multi_sub refraction bump

[ior=0]

Can someone explain why I'm not seeing the bump map refractions on the reverse side of the object?
All 4 objects are the same simple cube with 2 mat ID's. Front face and sides are ID1, rear face is ID2.
I have 2 identical glass shaders, 250,250,250 refraction, IOR 1.46, max depth 20, no reflection, except mat2 has a bump (cube 1 = mat1, cube 2 = mat2)
Cube 3 & 4 are instances just rotated 180 degrees multisub mat comprising of mat 1 and mat 2 applied. Cube 3 has mat1 (no bump) facing forwards and cube 4 obviously has the bump facing forwards.
What I don't understand is why I'm not seeing the bump refracted through the mat1 of cube 3?
What I'm after is flat glass on one side and bumped on the other but to see through the flat glass but have the bump glass distort the scene behind. Am I totally missing something here?
thanks

[ior=0]

this doesn't seem to be bump map related, as I have just tried putting the same mat (basic glass) into both sub-mat slots. So the same object has a identical material but on different matIDs - this breaks the refraction. If you use the multi-sub on/off check box to turn off one of the subs, refraction works again. Should this be happening?

[ior=0]

ok having an identical material in different multi-sub slots doesn't break the refraction in the vray render but does in VRAY RT. Having a slightly different IOR in the different multi-sub slots (or a bump map) breaks the refraction.
Are multi-sub materials compatible with vray mats and refraction? I wasn't aware this was an issue.
Has anyone every successfully made glass with a textured surface on one side and smooth on the other?
I'd love to know if I'm barking up the wrong tree here or this is a genuine problem.
cheers

[vaslavo]

HI, i have experienced this problem too with a building glass box, ive try to give different bump ids to the glasses ant enconuntred that the problem is the fog color or bias, if there is a multi sub object or a diferent material on diferent objects one fornt to another it gives error, did some one have a solution for this????

[vaslavo]

Did anyone have a solution for this or im missing something here? tnx.

[ior=0]

I didn't find a solution - I guess everyone is having problems accessing the forums with the sp4 problem.

[vlado]

One solution is to include a multi/sub map instead of a material (e.g. MultiIDMap2 by Grant Adam) instead of a multi/sub-object material. Won't work in the RT (as of yet), but should be fine for the normal V-Ray.

Best regards,
Vlado

[vaslavo]

Thanks, Vlado ill give it a try and let you know the feedbak.

[ior=0]

Vlado, that works nicely thanks.