X-bit labs

NVIDIA GeForce 6800 Ultra and GeForce 6800: NV40 Enters the Scene (page 13)

Category: Video

by Tim Tscheblockov , Alexey Stepin , Anton Shilov

[ 04/14/2004 | 01:48 AM ]

Rotated-Grid Multisampling in Practice

We launched Max Payne 2 for checking out the quality of FSAA of NVIDIA GeForce 6800 Ultra, GeForce FX 5950 Ultra and ATI RADEON 9800 XT graphics cards:

The red rectangles mark image fragments that we’re interested in. They have polygon edges positioned at different angles and one fragment (low right) has a transparent texture.

So, let’s first have a look at nearly-horizontal lines. We will use 2x, 4x and 8x modes for graphics cards on GPUs from NVIDIA and 2x, 4x and 6x for the RADEON 9800 XT.

You see the image as produced and antialiased by the GeForce 6800 Ultra to the left; the work of the GeForce FX 5950 Ultra is presented in the middle; the RADEON 9800 XT shows its FSAA skills to the right:

GeForce 6800 Ultra	GeForce FX 5950 Ultra	RADEON 9800 XT
2x
4x
8x/6x

• The three graphics cards all offer a similar quality of jaggies-smoothing in the 2x mode as they all use the same multisampling with two sub-pixels, located along the pixel’s diagonal;
• The GeForce FX 5950 Ultra offers nearly the same quality in both 4x and 2x modes – the angle of the line is “difficult” for the ordered-grid FSAA method to process. The GeForce 6800 Ultra and the RADEON 9800 XT show advantages of rotated-grid multisampling, providing a much higher antialiasing quality. The NV40 alternates halftones more evenly, so the new chip from NVIDIA can be considered the best in this situation;
• On the transition to 8x/6x modes, the graphics cards on NVIDIA GPUs don’t practically change the look of the image. The ATI RADEON 9800 XT makes good use of the increased number of samples in this example and smoothes the jaggies better, producing a nicer-looking image. Note that the images produced by the NV38 and the NV40 are absolutely identical, so both chips seem to have the same method of 8x FSAA.