how do I use ambient occlusion and what does it do. I’ve never used it before and it kinda never got in the way 
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If you can tell me what it does, how i use it etc. and if not give me a link to a good tutorial.
Thanks [!]
i am not a pro myself but i think AO produces a global illumination effect from within blender; the code is borrowed a bit from yafray.
and to use it, simply turn on the ambient occlusion button in the world buttons and you’ll get the effect.
and further, please search google for ‘Ambient Occlusion in Blender’
Ambient occlusion basically shades/ adds noise/ darkens the areas where two objects get closer together. Its basically GI, except it doesn’t get darker the further away from the camera you go.
You enable it in the world panels. Note that you must have raytracing enabled to use it.
For a better overview look at the wiki page.