Is AF a bottleneck for Xenos?

[tema]

Why does textures on every Xbox 360 game look like they are using trilinear filtering?

FC
http://xbox360media.ign.com/xbox360...tincts-predator-screens-20060307083757266.jpg

Outfit
http://xbox360media.ign.com/xbox360/image/article/689/689178/the-outfit-20060216035250807.jpg

NNN
http://xbox360media.ign.com/xbox360...7/n3-ninety-nine-nights-20060210102236465.jpg

Top Spin
http://xbox360media.ign.com/xbox360/image/article/693/693515/top-spin-2-20060303044029609.jpg

ES
http://xbox360media.ign.com/xbox360/image/article/676/676681/oblivion-updates-20051216015656083.jpg

GRAW
http://xbox360media.ign.com/xbox360...con-advanced-warfighter-20060307070030222.jpg

Dead Rising
http://xbox360media.ign.com/xbox360/image/article/652/652961/dead-rising-20050922043815688.jpg]

PDZ
http://xbox360media.ign.com/xbox360/image/article/670/670581/perfect-dark-zero-20051123110203506.jpg

Xbox360 IGN
http://xbox360.ign.com/index/reviews.html

 

[Titanio]

Yeah, I've noticed this too. The worst offender I've seen lately is Test Drive.

It's probably an issue with main memory bandwidth - filtering is taking multiple texture samples for each pixel, which requires increasing amounts of bandwidth depending on the sampling level, and it may be that things are typically too tight on the main pipe to allow for higher levels of filtering. Others here may have a better explanation, but that's all I can come up with for now.

 

[Inane_Dork]

Well, it could be that there's just not enough memory bandwidth with the way X360 games are made right now.

Or, it could be that the texture cache is small enough that games get significant cache misses when they turn it on.

Or, it may be that there's something crippled in the texture fetching that is not public knowledge.


My bet would be on the first option.

 

[tema]

Test Drive

http://xbox360media.ign.com/xbox360...04/test-drive-unlimited-20060308103309545.jpg

http://xbox360media.ign.com/xbox360...04/test-drive-unlimited-20060308103304217.jpg

http://xbox360media.ign.com/xbox360...69/test-drive-unlimited-20060208104305610.jpg

Very bad.

A budget 7600GT has quite consistent AF performance.

 

[inefficient]

I've suspected that lack of AF explains why many have pointed out Oblivion is not as sharp on the 360 compared to the PC version.

 

[Titanio]

Well, it could be that there's just not enough memory bandwidth with the way X360 games are made right now.

I was wondering about potential implementation issues, but isn't this something that you should just be able to turn on and off? It's not like AA and tiling, AFAIK (?)

 

[superguy]

I think all PC cards have good AF performance. It's not a big hit like AA.

This is another one of those things I dont understand though. What am I looking for?

 

[Inane_Dork]

A budget 7600GT has quite consistent AF performance.
http://www.beyond3d.com/previews/nvidia/g73/chart/image020.gif

That is one of the more useless charts I've seen when used out of context. The performance hit with AF varies depending on the game and it depends on the individual frame being rendered. There's no one chart to rule them all when it comes to AF.

I was wondering about potential implementation issues, but isn't this something that you should just be able to turn on and off? It's not like AA and tiling, AFAIK (?)

Yes, it is, unless they made it harder than the regular version of D3D. Turning it on and off (per texture) takes about 3 lines of easily-read code.

 

[Titanio]

This is another one of those things I dont understand though. What am I looking for?

Look at how texture detail falls off as you move away from the camera.

Here's an example:

2xAF:
http://img70.imageshack.us/img70/1120/wow28nz.jpg

16xAF:
http://img109.imageshack.us/img109/6418/wow13et.jpg

If I could get you an example with trilinear I would, but it would be worse again from the first pic.

edit - or here's a 3DMark comparison between trilinear and anisotropic: http://common.ziffdavisinternet.com/util_get_image/7/0,1425,sz=1&i=73047,00.jpg (trilinear is the left half, aniso is the right) or a comparison between no aniso and aniso here: http://images.tweaktown.com/imagebank/AAAF4.jpg

 

[Shompola]

I remember a lot of bitching about Xbox games lacking AF....You would think MS would take that in account.. But no lack of AF is still present. I am very dissapointed.. Lack of AA I could live with, but lack of AF can make an otherwise very good looking game look uneven.

 

[tema]

MS made a big meal about the free AA but where is the AF? You can get some AA from your TV. Poorly filtered textures just stick out like a sore thumb.

