with the Zarkow's model (Thx to him) http://moi3d.com/forum/index.php?webtag=MOI&msg=7958.6

SimLab (easy to use) here without any regulates: http://www.simlab-soft.com/


you have also a free one (for enthusiast, hobbyst, student and StartUp) : Fusion 360 : http://www.autodesk.com/products/fusion-360/try-buy
(you must have a computer not more 2 years old ) A real true gem for the price! ;)
the render is easy to use like Keyshot ;) (And of course it makes also some other little things! (helping critic Moi's fillets...;) )
Export format from Moi: SAT (or IGES, Step) (here half size image)



and a funny another free one inside free Sketchup Make: https://www.sketchup.com/products/sketchup-make
Visualizer: http://www.getvisualizer.com/ the more easy render prog in the world! (quasi nothing to do ! )
Export format from Moi: SKP

Of course free to you to put any colors, textures etc...