On the IBL Properties, under the Ambient Occlusion checkbox, there is a button called Scene AO Options. Push that.

But I guess since you never pushed it, they are at the default values.

Which is why you can't see any AO at all. The default values do not produce large area AO effects - only small crevices.

But first let's get your renders down to a couple minutes. Then we can adjust the AO.

Also, for test rendering, don't render big. I always render to my document window size while testing. I shrink my window, and move the camera to zoom into an area that I'm interested in. Most of my test renders are done under 600 pixels in each dimension.

The amount of work goes up with the area of the render, i.e. the width times height. If you compare render times of 1000x1000 versus 500x500, the larger will take four times as long because that is a million pixels instead of 250 thousand pixels. A test render at 300 by 300 is only 90 thousand pixels, less than one tenth the time of the full size render.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)