MSAA works by having the GPU sample multiple locations of each pixel in a scene, and then fully rendering and combining those pixels in the image that's ultimately rendered on the display. In 4X MSAA, four samples of each pixel are taken. For all its effectiveness, MSAA is very computationally expensive and can significantly reduce frame rate when it's enabled in a game.
Nvidia's Multi-Frame Anti-aliasing (MFAA) functions in a similar fashion, but it samples pixels over two frames while rotating the pixels. The technique, according to Nvidia, delivers results that are very similar to MSAA without the performance hit that MSAA exacts. Herkelman says MFAA is up to 30 percent faster than MSAA.
Voxel Global Illumination (VXGI) is the third big improvement to be found in the GeForce GTX 970 and -980. Briefly, it's a new lighting technique that promises to deliver much better image quality without requiring a significant performance hit. As Herkelman explained it, a voxel (a portmanteau for volumetric pixel) stores information about the light in a rendered environment.
Games designed to run on previous-generation GPUs depend on what Herkelman described as "hand-placed lights." A few light sources in a game environment are placed in fixed locations, so the manner in which the light behaves and its impact on the environment is predetermined in the game's programming code. That's part of the reason why only certain objects in a game can be destroyed, the programmer must hard code the manner in which the light and shadows will be rendered on those objects.
VXGI enables programmers to place dynamic light sources in a game's environment. Objects in the game can be assigned properties that determine how they'll reflect or absorb the light cast upon them. With this technology, the game programmer can simply place light sources, and those lights will react dynamically to any changes in the environment. In the rendered image of the Apollo moon landing, above, Herkelman changed viewpoints by moving the camera all around the scene, and the lighting changed accordingly. The way objects reflected or absorbed light changed dynamically, and cast shadows moved in relation to the point of view.
Oculus Rift support
Nvidia's VR Direct technology is intended to benefit upcoming virtual reality headsets such as the Oculus Rift. This bundle of features is designed to reduce latency, allow headsets to take full advantage of Nvidia's dual-GPU SLI technology, and improve stereo-vision support. Herkelman demoed a new space-combat game for me Tuesday, and it looked leagues better than anything I saw over the course of Nvidia's 3D Vision initiative.
Like the original Maxwell architecture Nvidia announced in February, these new GPUs adopt power-savings tricks originally developed by Nvidia's Tegra CPU team. Where a GeForce GTX 680 card with 2GB of memory has a thermal design power (TDP) rating of 195 watts, and a GeForce GTX 780 with 3GB of memory has a TDP of 250 watts, the TDP for the GeForce GTX 980 with 4GB is just 165 watts.
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