Nvidia GeForce 6800 Ultra

Most impressive graphics chip yet?

Another new feature is Displacement Mapping, which is a simplified way of making complex objects look more realistic and adding more depth to graphics without creating the performance overhead previously associated with this. The easiest way to think of Displacement Mapping is as an advanced version of Environment Bump Mapping, but rather than adding bumps, the shape of the object is physically changed. An object with Displacement Mapping applied also reacts to the way light is applied to it with the textured surface of the object casting shadows in a way that Environment Bump Mapping would not.

The bottom line here is that Displacement Mapping will add a new level of geometric detail to objects making it easier for the game developers to add life like three-dimensional surface textures.

Next up is Pixel Shader 3.0, which is the one feature nVidia has been pushing hard. Along with similar Infinite-length Pixel Shaders and Dynamic flow control so fundamental to Vertex Shader 3.0, Pixel Shader 3.0 introduces Flexible Data Support and Multiple Render Targets. To fully understand all of these features you need a degree in 3D graphics, but I will try to touch on the core points of each of these new technologies.

Flexible Data Support gives programmers the flexibility to work in either 16- or 32-bit data precision depending on what they want to achieve and the resources available. Multiple Render Targets (MRT) is a variant of deferred shading, whereby pixel data is stored in multiple buffers until a scene's geometric detail has been calculated and rendered; at which point lighting data can be applied to the rendered scene. This saves multiple passes through the graphics pipeline, while also offering all the benefits of photo realistic lighting effects. The advantage of this is that the GPU has to do less work applying light and shadows to scenes for which it doesn't yet have all the information.

Nvidia is also introducing Rotated-Grid Anti-aliasing, which should vastly improve the quality of anti-aliased scenes. Traditional anti-aliasing using a two by two sub-pixel grid arrangement samples only two horizontal and two vertical values per pixel. By rotating the grid it can be positioned so that each sub-pixel samples four horizontal and vertical subpixel colour values instead. This is generally a far more accurate way of calculating colour values at the edges of polygons.

With complex lighting effects come complex shadows and though we give them little thought in the physical world, rendering them in games can cause a significant drop in performance. Although UltraShadow technology made its debut on the GeForceFX, the GeForce 6800 improves on this with UltraShadow 2 and a claimed potential fourfold increase in performance.

By removing the need for colour or texturing updates the GeForce 6800 generates stencilled shadow volumes at up to twice the standard pixel-processing rate. Nvidia also claims that game performance can be improved further with the use of a few specific UltraShadow 2 hardware calls.

Another acronym worth remembering is HPDR, or high-dynamic per-pixel radiance. Without throwing you a page of fancy equations, this allows a scene to contain the brightest of highlights and the deepest of shadows all displayed at once. Because standard 32-bit per-pixel frame buffers only gave 255 values to store the entire range of colour data, compromises often had to be made when scenes were rendered with a broad spectrum of lighting and colour intensities. HPDR technology broadens the programmer's palette and delivers greater data precision during shading, blending and filtering operations for both static and moving images.