HyperZ Technology

HyperZ Technology

Current graphics accelerators must render a scene in three dimensions, although our monitors are only two-dimensional. What we actually see on the monitor is only a fraction of the data that the graphics chip must keep track of and render.

One way around this inefficiency is to only render the parts of a frame that will be visible. The PowerVR chip used in the Sega Dreamcast does just this with a tile-based rendering system. Deferred rendering is another example of this. Gigapixel, which was recently purchased by 3dfx, also uses a similar technique.

ATI's HyperZ technology doesn't render some of the pixels that are not visible on the screen. Whether or not a pixel is visible is determined by analyzing the Z-buffer, hence the name. ATI claims a performance improvement greater than 20% with HyperZ. No additional programming code needs to be written by game developers to take advantage of this technology, it is all done on ATI's side.

With respect to the fill-rate performance, HyperZ gives the Radeon 256 an additional 300 megatexels of fill power. This number is determined from multiplying the clock speed, (200MHz) by the number of textures that can be filled per pass, (6) and subtracting this from the claimed effective fill rate of 1.5 Gigatexels.

This performance gain is very reasonable as the PowerVR Series2 used in the Sega Dreamcast claimed gains of more than 25% due to its use of tile-based rendering.

Pixel Tapestry

Our GDC report on ATI already talked about the Pixel Tapestry technology which is really a term that encompasses many 3D quality feature sets that may be found on other cards. One example is the inclusion of Environment Mapped Bump Mapping in the Radeon 256 - something that was previously only found in the G400. The Radeon 256 will also support texture compression in both DirectX and OpenGL.

Another interesting feature of Pixel Tapestry is the use of 3D textures. We can see this feature being very successfully implemented in smoke and fire effects. We can also picture better representations of multi-dimensional objects such as clouds or bodies of water.

ATI is also making a great effort to inform game developers about these technologies so that they may be incorporated into the next generation of games. The list of supported games at the end of the presentation suggests that the developers were just as impressed as we were.

Charisma Engine

With Radeon 256, ATI claims that they have the best hardware transform and lighting implementation on the market. Of course, that's also what NVIDIA is saying!

Regardless, ATI does claim to suffer from less of a performance hit with eight lights in comparison to other T&L solutions. The last time ATI made a claim such as this, it was regarding 32-bit color performance on the Rage128. We all know what a good performer the Rage 128 was in 32-bit color.

What we found most exciting about the Charisma Engine was its animation character accelerator. Basically, a developer just needs to define the start and end positions of a character's face and the ATI card will make the necessary calculations to morph the images. Think of it as a 3D Studio Max Character Studio for facial expressions.

The ATI Geometry Pipeline