The GeForce4 Ti — continued

  • Accuview anti-aliasing — The GeForce4 Ti's basic approach to anti-aliasing—multisampling—is the same as the GeForce3's, but NVIDIA has made some very worthwhile tweaks to the AA implementation in the GF4 Ti, and they've given it a new name. Accuview AA uses NVIDIA's multisampling approach, which effectively provides edge-only antialiasing in a more efficient manner than the traditional super-sampling approach.

    Among the improvements:

    • NVIDIA claims the GF4 Ti includes wider internal data paths, so it can accommodate multisampled anti-aliasing with very little performance loss.

    • The sample patterns for Accuview are improved. The GeForce3 used a rotated grid sample pattern for 2X AA and an inferior ordered grid pattern for 4X mode. The GeForce4 family uses rotated grid patterns for both 2X and 4X modes. NVIDIA denotes this difference in 4X mode by dubbing the rotated grid 4X mode "4XS". The grid rotation is undoubtedly a good thing; it interrupts the regularity of the pixel grid, helping fool the eye to detect less aliasing. Unfortunately, Accuview doesn't include a semi-randomized sampling pattern like the Radeon 8500's SMOOTHVISION does—that would be even better than a rotated grid.

    • Also, as you can see in the diagrams below, Accuview's AA sampling points are more centered in the pixel. At the subpixel level, the GeForce3 was sampling at the very center and at the edge of the pixel. NVIDIA claims these new sampling patterns provide more accuracy than the previous arrangement.


      GeForce3 2X anti-aliasing sample patterns


      Accuview 2X anti-aliasing sample patterns

      My understanding is that these new sample patterns ought to cause NVIDIA's multisampling routine to decide to do blending more often, which is probably why NVIDIA didn't use these patterns with the GeForce3—out of a concern for performance.

    • Quincunx remains, for those of you who prefer 2X AA plus full-screen blurring. NVIDIA claims turning on Quincunx doesn't slow performance at all versus 2X mode. I hear adjusting your monitor to run out of focus doesn't, either.

    • Accuview AA now encompasses anisotropic filtering as well as edge AA. This combination of edge antialiasing (multisampling) and texture antialiasing (anisotropic filtering) is simply The Right Thing To Do. Multisampling is just as effective as supersampling for edge AA, and anisotropic filtering is more effective than supersampling for texture AA. The GeForce3 could do both things at once, but the features weren't logically grouped together as they are with Accuview.

    All in all, Accuview is a sensible upgrade to the GeForce3's multisampling AA. The combination of efficient edge AA, better sample patterns, and anisostropic filtering (with trilinear, if you so choose) probably puts the GF4 Ti on level with the Radeon 8500 for AA. The Radeon's edge AA may look a little nicer, but it's probably a fair amount slower than Accuview. We'll see.

  • nView multi-display support — The GeForce4 chips both incorporate dual RAMDACs, dual TDMS transmitters, and a TV-out encoder, so they can drive a wide variety of display combinations, from a single VGA monitor to dual digital flat panels. The GF4 cards are the first cards outside of the Matrox G500 to have dual DVI output capability, which puts them into an industry-leading position. This is also the first time NVIDIA has emphasized dual-display features in one of its high-end graphics chips. On this front, the GF4 moves ahead of the dual-display Radeon 8500, which lacks a second DVI out.


    The GeForce4 Ti reference card with dual DVI outputs

    NVIDIA has underscored the utility of multi-monitor support by introducing a new feature set in its drivers that helps manage multiple displays, virtual desktops, and the like. The nView software suite was designed by former Appian engineers, so it ought to be very nice. The nView feature set will extend back to existing NVIDIA cards, as well.

    We were able to confirm that the GF4 will be able to run displays concurrently in multiple, independent resolutions. However, we'll believe it can happen in Windows 2000/XP when we see it, because such things are famously difficult.

And that's about it for the GeForce4 Ti. The improvements aren't anything special in terms of 3D capabilities, but they do bring NVIDIA's high-end product offering up to snuff feature-wise versus the Radeon 8500. And the GF4 Ti 4600 will no doubt be a supremely fast graphics card.