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-   -   Anti-aliasing slow with Linux drivers (http://www.nvnews.net/vbulletin/showthread.php?t=34505)

lynedavid 08-11-04 01:15 PM

Anti-aliasing slow with Linux drivers
 
Has anyone else noticed that the overhead is much bigger for turning anti-aliasing on under Linux?

Running a simple opengl app under windows in 1280x1024 with 4X FSAA runs at nearly the same speed as no anti-aliasing.

However, the same program in Linux with the 1.0-6111 driver is 2x slower when anti-aliasing is turned up to this level.


Any ideas?

system:
dual XEON 3.06 ghz
Geforce 6800 Ultra
1gb ram
2.4.20-8 linux kernel.

FreeCatalonia 08-11-04 01:20 PM

Re: Anti-aliasing slow with Linux drivers
 
It looks like someone is cheating with their drivers. It wouldn't be the first time.

lynedavid 08-11-04 02:34 PM

Re: Anti-aliasing slow with Linux drivers
 
I'm not entirely sure what you mean.

The Linux or Windows drivers are cheating?

Thunderbird 08-11-04 03:03 PM

Re: Anti-aliasing slow with Linux drivers
 
Both the windows and linux drivers share a lot of code (roughly 90%). The opengl code is allmost fully the same (except for GLX on linux and WGL on windows). Because of this performance should be about the same. Really make sure you are doing a fair comparision as there are differnent types of "4x FSAA", so make sure you use the same type of FSAA on both systems. Further using what apps were you testing?

FreeCatalonia 08-11-04 05:09 PM

Re: Anti-aliasing slow with Linux drivers
 
Quote:

Originally Posted by lynedavid
I'm not entirely sure what you mean.

The Linux or Windows drivers are cheating?

I mean maybe in the windows version instead of using the real thing they put an anti-aliasing mode that looks many times the same but at a much cheaper price.

Both ATI and Nvidia do this continously for mip-mapping and this stuff.

lynedavid 08-12-04 06:00 AM

Re: Anti-aliasing slow with Linux drivers
 
I have now tested with a new simple benchmark app that basically draws a textured sphere (source code attached).

With this app I get the following frame rates in Windows:

FSAA OFF: 1730
FSAA ON (4x): 888


In Linux I get the following frame rates:

FSAA OFF: 1869
FSAA ON (4x): 498

With anti-aliasing switched on the app is almost 2x slower than in windows!

Target system:
Windows:
NV Driver 61.77
Linux:
NV Driver 1.0-6111

All tests carried out on a dual CPU PC with FX 6800 Ultra.

lynedavid 08-12-04 06:01 AM

Re: Anti-aliasing slow with Linux drivers
 
BTW. The FSAA mode I used in Linux for the test was mode 4 (the lower quality of the two modes available).

There is only one choice for 4x AA in Windows.

Thunderbird 08-12-04 06:30 AM

Re: Anti-aliasing slow with Linux drivers
 
Note that the algorithms that are available on windows are available on linux too. Not all 4x modes are called 4x, nvidia introduced lots of different names.
This are what nvidia calls the modes available on linux:
0 FSAA disabled
1 2x Bilinear Multisampling
2 2x Quincunx Multisampling
3 FSAA disabled
4 4x Bilinear Multisampling
5 4x Gaussian Multisampling
6 2x Bilinear Multisampling by 4x Supersampling
7 4x Bilinear Multisampling by 4x Supersampling

Useally on Windows they call it lets say only "Gaussian Multisampling".

lynedavid 08-12-04 07:17 AM

Re: Anti-aliasing slow with Linux drivers
 
I have tested both Bilinear and Gaussian 4x on Linux. They both get about the same results. Windows has to use one of these two algorithms right?


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