But there are two things here, Real Time Rendering, and Rendering.
Ray Tracing technique it will USE AND ABUSE your processor and your RAM. And even with that, the results are not good enough, often the shadows that offers are not realistic if are not rendered at full resolution (because are mostly hard shadows), I mean, to get realistic results you can use the ray tracing technique but you must use other adjustments as well.
Use another software to render! That's the best solution.