RMA (rougness, metallic, AO) material question

[tricky]

I am trying to get my head around optimised RMA material creation.

Each of the RMA channels is a greyscale image (plugged into the RGB channels of a bitmap/jpeg etc). Presumably, black means 'zero' and white means 'maximum', so:

Roughness - Black means completely smooth (like a mirror), and white means completely rough (like sandpaper)
Metallic - Black means not at all metallic (like wood) and white means absolutely metallic (like chrome)
AO - Black means no effect, white means full effect (though I don't quite get how this affects the look of a material yet).

Does this seam about right?

[PIXELBOX_SRO]

am i missing some vray map or kind of vray material or are you generally refering to 3 paramaters of vray material?

[tricky]

I'm actually looking at physically based shaders for use in realtime applications, like Stingray. It has been suggested in several tutorial videos that creating custom shaders is 'the way to go' as they are very efficient. I'm not massively familiar with PBR shaders.