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Blender - AO and renderlayers

recently ive been playing with AO in blender, and theres objects i dont want considered by AO, so i use a different renderlayer for them and alpha over in composite. but if i have the layer that these are on active, but not in the renderlayer, why does AO consider these objects despite not actually being rendered? Or is there any way to set which objects AO uses and doesnt? Using blender 2.49 atm.

Thanks

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AO is a world setting, so I tried to figure out what you did...

If you put objects on a layer which is not active it will not be rendered, AO or not,

so if you want Objects AO rendered and others not, the only way is to use Renderlayers. and composite them

so what did you want to achive actualy?

basically, this is my setup. i have the face on layer1, and i have eyelashes and eyebrows on layer 5 for instance (i have to keep as separate objects). If i were to render both layers in the same renderlayer, or just on active layers, the AO will use the eyelashes/eyebrows incorrectly (as these are mostly alpha and dont need AO and shouldnt affect the face's AO).

So, to get around this i put them both on separate renderlayers (1 in one, and 5 in the other), render separately and just composite them over one another. this works ok tho could be better. the prob comes when i want to render more than 1 frame in an anim or automate it. I would have to set 1 and 5 as active layers and let the renderlayers separate them. This always works except in the condition of AO. if i were to render the first renderlayer (that only uses layer1) with both 1&5 active (so i can later do 5 separately in the anim composite), the AO uses both.

I ideally want a way to control which objects AO can 'see' which is usable in rendering a long animation. i think i have an idea of a shortcut solution (creating a python file to dynamically change layers and render to files just like anim but better control for AO layers) but it doesnt change the problem. Any further ideas guys?

Thanks
Holly
those layers are the scene layers not the render layers, its a bit confising what a render layer is, but check my example in the next answer and you will see how to do it :)
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thats what i doubted you didnt use renderlayers but just layers :)

given a sceen with 2 cubes

the blue cube should use AO so i moved him to layer 2,

the plane and the red cube sit on layer 1

the RENDERLAYER named "no AO" renders layer 1 and delivers no AO pass (CTRL+LMB on the AO button)

the RENDERLAYER named AO renders Scene layer 2 and delivers the AO pass

both will be composited alpha over

if you check "composite" in the rendersetting and press "anim" you can render the whole animation followed by the compositing :)

render layers .blend

aah, i didnt know about the excluding for the options. i get funny results with your file. the no-ao result seems to change drastically if i move the bluecube out from the 2 visible layers (take it out of the scene). with the bluecube, the entire noao render is darker, without it, the red cube has a nice shade. confused me a little.

i found a workaround solution before i seen your answer fish (different scenes for each layer instead, with control-L to put the specific objects in the other scene). seemed to work fine. ill def give your way a go fish. im worried it may not work tho, as i dont use the combined output in my composite, and the AO output would prob still be the same overall. thanks tho dude! def gonna give it a go tho ^.^
you dont have to use combined at all :)
the most important thing is the exclusion option of passes (CTRL+LMB on a layer z masks it by the way :)
about the darker render: sure its darker (did you messure it?) or is it one of those optical things where you see bright parts even brichter if they are surrounded by dark parts?

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