Hi Vlado and dev team.
I would like to put in a request for a fast occlusion shader. I am wondering if its at all possible to make something like renderman’s occlusion or similar?
I know new mental ray has support for fast occlusion and it looks half decent.
Thanks.
It is possible, yes. VRayFastSSS2 uses a similar approach to calculate sub-surface scattering.
Best regards,
Vlado
well if its not too much to ask 
actually vlado, these days I try to go more of a renderman approach. Using vray shadow map, + various fakes to get frames to render fast. Kind of tired of working with ray tracing in a seance that you always have to fight it to win…and sometimes you lose.
I think for the vfx guys out there, the more fakies available to get the job done, the better.
Yes and preferably an occlusion shader that we can easely assign in the ambient zone of lighting. Sometimes it is frustrating seeing other people with mental ray (using mix8layer) or renderman (using similar layered shader workflow) doing fast photoreal renders withj using only raytracing in the ambant occlusion and reflection part of rendering. For a lot of things this works perfect.
example by master zap:
well I dont see a particular problem there from vray. This is just a way to layering the occlusion. This same result is possible with vray as well.
Yes, doing this in post is easy, but doing this in one pass is more troublesome as far as I know (at least in 3ds max). In a scene with no reflection you can easely use compositing to get the correct ambiant occlusion.
But when using reflections it is more tricky. Then you are obligated to do it in one pass to get your correct ambiant occlusion reflected.
(Don’t mean to hijack your thread but it is I think on topic, getting more flexible ways in vray to fake effects.)
I’d love to see more cheats in VRay!
I second that fast occlusion shader. Turtle for Maya has really fast AO aswell (at least when I tried it a couple of years ago).
I disagree. V-ray is designed to be a physical correct renderengine and should be used that way. On the otherhand unlike engines like fryrender and Maxwell V-ray is pretty flexible.
If you wanna cheat, use the scanline render.
this is a pretty limited viewpoint, in my opinion. for one thing, V-Ray is based almost entirely on the idea of cheating. GI would not be possible in production rendering (where speed is a requirement) if it wasn’t for biased rendering. until hardware is powerful enough to recreate reality (someday! 
), we will always need shortcuts to achieve a desired visual result.
although vray has a solid “physical” core, adding more functionality that allows for feasible, quick results is never a bad thing.
greg
use scanline?
how to use adaptive sampling with scanline?
how to use 3d motion blur with scanline?
how to use mtd with scanline?
how to output gbuffer from scanline
etc etc etc
please tell me how more options are a bad thing.
Yeah that’s a pretty ridiculous statement. VRay cheats to give you good results. It tries to stay physically accurate but you can break out of that - consider that you can still have specular highlights, it still works with the standard camera, etc. If you wanted physically accurate results you wouldn’t use anything other than the physical camera and ppt. In a production environment, people don’t want to be told “oh sorry, VRay says noooo”, they want flexibility which VRay currently offers. This request is just for another tool to add to the arsenal.
Well it was kinda short for me to say “Use Scanline!” but there are so many software packages back in the day wich were good tools in the beginning but with too many useless additions they became a hog.
I’m not saying it’s a bad thing to add more options but for a specific area of software like a GI engine you should set a limit on how far you are preparing to go.
Don’t get me wrong, I like V-Ray alot as it is and what it will become in the future.
Here is an interesting post on using a raytrace engine (xsi’s mental ray) to fake GI with ambiant occlusion, I am wondering if this is possible in vray.
thats quite common knowledge and is not limited to xsi. Maya and max mr also can do this.
I actually asked developers for vray to include this once before…but I guess we need to wait
Yes, we use this aproach quite often (as a light shader) when render times need to be super fast. It works suprisingly well. IMO it doesnt look as good as GI, but is helpfull in a pinch. This would be a nice feature in Vray.
BTW, cant this aproach be used by multiplying the dirt shader over the diffuse in the Vray Material ?
Regards,
Mike
Is there a tutorial for that technique in 3ds max? And yeah, vray should be able to do the same thing.
if you get - Ambient/Reflective Occlusion (3ds max)
there is a section called type, and in the brackets there is description of what the values do,
0 = occlusion, 1 = environment etc.
If you set that value to 1, and then put that occlusion into the shaders diffuse or ambient color you should get sampled environment. (you should place some hdr into 3ds max environment slot first).
Ok tnx Morbid Angel, about the renderman ambient occlusion, I heard it even supports some simple color bleeding, that should also be a cool feature if there ever gonna be a fast occlusion shader.