Speaking of complex transform and lighting effects, the 7800 GPU features full support for the DirectX Shader Model 3.0 and optimizations for several of the latest advances in eye candy such as HDR (High Dynamic Range) lighting, subsurface scattering and nVidia's UltraShadow II technology. These technologies also worked fine with the 6800-series GPUs, but often with a performance hit that substantially reduced the gaming experience.

Vertex Boosting

nVidia has apparently increased the speed and efficiency of certain vertex shader operations, resulting in an overall boost to their output. The texture engine has also undergone an overhaul, with non-specific increases to its speed and efficiency stated.

nVidia's new transparent Anti-aliasing technology

With the introduction of the 7800 GPU, nVidia also debuts two new Anti-Aliasing technologies, transparency adaptive supersampling and transparency adaptive multisampling (TRSS and TRMS respectively). These provide a potential solution to what has long been a thorny image quality problem: The difficulty of anti-aliasing pixels inside a polygon.

Conventional multi-sampling AA only performs anti-aliasing on pixels detected to be at the edge of a given polygon, incurring less of a performance hit but only applying the smoothing effect of AA to the edges of 3D objects. This is fine for a solid 3D object such as a wall or tree, but what about grass? Or leaves? Or a chain link fence like the thousands found in the world's most action packed fence simulator (Half-Life 2)?

The polygons making up 3D rendered foliage and fences use transparency (alpha) effects to allow realistic sight lines through them, but this means that the pixels making up the visible edge of a blade of grass or leaf are not always on the edge of their polygon, but rather somewhere inside it next to other pixels which have been made transparent. Multi-sampling AA will not smooth out these pixels, meaning that textures that use transparencies will always appear to be jaggy, even in an otherwise glass-smooth 8xAA sampled scene.

The other common method of Anti-Aliasing, SuperSampling, can solve this problem in a way. SuperSampling renders each entire frame at a higher resolution then blends the colour and shade of areas where there is a large amount of difference between pixels, then re-renders the image at the display resolution. Supersampling does not care whether it is blending pixels at the edges of polygons or in the middle of them. The disadvantage though, is that supersampling incurs a huge performance hit, making it difficult to justify.

nVidia's TRSS and TRMS AA technologies provide a more elegant solution. Transparency Adaptive Multi-sampling performs the same AA operations as conventional multi-sampling does, blending pixels on the edges of polygons. It then goes one step further by examining each polygon for pixels with alpha (transparency) information. If it finds them, it applies AA to the pixels adjacent to the transparent areas too.

As far as we can tell, Transparency adaptive SuperSampling performs simple multi-sampling on most of the image as normal, but applies full supersampling to polygons with alpha pixels in them. This results in higher image quality and a larger performance hit than TRMS.

In all, TRSS and TRMS seem like a sensible upgrade to current AA technologies, enabling better all-around image quality without the performance hit associated with full supersampled AA. Games like Far Cry and Half-Life 2 should benefit considerably from nVidia's new tech. We'll see this effect on the next page with a couple of screen shots.