Object close to acrylic surface rendering black

[Dottedline]

Hi this is probably a really simple setting, but I can’t find how to resolve it currently.

I have a clear glass model that I’ve applied an off the shelf acrylic material to. The glass has a red puck detail on the bottom, a separate piece of geometry that’s inset to the base. I’ve added a small ‘air gap’ to the acrylic side of the design but top down and at oblique angles though the glass this detail renders black. I though this maybe down to a trace depth setting or similar but I can’t get it to work. If I pull the part apart, this renders fine (but not the way I need to communicate the design). Its down to the proximity of the two parts and light I think not getting efficient amount of light into this space perhaps. Hard to explain but something I can’t quite work out.

All input massively appreciated – under pressure to get a couple concepts off!

Cheers

Will.

[frankmci]

If the object detail is very small, I'm guessing you need to tweak the tolerance of the Ray Epsilon in your Kernel settings.

[Dottedline]

Hi thanks so much, what does this number refer to please? Does this relate to system units? The gap I put in was .1mm - in the days of working with mental ray I'd make sure of a small gap and things usually worked out fine. I'll take a look about to get back the office. Input appreciated! W.

[Dottedline]

Big thanks for that - issues sorted, i can crack on now. Many thanks!