Nvidia Intellisample OpenGL Driver 43.45 - 43.51 Optimization

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Digit-life's Aleksei Nikolaichuk aka Unwinder has thrown up his Nvidia Intellisample Technology OpenGL Driver 43.45 and 43.51 optimization guide! This is Part I.

If you ask an average gamer which GPU's feature he considers the most important for image quality in modern games, you will most probably be answered: anisotropic filtering. Unfortunately, the anisotropy, this high-quality but resource-hungry (because of the universal direct realization) element, is the weakest point of the NV25 graphics processors. No wonder that the follower of the NV25, NV30, was expected to come with fast anisotropic filtering able to provide a high playable fps level in high resolutions. NVIDIA did understand it. Exactly to eliminate that weak point and prevent that awful performance drop because of the anisotropic filtering they launched the Intellisample technology announced together with the NV30 family. To all appearances, the term Intellisample comes from Intelligent Sampling, i.e. NVIDIA hints at certain intelligent scene analysis technologies that reduce the computational resource consumption for anisotropic filtering by simplifying its algorithms if the image quality does not suffer much. As you know, yet the OpenGL v28.90 driver had scene geometry analysis algorithms that could texture certain polygons without anisotropy enabled and allowed for a considerable performance gain in the multitexturing mode. Determination of the texture stage indices and application of this algorithm only to the stages with nonzero indices let NVIDIA make the polygon culling algorithms unnoticeable for image quality tests because mostly secondary textures (like light maps) that were not determining for image sharpness were simplified. This algorithm was enabled by the OpenGL driver in the Balanced and Aggressive modes with the anisotropic filtering forced, but it was the only component of the Intellisample technology available for the whole GeForce family in the OpenGL. Today we are not going to touch upon the code specific for NV3x processors (optimizations concerning trilinear filtering, LOD bias etc.), but we will deal with anisotropy optimization algorithms general for the whole GeForce family. The Detonator 43.45 and 43.51 drivers, arrived quite recently, raised the level of anisotropic filtering in OpenGL and got the support of cardinally new optimization algorithms for all GPUs of the GeForce family. These optimizations will be the today's subject.

NVIDIA Intellisample Technology OpenGL Driver 43.45 and 43.51 Optimization Part 1