The great Lod bias mystery. Amd users must know !

Discussion in 'Videocards - AMD Radeon Drivers Section' started by HiCZoK, Mar 29, 2015.

  1. HiCZoK

    HiCZoK Master Guru

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    For some time now, I've been having problem with textures being too sharp... or kinda crawling/shimmering in distance when moving in some games.
    And no. That is not aa. And after 2 days of research, I think I've got it all sorted out. Still need to test it on more games.
    SO! :

    Testing subject is Half-Life 2: Update. Also tested on hl2 with the same results.
    Totally removed all drivers and registry. reinstalled to new 15.3 beta drivers. Tried the same with old 12.11 drivers and had same result. My card is 7870.

    Hl2 set to max and 4xaa ingame. (imgur is not the best for this but sufficent)

    First image - ccc at default.
    http://i.imgur.com/lNe0y6e.jpg
    You can easily notice floor texture being too sharp and aliased. walls too. it looks horrible in motion. That is at drivers and ccc set to default. No option in ccc changes that (ssaa aside but more about that later)

    Now I've been searching and trying everything and finally found a solution. It's lod Bias. it can be either found in registry or in radeonpro under texture lod. it defaults to 0 in radeonpro. But keep in mind, if changed to other value, restoring factory settings in CCC does NOT restore lod bias. it can be only changed back either in radeonpro or registry.
    so. I am using registry method to avoid any radeonpro involvement. all settings still at default at ccc but this time lod bias set in registry to 1.
    http://i.imgur.com/SoebQTm.jpg

    ha ! What an astonishing result! no more crawling and shimmering. value -1 looks exactly the same as 0. from 0 to 1, it gets better but shimmering is gone only at 1. above 1, textures get blurred. values above 2 make it look like n64 game.
    but 1 fixes it clearly... so what happened? I remember finishing hl2 multiple times over the years and it's first time I've enountered this. And it's not the game fault. One person on other forum posted his screenshots from nvidia 970 and it looked like 1 setting on amd. So clearly, there is something off with rendering of lod bias at default 0 setting here.
    can't explain what tho. it's not fault of the game, configs, ccc, radeonpro or my system. I've deleted every config and reverted everything to defaults and results are still the same. default 0 is ugly and 1 fixes it.

    but the image is still not perfect, I've discovered something interesting tho. If I am to set lod to it's default 0 and enable fxaa with radeonpro... it looks like 1. it just does. even after turning fxaa with hotkey, the effect stays until restarting the game. This means that fxaa layer somehow overcomes lod bias setting and corrects it to 1. But only for the time of game running.


    I've also tested Lod bias setting with adaptive transparent 4xMsaa and with 4xSSAA. Alos discovering something very interesting. I was expecting negative lod values to sharpen image with 4xSSAA but that does not happen. Image is the same on -1,0,1 except transparent textures like fences. Lod bias smoothens those out! With default 0 value at either 4xadaptive msaa or 4xSSAA, transparent textures arent antialiased enough. Again, setting lod bias to 1 totally smoothens those !
    here are screenshots:

    4xADAPTIVE MSAA: look at the fence on the right. or any other place really.
    -1 lod
    http://i.imgur.com/TBoFIGf.jpg

    0 lod
    http://i.imgur.com/aT3lDNx.jpg

    1 lod
    http://i.imgur.com/jYW57XJ.jpg
    Just look how better the fence and image overall looks with lod set to 1.

    Same are the results with SSAAx4
    -1
    http://i.imgur.com/0gjqPHL.jpg

    0
    http://i.imgur.com/J3xaYOz.jpg

    1
    http://i.imgur.com/IVxiYYU.jpg


    So... I hope I am not mad and this is legitimate issue. if so, AMD, please give us an option to change LOD in ccc or make it default to 1.
    Also, to All users, (ofc I can only text on 7870) try it out. The image, textures and transparent textures look way way better on 1 lod bias instead of default 0. Without aa and with all types of classic aa.
    You can change the setting in radeonpro or in registry. Thanks to old post of user ankinferno, here is a way how to change it
    Code:
    "Open Registry -> 'regedit'
    
    Navigate to :
    
    HLM/System/CurrentControlSet/Control/Video/
    
    Now under Video find the Key that has a '0000' subkey which has a 'umd' subkey.
    
    eg. for my system its:
    
    HLM/System/CurrentControlSet/Control/Video/{62B0C7BD-B807-45BE-8AAC-3176AB0DBF51}/0000/umd
    
    Under 'UMD':
    
    Create a String Named 'LodAdj' and assign value between -5 (Crisp Detail) to 5 (Faded Detail) ."
     
