Tutorial: Ambient Occlusion in Maya - by Alchemist101

[benclark]

Originally Posted by canndis

You had mentions that there are different ways to do this in maya , do u know any other method or any links which can help.

I know you can setup the Ambient occlusion using Maya's default render layers, I'm not sure if you can bake it using that method though but it renders well. to be honest this method works for me so i have just stuck to it

[Talon]

Quick question;

How do I tell it to use a certain UV channel?

I'm baking out an AO pass to a second set of UVs that gets multiplied over the diffuse textures (which use the first set of UVs) in-game. As far as I can tell, the baker is using the first set of UVs to bake to (and resultantly the AO map looks totally ballsed up) and I can't for the life of me find where to tell it to use the second set :x

[benclark]

I've never done this but I have a feeling it relates to sets.

Its in Maya help under "Bake-sets" I've just had a wee gander through the menus and thats all I can see that might help

I'm not sure if I'm totally understanding the problem but can you not just lay out the second set of UVS in right next to the 0-1 space and then just slide those UVs into the default 0-1 uvspace for when you are baking and move the original set out?

If you use Move Component it assigns a history node to the movement so you can slide the uvs sets exactly 1 unit and back again, thats how I've dealt with multiple uv sets before

[Talon]

Cool stuff, cheers.

I think I worked it out. Basically the AO map was so fragmented and full of tiny pieces that it looked like gibberish output when it wasn't.

The problem stemmed from the fact that it wasn't using the correct UV channel to display the baked texture even after I told it to.

I tweaked it around a bit and it's pretty much working now



Quite liking this Maya stuff, seems a lot nicer than 3DS Max and with LXO2Maya plugin I can model, unwrap and texture in modo then just pull stuff in from the raw modo files

[Taehoon]

Very nice.... it helps a lot.. for making realistic texture ~

THanks

[NTaylor]

Your tutorial is great, very handy and clear starting point for making Occlusion.

But... what you're finally showing is not really Ambient Occlusion.

Ambient Occlusion should only really affect the Ambient part of your shading model :

A simple version of a shading model : Ambient + Diffuse + Spec = Beauty

I noticed that you're multiplying your beauty by your Occlusion results, meaning you're not actually making Ambient Occlusion in the end.

Ambient Occlusion should fit into the simple shading model above like this :
(Ambient_Occlusion * Ambient) + Diffuse + Spec = Beauty

Your tutorial has more in common with the ideas of 'Contact Occlusion', an odd (imho) artistic rendering of shadows. eg we'd still get occlusion even if a bright light aimed directly into the nooks and crannies, which cannot be correct.

Ambient Occlusion's not really a shadow, so much as 'an-absence-of-ambient-light'. It looks good when you use a longitude/latitude environment map for your ambient light.

Ambient Occlusion is a, highly and easily tweakable, artistic nod towards 1 of the visual features of Global Illumination (or radiosity rendering).

Sorry to nit-pick, but nomenclature's important.

[Talon]

Originally Posted by NTaylor

Ambient Occlusion's not really a shadow, so much as 'an-absence-of-ambient-light'.

And it's not so much "an-absence-of-ambient-light" as it is the occlusion of ambient light...

[benclark]

regardless of how you use the end result, what you are setting up is still an ambient occlusion pass