View Full Version : Ambient Occluding massive poly scene

05 May 2012, 03:41 PM
Hi guys, i have a scene with trees and a carpet with a polygon made fluff, and some other stuff... The massive poly-count objects are mental ray binary proxies and i wonder is there some way to ambient occlude this objects without importing them back as a big poly number.
Imagine if i have a forest with 160000000 polys..i cannot pass without them being proxies..Please help a little :)

05 May 2012, 12:26 PM
isn't there someone who had been made ambient occlusion on a forest or something?

05 May 2012, 12:54 AM
I use mental ray and render pretty big forest and flower scenes, even with billions of polys not millions, and use the built-in AO of the mia_material_x shader for all of my ground foliage and dense leaves, and also sometimes on flower petals (reverse AO) to help give them more realism and distinction, and more color shift. This works great and won't take up any more RAM at rendertime, but will increase the rendertimes a bit. Sometimes you can get away with 4 samples and low density, too, to speed things up.

Alternatively, you could do it with passes. Just be sure everything you need AO working on/with is using the mia_mat_x_passes shader instead of the regular mia_mat_x.

05 May 2012, 06:13 AM
thanks very much i will try it :)

05 May 2012, 11:24 PM
you can try setting up a spot light to cast ambient occlusion...?

if you haven't found a solution, I can show you how / what to connect for this.


05 May 2012, 02:51 AM
Hi divanovic, I would love to see what is your method of generating fake Occlusion does it include shadow resolution.
If possible please provide details or tutorial for this method as it sounds interesting.

05 May 2012, 05:50 AM
yep can you provide us with that info?

05 May 2012, 06:04 AM
A workaround involving lights with lots of instances/proxies and tons of raytracing going on, especially with cutout opacity for your leaves, may be a far heftier solution. If you use the Ambient Occlusion in your mia_mat_x however, you can tune it on a per-shader level outright. Sometimes you only need 4 samples, especially if something's only going to end up taking up a few pixels of screen space in the end. And it's still faster than say blurry reflections or refractions, for example. Not a huge hit at render time for shader-based AO.

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