[3DS Max & Arnold] How do I render with Ambient Occlusion?

BTDarmstad

Hello!

I'm currently learning 3DS Max, and I have chosen to render using Arnold. As someone coming from Cinema 4D, where Ambient Occlusion is achieved with the press of one button, Ambient Occlusion has been an absolute pain to get to work in 3DS Max and Arnold.

Unlike Cinema 4D, which seemingly has global Ambient Occlusion that you don't have to set up or anything, AO is applied to materials in Arnold - but where exactly do I put them in? The base color? In theory, I don't think AO belongs in the color information, but rather something to do with exposure to light, or light bounces, if there are even inputs for those. It doesn't seem to be set up in any way in Arnold other than an AO node that I don't know where to plug in.

I would prefer to render everything in one pass, but if I have to render AO in a separate pass, I'd be happy to do this as well.

musashidan

Arnold is an unbiased path tracer. The AO is part of the convergence. It doesn't use hacks to fake AO in the way that a ray tracer does.

Noren

If you want AO anyway, you could check out the method described here at the very bottom:
https://forums.autodesk.com/t5/3ds-max-forum/quick-ambient-occlusion-pass-in-max-2018/td-p/7724645

BTDarmstad

Aha, so I do already have AO in my render. I had a sneaking suspicion about it, because it looked pretty good already, but I had the mindset that AO was not turned on. Thanks for the clarification.

Noors

Not really. AO is a "hack" that can be used as a fast fake GI, or as mask to make some shader effect (dirt, rust...). It's not something that exists physically.

Arnold does the physically correct GI that takes forever to render, so you shouldn't need an extra AO pass, though AO could help for small contact shadows or whatever aesthetic reason. But i don't know where you should plug it for this purpose. it should only occlude indirect (ambient) lighting to be kind of physically correct.

Violet

I loved Mental Ray in Max, it just does the job, I know it doesnt' do it according to Arnold, but I'm just trying to bake AO, not observe a physical IRL lighting law.

The above 'tutorial' with the video works in theory, but is missing some parts, so it won't work. You won't get anything but a black scene if you try it.

Eric Chadwick

Scanline still works for baking AO, and it's fairly fast. Though Autodesk has talked about removing Scanline.

Make a Skylight, and enable shadows. Render To Texture, Shadow Map element. You can increase quality with the sampling in the Skylight, IIRC.