hot to make object invisible to GI?

[themaxxer]

hello all

I have found some issues when rendering interiors with curtains (2sidedMat). there are a lot of splotches when the light has to pass the 2sidedMat of the curtains.
If I now want to make the curtains invisible to GI what do I do? I don't understand the different options.

one thing is the "cast shadows" in the "Object Properties" an other is the "generate GI" in the "Vray Properties" and the last that make sense is "visible to GI" also in the "Vray Properties".

in general. what's the difference between "generate GI" and "visible to GI"?
and the second. what to do if I want to hide the curtains from GI? the image should looks right so the curtains should receive GI, am I right?

bets regards
themaxxer

[Morbid Angel]

generate gi - will bounce the gi to other surfaces only (it will produce color bleed i.e. if a red box has this option checked the red gi bleed will bounce to other surfaces)
receive gi - will receive bounced gi from other surfaces as well as illumination produced by gi such as environment.

visible to gi - will not generate any gi or shadowing from gi, yet it will be illuminated by gi from other objects and environment.

I think in your case you would leave the first two check marks on, and turn off visible to gi, that way your curtains will get illuminated by gi, but will not obstruct it from getting past the curtain into the interior.

[themaxxer]

thanks for explanation dimitry.
I will try that.

best regards
themaxxer