[H]OCP does Radeon9700 I.Q....

Discussion in 'Architecture and Products' started by martrox, Sep 10, 2002.

  1. Humus

    Humus Crazy coder
    Veteran

    Joined:
    Feb 6, 2002
    Messages:
    3,217
    Likes Received:
    77
    Location:
    Stockholm, Sweden
    Here's an illustrating example of why gamma correct AA is important.

    http://hem.passagen.se/emiper/gammaAA.html

    I've rendered a very simple white against black edge with 6x SSAA ala Radeon 8500. If you examine the image on the left you'll see that while the image certainly is better than a non-AA shot would be you can still see jaggies even though I used 6x AA. In the image on the right I changed the gamma to 2.0 use paint shop pro. Now look how much smoother it looks when we moved the linear averaging into a proper linear space. An even better way to see it is to look at the left image while slowly raising you gamma towards 2.0-2.5, (whereever your monitors sweet spot is), as you're approaching the optimal gamma value you'll see how the edge slowly smoothes out and jaggies goes away :)

    I must say that being gamma correct is just as important or even more important that taking lots of samples. A gamma correct AA of 4x probably matches or beats a non-gamma correct AA of say 6x or even 8x. I think gamma correct AA is going to be standard more or less in the future. I'd be surprised (and disappointed) if NV30 didn't have it.
     
  2. KimB

    Legend

    Joined:
    May 28, 2002
    Messages:
    12,865
    Likes Received:
    192
    Location:
    Seattle, WA
    Humus, am I to assume that you rendered those images in software?

    I'd still really like to see a wireframe shot of the Radeon 9700...given what we've seen so far in this thread, the difference should be immediately obvious.
     
  3. Humus

    Humus Crazy coder
    Veteran

    Joined:
    Feb 6, 2002
    Messages:
    3,217
    Likes Received:
    77
    Location:
    Stockholm, Sweden
    No, they were rendered in hardware on my Radeon 8500. What I've done is to move the linear averaging into a linear space, which is what gamma correct AA tries to do. I've added some line shots too, the effect is even more obvious on those.
    For this reason I'm also very interested in seeing AA wireframe shots from a Radeon 9700, preferably with comparison shots from a GF4.
     
  4. Pete

    Pete Moderate Nuisance
    Moderator Veteran

    Joined:
    Feb 7, 2002
    Messages:
    4,925
    Likes Received:
    315
    OT: About them BMP's...

    PNG compresses better than a ZIP'ed BMP, there's no un/zip hassle, and it's still lossless. Brent, get yourself IRFanView* and start compressin'! :)

    *Not sure if it's free for business use. It's a sweet program, though.
     
  5. KimB

    Legend

    Joined:
    May 28, 2002
    Messages:
    12,865
    Likes Received:
    192
    Location:
    Seattle, WA
    Interesting. May I ask exactly how you managed to do that on the 8500? Pseudocode would be nice...

    Heh...hopefully somebody will listen to you :) Either nobody with a 9700 has read the later posts in this thread yet, or has just ignored me...I wonder if Donald would be willing to do a couple more shots?

    Anyway, here's what I think the ideal shot would be:

    1. Wireframe shot at the same position on the different video cards (should be easy enough with a saved game...).

    2. Optimal situation would be one in which there are lines at may different angles, which is why I like Morrowind...but that won't work for a GeForce4, as the shots don't show FSAA (Which brings up an important point...it may not be so easy to capture FSAA on the GeForce4...).

    3. Good comparisons would be between the 2x FSAA modes (which, presumably, use the exact same sampling pattern, and so the main difference should be in the gamma correction...), and 4x FSAA on the 9700 vs. 4xS FSAA on the GeForce4 (not the exact same sampling pattern, but more similar than 4x FSAA, which should help to isolate the gamma improvements).
     
  6. Bigus Dickus

    Regular

    Joined:
    Feb 26, 2002
    Messages:
    943
    Likes Received:
    16
    I'd be happy to take the screenshots, but I don't have a 9700. Or a GF4. Oh, and I don't have Morrowind either. :D
     
  7. Althornin

    Althornin Senior Lurker
    Veteran

    Joined:
    Feb 6, 2002
    Messages:
    1,326
    Likes Received:
    5
    Gee thanks!
    We'd like you to try to draw what you imagine they'd look like though, anyways, ok?
     
  8. Nagorak

    Regular

    Joined:
    Jun 20, 2002
    Messages:
    854
    Likes Received:
    0
    They're probably too busy playing, I know that's what I'd be doing. 8)

    Better get them to take those pics fast, UT2003 demo is coming out this week! :wink:
     
  9. KimB

    Legend

    Joined:
    May 28, 2002
    Messages:
    12,865
    Likes Received:
    192
    Location:
    Seattle, WA
    Oh, man, you'd better believe I'm getting that the day it's released!

    And, fortunately, DSL should be up and running tomorrow! Excellent timing, if I do say so myself 8)
     
  10. gkar1

    Regular

    Joined:
    Jul 20, 2002
    Messages:
    614
    Likes Received:
    7

    Exactly. 8)
     
  11. maskrider

    maskrider Henshin !
    Veteran

    Joined:
    Feb 12, 2002
    Messages:
    1,279
    Likes Received:
    0
    Location:
    Hong Kong
    :lol:

    That's what I am doing, ha ha ha !
     
