Image Quality and Features Elsewhere

We've mentioned that G80 is largely orthogonal in the ROP and filter hardware, but without much concrete proof. As a D3D10 part it's safe to assume various support for surface formats and how you can use them, such that they help define final pixels, but without a driver we're stuck using D3D9 (still) to check what the chip is capable of as far as DirectX goes.

To that end, we engineered a small D3D9 test application that queried all available surface formats across the common types used for filtered textures (RTs, cubemaps, basic surfaces, volume textures, etc) for the D3DUSAGE_QUERY_FILTER flag, and whether they support the multisample modes (D3DMULTISAMPLE_ X_SAMPLES, where X is the sample count).

The results are telling, with every surface format filterable and everything bar X1R5G5B5 supporting multisampling, backing up what NVIDIA claim for G80's image quality abilities, as concerns filtering and antialiasing as least. The chip only exposes support for point sampling of vertex texture formats under D3D9 though, as expected, and you can only linearly filter volume and cube textures, with non-linear filtering mostly the realm of RTs and basic texture surfaces.

As far as filtering quality goes, the current G80 driver doesn't under- or over-filter across MIP texture boundaries (the cause of shimmering complaints in prior NVIDIA hardware) so hopefully that's the case for the product's entire lifetime. In terms of the hardware helping to remove other aliasing artifacts, we look to the Performance article for that, since it'll help (in part) to explain how developers can use available features and performance to enhance IQ outside of the usual hardware-based (and somewhat fixed function) remits.

Blending wise, our small test application for D3D9 caps shows every texture format bar 2- and 4-channel 16-bit integer formats (G16R16 and A16B16G16R16) are supported as far as post-PS blending goes. Every tested cap on G80 seems to be agnostic of whether the app is exclusive (full-screen) or windowed, too.

Lastly, it's worth quickly mentioning NVIO as the conduit for getting G80's pixel drawing abilities to your monitor since, as the final arbiter of what gets drawn, it's as responsible for image quality as G80 is. It's not crystal clear what NVIO can do about final pixel-level image quality or whether it's just effectively a pass-through device in that respect. A large part of the chip appears to just be filler transistors just to get a die big enough for the pad count needed, and thus speculation is ill-informed when basing it around use of all possible logic. To that end, we'll be digging deeper into NVIO in a satellite piece to let you know exactly what it's capable of.