Im right with you there on the mixed media. A render is in my opinion not finished after some proper post processing in Photoshop or some other image editing program.
And I know where you are coming from. When taking a photograph light defines everything you see. Even when I paint (though be it digitally) it's not material you are painting, no you are actually painting light itself, not objects. Something I came to realise when I went deeper into matte painting and space art.
I remember myself trying to sketch several objects on my desk without looking at them and trying to visualise different light sources.
However if you are experiencing troules with kerky and it's interface I recommend V-Ray for Sketchup. I creates photorealistic images, and it is the industry standard render app. It comes with a GREAT manual which will run you through the basics. I got the app down within 3 days. And can get amazing results out of it now. a 30 day trial is available on their site.



