ambient occlusion shader

[vance3d]

Ok, I know this has been covered before but I think an ambient occlusion shader for vray would be a real plus.

Sure everybody says you can get the same results doing it with a gi pass with one bounce but I just finished using MR dirt map/ambient occlusion shader and man it was fast.

I know its not the perfect replacement for full up gi lighting but I do a lot of NPR rendering and usually don't have the time to devote to gi renders.

and the great thing is that there's no jerking around with ir passes and the like. It's flicker free and fast.

From what I've read the ao shader relies heavily on the raytracing abilities of the renderer. It just stands to reason that an ao shader for vray would be even faster than the one for MR.


Just a thought.

Vance Miller

[LuKa]

I would second that

[cpnichols]

The dirt map shader for MR is NOT an Ambient Occlusion SHader... the results are similar, but keep in mind that it is not the same.

To achieve an ambient occlusion "shader" in Vray do the following. Trust me, this IS and Ambient Occlusion shader.

- select all your objects and make them a Vray material that is 100% white
- make sure the default lights are off and no other lights are on
- turn on GI and select primary bounces to Irradiance map (or direct GI (QMC) if you want to recreate the gritty low quality look of MR or Renderman)
- select secondary bounces to none
- select overwrite environment and turn on the skylight with a color of 100% white
- Render... you are done

I deal with AO all the time... and trust me on this... you are much better off with full GI... Vray does it almost as fast. There is nothing better then light actually bouncing off of objects.

[oconv]

Vance, can you post an example image of your NPR rendering style.
I'm just curious, what this AO technic could be looking.

-oconv

[egz]

Where it would be useful as a shader is cases where you would use the AO shader for instance as a blending mask in complex materials. This is something currently not possible with VRay GI

[cpnichols]

Actually it is... if you use the G-buffer output you can split out the GI pass, and that will essentially be the AO pass.

you can then use it to mult it on to your non GI scene scene in AE, Shake, etc...

or for stills photoshop.

[egz]

Yes of course, but you can't use it as a mask in a material that way I'm talking in renderer, not post.

[Seraph135]

No...you can still use that render as a mask for your materials....Just apply it as "screen" environment mapping.

[egz]

That wouldn't work well in reflections for instance, and it is still in need of a 2 pass process. Of course there are tons of ways to do the same thing, I'm just saying it would be nice to have

I should clarify that this would be applied as a map, not a complete material. That didn't come across clearly in my previous posts.

[Geddart]

Yes, there is really some use of it in a Shader.

http://www.informatik.hu-berlin.de/~goetsch/AmbOcc/
Look here, it's an Amb Oc Shader for Lightwave.

[vance3d]

whether or not the dirt map in MR is true ambient occlusion, I still think that style of shader would be a great addition to vray. I think that in general any shaders that can make use of vray's fast raytracing to produce ambient occlusion style effects or anything else that can be calculated based on ray length and and direction could only add to the advantages of using vray over other renderers.

The only reason that I was using the dirt map shader in mental ray was because I couldn't do the same thing in vray as fast as I could in mental ray.

I want vray to be my only renderer and because of the free network rendering model they've adapted. trying to render mental ray on a small render farm gets very expensive.

V Miller

[J_Bug]

Vance, You convinced me. When I read your post I thought it completely made sense. Would be nice to have You should go vote for it at vray.info if you haven't yet.

--Jon

[cpnichols]

I tend to agree at this point with J_Bug and Vance. Those types of elements may be useful. Hopefully it will be possible to write your own if they release their own shader language. That way one could write AO shaders, or even better, Bent Normals, or Reflection Vectors and Refraction Vectors so that we can do a post refraction on a plate... ooohh... yeah great idea.

[neods]

this is something that is really needed, and it shouldnt be too hard to make. Would love to see this in 1.5. any possibilities?