  12. Mize

    Mize 3dfx Fan
    Moderator Legend Veteran

    Joined:
    Feb 6, 2002
    Messages:
    5,048
    Likes Received:
    1,097
    Location:
    Cincinnati, Ohio USA
    Give me a wireframe-only command for a game I have and I'll do it (when time permits):

    Q3A?
    UT?
    DungeonSiege?
    Commanche 4?


    Mize
     
  13. Peeps

    Newcomer

    Joined:
    Sep 11, 2002
    Messages:
    1
    Likes Received:
    0
    Does anyone know if the 9700's AA being gamma correct will make as much of a difference with an LCD screen?.

    I'm wondering because of reading articles about cleartype and LCD screens but that's probably just related to improving clarity as opposed to reducing aliasing.
     
  14. sumdumyunguy

    Newcomer

    Joined:
    Feb 6, 2002
    Messages:
    94
    Likes Received:
    0
    Location:
    HotLanta!!! :)

    Good God man!!! You can't go about posting stuff like this without some linkage for heaven's sake. I think I soiled my armor!
     
  15. KimB

    Legend

    Joined:
    May 28, 2002
    Messages:
    12,865
    Likes Received:
    192
    Location:
    Seattle, WA
    Thanks :)

    I did some looking, and here's how you'd do it in Q3A:

    \devmap q3dm1 (You could use another map...but q3dm1 just has one entry point...)
    \r_showtris 1
     
  16. jb

    jb
    Veteran

    Joined:
    Feb 6, 2002
    Messages:
    1,636
    Likes Received:
    7
  17. Humus

    Humus Crazy coder
    Veteran

    Joined:
    Feb 6, 2002
    Messages:
    3,217
    Likes Received:
    77
    Location:
    Stockholm, Sweden
    Ehm, I suppose you misunderstood what I did. There's nothing fancy going on here. I just draw a white quad, no more advanced than that. I also enable 6x FSAA. This in on a Radeon 8500, so no gamma correct AA, it just averages the values linearly. So the shot at the left is just that, a white quad drawn with 6xFSAA enabled. The edge doesn't look quite smooth though.

    I then took this image into paint shop pro, and raised to gamma to 2.0, that's the image on the right. Now all of a sudden it looks very smooth. Why? Because with a gamma of 2.0 - 2.5 (depending on the monitor) you get linear output, which fit's well with the linear blending of samples done in the AA implementation.

    We could of course always use a gamma of 2.2 or so in games and all FSAA implementations would look much smoother. Unfortunately, this will of course make everything look washed out though, because game contents are made with gamma 1.0 in mind. Now say a game were to be implemented with correct gamma from the start, and make textures such that they will look good at gamma 2.2. The problem that would now occure is that we'll get banding in dark areas of the image, and to get rid of that we'll have to use high precision textures, 32bit textures wouldn't do.

    If we can use 16bit/channel texture and gamma of 2.2, then the problem would be gone. Not only that, we would also get better results of alpha blending and similar operations. In the far future this will probably be the way to go. This + independent gamma for each window and we'd fine.

    In the shorted term though, ungamma the textures, then blend linearly and then gamma the result is probably a better method. This is because the eye's response to light is quite non-linear, similar to the output curve of a normal monitor at gamma 1.0. So for most uses still a gamma of 1.0 is the most optimal way to represent texture data.
    This is one of the interesting features that will appear in DX9, the possibility to ungamma textures when sampling them.
     
  18. KimB

    Legend

    Joined:
    May 28, 2002
    Messages:
    12,865
    Likes Received:
    192
    Location:
    Seattle, WA
    Oh, that's all? Heh, I thought you actually did something within rendering.

    Yeah, for just white on black, what you did should be the same as gamma-correct rendering...

    Btw, one other thing. I'm not sure high-quality source art is needed for good gamma...just high-quality internal rendering (Assuming, of course, that the textures aren't too smooth...that will cause banding no matter how you render...).
     
  19. Mize

    Mize 3dfx Fan
    Moderator Legend Veteran

    Joined:
    Feb 6, 2002
    Messages:
    5,048
    Likes Received:
    1,097
    Location:
    Cincinnati, Ohio USA
    It looks from jb's post like I'll need to use D3D. Anyone know how to go to wireframes only in UT, Shogo, SS, SS:SE demo, Giants or Commanche 4, GroundControl or Dungeon Siege?

    I can put some screenshots up tonight if anyone can get me to a wireframe only output.

    Mize
     
  20. hax

    hax
    Newcomer

    Joined:
    Jul 18, 2002
    Messages:
    59
    Likes Received:
    0
    Heh, weird. What driver version are you on? This problem was fixed some time ago (unless it's a different bug all together), but I don't track which bug fixes go into what releases.
     
Loading...

Share This Page

  • About Us

    Beyond3D has been around for over a decade and prides itself on being the best place on the web for in-depth, technically-driven discussion and analysis of 3D graphics hardware. If you love pixels and transistors, you've come to the right place!

    Beyond3D is proudly published by GPU Tools Ltd.
Loading...