GPU Technologies - Intellisample 3.0
Intellisample gets a 3.0 designation too. It's the marketing umbrella for the antialiasing and texture filtering hardware that the GPU has.Texture Filtering
NVIDIA, with GeForce FX, took a lot of flak for its texture filtering performance and image quality. Trilinear filtering was optimised without the user asking for it, resulting in the now famous brilinear filtering mode, a combination of bilinear and trilinear texture filtering. It's fast on GeForce FX, but image quality is reduced. The chief complaint centres around the driver offering no way to turn the optimisation off. If the user was given a choice as to whether they could enable the optimisation, nobody would have cared, benchmarking it would have been much easier and you could get full trilinear if that's what you wanted, sucking up any performance hit.The anisotropic filtering wasn't too bad with trilinear enabled, offering 8-bit precision to the trilinear filter and generally looking pretty good. Up to 8X aniso was supported and it was a straight algorithm, doing whatever aniso level was selected on all textures.
The driver for GeForce 6 finally allows you to choose whether you want the optimisation enabled and the toggle actually seems to work. The hardware does full trilinear as its default filtering method and it appears it was designed that way from the outset, so it could be as fast as possible with maximum image quality. A welcome change from NV3x whose default texture filtering mode is bilinear. The default driver option is for the optimisation to be turned on.
GeForce 6 changes its aniso algorithm somewhat, adopting a similar angle-adaptive model of aniso filtering to ATI. It now supports up to 16X aniso filtering and the driver claims to support both angle-adaptive and non-adaptive aniso, but it's currently broken in the review driver. Angle-adaptive is your only choice currently, like ATI provides.
Antialiasing
Antialiasing gets a semi overhaul with NV40 and its new driver, compared to NV3x. NV3x used ordered grid multisampling for all its AA modes, sometimes combining them with supersampling for extra quality, sacrificing it for a performance hit. The problem lay in the way their ordered grid multisampling sampled the geometry it was aliasing. Modes higher than 4X needed supersampling for extra quality, the ordered grid not sampling in a way that gave good coverage, and at the time of NV30's launch, ATI's aliasing methods, using pseudo-stochastic AA with 'random' sample grids, offered better quality. Recent Radeon's 2X AA quality is arguably just as good quality wise as NVIDIA's 4X multisampling mode and it's faster. Quincunx, while offering 'free' extra AA by sampling in the DAC, ended up pretty blurry in most cases, sacrificing overall image quality.So things really needed changing for NV40. The new GPU still implements multisampling, but this time it's rotated grid, offering better image quality due to sample distribution. 8X is a strange mode as you'll see later, but on the whole the new modes offer a better sample set and hopefully more performance to go with the new image quality.
So RGMS with a strange RGMS+SS mode thrown in at the top end for good measure.
