If a material has a reflect. glossiness and refract. glossiness of 1.0 is there any need for 8 subdivisions? Can this be set to 1, if so will it speed things up? Does the subdivisions effect the transparency of the material? ie a fully transparent materia requires higher subdivs.
I have seen some glass materials with 50 subdivs for both reflection and refraction when the glossiness value is set to 1.0.
Thanks
Glossy subdivs are only taken into account if material glossiness is less than 1.0. Reflect/refract amount generally doesn’t have an effect on glossy subdivs needed.
Recommended reading: Demystifying V-Ray DMC Sampler
So why do people put 50 subdivs in reflection/refraction for materials such as glass when the glossiness value is at 1? Makes it confusing.
If I remember rightly, years ago in the early builds of VRay, the material subdivisions used to default to 50. Maybe the mats you have seen are old, or originated in the older builds?
If that were true then it would make sense 
Vlado, can you confirm?
I’m not Vlado but as an oldtime VR user I can confirm that old default value was 50
Just remember to think about subd. value as a sort of “limiter”, it sets the MAXIMUM value available for subd but VRay can decide to terminate the render early
Thanks for confirming