I want to make rectangles or just polygons with 4 corners each, but it should be fully colored (which means not only the edges but also whole figure itself) white/gray and transparent so it should looks like polycarbonate/glass in reality. How can I do that?
Create a plane in desired shape, and for the coloring, you will want to use a material. A material you can give a color & a % of transparency which will give you the desired result when you render the image.
I made a new layer with gray color and added 72% of transparancy, then I made a planar inside of a rectangle devided in three (not really a rectangle but rather 4 lines connecting each other and together they form 1 rectangle) and set that planar into that layer with color gray and 72% transparency. But after rendering, it isn’t transparent. Here is the picture:
Hi Amin,
I’m not certain, but did you assign a material to the plane yet? It looks like it’s still a default grey color. Check out this video tutorial on applying materials in Rhino 5 http://vimeo.com/59268869
Hey, yes I solved the problem with transperancy. It worked but there is one problem though: when checking ‘render curves’ at render options, the wallpaper I get is wrong by color: everything is pink and I don’t know how to solve it 
The Wallpaper discoloring when using the Render curves post effect appears to be a bug and I’ll file it now. I’d actually suggest using Neon here though instead which is a free raytraced viewport display mode. It will allow a static background image like wallpaper but will have the advantage of anti-aliasing the curves too and allowing for width control in the Neon display mode options.
Ahn I see. Thank you guys very much. I actually solved the problem by typing ‘print’ which didn’t worked in the first place which is kinda strange but anyway, thanks again 
By the way BrianJ, the background you put in the perspective view, how did you do that? prntscreen from Google maps or Bing maps or from something else? Because that background looks very good.
I went old school for that one and took a photograph… well maybe not that old school, it was digital.