SSAO and white halos

Discussion in 'Beginners Zone' started by DavidGraham, Jan 2, 2013.

  1. DavidGraham

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    I noticed several white halos effect in many scenes in this current generation of games while using SSAO , particularly around characters . It looks out of place , is there a cause for this problem ?

    I read that black halos appear because of depth discontinuity in cases of large depth differences , but what would cause them to become white ?
     
  2. Ethatron

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    Some AO implementations are so crude that they consider >180° angles like this:

    000
    090
    000

    Now, the pixel hit in the middle has fe. say -160° to the left and +160° to the right slope. The renormalization can causes things actually to be white at edges and grey at flat slopes (instead of white at flat slopes). The initial SSAO implementation of Crysis is this way. It's surprising because it was innovative, but in reality it's probably the worst SSAO-concept/implementation I've seen. [strike]I've somewhere screens of 10 different ones, if you want to see them and I find them I can post them?[/strike] Well, 6 it is:

    Crysis' AO:

    [​IMG]

    HBAO:

    [​IMG]

    HDAO:
    [​IMG]

    Ring SSAO (from tomerk, don't know if his own):
    [​IMG]

    Volumetric SSAO (tomerk's):
    [​IMG]

    They are all available as FX-files. Didn't make screens of them all.
     
    #2 Ethatron, Jan 2, 2013
    Last edited by a moderator: Jan 2, 2013
  3. itsmydamnation

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    are you working on OBGE again? <3<3<3
     
  4. Ethatron

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    :lol: No, they are old screens. I just finished a DDS-compressor 10% smaller than 7z and at 120MB/s decompression. Afterwards maybe I get a job in the industry, wish me luck.
     
  5. itsmydamnation

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    you really love your data compression..... so German :grin::lol: . Good luck!
     
  6. DavidGraham

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    Thanks , so the error really stems from the overly simple calculations .
     
  7. Ethatron

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    That's my guess without seeing the code/description of the particular SSAO. It also might be a conflict of post-processor algorithms (unlikely but possible) or instability from a low(er)-resolution z-buffer. But Ocam would say: oversimplified algorithm.
     
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