I have a scene that looks like this...
The renderer is Cycles (probably obvious from the screenshot :) ). Blender 2.78.
I'd like to be able to highlight components, such as the gearbox, in a highlight color such as a slightly emissive orange. This would be for stills and for animation; and for animation it would be cool to be able to fade from current materials to highlighted material over a few frames.
The main question I have relates to materials strategy. Currently, I've got materials such as aluminum, shiny_steel, powder_coat, etc. So this means that if I want to highlight, say, the gearbox, I need all the objects in the gearbox (which are more than one material) to change color, without affecting everything else in the scene that also has the same materials.
At this point, I don't have a handy hierarchy as these meshes were imported more-or-less flat; but I'd be happy to parent all the gearbox parts to an empty called "EMPTY_gearbox", for example. Then maybe the ideal thing would be to add a custom property to the parent that allows me to fade from assigned materials to highlight material, perhaps through a driver (I'm kinda guessing here - I'm not an expert yet... :) )
What's the best strategy for achieving this? How do I get my head around material slots, mix shaders, etc.? I'd rather not have to have several different aluminums, such as aluminum_for_gearbox, aluminum_for_manifold, etc. But if this is what it takes, I can do it, but it seems like a clunky approach.