I was wondering if they're unnecessary when playing Crysis. They smoothen renders but I'm already running at 1650x1050, everything at ultra high, 8x AA and 4x AF. AA and AF drops my fps a bit in the last few missions when dealing with those aliens. Here are my specs:

INtel Core 2 Extreme Qx9650 OC at 3.7GHz
4GB DDR2RAM
1.5TB HDD
Ati Radeon HD 3870x2

Every single game runs perfectly I am just wondering why does AA and AF affects fps in Crysis.

The higher the resolution, the less useful they are, as increasing the resolution has pretty much the same effect as increasing AA and AF. Really, its a matter of opinion; some people refuse to play with anything less than 16x FSAA, while others (like me) happily make do with none.

If you don't like the jagged edges, turn it up. If you don't mind, leave it.

Yea most of my friends said that too. Since the resolution is high and I have a 30inch LCD, I can hardly see the difference. Every single texture is rendered perfectly.

Actually, you may want to use AF anyway since looking at textures from oblique angles almost always looks weird without. AA doesn't matter since you've already got a large enough viewing area. BTW, you said you've got a 30" LCD? And you run it using 1680x1050 px? I've got a 22" LCD, and the only res I'm able to use is just that (1680x1050). If you've got a 30" LCD, you may actually want to increase your desktop res to what your monitor suggests (which would be higher than 1680x1050). But don't mind me, I'm just making a suggestion; don't take my word for it.

Rob_b has a point- it's generally better to run games at your monitor's native resolution. That's why it's not always a good idea to buy a massive one, your PC might not be able to handle it.

Short answer: because you're doing incredibly demanding processing on the image, in a game that's already pushing the limits of your hardware. I think it should be blindingly obvious that you are going to lose framerate by adding more AA/AF.


Long answer: you're using 4x AA/AF. I assume you know what those actually do, right? Especially in a game, high-level antialiasing is not that important. The image is always moving, so you don't have the same opportunity to notice edge problems as you would with a still image. What you're doing by bumping it up to 4x is essentially taking the same process as 2x, and running twice as many passes on the image before your video card sends it to your monitor for display. The result is as you increase AA/AF levels, you exponentially increase the calculations required. Not only does Crysis have a lot of polygons/textures on screen at once to process, but it's also coming very close to using all of your processing power before you even start on antialiasing. Now, add in this huge amount of extra work for your video card, and the obvious result: your framerate drops below the ~30fps threshold, and you start to notice the delay on each frame.

Apart from what Duskrider said, i had a problem like yours but only on that area of Crysis and i saw many people having the same fps trouble at the same area while other games or the rest of Crysis runs perfectly even when you max out everything. If you dont like having low fps like me you may want to reduce the aa a bit like to 2x until you pass that snowy field since the mission itself is fast and theres no meaning of losing fps to watch snowflakes (at least for me).