Lampshade Material Question

[Mokiki]

I am currently trying to replicate something I thought was fairly simple but has me stumped for a while now. My goal is to replicate one of those lampshades which are folded repeatedly and overlap themselves. Like in these example picture:

http://www.stylepark.com/db-images/c...200_1515-2.jpg
http://www.stylepark.com/db-images/c...200_1515-1.jpg
http://ecc.co.nz/media/cache/d7/ab/d...66a812c13b.jpg

I have my basic geometry following the same folding pattern but I don't seem to be able to get rid of the heavy darkening where the fabric overlaps.



My first attempts were done with single sided geometry and the vray 2 sided mat but I didn't get very far.

Most success I had with the fastsss2:


But I hope there is a less render intensive method to recreate the wanted effect.
I'm 100% sure I am missing something quite obvious here and hope somebody could point me in the right direction.

[svetlozar.draganov]

You can get this effect even with 2SidedMtl if you set some transparency of the assigned shaders:

scene: http://ftp.chaosgroup.com/support/scenes/2sidedmtl.max

[Mokiki]

Thx Svetlozar for the help. Sadly your approach won't work if there is actual geometry involved inside and behind the lamp. Because now you can actually look through the geometry.

[vlado]

The darkening with the two-sided material is odd; can you post the lampshade geometry so that I can play with it?

Best regards,
Vlado

[Mokiki]

Sure thing. Here is the Scene (Max 2016 and Vray 3.20.02)

There is a Shell deactivate Shell modifier on the lampshade but it was only for testing SSS/Transclucency materials. Other than it seems that the shadows are too strong where the darkening occors. Disbabling Shadow casting removes the darkening completely but obviously looks wrong since some darkening appears in the real life examples.