  2. (.)(.)

    (.)(.) Banned

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    So, AA methods affect texture detail, if im understanding this?

    Also, in the second to last set of images, the reflections on the floor are reduced?
     
    Last edited: Mar 29, 2015
  3. HiCZoK

    HiCZoK Master Guru

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    hl2 might not be the best example because ssaa is overall more blurry in this game than msaa.
    But the point is about Texture Lod Bias. It indeed affects texture quality. mipmaps and transparent textures. I've thrown in -1,0 and 1 lod bias comparisons with different aa methods just for kicks, to show that it also can help to improve quality of aa.

    The reflection on the floor is reduced because this is how it is suppose to look I think.
    on -1 and default 0 settings, reflection is longer but textures are overly sharp, shimmery and fence looks aliased. on 1 all of those problems are gone and reflection is a bit shorter as texture renders closer. Somehow reflection does not get shorter when ssaa is used. With ssaa, lod bias setting only seem to affect transparent textures
     
  4. sammarbella

    sammarbella Ancient Guru

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    @HiCZoK

    Thank you VERY much too share this information! :)

    It's an intersting subject to look into.
     

  5. xacid0

    xacid0 Master Guru

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    Only works in DX9 games similar to FlipQueueSize options.
     
  6. HiCZoK

    HiCZoK Master Guru

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    Could be. it reduces shimmering in Dark Souls too but also introduces some blur to textures so results seem a bit different than hl2
     
  7. xacid0

    xacid0 Master Guru

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    tested this in rF2 and Dota 2, noticeably blurry when using 1.
     
  8. SabotageX

    SabotageX Active Member

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    LOD 1 will decrease the original texture quality.
     
  9. razorbackdb

    razorbackdb Member

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    you are just reducing the texture quality, reducing the detail on the distant textures reduces the noise or "shimmering".
     
  10. HiCZoK

    HiCZoK Master Guru

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    I know. But it clearly doesn't reduce texture quality ... at least in hl2.
    It just makes it look like on nvidia gpu. There is something wrong with default setting anyway. at least in hl2 and maybe few other titles
     

  11. PrMinisterGR

    PrMinisterGR Ancient Guru

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    There was a debate some years ago, the shimmering is because you actually get better textures with AMD.
     
  12. stevvie

    stevvie Member Guru

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    But the shimmering is ugly, I had this problem in Eurotruck , set everything to the highest in the settings and shimmering road in the distance. I tried this and low and behold it looks SOOoooooo much better whilst moving. Sure with sharper texture it might look better for screenshots and bragging, but in reality I actually brought my Video card to play games not nit pick the finner details. So kudos HiCZoK.
     
  13. HiCZoK

    HiCZoK Master Guru

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    now thats just silly...
    The problem wasnt there before valve changed their engine to "orange box".
    that + the way amd treats mipmaps and their lod bias, makes it look bad. So 1 setting might be good for hl2 and some other games, but might break other.
     
  14. PrMinisterGR

    PrMinisterGR Ancient Guru

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    That is a good observation actually. Have you tried to run the game with these settings from RadeonPro, and see what you get?

    [​IMG]
     
  15. janos666

    janos666 Master Guru

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    You might want to factor it into your empirical analysis that AMD's SSAA (the one you engage in CCC) uses an "Auto LOD" system which offsets the LOD based on the SSAA level (and only AMD knows what if anything else). As much as I know, this offset is always negative (-0.2 and -0.8 or something like that if I recall).

