Round 2: Unigine Heaven demo
And now we begin round two, with a little more focus on high-end solutions and DirectX 11. As you have hopefully gathered by now, one of the distinguishing characteristics of the Fermi architecture is its potential for geometry processing throughput. Nvidia has made a big bet here on the usage model for real-time graphics shifting in the direction of much, much more geometric detail. Generally speaking, the Radeon HD 5870 seems to be quite good at tessellation, although once you get to a certain point with a very large number of triangles in a scene, the GF100 ought to outperform the 5870 thanks to its quad rasterizers and the like.
Few current games (and quite likely, not many in the near future) will really push on this point. Even if they do use tessellation, they're not likely to put an inordinate strain on the geometry processing throughput of Radeon HD 5000-series GPUs. To do that, we'll turn to a synthetic benchmark: Unigine's Heaven 2.0 demo.
This DirectX 11 demo looks pretty nice, overall. One of the major highlights of the demo is its use of tessellation, and the new 2.0 release takes that even further than earlier versions. I think this demo presents us with a nice opportunity peek into the Fermi architecture's geometry processing abilities, but I do have some reservations to note.
Although the Heaven demo does push through a lot of triangles, it's apparently not especially smart about how it does so. To my eye, the three levels of tessellation available in the demo, "moderate," "normal," and "extreme," are visually indistinguishable unless you switch to a wireframe view. That suggests, well, that one shouldn't use the higher levels of geometry subdivision, since they're not really helping.
Once you do switch into wireframe view, you can begin to see the problem. Here's an example from the demo.
That's a tremendous amount of detaillarge portions of the screen are just white with polygon edges. Nifty, right? But look at the close-up of the hull of the ship, and you can see that its silhouette isn't a smooth curve as one would expect with a nicely tessellated object. Instead, major transitions between large polygons create visible seams, while all of the detail goes toward subdividing the geometry inside of those large, essentially flat triangles, where it's pretty much useless.
Toggling tessellation on and off for this object reveals that tessellation imparts a kind of "inflated" look to it, where the white areas covered by lots of detail tend to swell as if they'd been exposed to a Joe Biden speech. This is one use of tessellation, I suppose, but it doesn't seem to be a very good one. One hopes Nvidia won't be tempted to persuade game developers to make inappropriate use of tessellation just so it can demonstrate the hidden virtues of the Fermi architecture. True progress on this front will require perceptible and unequivocal visual improvements, not just... inflation.
Nevertheless, we do have a heaping load of triangles, and we can see how the GF100 handles them compared to the competition.
The GF100 cards perform quite well in the Heaven demo, and they become relatively stronger when we move from the "normal" tessellation level to "extreme." It is nice to see that this attribute of the Fermi architecture pays off in a measurable way. Of course, whether or not that will translate into higher image quality and better performance in real games any time soon is another question, one whose answer may not be so positive.
Round 2: Antialiasing scaling with Far Cry 2
My thought here was to show you how performance scaled at different antialiasing levels, because this has been a point of distinction between AMD and Nvidia GPUs in recent years. Starting with the 4000 series, Radeons have handled 8X multisampled AA with a fairly small performance hit compared to 4X AA. Meanwhile, the GeForce GTX 200 series has seen a steeper drop in frame rates when going from 4X to 8X MSAA. (The obvious solution with GeForce cards has been to use one of Nvidia's coverage-sampled AA modes, which achieve similar image quality with less of a performance hit. However, doing so complicated direct comparisons between GPU brands, since AMD has no direct analog to CSAA.) Nvidia expects the GF100 to remedy that problem thanks to improved color compression in its ROPs.
Trouble is, I'm not sure these results show us what we expected to see. The GeForce GTX 285 doesn't slow down inordinately when asked to run in 8X MSAA mode, upending our expectations. The contest between the Radeon HD 5870 2GB and the GeForce GTX 470 may be instructive, though. The 5870 2GB churns out more frames per second without antialiasing and with 2X AA enabled. At 4X and 8X, the GTX 470 proves quicker. I'd like to confirm this with a similar set of directed tests using another game, but perhaps the GF100's ROPs have been brought up to snuff in this respect.
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