How to create fast architectural glass in Vray for Modo?

[Angus Hume]

I can create a fast glass in Modo easily by adding a custom shader and switching off cast shadows and visible to GI but this seems to have no effect in Vray. I even bought Richard Yot's Vray material set with architectural glass just to see how he did it, but it does the same thing and it does not seem to render any quicker to me. While in Modo render that option makes a huge difference. Am I missing something really obvious?

[Robert]

Well, Modos GI Engine is way out dated, so that’s the difference you get.
Vray does have both the ignore alpha and GI, but if your glass diffuse is black, it ignores GI anyway. And yes, there should be no big difference, would be a bug if not. The only speed up I can think of, is having single sided polygons, refraction to 1.0 and reflect on backside to off.

[Angus Hume]

OK thanks Robert.