issue--which is that we've simply added a second, repetitive pattern on top of the first. There are a number of ways an artist can make an area seem unique, but they all rely on disguising an underlying pattern.

MegaTexturing approaches the need to conserve memory bandwidth and GPU storage from the opposite direction. MT uses a single large texture to map the terrain of an entire area. Data from that texture is streamed in depending on where the player is standing and what's visible, but the jarring texture-load issue that plagues console ports isn't necessary. Effects that would normally be blended in traditional tiled texturing can be baked into the megatexture and streamed off disc when needed.

The upper-right image shows the same bits of grass duplicated. MT doesn't preclude the use of more standard texturing methods.
The advantage of megatexturing is that it allows artists to create unique environments rather than resorting to a variety of tricks to hide repetitive ones. The approach isn't a good fit for everything--id has flatly stated that the Rage engine would be a very poor fit for a truly open-world game like Elder Scrolls: Skyrim, and can't handle a normal day/night cycle. id Tech 5 also doesn't support global dynamic lighting but will (reportedly) add support for soft-edged shadows via shadow maps, crepuscular rays (evident on the flying car image at the bottom of the previous page), alpha to coverage, depth of field, and motion blur. Anisotropic filtering support, however, may be limited--several of id's presentations imply that 4x AF may be the engine's limit, although this is unconfirmed.

id hasn't publicly released a laundry list of the engine's full capabilities, but one feature we know Rage doesn't support is tessellation. While Carmack acknowledged that tessellation is one way to create more detailed terrain, he noted that supporting tessellation in id Tech 5 would've required bolting it on rather than incorporating it from the beginning.

Under The Hood -

Some of the most important features of id Tech 5 operate behind the scenes. One of the major features of the engine is its ability to run on a wide variety of architectures. In contrast to the Doom 3 engine, which didn't scale particularly well, id Tech 5 is built to run on a huge range of products and in very different environments.

From a 2009 SIGGRAPH
presentation, given when Larabee was still on the table

Carmack's latest keynote makes it clear that while he prefers the PC for development purposes, the id team didn't shirk when it came to optimizing Rage for the XBox 360 or PS3. The engine exploits CPU parallelism by categorizing the engine's tasks by job, then assigning those jobs to various SPE's. The technique may be a response to the challenges of programming for the PS3, but it shows how much work has gone into insuring that Rage's engine can scale across devices.

We suspect id Tech 5's multiprocessor, multiplatform support may be one of its most attractive features. Carmack demonstrated part of the engine running on the iPhone 4 back in 2010, and while the company isn't planning to aggressively license id Tech 5, its multi-platform awareness could make it uniquely suited to cross-platform development.

Ultimately, id Tech 5 will rise to prominence (or not) based on the success of its shipping titles. For now, that means Rage. Doom 4 is still scheduled for a 2012 launch, but Carmack isn't sharing details or screenshots on the new title yet.  Either way, it's obvious id has further developed their proprietary technologies such that Rage is shaping up to offer yet another environmentally immersive experience for gamers; that and potentially a whole bunch of fun.

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