Quote - things like yafray render to a final image and are not realtime.  blender's game engine uses directX or openGL,  There would be no reason whatsoever to render with yafray.  there are a couple of other realtime renderers like unreal engine, but i dont think you can use it directly with blender's game engine.

 

Right. Never use YafRay as a realtime engine. Assuming that you've used it before, YafRay takes at least 15 minutes to render even a simple scene. You need a game engine designed specifically for, well, games. Try en.wikipedia.org and search for "game engine." 
Hope that helps.

It is better to do one thing well, than to do many things and excel at nothing.