Personally, I very-much like the OpenGL Preview renders, which are entirely OpenGL, and I have found various ways to turn-off some of the “extra garbage” (guidelines and so on) that typically show up in them.
The BGE is very powerful in this regard, and there are certain “tricks” that you can use to store its outputs in a file.
I’ve said for many years now that what I desperately want is a set of rendering-nodes which employ OpenGL alone to produce their outputs. I want access to the BGE without having to define a “game.” I want ready access to OpenGL-generated outputs, which I can (and do …) use as a “foundation layer of paint” upon which other layers can be added using other, more computationally-expensive techniques. And, I want to do all of it “in Blender.”
I’m fairly sure that “Python-based nodes” could be the glue that gets me what I want, but I really don’t have the visual-programming “chops” to do it myself, nor necessarily the time.
It’s great that we’re using the GPU, through Cycles, to do something that it was not designed-for. Why, indeed, don’t we have effortless access to what it was designed-for? :spin:
I already “render in passes,” because I’ve never really had super-souped-up hardware. OpenGL is excellent at producing, in near-real time(!), “85% or more of what I need,” such that the remaining work is basically “spices not the main-course.” I want that process to be easier … much easier.