VRay light properties - Diffuse subdivs

V-Ray V-Ray for 3ds Max General
1

I’ve worked with VRay so many years but never touched this value. What is it for and when i have to change it?

Thanks for help!

2

I think you need it when you are using photon mapping as your gi engine

3

Yep, it’s only meaningful when you use the “global photon map” GI engine.

Best regards,
Vlado

4

I’ve never used the Photo Map GI engine, when is it better to do so?

5

Thanks for clarify that. I’ve seen tutorials with Irrmap/LC GI and recommendations for crank up the diffuse subdivs for vray plane lights. So these tutorials seems to be incorrect.
BTW: I’ve also never used the global photon map GI engine.