    Also, you might not see this but believe me, I can clearly see it on your screenshots that setting the LOD to 1 does result in lower texture (and reflection, etc) quality, even if I otherwise agree with you that the image looks better OVERALL (because shimmering is indeed ugly and this setting does get rid of them).

    As for the shimmering in general... I had a Geforce card (Gef6 or Gef8? I cannot tell) and I was a semi-active CS:S player when it all started (I can't remember the date but I remember to the experience very well). It was irritating as hell for the first few days (I got more or less used to it later or it got better with updates, I don't know). I can't remember if they ever went away (despite the LOD "clamping" option in the nV CP which I think they introduced to counter this shimmering).
     
    Last edited: Mar 30, 2015

  16. HiCZoK

    HiCZoK Master Guru

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    I did tried this and to no avail. Makes no difference if set to high.

    @Janos - It's good to know that lod mipmap is actually automated with ssaa but that don't explain why, when using 4xSSAA in attached example, I am seeing a big difference on the transparent fence texture.

    Also - I might have went to far but couldnt find a way to revert hl2 to 2004 engine... so I've found old cracked offline version of hl2 (keep in mind that I own hl2, episodes and all on steam) just for testing... AND Both hl2 from 2004 and episode2 from orange box look correct on default 0 lod bias... actually they look identical to my steam version set to 1. So this actually seems to be a problem either totally on my side or connected to updated source engine. I've disabled cloud saves and reinstalled hl2, deleted cfg and all. It seems that current steam source engine lowers lod bias by one value from set in drivers. so 1 looks like 0 on older engine revision.

    Or I am a fool and this is totally on my side. Not sure what to do next. I would just play it with SSAA anyway and it looks great with it and as Jason said, seem to run correctly with ssaa as it have it's own lod bias.

    ________________________________________________________________________________________
    But I have another really weird observation. So, having set drivers to default and(lod bias at normal 0).
    I've discovered what might be another cause of the problem. So, it looks like if the mipmap bias is off on default 0 setting. everything is shimmery and textures are crawling... ok. If I enable fxaa with radeonpro, with hotkey during game running, The shimmering is GONE. Even if I disable fxaa with hotkey again, the game looks normal. as if I changed lod to 1 (but I didn't, I just switched fxaa on and off, and the lod stays at 0)
    So it might be something connected to fxaa layer not rendering properly. It was once and issue with one of the windows updated. Not sure if I will be removing all windows updates today, but I will investigate.
    And Yes, I took screenshots. The game with 1 lod bias and the game with 0 lod bias but fxaa enabled and disabled, look exactly the same.

    what gives ?
     
    Last edited: Mar 30, 2015
  17. haz_mat

    haz_mat Master Guru

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    I've seen the shimmer you speak of, but its really hit-or-miss depending on the game. It is a form of aliasing, however traditional MSAA will not do anything to help because msaa is only applied to geometry edges. This is precisely the reason SSAA works well in this scenario, since the whole scene is rendered at a higher resolution and thus more samples within texture regions This also helps with the associated shader aliasing that occurs with high-res normal and specular maps.

    SSAA was improved to adjust texture LOD automatically for DX10/11 in the 12.4 driver. For DX9 this feature dates back to the 9.11 driver.
     
  18. chinobino

    chinobino Maha Guru

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    Hi HiCZoK, interesting thread - shimmering can be so annoying and distracting when it happens in the distance.

    I remember having this annoying issue (although on Nvidia hardware) and it was the changes to Anisotropic Filtering in the driver that was causing it for me.

    May I suggest that you use the PNG file format for your screen shots rather than JPEG (as the JPEG compression adds artifacts of its own)?
     
  19. fr33jack

    fr33jack Maha Guru

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    Can we enable LOD control in CCC like in RadeonPro...via slider? Other hidden options?
     
  20. HiCZoK

    HiCZoK Master Guru

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    Uploaded as png and imgur done its thing... But the difference is clear enough. Cant upload anything now from work.

    Fr33jack
    There is texture lod slider in radeonpro
     

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