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Kerkythea is a good package, with an excellent bunch of experts who are very helpful on the forum. For those who know how to use it will provide superb results & decent output for the rest of us! If you want pay a little money, Twilight Render provides an easier front end to the Kerkythea engine, with a template based workflow.
Never tried, but there is a plugin for the POV-RAY rendering package created by Didier Bur. I see the POV-Ray package bundled with engineers lighting calculation software.
Free Download Render[in] For SketchUp - to create a photo-realistic project environment (water, sand, grass) and a 3D sky with clouds, create artificial light sources, see the final result in a real-time radiosity preview window. IRender nXt is fast and simple SketchUp rendering extension for architects, interior designers, industrial. Download Free (Fully Functional) 30-day Trial.
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Top Free Rendering Extensions /Addons for SketchUp are suited for both MAC and PC and can exponentially increase the efficiency of your SketchUp version today. These SketchUp Rendering Extensions include different design studios which come packed with 3D tools, Photorealistic Renderings, Attributes and custom reports and interactive 3D PDF among the many mentioned features.
Sketchup Render Free
These not only help in creating quality work but also help to make the work easier and faster. Using the IRender/ nXtRender rendering engine adds oomph to the photorealistic rendering. But for the ones who believe in everything old school there are the non-photorealistic rendering options which allow sketchy, soft and shadowy qualities to be imparted to the models. 
The 3D tools that come with these are the most efficient in creating buildings, landscapes, products and 3D structures by using SketchUp. There are specially created extensions which focus on channel arrangement on the basis of magnetic points and input of numeric values. Free download windows 10 password unlocker.