More DSR image quality in action
We'll use this sample scene from Skyrim to demonstrate the impact of tweaking DSR's "smoothness" slider. Each of the images comes from DSR 3840 downscaled to a 1920x1200 native resolution.
The differences between the individual steps can be difficult to detect, so you might want to start by clicking on "0%" and then on "100%" to compare between the extremes. I see the contrasts most readily in several places. For edge antialiasing, watch the high-contrast edges around the dude's cloak and around that dragon thingy on the right. To see changes in sharpness elsewhere, watch the stiches on that guy's cloak and the interior texture on the wooden beam to the right.
My sense is that Nvidia's default of 33% smoothness is pretty soft. That choice works out well along the high-contrast edges; those look feathery smooth in the example above. The wood texture on that right-hand beam does lose some of its definition, though, compared to the 0% or 15% levels. So do the stitches in that cloak. As I've said, I really don't mind this minor loss of sharpness, since the softer images produce less sparkle and crawl while in motion.
The loss of definition is even more pronounced at the 66% and 100% smoothness settings, and it begins to look like overkill. I suspect that these higher amounts of blurring might become useful when scaling down from weird DSR ratios like 1.5X or 1.7X. In our example, we're scaling down from four times the native resolution, so the sharper filter settings are sufficient to make things look nice.
While we're on the subject of smoothness and blurring, let's have a look at this same scene using some other AA methods.
Check out the wood grain on that right-hand beam in the shots above. Flip between the native-res or MSAA screenshots and the FXAA one, and you'll see that FXAA blurs that texture considerably, likely because it detects the grain in the wood as edges and wants to smooth them. Whoops.
Next, watch the wood grain as you flip between the other images and the DSR 3840 shot. Although DSR does soften the final image somewhat, it also samples the underlying texture multiple times per pixel. The result is a more detailed rendition of the wood grain than in any of the other shots. Also, that wooden surface should be represented more consistently from one frame to the next, even as the camera shifts, since DSR pulls multiple samples from the underlying texture.
For my next trick, I'm going to try looking at AA methods using an example from a busy, low-contrast scene. Kids, this is high-risk behavior, so don't try it at home. Here's a shot from Crysis 3 with a ton of on-screen detail. This sort of thing presents a formidable challenge for most current AA techniques.
I've circled a few areas in this scene where I'd like to focus our attention. The mess of tree branches and foliage on the left is complex and organic. Without AA, it's just kind of a pixelated mess. In the middle of the shot, the tree branch full of tiny, single-pixel leaves looks like it's being viewed through a screen door; in motion, these leaves will shimmer and pop unrealistically. On the right is a series of near-horizontal edges that are marred by jaggies.
Let's talk first about the branches on the left. As we move from the native resolution to 2560 DSR and then to 3840 DSR, two contrasting things happen. The areas of the screen stippled with single-pixel leaves become softer and less contrasty, while the darker tree branches become more clearly defined. The smallest branches, made of fine geometry, are easier to pick out. Pretty much the same is true of the tree branch and leaves in the middle of the shot, too.
On the right, the edges in the building look a little blurry at 2560 DSR, but switching to 3840 DSR increases the clarity of the image while further reducing jaggies.
Overall, my takeaway is that DSR—especially at a 4X ratio—offers a considerable improvement in image quality for this extremely complex scene.
Crysis 3 has a couple of other popular AA methods built in, so I've included screenshots from them. SMAA is a post-process AA method similar to FXAA, but its 2X mode incorporates some spatial multisampling, as well. 2X SMAA somewhat reduces the jaggies on the building ledge, but it doesn't clarify the fine geometry in the leaves and branches nearly as well as 3840 DSR.
Nvidia's TXAA combines multisampling with a couple of tricks: varying sample patterns temporally and borrowing some samples, lightly weighted, from neighboring pixels. In this last respect, it's similar to DSR's downscaling filter. As you can see, TXAA softens on-screen images somewhat. The results, I think, are pretty darned good. TXAA looks strikingly similar to 2560 DSR in this example, and it handles nearly everything well, even the fine geometry in the tree branches on the left.
TXAA has to be integrated into the game engine in order to work, and it's only available to owners of GPUs in Nvidia's Kepler and Maxwell families. If it's an option for you, though, it's worth considering. I'd say TXAA is a nice consolation prize for owners of Kepler-based GeForce cards who can't yet get access to DSR.