What is "Interactive Devices" on render Pane?

Morphious-2630405

Attached is screenshot. What does checking these do? Also, do I want the CPU and GPU checked? Thanks.

SpottedKitty

Look again at the top half, where it says "Photoreal Devices" Those are the two render modes for the Iray renderer — apparently you can set different preferences for the two modes.

Whether you check both CPU and GPU depends on your graphics card's capabilities; if it's a recent NVidia card with enough CUDA cores and enough fast VRAM to handle your average scene, then select both. My card's too old and creaky to do anything in Iray, so I only have CPU ticked.