Ambient Occlusion maps. Best Practice

Ambient Occlusion maps. Best Practice

Postby Nobkins » Mon Apr 14, 2014 9:31 am

As some of you will be aware I am working on creating some OHLE for TS. I have started having a quick play with baking Ambient Occlusion Maps (AO). To save on poly count in many areas I have not joined meshes together. For example. A hexagonal bolt head will not be joined to the plane which it sits on top of. Joining it adds a lot of faces to the plane as I have to divide a single plane up to join the hexagon bolt head on.
This video starting at 3m 43s shows the creation of a bolt sitting ontop of a plane (rather than joined with it).
http://www.youtube.com/v/S70B1gHH1TQ?start=223

However, because of this Ambient Occlusion bakes are not as good as they could be as the bake process is not able to calculate the settings 100% correctly without the meshes all being joined.

Some questions for the more experienced modellers.

  • How do you deal with this? Do you join things all together for the bake process and then revert to a previous save to reduce the poly count again? Joining a single bolt to a plane adds 10 or so faces more than I needed with it just sitting ontop.
  • If you do join the meshes what is the best way of doing this. Does there happen to be a shortcut or mod that quickly divides up my plane so it can accept my bolt without me having to divide it by hand?
  • Also is it best to apply the bake to your texture (using gimp or something) or should I use one of the more advanced shaders that can accept an AO map.
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Re: Ambient Occlusion maps. Best Practice

Postby Pauls » Mon Apr 14, 2014 9:49 am

Not an answer to your questions but I've found this Blender tutorial useful - even though I don't use Blender since it gives clues and ideas of how to proceed in other 3D programs.....

http://www.44090digitalmodels.co.uk/tutorials/blender2.html

Cheers
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Re: Ambient Occlusion maps. Best Practice

Postby Nobkins » Mon Apr 14, 2014 9:59 am

Load of good info their. Thanks Paul. Couldn't see anything about how to handle joining objects onto faces but I only skip read it as she who must be obeyed is telling me to get ready for our holiday. Blender is far more important ;)
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Re: Ambient Occlusion maps. Best Practice

Postby AndiS » Mon Apr 14, 2014 10:43 am

Revert after joining. Just do the AO on a copy of the blend file and you will be safe and also safe from learning too many confusing things. Even more so since I cannot think of an easy way to "unjoin".


Join meshes. Not a true join but maybe enough for AO to do the calculations right: In object mode, menu object - join. Or Ctrl J. "Joins the selected objects into the active object." I often do a few trials to remind me of the Blender logic of active and selected and how your clicks modify these states. In your case, it may not matter anyway.

I vaguely remember some option somewhere to tell Blender to consider near objects (within the given threshold) in AO, but I cannot find it now. I always found that AO of more than one object can be "interesting"/"challenging", whatever you name such things today.

Anyway, I don't think that you need to split the plane into all the pieces required to connect to the vertices of the bold. Just have the bottom vertices align with the plane and maybe remove the useless back face of the bolt (the hexagon no one sees). But even that should not confuse the AO.


Further processing of AO result. Sure enough, combining it with the rest in Gimp is the best bet. These shaders in Blender are badly documented and I read that they are in the process of restructuring them, as part of the change to the new rendering engine. So I pulled out of learning their details. This is fascinating stuff, though. But of limited use if you export to a dated game like RW. By the time RW is based on some Unreal Engine, Blender will be consolidated (hopefully) and then it will be very rewarding to learn the new scheme of things.
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Re: Ambient Occlusion maps. Best Practice

Postby VictoryWorks » Mon Apr 14, 2014 11:06 am

Nobkins wrote:However, because of this Ambient Occlusion bakes are not as good as they could be as the bake process is not able to calculate the settings 100% correctly without the meshes all being joined.

What do you mean by this Jim, I've never had a problem with AO bakes being unsatisfactory due to non-joined meshes? Do you need to increase the sample rate for the bake?
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Re: Ambient Occlusion maps. Best Practice

Postby Nobkins » Tue Apr 15, 2014 9:56 am

A screenshot would be good but not home for a few days now. When I bake I get a black hexagon shape from my bolt on the plane the bolt sits on as you would expect. However that black shape exceeds the size of the bolt fractionally and so where the bolt and plane meet you get a small black line round the base. If I join the bolt to the plain by dividing up the plane and joining the vertices then bake this does not happen.

I get smooth shading instead. I have tried using higher res textures and increasing the bake settings to make it better but unless the plane is physically joined to the hexagon mesh I get this black thin line.

Now I have not actually textured the model yet so I might be able to just ignore it as it should be dark arround the base of the bolt. Just not that dark in my view.

am I worrying over nothing?

I can post an image or two at the weekend if it is still not clear what I am talking about.
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Re: Ambient Occlusion maps. Best Practice

Postby VictoryWorks » Tue Apr 15, 2014 11:27 am

Nobkins wrote:am I worrying over nothing?

Yup :D
Once you get your head more than a foot from the object it'll all just fade together. Because when you build you tend to fill the frame close up you notice things that in reality are never seen. I'd put it in game and look at it from 6ft away before you start to worry too much.
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Re: Ambient Occlusion maps. Best Practice

Postby Nobkins » Tue Apr 15, 2014 12:26 pm

VictoryWorks wrote:I'd put it in game and look at it from 6ft away before you start to worry too much.

Excellent advice. A lot of the detail of my model is probably never going to be seen but I'll try to handle that with lods. OHLE is close track content so needs to look good but as there is a lot of it lods and poly count are important.
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