Keeping 3-D True to Form

One of these days, ATI wants to bring the same cinematic style and quality to your computer screen that you see in movies such as Toy Story 2 and Shrek . Until then, however, the graphics processor maker will just have to settle for bringing added detail to 3-D objects.

Windows developers familiar with Microsoft’s DirectX technology know this technology as “N-Patches”; to OpenGL mavens, it’s called “PN Triangles.” ATI Technical Marketing Manager David Nalasco says that it’s been available to developers for about the past six months, but ATI has kept it under its hat until the technology was used enough to be able to show off some impressive demonstrations.

ATI’s ultimate goal of bringing cinema-like quality to 3-D graphics may be easier said than done, though. Cinematic computer graphics use a fundamentally different way of representing 3-D models, according to Nalasco — they use curved lines, rather than polygons.

Why not just use curved lines, then? Nalasco says it would require personal computer software programmers and hardware makers like ATI to adopt a completely new way of thinking about 3-D imagery, thus sacrificing backward compatibility and creating a comparatively tiny, delicate niche in the hugely competitive 3-D-graphics hardware market.

And while the industry may head that way eventually, Truform gives ATI a great interim solution. The secret, in a nutshell, involves converting triangles to curves, then back again.

Polygons provide a fairly compact and convenient way of measuring the position of 3-D graphics. But there’s a finite amount of polygonal data that you can make a computer or a graphics card calculate before such data processing takes its toll in the form of reduced frame rates, even on today’s fastest chips. Hardware transform and lighting capabilities aside, there are other bottlenecks to deal with, such as the speed of the CPU and the bandwidth of the various bus interfaces on the computer.

Triangles to Curves, Then Back Again

Truform will provide ATI’s next generation of graphics hardware — which will get a more formal introduction later this year — with the ability to recalculate polygonal data on the graphics chip itself, thus removing other bottlenecks in the computer from the equation.

“With Truform, we’re taking the triangle, converting that into a higher-order curved surface, and converting that data back into triangles again,” Nalasco says.

By doing this, Truform is able to yield a model with a much higher polygon count — providing more detail on the surface, a smoother mesh, and more-accurate lighting information, Nalasco says.

“Basically, we get the best of both worlds — we’re able to accept triangles as input, but we output as triangles, and we calculate in curved surfaces,” he adds.

Low Barrier to Entry

Programmers who make use of ATI’s Truform technology can tell their software applications to use Truform on the entire screen image or just on specific models.

Implementing Truform in a 3-D application is as easy as writing a single line of code that activates support for the technology, Nalasco says. Chances are, though, that software developers will want to customize Truform support in their applications. That’s because there are entire libraries of objects that wouldn’t really benefit from an increased polygon mesh, such as walls, floors and ceilings in a game — in other words, any object that’s comprised of straight surfaces. Programmers can also define the level of detail they’d like to apply using Truform.

The new technology is supported by DirectX, Microsoft’s proprietary Windows application programming interface (API), but it also works as an OpenGL extension. This means that Truform will work on the Mac just like it’ll work on the PC, although Nalasco admits that DirectX programmers have an easier time than OpenGL programmers do. DirectX enables programmers to take for granted some operating parameters that OpenGL programmers must pay closer attention to.

But the bottom line, Nalasco adds, is that Truform is extremely easy to use.

“The fundamental process involves making a function call — there are no new languages to learn, and nothing fancy to get your head around,” he says.

ATI emphasizes the use of Truform in games because games are a major market for 3-D hardware these days. But Nalasco says the technology goes well beyond games. It can be used for potentially any 3-D application, such as modeling software or CAD/CAM — anywhere that more detailed 3-D models can be applied.

Regarding Artists

Programming implementations are fine, but that’s only one half of the issue — the other is 3-D artwork itself. To that end, ATI has developed tools for 3-D artists who create models for games.

“Artists can use some tools that ATI has been developing to look at their artwork to see how it’ll look in Truform,” Nalasco says. “Truform enables them to tag specific edges to prevent them from being softened.”

Take a model from a 3-D shooter holding a weapon — the artist can tag the edges of the weapon or the model’s armor to tell Truform not to make that edge soft. This means that other organic elements — the model’s face, or bare arms, or legs, for example — may have more rounded, natural-looking features, while the gun or sword still looks real.

Nalasco describes the effect in motion as “shrink-wrapping.” Meshes that were blocky before Truform is applied appear much smoother afterward. Nalasco also suggests that this would aid 3-D games with “popping” problems, when objects suddenly gain detail as the game’s engine replaces a low-poly count model with a high-poly count model. The effect using Truform would be much more realistic, with detail gradually filling in as the player gets closer to the object.

Better Detail, No Performance Hit

Truform-enhanced software applications will be able to provide much more detailed, complex models than users have seen previously, without significantly impacting the application’s performance, Nalasco says. In fact, performance won’t be affected at all in many cases.

“Truform all happens inside the chip. You can almost think of it as pre-processing,” Nalasco says. “It happens before you do your rendering and texture mapping. Things like bumpmapping, keyframe interpolation, and per pixel lighting happen after Truform has already been applied.

“In today’s games, you don’t even come close to maxing out transform and lighting capabilities in the graphics chip itself,” he adds.

What’s more, ATI’s new technology will use a memory bandwidth architecture with several times the capabilities of its current high-end architecture, Radeon. “Truform usually won’t affect performance at all,” Nalasco adds.

Quality over Quantity

Soon, Nalasco suggests, the frame rate of a 3-D card won’t be the overriding issue. Instead, the focus will be on what the 3-D chip actually does with the graphics to make them look better. Truform, Nalasco adds, is an example of quality over quantity.

That analysis is probably more applicable to the PC market, where some video cards are already regularly turning in frame rates of more than 100 frames per second. Users can certainly see a measurable, playable difference between 30 and 60 frames per second, but there’s a point of diminishing return where the average user just can’t tell the difference anymore.

We’re still not at that point yet on the Mac, but technologies like Truform certainly stand to benefit us, regardless.

This story appeared earlier on Macworld ‘s sister site MacCentral.com.