After a year, I have managed to improve the quality of the Corinthian capital, in order to obtain a simplified one... in other words, I have made this:
http://1.bp.blogspot.com/-cqD80auWISA/T56tMbAZ7FI/AAAAAAAAA5o/EAQN0Xfac7o/s1600/1.jpg
To obtain this (Render and captures made with Blender)
http://4.bp.blogspot.com/-8eDw3y3J9xk/T8KJwjoMn6I/AAAAAAAAA50/Vne28z-2zwo/s1600/render467.jpg
http://2.bp.blogspot.com/-pkUpAEIbEGE/T8KLB3VNoMI/AAAAAAAAA58/7dsVDSfJcYo/s1600/porfin2.jpg
As you see, now I have a capital with one hundred times less faces than the previous one, but... I can't manage with Blender when trying to export it to Sketchup. UV doesn't import in sketchup at all (I have tried with Collada, .Obj, .3DS... no luck). What I want to do is to export it textured. The normal map in grayscale may be useful to texture a low poly version of the capital in Sketchup, as capitals are white (well, some day I could paint them with their original colours, as the marble was painted...), but at this moment I am looking for a way to export the textured capital into sketchup.
I keep fighting with this, I have used Blender 2.63.
One day I would like to export the model to a game engine.
Edit: Yes, I know that Sketchup doesn't handle normal maps, bump maps... and so on. But I want optimized versions of the columns 😉