 

[Dave Baumann]

Test Drive

http://xbox360media.ign.com/xbox360...04/test-drive-unlimited-20060308103309545.jpg

http://xbox360media.ign.com/xbox360...04/test-drive-unlimited-20060308103304217.jpg

http://xbox360media.ign.com/xbox360...69/test-drive-unlimited-20060208104305610.jpg

Very bad.

Sorry, but whats bad about that in terms of AF? Do you understand what AF is?

Clue - take a look at the road markings. They are staying relatively consistent in thickness and clarity into the screen. If AF wasn't there you would first notice a disjoint as it moves into the screen (this is lessened by Trilinear filtering, but probably sill noticable) and then the lines get blurrier and thicker as it goes into the screen as lower mip levels are used with lower levels of filtering.

There is a general level of texture blurring going on ther but thats because these are clearly still images of motion blurred shots.

 

[Xmas]

Why does textures on every Xbox 360 game look like they are using trilinear filtering?

[...]

Outfit
http://xbox360media.ign.com/xbox360/image/article/689/689178/the-outfit-20060216035250807.jpg

That one doesn't.

 

[Titanio]

Sorry, but whats bad about that in terms of AF? Do you understand what AF is?

Clue - take a look at the road markings. They are staying relatively consistent in thickness and clarity into the screen. If AF wasn't there you would first notice a disjoint as it moves into the screen (this is lessened by Trilinear filtering, but probably sill noticable) and then the lines get blurrier and thicker as it goes into the screen as lower mip levels are used with lower levels of filtering.

There is a general level of texture blurring going on ther but thats because these are clearly still images of motion blurred shots.

Good point, but when things look so blurry, one might be forgiven for attributing it to filtering given the issues in other games (although it's unfair to do so). They should definitely rethink the approach they're taking in that game IMO, though, it just looks strange, at least in screenshots.

 

[Dave Baumann]

Or, it could be that the texture cache is small enough that games get significant cache misses when they turn it on.

Texture cache is 32KB on Xenos, which is actually quite a lot by many standards - first generation DX9 cards were about 256B per quad. Larger texture caches, of course, also lowers texture bandwidth use as AF resuses local texture data alot and this operation can be very cache efficient. (Note: G71's texture cache has been increased - in relation to G70 - to 32KB as well, from what I understand).

Again, the difference between PC's and consoles is that PC's are mainly utilising AF in a very inefficent way and applying them across everything, but its up to the console developers to pick and choose the textures and AF levels selectively.

 

[Titanio]

Again, the difference between PC's and consoles is that PC's are mainly utilising AF in a very inefficent way and applying them across everything, but its up to the console developers to pick and choose the textures and AF levels selectively.

Is the option to apply it in a blanket fashion available to them?

And though this may be inefficient, is it really so expensive in absolute terms that many of these titles could not use it?

 

[Xmas]

first generation DX9 cards were about 256B per quad.

That's highly unlikely.
But Xenos needs more cache, as it switches threads/textures more often.

Again, the difference between PC's and consoles is that PC's are mainly utilising AF in a very inefficent way and applying them across everything, but its up to the console developers to pick and choose the textures and AF levels selectively.

Enabling AF for all textures would be a fairly minor code change.

 

[tema]

Thanks Dave.

I can tell where the filtering stops in this image.
http://xbox360media.ign.com/xbox360...04/test-drive-unlimited-20060308103319778.jpg

Xenos mipmaps level must be at High Performance settings.

 

[Dave Baumann]

That's highly unlikely.
But Xenos needs more cache, as it switches threads/textures more often.

According to some test documentation I found 9800 was rated at around that.

Enabling AF for all textures would be a fairly minor code change.

Yes, but its also highly inefficient, and undesirable in a console environment where the resources have to be balanced more.

 

[PeterT]

That one doesn't.

Yeah, I wanted to point that out as well. Really, Bilinear?
I hope PS3 and future 360 games will feature at least 8xAF.

And Dave, this statement:

Again, the difference between PC's and consoles is that PC's are mainly utilising AF in a very inefficent way and applying them across everything, but its up to the console developers to pick and choose the textures and AF levels selectively.

Just doesnt't make much sense. First of all, most recent PC games request AF themselves, and secondly, there aren't many textures that you don't want to filter anisotropically. The Far Cry or NNN ground textures in the first post may be efficient - but they're also about the level of visual quality PCs had 5 years ago.