Backface culling of GAS in OptiX7

Simple question. As the intersection program of a GAS isn’t user defined, how can i enable backface culling when tracing a GAS object in OptiX7?

For built-in triangle primitives, that is.

You can use the OptixRayFlags for that:

Also have a look at the OptixInstanceFlags which can control the triangle facing.
You would need to have a dummy IAS with identity transform over the GAS to make use of those.

Please check the OptiX 7.0.0 online programming guide here and put in “cull” into the search field in the top right.
I’m normally using “Find In Files” on the OptiX 7.0.0 SDK headers and sources first.