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Ambient Occlusion Confusion

Hey guys, long time lurker first time poster. And still rather new proper modeling methods. I'm going through a tutorial on Ambient Occlusion map creation through the transfer maps feature for a very simple brick wall I've followed the settings and instructions. But when I bake my map the image turns out almost completely blank. I'm not sure what I'm doing wrong. Any help would be very appreciated.

AO Map
Brick Wall Model
Transfer Map Settings

Replies

  • SinisterChef
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    Heh, I got it. I had my surface I was baking on too actually inside the model I was using to generate the map... I'm dumb.
  • CheeseOnToast
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    CheeseOnToast greentooth
    I'd advise against using Maya's transfer maps for baking AO. You've already come across one problem which is actually caused by the way Mental Ray generates AO. Whether your low poly is inside, outside or a mixture of both shouldn't be a factor when baking. Mental ray (wrongly) includes the bake target (i.e. your low poly mesh) when raycasting. If I remember right you can get around it by hiding (ctrl+h) the low poly mesh before baking, but really you shouldn't have to.

    Try using Xnormal (freeware) instead. It's ten times faster and you shouldn't run into problems like this. If you do try it, change the ambient occlusion settings to something like this :

    Rays : 256
    Distribution : Cosine
    Bias : 0.08
    Spread Angle : 178
    Limit Ray Distance : off
    Allow 100% occlusion : on
  • Mark Dygert
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    I agree with Cheese, mental ray is a pig and it messes up more than it gets right when baking. In max it also includes the target when calcuating AO, and it incorrectly assigns black as the background color for the normal map, even when the correct color is set in the "normal map background color" option.

    It also issues with creating padding around UV shells which normally leads to seams, which is why you're having it calculate padding in the first place to help prevent the background from bleeding in.

    By default Mental Ray takes longer to render normal maps and the default settings cause them to be more blurry than the standard rendering method. Only if you add more time to the rendering by turning on Final Gather can you get something that matches the standard rendering method...

    So for baking maps mental ray is only really good at rendering AO but it has issues doing that. You're better off creating a ambient light set up like a light dome, applying a white material and rendering out a diffuse map that includes lighting. I prefer this method because you have more control over the lighting. Like you can bake in an overhead light or color the lights in a way that it will help you create your diffuse, like a gradient that blends from the top to the bottom of the character but because it's baked it lands on all the UV shells correctly regardless of their orientation.

    For rendering scenes Mental Ray can produce some great results but with an endless supply of options to tweak its a nightmare for a lot of people, for rendering maps its just a nightmare. Xnormal is a great solution, but it is another app and I prefer to do all my rendering in 3dsmax and stay away from mental ray.
  • SinisterChef
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    Cool, thanks for the tips! I've downloaded xnormal and I'll be sure to play with it when I get some free time.
  • Ace-Angel
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    Ace-Angel polycounter lvl 12
    Echo what Mark just said, baking in Max, especially MR is a nightmare beyond human understanding, I would say if you want to know what hell feels like, try baking your Map near a deadline using MR.
  • JacqueChoi
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    JacqueChoi polycounter
    uhhh...

    I love Maya's AO bake.


    If your high-rez model ISN'T unwrapped, then run an automatic unwrap on the entire thing. Then bake the AO directly onto the High Rez using the Batch Bake (with decent MR setting, and a decently sized texture.

    (This is gonna take a LONG ass time, so find a game to play or something).


    From there you can just Xfermap the high to the low.


    :) I like it. But I hear Topogun has some amazing AO.



    Anywyas, when I do a Max AO Bake, I just use a Skylight, and put in a ground plane. I generally prefer that over a MR bake.
  • Will Faucher
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    Will Faucher polycounter lvl 12
    I second what JacqueChoi said. I usually just pop on a skylight with a ground plane in max, and RTT it. The results are great, and pretty quick.
  • EarthQuake
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    JacqueChoi wrote: »
    uhhh...

    I love Maya's AO bake.


    If your high-rez model ISN'T unwrapped, then run an automatic unwrap on the entire thing. Then bake the AO directly onto the High Rez using the Batch Bake (with decent MR setting, and a decently sized texture.

    (This is gonna take a LONG ass time, so find a game to play or something).


    From there you can just Xfermap the high to the low.

    Ewwwww. You "love" that workflow? Thats easily the worst AO baking workflow of any major 3d app. Well I guess we know why Autodesk hasn't implemented a standard high-low ao bake workflow in Maya, people "love" it this way. =P

    Honestly, if you're baking in Maya, just do AO in XN.
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