What is anti-aliasing, anisotropic filtering, or ultra hdr?

I always look at these boxes, especially the first two, in the graphics menu of the games I play and dont know what to do. Are they speed increasers/reducers? Will they provide better frame rate and therefore faster gameplay?

My dxdiag says I have 1776 mb from the two gpu's i'm running and I got a good 4gb of ram installed.

Should I flip these on or leave em off?

3/7/2009 9:07:38 PM

http://en.wikipedia.org/wiki/Anti-aliasing
http://en.wikipedia.org/wiki/Anisotropic_filtering
http://en.wikipedia.org/wiki/High_dynamic_range_rendering

3/7/2009 9:14:46 PM

^ ha, I was reading them before I refreshed this thread

thought i'd get some human input though, kick up the conversation

3/7/2009 9:17:30 PM

In two words or less:
anti-aliasing = Jaggy smoother
anisotropic filtering = ?
hdr = overused gimmick

3/7/2009 9:39:45 PM

my opinion...

anti-aliasing = less pixelated
anisotropic filtering = unblur things that are far away
hdr = just a fancy word for increasing contrast

3/7/2009 11:07:03 PM

This is from memory from taking Computer Graphics 3 years ago... I could be totally wrong *DISCLAIMER*

Aniososotropic Filtering -- So say you have a polygon some distance away from the camera, and there's a texture painted on it. The texture itself is 256x256, but the polygon would be rendered as about 128x128 on the screen. So what the rendererer would do without Aniossstropic Filtering is just paint every other pixel in the texture onto the screen. If you were to go far enough away from the polygon so that it would only render to one pixel on the screen, the engine would just pick one pixel from the texture. You can kinda see it here:



Later renderers might do a little better on-the-fly interpolation of the proper color of that pixel, but doing that kind of thing is really process intensive. It's much better to precompute it.

Enter magic anisootropic filtering. For every texture loaded in memory, there's going to be a copy of it a quarter the size, scaled down and pixels averaged. Then another copy of that smaller one, yet another quarter in size. Then another, spiraling down to 1x1 (or however many iterations you want). That 1x1 pixel ends up to be the average color of all the pixels in the texture.



By doing this, when you're far away you get a pre-calculated smaller version. So in the example to begin with, if your polygon would render as a 128x128 on the screen, the renderer would use the 128x128 sized texture. If you were to go farther away, it would use an even lower resolution texture. If you were to go far enough away so the polygon would render as 1 pixel, it would have a pre-computed average color of the entire texture to paint in that 1 pixel.

3/9/2009 9:23:52 PM

^ You just described isotropic mip-mapping, not anisotropic filtering. Anisotropic filtering is a special filtering technique used when the projection of the texture on the primitive (not the primitive itself) is at a non-orthogonal angle with respect to the viewpoint. Basically it makes things sharper by reducing blur during extreme viewing angles.

In your examples, each mip-level's resolution is halved on each axis simultaneously (thus making it isotropic). Anisotropic filtering is a way to sample that isotropic mip so that you don't see equal frequency in each axis in the resulting texel. During extreme viewing angle conditions, what you want is for one axis to be a 'higher resolution' than the other depending on the viewing angle. What happens is the renderer will pick a higher resolution mip (or more than one) than is required and adjust the sample pattern (e.g. it is probably no longer a rectangle since the direction of anisotropy may not be axis-aligned) based on the degree of anisotropy (the extreme viewing angles) so that more samples come from the 'more important' axis. This is a lot more computationally intensive than simple isotropic filtering, and requires a lot more GPU memory bandwidth.

3/10/2009 5:09:14 AM

Thats cool. If you're trying to run these you really do need a beast of computer, especially when trying to run them all at the same time. Anisotropic filter really destroyed my fps and I got no discernable difference, infact none of them really showed any noticable difference in the game I was playing. Maybe my old sylvania monitor is playing a factor (yes, i'm still in the crt age).

Really though I wouldn't use this stuff unless I had a extremely fast rig or if I was just playing a scenic myst like-ish game. Thanks for the clarification techies.

3/10/2009 8:44:10 AM

check out the pictures from evan's wikipedia links. It should be obvious what each are doing.

play a game at 640x480. Now turn on 4x anti-aliasing. Big difference. Make sure you have it enabled from Display Properties as well.

j/w what games are you using to mess with these settings?

Quote :

"anti-aliasing = less pixelated (kind of like decreasing sharpness) anisotropic filtering = unblur things that are far away hdr = just a fancy word for increasing contrast"

I agree

[Edited on March 10, 2009 at 10:09 AM. Reason : ]

3/10/2009 10:08:47 AM

Quote :

"j/w what games are you using to mess with these settings?"

A substandard diablo incarnation called Legend, Hand of God. Lots of left clicking and the like. I wouldn't recommend it.

3/10/2009 10:48:57 AM

use a 3D game for best effect

[Edited on March 10, 2009 at 3:53 PM. Reason : you'll definitely see the difference]

3/10/2009 3:53:01 PM