vray Maya dirt/occlusion issues and questions

[roopsta]

hi people

 

I've jumped in right at the deep end with vray and am struggling to get an occlusion render that the job requires.

 

I'm going to try real hard to be succinct, stick with me...

 

I can't use mental ray on this geometry, because it's from CAD drawings and it glitches too much. Besides Vray looks great but i can't quite tame the wild stallion to do exactly what i want. I've trawled the internet but I've only come across rather simple tutorials and explanations.

 

In mental ray AO i could set the max distance and i knew exaclty what it was doing and i could get the result i want.

 

In Vray I've been toggling the radius, distribution and fall off all day but i still can't get it right. In the 2 examples in my link, i just can't get rid of the really dark areas and keep the areas on the outside of the structure looking as good as it does.

 

http://imgur.com/a/Efu8u

 

I also need to get render times down. These are test renders at 480x270, soon i need to press go on 4400 frames of HD.

 

Also there is a second 'blotchy black' render of frame 868. In this i am attempting to use the opacity map in the Vray material to make all the geometry invisible (i wont bore you with why), but instead of seeing nothing (which is what i want) i see this blotchy black version of the geometry. How do i use the opacity or whatever to make the geometry disappear?

 

Appreciate any help, or any little tid bits to help me with vray. I'm really new to it.

 

Thanks so much

 

http://imgur.com/a/Efu8u