Hi,
It would be a killer feature if Vray can IPR in debug mode and support a node or multiple nodes disabled in the shading tree. It is like in a node-base comp, one would constantly disable certain upstream nodes to compare the effect downstream.
I don’t know if one can disable nodes in hypershade/node editor. Maybe this feature needs Autodesk to build the functionality in Maya first for Vray to support it?
I don’t think Maya has an option like this. This sounds like it’s going in the Nuke world 
It sounds like a good idea, I just don’t know if there’s a way for us to pipe in such an option in Maya. Will make a note to explore that further.
@yolov I recall we’ve been here the same discussion before. I brought up that there is a node state “forzen” or exclude from evaluation as mentioned https://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2017/ENU/Maya/files/GUID-F69C44F3-1037-46DF-A1BE-56B96EA6ED43-htm.html
But it seems not useful or related in terms of shading evaluation.